NYSGA 1995.kmz

NYSGA 1995.kml
Field Trip Guidebook for the 67th Annual Meeting of the
New York State Geological Association
Edited by
John I. Garver
Jacqueline A. Smith
For the combined meeting of the
67th Annual meeting of the New York State Geological Association &
26th Annual meeting of Eastern Section of the American Association of Petroleum Geologists
Sponsored by
New York State Geological Survey/State Museum and Union College
Hosted by
Geology Department, Union College, Schenectady, NY
This guidebook was published by the New York State Geological Association. Additional copies may be obtained from the Executive Secretary of the NYSGA:
Bill Kelly, Executive Secretary
New York Geological Survey
Room 3140 Cultural Education Center
Albany, New York, 12230
Introduction
The Geology Department at Union College is proud to co-host the sixty-seventh annual meeting of the NYSGA and AAPG Eastern Section. Together this combined meeting has brought together academics, students, teachers, petroleum geologists, and environmental geologists. The Geology Department at Union College is happy to be a co-sponsor and co-host of the NYSGA meeting this year because it has been quite some time since we have been able to host such an event. The last time the annual NYSGA meeting was held at Union was 30 years ago when the principal movers in the Department were Philip Hewitt and Leo Hall (see Shaw, this volume). Shortly after this meeting the Geology Department was effectively disbanded and only recently came to life in 1985 after the College received a generous donation from a Geology alumnus. Now ,with four permanent faculty, one visitor, and several adjuncts, it is safe to say that we're back for good!
Since the last time NYSGA was held at Union, the Geological Sciences have experienced a major transformation. The first twenty of those years were clearly dominated by the then new plate tectonic paradigm. During the last ten years, and especially the last five years, we have seen quite a dramatic change in the focus of the geological sciences. Due in part to a number of external factors, the geologic community has placed a greater emphasis on issues associated with global change, hydrology, and environmental geology. This shift, has been away from the more traditional areas in geology such as field based studies in stratigraphy, sedimentology, paleontology, and structural geology. There is little doubt that NYSGA guidebooks reflect the focus and ideas of the times and if one compares the focus of the trips in this meeting to those in the guidebook for the previous NYSGA meeting at Union in 1965, you will see just how much our science has changed.
In assembling the trips for the 67th annual meeting of the NYSGA we tried to balance three important factors: our unique and exciting geologic setting; the breadth of interests of our members; and, importantly, the availability of field trip leaders. Certainly in terms of the first two factors, I feel that we have succeeded and we are looking forward to an exciting meeting!
The geologic setting of the lower Mohawk Valley is ideal for teaching and research. The lower Paleozoic stratigraphy has a regional tilt to the south so one can examine the Grenville-aged rocks of the Adirondacks to the north (Whitney and Olmstead, this volume; McLelland, this volume; Kelly and Hill, this volume), Cambro-Ordovician carbonates and clastic rocks in the Mohawk Valley (Garver, this volume; Kidd and others, this volume), and Silurian and Devonian rocks in the Catskill Mountains to the south (Friedman, this volume; Wolosz and Paquette, this volume; and Ver Straeten and Brett, this volume). The lower Paleozoic stratigraphy in eastern New York is punctuated by thick synorogenic sequences deposited during the Ordovician Taconic Orogeny and the Devonian Acadian Orogeny. To the east of the tilted lower Paleozoic stratigraphy, deformation in the section increases towards the front of the Taconic Allochthon where it and underlying rocks were deformed during the Taconic Orogeny (Hollocher, this volume; Kidd et al., this volume; Friedman, this volume). In the Taconic Allochthon, Cambro-Ordovician deep-water sedimentary rocks have been placed over shallow-water sediments of the Cambro-Ordovician margin.
The surficial and glacial geology in this area is as impressive and diverse as the bedrock geology. Ice dynamics related to the obstructing effects of the Adirondack Mountains resulted in non-uniform migration of ice sheets that coalesced south of the Adirondack massif only to encounter the Catskill Mountains to the south (Dineen and Hanson, this volume). During retreat, glacial Lake Albany (and its relatives) covered much of the Capital District and left an impressive sequence of glacial lacustrine deposits (Wall and LaFleur, this volume). During and after the most recent glaciation, karst and caves formed in the local carbonate strata, resulting in important landform development and interesting problems in hydrogeology (Rodbell and Hays, this volume; Rubin et al., this volume; Rubin, this volume). The long history of industry in the area and demand for space and water have resulted in some unique environment geology (Smith and Eslinger, this volume; Maswick and Snow, this volume; Hewitt, this volume). Finally, the neotectonic setting of eastern New York is examined in a unique trip aimed at understanding the seismic hazards in Columbia County (see Nottis and Cadwell, this volume).
It has become clear that the education of educators is and will continue to be an important priority for both Academe, government, and industry. With this in mind we have included several trips aimed at earth science teachers (Garver, this volume; Hollocher and Hollocher, this volume; and Kelly and Hill, this volume, and others) and we hope that many of the teachers who go on the field trips participate in the special one day workshop which will be held in Monday following the NYSGA meeting.
Finally, I would like to personally thank all of the people that have made this guidebook happen. First and foremost are the trip leaders who have spent a considerable amount of time putting together these trips and to my co-editor, Jacquie Smith, who helped with the endless task of reigning in papers and keeping track of things. Thanks are also due to the Organizing Committee and Committee Chairs for the combined NYSGA & AAPG Eastern Section meeting for their support, suggestions, and recommendations. Among them, Ken Johnson (Skidmore College), the General Chair, deserves special praise for keeping us together and focused for the committee meetings which periodically met for more than one year prior to the actual meeting. He also deserves special recognition for finally getting on EMail during that time (you can personally thank him at kjohnson@skidmore.edu). I would also like to thank Bill Kelly (N.Y. State Geological Survey), who is the N.Y.S.G.A. Executive Secretary, for his important contributions which include, but are not limited to advice and planning the logistics of putting this guide together. Finally, Gretchen Turner did a superb job handling the problems that editors face in terms of communication with authors and the nuts and bolts of putting the guide together.
To all who are just about to embark on the 67th annual NYSGA meeting -- have a great time and enjoy the fall foliage!
President, NYSGA, 1995
Geology Department
Union College
October, 1995
PLEASE READ THIS!
Landowners and outcrop defacement
In preparing this guidebook we asked the authors to do their best to ascertain landowner status at each stop. We have done this because increasing number of problems have arisen between landowners and geologists - in some cases geologists are no longer permitted to visit some localities in the Mohawk Valley. Additionally, a number of classic and important outcrops have been defaced, marked, or heaped with garbage by overzealous visitors who must leave their mark on every outcrop visited. Please pay careful attention to landowner status and cultivate a relationship with the landowner if you plan to use an exposure from year to year. Also remind your trip participants to use have respect for the future geologists who will visit these geological sites. Thank you.

A1: SEISMIC RISK ASSESSMENT OF COLUMBIA COUNTY, NEW YORK
GARY N. NOTTIS AND DONALD H. CADWELL
New York State Geological Survey
Room 3140 CEC
Albany, NY 12230
INTRODUCTION
In 1994 the New York State Geological Survey began a pilot study to assess earthquake hazards in New York State, on a county by county basis. This effort was modeled after studies done in Portland, Oregon, and Los Angeles, California. The goals of this work were to produce:
- an earthquake ground-motion response map,
- an earthquake-induced landslide-potential map,
- an earthquake-induced liquefaction map, and
- a combined earthquake hazards map.
Our analyses were done as a function of glacial landforms. The maps produced are a result of computer-based analyses of earthquake strong ground-motions, soil depth profiles, soil engineering properties, and topographic slopes. These maps are intended to aid civil engineers, building designers, and emergency managers on the subjects of earthquake preparedness and hazard mitigation.
Columbia County was chosen for the initial study because of its proximity to the Capitol District, and also because of the quantity and quality of geologic data already available. This pilot study was a learning experience. We are still in the process of analyzing the collected data, and the preliminary results are encouraging. During this field trip we will show why such studies are needed, how these studies should be conducted, common problems, and how the results of these studies can be applied.

A1: SEISMIC RISK ASSESSMENT OF COLUMBIA COUNTY, NEW YORK

Knickerbocker Lake, over hill to left.
Kames, kettles and kettle lake.

Outwash sands and gravels
Outwash sands and gravels, prograding southward to delta at Kinderhook, deposited in Glacial Lake Albany.

STOP 1. DEMONSTRATION OF SEISMIC LINE
The Pleistocene equivalent to the Kinderhook Creek deposited the large delta complex into Glacial Lake Albany 18,000 to 15,000 years ago. Abundant meltwater was transported from both the retreating Wisconsinan glacier terminus and the bedrock uplands toward the delta. The present channel of the Kinderhook Creek is incised 17-20 m (50-60 ft) into the delta (Figure 6) and the location of this seismic line is on the floodplain. Water well information suggests bedrock is 12-24 m ( 35-55 ft) beneath the floodplain.

Martin Van Buren Historic Site

Columbia County Airport

As we descend the hill, note the old marsh ahead of us.

STOP 2: Clay Pit
This clay pit, shown in Figure 7, is owned by the City of Hudson, and permission should be obtained prior to visiting the site. Today we will be able to see a small remnant of the original working area. These alternating bands of dark clay and lighter colored silt-clay are rhythmites, rhythmically deposited fine-grained lacustrine sediment. If the dark and light couplet represent an annual winter and summer accumulation, then they are varves. This 10 m exposure has couplets 2-5 cm thick and could represent 200-300 years of sediment accumulation into Lake Albany. When wet, these clays are very plastic.
1. What do you suppose would happen during an earthquake to the dams of Underhill and Oakdale ponds?
2. What would be the fate of these clay banks?

Note the landfill to the right.

Note Underhill Pond to right.
This is a man-made pond within the gully.

Turn left into entrance for Fireman's Home -- Lunch
Note: To eat lunch at the Pavilion it is necessary to obtain permission in advance.
If time permits, the Fireman's Museum is excellent.

STOP 3: Discussion of buildings, etc., City of Hudson.
See Figure 7 for specific location. Discussion will concentrate on types of building structures, and location of emergency services.

STOP 4: Home damaged by land slump.
NOTE: This road log has stopped several miles from the property owner of STOP 4 because this is a private residence and the NYSGA trip has been given special permission to visit. The owners prefer not to be disturbed by an onslaught of people in the future.
The damage resulted from land failure on October 7, 1983, coinciding with the 1983 Blue Mountain Lake, magnitude 5.1, earthquake, with the epicenter 180 kilometers away.

A2: WOLLASTONITE DEPOSITS OF THE NORTHEASTERN ADIRONDACKS
PHILIP R. WHITNEY
New York State Geological Survey
Room 3140 CEC
Albany NY 12230
JAMES F. OLMSTED
48 Haynes Road
Plattsburgh NY 12901
INTRODUCTION
The presence of wollastonite near Willsboro in the northeastern Adirondacks (Fig. 1, 2) has been known since the early nineteenth century. The earliest reference to it in the geologic literature is by Vanuxem (1821). For over a century, the wollastonite was of little interest except as a mineralogical curiosity. Mining on a small scale began at Fox Knoll near Willsboro in 1938, with the wollastonite being used as a flux for arc welding. In 1951, the Cabot Corporation gained control, and began underground mining in 1960. Interpace Corporation took over and expanded operations in 1969. Product development resulted in uses in ceramic bodies and glazes, as a reinforcing filler in plastics and resins, and as a substitute for short-fiber asbestos. The operation, now known as NYCO, was purchased in 1979 by a subsidiary of Canadian Pacific (US), Processed Minerals Inc. Open pit mining at the Lewis (Seventy Mountain) Mine, ten miles southwest of Willsboro, began in 1980 and in 1982 the underground operation at Willsboro was closed. Both properties are now owned by NYCO Minerals, Inc., a subsidiary of Fording Coal Company of Calgary, Alberta.
The Willsboro deposit was mentioned briefly by Buddington (1939, 1950) and Buddington and Whitcomb (1941); the geology is given in more detail by Broughton and Burnham (1944). Putman (1958) described several occurrences of wollastonite in the Au Sable Forks and Willsboro quadrangles, including those at Willsboro, Deerhead, and Lewis (Figure 2). De Rudder (1962) studied the mineralogy and petrology of the Willsboro ores, and attributed them to contact metamorphism with localized alumina metasomatism. Oxygen isotope work by Valley and O'Neil (1982) demonstrated extensive metasomatism involving meteoric water.

A2: WOLLASTONITE DEPOSITS OF THE NORTHEASTERN ADIRONDACKS

STOP 1: METANORTHOSITE OF THE WESTPORT DOME
Massif anorthosites are plagioclase-rich igneous rocks. Their origin is controversial; the debate is summarized in Ashwal (1993). Most current models involve variations on this theme: Large volumes of mantle-derived basaltic magma fractionate in the upper mantle or lower crust toward an aluminum-rich residuum. Appreciable contamination may take place from partially melted lower crust. As the magma rises through the crust, plagioclase crystallizes to produce a crystal-rich magma or mush which is emplaced in the middle or upper crust. Further fractionation may follow emplacement; iron-enriched residual liquids may sink or be expelled by filter pressing.
In the Adirondack anorthosites, plagioclase occurs in two forms: dark-gray megacrysts and smaller, light-gray to white interstitial grains. Compositions range from An42 to An60, most commonly An48 to An55. Antiperthitic megacrysts are locally common. The interstitial feldspar, which may include some K feldspar, consists of varying proportions of crushed megacryst ("protoclastic") plagioclase and feldspar crystallized from residual liquid. In addition to plagioclase, the principal minerals of igneous origin are orthopyroxene, clinopyroxene, and iron-titanium oxides. Metamorphic minerals include garnet (in the more iron-rich varieties), hornblende, and biotite.
The Westport Dome is the largest anorthosite body in the Adirondacks outside the Marcy Massif. This exposure, near the southern end of the dome, illustrates the outcrop-scale lithologic variability common in Adirondack anorthosites. Gabbroic anorthosite is present in the eastern third of the cut; anorthosite in the remainder; textures and abundance of megacrysts vary widely. Note the vertical, ENE-trending ductile shear zone and the small, deeply weathered fault near the middle of the cut.

STOP 2: ANORTHOSITIC GNEISS
Cuts along the E side of the parking area expose strongly foliated anorthositic gneiss. The foliation here ranges from nearly horizontal to gently north-dipping; a NNE-trending lineation, common throughout the northeastern Adirondacks, is visible on some surfaces. Intense ductile deformation is common along the margins of the dome but is also present in the interior in zones such as this one. The timing of this deformation is unclear save that it postdates consolidation of the anorthosite. Walk north 0.1 miles along the road. On the left, blasted outcrops of anorthositic gneiss contain an irregular, tabular body of garnet-two pyroxene-plagioclase gneiss with minor K feldspar. "Jotunites" such as this one may be residual liquids from the anorthosite.

Moderately deformed anorthosite
Outcrops on left are moderately deformed anorthosite containing lenticular dark patches rich in pyroxene that may be the remnants of large pyroxene oikocrysts.

Good view from a small rise
Crest of small rise overlooking the Champlain Valley with Lake Champlain and the Green Mountains of Vermont visible in the distance.

To the right, a fine view of the Green Mountains.
To the right, a fine view of the Green Mountains, from Mt. Mansfield (L) to Camel's Hump (R).

This is private property.
This is private property: be sure to obtain permission from NYCO before entering. Proceed through the gate and about 0.4 miles up this road to the lower portal of the Willsboro Mine.

STOP 3: WILLSBORO MINE
The Willsboro deposit is located near the base of the ore-bearing zone (OBZ), separated from the underlying metanorthosite by, at most, several tens of feet of amphibolite. Average strike of foliation and compositional layering within the OBZ is N 60°-65° W with considerable local variation; dips range from 15°-35° north. DeRudder (1962) cites drill core evidence for as many as seven ore layers, with maximum thickness of the principal ore horizon on the order of 50 feet. Numerous small brittle faults and unmetamorphosed mafic dikes (Isachsen et al., 1988) cut the ore.
We will examine exposures at both the lower and middle portals of the now-abandoned underground mine. The area around the middle portal was formerly operated as an open pit. Observe the straight, sharply defined garnet-pyroxene rock (GPS) layers in the ore as well as diffuse compositional layering within the ore; the latter shows complex folding in a few places. One GPS layer appears to crosscut foliation and compositional layering at a low angle. At contacts of the ore with gabbroic anorthosite or amphibolite, discontinuous layers and lenses (boudins?) of pale orange-brown garnet rock ("garnetite") are locally present. If time permits, we will traverse part of the OBZ overlying the ore, to examine a complex section of interlayered rocks including garnetite, amphibolite, gabbroic anorthosite gneiss, mafic calcsilicate rocks, and olivine metagabbro.

Outcrops of unmetamorphosed carbonates
Outcrops of unmetamorphosed carbonates in the woods just east of this intersection attest to the presence of a N-S normal fault, mapped by Buddington and Whitcomb (1941), that separates the Precambrian and Paleozoic rocks in this area. Going North on Fish and Game Road, the outcrops on the left are Precambrian marbles and gneisses.

Long Pond on the left.
The outcrops along this road are gabbroic and anorthositic gneisses with some interlayered metasedimentary rocks, occupying a structural saddle between the Westport dome to the south and the Port Kent dome to the north.

STOP 4: MARBLE XENOLITH IN JOTUNITE
Climb the bank on the right side of the road. At the top, climb over the fence and examine the rocks at the top of a large roadcut on the northbound lane of I-87. Please exercise great caution near the edge of the cut cliff facing the Northway. Also, please do not climb down to road level, as it greatly distresses the State Police.
The white rock is a large xenolith of calcite marble surrounded by mafic gneiss. The marble contains varying amounts of phlogopite, diopside, chondrodite, grossular, graphite, and sulfides. Phlogopite also occurs in clots a few centimeters across. A few lens-like masses of amphibolite are folded in a manner that suggests the "fishhook" forms commonly found in other intensely deformed marbles. Diopside-plagioclase rock with very calcic plagioclase occurs near contacts with the host rock; identical rocks are found in the OBZ upsection from the Willsboro Mine.
The host rock is strongly foliated and lineated garnet-pyroxene-K feldspar-plagioclase gneiss, similar to the jotunites at Stop 2. This is one of many locations where carbonates in contact with rocks of the anorthosite suite have not developed large amounts of wollastonite. The outcrops on both sides of Route 9 at this location are also jotunites; those on the east side contain a layer or lens of garnet-rich gabbroic anorthosite gneiss, as well as masses of quartz (quartzite xenoliths?).

Strongly foliated gabbroic anorthosite gneiss
Roadcuts beneath and to the south of the I-87 overpass are strongly foliated gabbroic anorthosite gneiss with garnet- and pyroxene-rich zones.

Cliffs are granitic gneiss; road level crops are anorthosite gneiss
The cliffs on the right, on the east face of Pokomoonshine Mountain, are granitic gneiss; the outcrops at road level are gabbroic anorthosite gneiss.

Entrance to Pokomoonshine State Park on right.

Outcrops of fault breccia on right.
A NNE-trending brittle fault roughly follows the road here.

Alternate stop if time permits.
Park on the left, just North of a small outcrop of gabbroic anorthosite gneiss. Cross a narrow strip of woods to the southbound lane of the Northway. The roadcuts here are anorthositic gneisses with marble inclusions. Again, please remain on the top of the outcrop, and do not cross the road.

STOP 5: GABBROIC AND ANORTHOSITIC GNEISSES
Two fault-shattered outcrops on the West side of the road and one on the East contain very strongly foliated gabbroic and anorthositic gneisses. We map these as part of the OBZ, at the NW comer of the Westport Dome. The gabbroic gneisses contain millimeter-scale layers of garnet-pyroxene rock. Marble is present at the base of the outcrop on the East side. The more northerly outcrop on the West contains an undeformed hornblende-quartz-feldspar pegmatite. If wollastonite-rich layers are present in this section of the OBZ, they are not exposed.

Gate to Lewis Mine.
Get permission from NYCO before proceeding. The large open pit of this operating mine is a short distance up the gravel road.

STOP 6: LEWIS MINE
While the immediate geologic setting of the Willsboro deposit is well known (Putman, 1958; DeRudder, 1962; Olmsted and Ollila, 1988), that of the Lewis deposit is less clear due to lack of natural exposures in the immediate vicinity. The orebody strikes roughly E-W and dips gently south, approximately parallel to the topographic surface, on the south limb of an open, E-W trending anticlinal crossfold. On the west side of the open pit, where the ore is close to 80 feet thick, it is overlain by strongly foliated charnockite; to the east the overlying rock, where exposed, is mainly anorthositic gneiss. Throughout much of the present mine area, the ore was exposed at the erosion surface. When the overburden was removed to begin mining, a karst-like surface was present, owing to the fact that wollastonite is one of the few silicate minerals that are appreciably water-soluble. Based on drilling data and temporary exposures within the mine, the footwall appears to be amphibolite and gabbroic anorthosite gneiss.
The hills north of the mine are gently N-dipping gabbroic anorthositic gneiss, underlain by deformed olivine metagabbro of the Jay Mountain body; both of these units are structurally above the ore-bearing horizon. Unlike Willsboro, where the ore is at most a few tens of meters above the anorthosite of the Westport Dome, our mapping suggests that the ore at Lewis is underlain by a considerable thickness of mixed gneisses and metasedimentary rocks. At one point during mining, a 4-6 m wide unmetamorphosed diabase dike was exposed.
Throughout much of the Lewis orebody, ore is interlayered with straight, sharply defined, discontinuous GPS layers parallel to foliation in the ore. We interpret this as tectonic layering. The regional NNE lineation can be seen locally on foliation surfaces in the ore here and at the Oak Hill prospect two miles to the east. A few thin, discontinuous layers of pyroxene-plagioclase-sphene granulite, rimmed by garnet-rich GPS, are present locally within the ore. Toward the north end of the present pit, layering and foliation are less prominent and the ore is leaner, rich in pyroxene and grossularitic garnet. At the northwest corner, a folded dike of GPS clearly crosscuts foliation.

A3: GLACIAL DEPOSITS IN THE MOHAWK AND SACANDAGA VALLEYS OR A TALE OF TWO TONGUES REDUX
ROBERT J. DINEEN
Roy F. Weston
1 Weston Way
West Chester, PA 19380-1499
ERIC HANSON
Continental Placer
26 Computer Dr.
Albany, NY 12205
PURPOSE
The purpose of this field trip is to examine the late glacial deposits of the Mohawk and Sacandaga Valleys, particularly the recessional and interlobate moraines preserved in the vicinity of Gloversville, NY. The glacial sediments exposed in the area were deposited during the waning stages of the last ice sheet, when the local topography split the thinning and wasting ice sheet into the Mohawk and Sacandaga glacial tongues. Sediment-laden meltwaters from these lobes deposited a complex of moraines and glacial lake sediments from Gloversville to Galway. The three-dimensional distribution of sedimentary facies record the demise of these tongues and provide a framework for one of the most productive aquifers in NYS.
This study focuses on three 7-1/2 quadrangles: Gloversville, Broadalbin, and Northville. Adjacent 7-112 minute quadrangles studied include Amsterdam, Tribes Hill, Galway, Jackson Summit, and Peck Lake (Figure 1).
INTRODUCTION
The study of the glacial stratigraphy of the Mohawk and Sacandaga Valleys has enjoyed a resurgence in the past thirty years after a lull of nearly forty years. Brigham (1928) published a map and lengthy interpretation of the glacial deposits of the central and western Mohawk Valley. This map and its associated text stood as the "last word" until Robert LaFleur and his graduate students began to re-examine glacial deposits and glacial history of the area in the early sixties (LaFleur, 1965; Yatsevitch, 1968). Yuri Yatsevitch completed a Masters Thesis in 1968 that outlined the framework of the late Wisconsinan history of the valleys. LaFleur (1969, 1975, 1979, 1983) built upon Yatsevitch's thesis, paying particular attention to evidence for a Late Wisconsinan readvance (the Yosts Readvance) and the wide-spread distribution of a dark gray, clay-rich till (the Mohawk Till). Later, Dineen and Hanson continued LaFleur's and Yatsevitch's work while mapping for the New York State Geological Survey's Surficial Mapping Project (see Cadwell and Dineen, 1986). They refined the geologic mapping and stratigraphy in the eastern Mohawk Valley while Jack Ridge refined the mapping and stratigraphy in the western Mohawk (Dineen and Hanson, 1985; Muller and Ridge, 1986; Ridge, 1991; Dineen et al., 1992).

A3: GLACIAL DEPOSITS IN THE MOHAWK AND SACANDAGA VALLEYS OR A TALE OF TWO TONGUES REDUX

Crossing the western edge of the Hudson Lowlands.

Crossing the trace of the Hoffmans Fault.

We are proceeding across ground moraine
We are proceeding across ground moraine of Mohawk Drift. The hills are drumlins, many of which have stratified drift cores.

Crossing the Perth Recessional Moraine.

STOP 1: Town of Broadalbin (see Figures S-1 and S-2a).
This exposure is in the southeast, Mohawk Drift portion of the BIM. The eastern slope was the ice-proximal side. The area was overridden from the southeast by the Yosts Readvance. The overriding ice plowed into the moraine, shearing and displacing the drift to the northwest. The deposit later collapsed by normal faulting and slumping when the Yosts ice melted. The outwash and ice-contact stratified drift exposed in the pit was deposited by meltwater flowing east to west along the margin of the Mohawk tongue. This conclusion is based on cross-bedding and climbing ripple orientations.
In 1984, the Section exposed at the Town of Broadalbin Town Pit was as follows:
6 m: Top of section.
4.5 to 6 m: | 10 YR 6/4 Fine sand with little gravel, in planar beds and climbing ripple laminae. Contorted to the east. Upper 50 cm is massive and fissile.
4.5 m: | Disconformity.
3.5 to 4.5 m: | 10 YR 6/2 Climbing-ripple and ripple-trough-laminated fine sand with lenses of gravel near its base.
3.5 m: | Disconformity.
2.5 to 3.5 m: | 10 YR 6/4 Trough cross-laminated, fine to coarse sand with fine gravel in I to 3 m wide, 1 to 1.5 m deep channel fills inset into ripple laminated very fin e sand. The unit is contorted and overturned to the northwest and gravity faulted to the east. The upper 50 em is fissile and sheared. The unit contains lenses of coarsening-up, silty, sandy matrix-to clast-supported diamicts.
2.5 m: | Disconformity.
Base to 2.5 m: | 10 YR 6/4 Planar cross-laminated fine sand with lags of gravel on truncation surfaces. Ripple laminated to the east. Faulted down to the southeast.
A pit 70 m west of this Stop contained 5 meters of contorted, ripple-bedded sand. The upper portion of the sand was deformed by shearing, and was overturned to the northwest. The sand was overlain by 1 to 2 meters of compact, fissile, sandy matrix-supported diamict.

STOP 2: Scotia Sand and Gravel (see Figure S-1 ):
This subaqueous fan contains planar, trough, and ripple-laminated sand and silty sand. Cross beds suggest that the sand was deposited against the ice by meltwater flowing from the east and southeast. The Sacandaga tongue lies to the northwest, in the vicinity of the present shoreline of the Sacandaga Reservoir.

STOP 3: Herba Pit (see Figures S-1 and S-2b).
This exposure is in the northwestern portion of the BIM, on the Adirondack Drift side. The ice was on the northwestern side of the moraine. Many flow tills and a few compact lodgement tills are observed in this pit.
In 1983, the Section exposed at the Herba Pit was as follows:
9.7 m: | Top of section.
9 to 9.7 m: | 7.5 YR 6/8 Sand and silt matrix-supported diamict. Some cobbles are present.
8.6 m to 9 m: | 10 YR 6/3 Trough cross-bedded, cobbly gravel.
6 to 8.6 m: | 10 YR 7/6 Lenticular, trough cross-bedded, cobbly sand and gravel.
4.8 to 6 m: | 10 YR 5/4 compact, sandy matrix-supported, massive to laminated diamict. Lenses of fine sand are present.
3.9 to 4.8 m: | 10 YR 7/2 Interbedded sandy massive to planar-bedded diamict with greasy, rotten shale clasts. The lower 20 em is sheared.
3.9 m: | Truncation surface;
Base to 3.9 m: | 10 YR 7/2 Cross-bedded cobbles and sand. The cross beds dip 10 S80E.

STOP 4. Rex Excavating
This exposure is in the southwestern portion of the BIM, on the Mohawk Drift side. Southeast was the ice-proximal side. The pit contains several till and lacustrine sequences that suggest the ice margin was oscillating. It was overridden by the Yosts Readvance. A similar exposure lies 1.7 km to the east.
In 1984, the Section exposed at the Rex Excavating Pit was as follows:
11.3 m: | Top of section.
9.7 to 11.3 m: | 10 YR 4/2 silt matrix-supported diamict. The unit is faintly laminated with sand stringers at the base. The base has a sheared contact with:
8 to 9.7 m: | 10 YR 6/4 Irregularly-laminated fine sand and silt. Cobbles of rotten shale are present.
7.7 to 8 m: | 10 YR 4/6 Laminated, silt matrix-supported diamict.
6.6 to 7.7 m: | 10 YR 6/3 Planar-laminated fine sand with cobbles. Unit is locally cemented.
2 to 6.6 m: | 10 YR 5/3 Planar cross-bedded, gravelly sand with a trace of boulders. The cross beds dip 10 to 15 N60W.
Base to 2m: | 10 YR 5/3 Silt matrix-supported diamict with striated boulders.

STOP 5: Twin Cities Sand and Gravel (see Figures S-3 and S-2d)
This pit is in the distal portion of the BIM and contains distinct subaqueous fan features (foreset beds and starved ripples). Both gravity and thrust faults are common in the eastern (proximal) portion of the pit. Aeolian sand mantles the upper 4 m of the pit. The upper cross-bedded sand is the leading edge of an aeolian dune. The upper sandy diamict is wind-blown silt and sand.
In 1984, the Section exposed at the Twin Cities Sand and Gravel Pit was as follows:
14m: Top of section.
12 to 14m: 10 YR 5/4 Cross-laminated fine sand.
10 to 12 m: 10 YR 6/3 Laminated to massive (west to east) sand matrix-supported diamict. This unit fills in depressions in the lower unit. The top contact has a soil zone.
Base to 10 m: 10 yr 6/4 Planar cross-bedded fine sand with lenses of trough laminated medium to coarse sand. Faulted and interbedded with contorted lenses of silty matrix-supported diamict to the east.

STOP 6. Mayfield Pit (see Figure S-3 and S-2e).
This pit is in an esker that pokes above the Glacial Lake Sacandaga plain.
In 1984, the Section exposed at the Mayfield Pit was as follows:
6.5 m: | Top of section.
5 to 6.5 m: | 10 YR 7/3 Beds of contorted laminated fine to medium sand to thin rhythmically laminated, very fine sand to silt.
2 to 5 m: | 10 YR 7/3 Fining-upward, planar-bedded, imbricated cobbles to silt, beds dip 10 S50W.
Base to 2m: | Covered.

STOP 7. Bradt Pit (see Figures S-4 and S-2!)
This pit is a deep cut into a kame delta that was built into a 900 ft as! glacial lake, possibly an ice-marginal portion of Lake Gloversville. The exposure was 65+ m high and 350m long in 1984!
In 1984, the Section exposed at the Bradt Pit was as follows:
65 m: | Top of section
50 to 65 m: | 10 YR 5/4 Shallow, trough cross-bedded, fine to medium sand, some gravel grading down into fining upwards, 10 YR 6/2 planar cross- bedded boulders through coarse sand, dipping 5 to 10 S60E.
45 to 50 m: | 10 YR 6/4 Planar cross-bedded, fine to medium sand and ripple-laminated, gravelly, fine to medium sand, dipping 15 S30W.
30 to 45 m: | 10 YR 6/2 Coarsening upwards, planar cross bedded, cobbly, gravelly, fine to coarse sand, dipping 15 S50W. Cobbles are subangular to subrounded.
15 to 30 m: | 10 YR 6/4 Planar cross-bedded, fine to medium sand with trace cobbles. Beds dip 10 to 15 N60W.
Base to 15m: | 10 YR 6/2 Imbricated, open-work, subangular to subrounded boulders in 1 to 1.5 m cross beds. Imbrication dips N20E.

A4: LITHOFACIES AND STRUCTURE OF THE TACONIC FLYSCH,
MELANGE, AND ALLOCHTHON, IN THE NEW YORK CAPITAL DISTRICT
WILLIAM S.F. KIDD, ANDREAS PLESCHI
Dept. of Geological Sciences,
University at Albany,
Albany, NY, 12222
FREDERICK W. VOLLMER
Dept of Geological Sciences,
SUNY College at New Paltz,
New Paltz, NY, 12561
The Taconic Allochthon of eastern New York is bordered to the west by a zone of mid-Ordovician shale and greywacke turbidites, which are appropriately characterized by the term "flysch". These synorogenic deep-water clastics are now interpreted to represent the fill of the migrating flexural basin created by the advance of the Taconic thrust sheets onto the Cambro-Ordovician passive margin of eastern North America (Rowley and Kidd, 1981; Bradley and Kusky, 1986). The flysch is markedly diachronous, with a thick basal carbonaceous shale unit, the Utica Shale, and extends many hundreds of kilometers west of the present margin of the Taconic Allochthon. The Allochthon consists almost exclusively of sedimentary rocks that represent a sample of the continental rise part of the Cambro-Ordovician passive margin, and of the latest Precambrian-earliest Cambrian clastics of the late-stage rift fill, and rift to passive margin transition; all are strongly folded and have been transported westward on a complex system of thrusts at least 150 to 200 km relative to the North American craton (Bradley, 1989). In the New York Capital District, a zone about 16-20 kilometers wide of the Ordovician flysch adjoining the western margin of the Allochthon has also undergone strong deformation, including widespread conversion of once stratified rocks to melange, associated with the later stages of the Taconic Orogeny. It is the purpose of this guide and field trip to examine these rocks, to attempt to illuminate the structures which they contain, to try to roll back at least some of the nomenclatural and stratigraphic confusion they have suffered, and to place them in the larger regional context of the Champlain Thrust system.

LITHOFACIES AND STRUCTURE OF THE TACONIC FLYSCH,
MELANGE, AND ALLOCHTHON, IN THE NEW YORK CAPITAL DISTRICT

View over Mohawk to flat Schenectady Fm in south bank

STOP 1. View of flat-lying Schenectady Fm. flysch and shale
View of flat-lying Schenectady Fm. flysch and shale outcrop on south bank of Mohawk River from end of Brian Drive.
Outcrops are scarce in the belt of flat-lying to gently dipping greywackes and shales [flysch] east of the trace of the Saratoga-Ballston Lake normal fault. The best are in the south bank of the Mohawk River, and are not readily accessible to large groups. At this stop (see Figure 2 for location) a shaly unit of the Schenectady Formation flysch can be seen across the river underlying medium-bedded greywackes and shales with gentle west dips and no signs of internal deformation.
These rocks are autochthonous and have not been transported by thrusting during the Taconic Orogeny. About 300 meters to the east of this location, along the southern shore, there is an abrupt contact of these flat-lying strata with significantly folded and faulted thin-bedded greywackes and shales, defined by the first thrust fault encountered in a west-to-east transect. This is not clearly apparent from this viewpoint, but a representative outcrop of the folded and faulted flysch is seen at the next stop.

STOP 2. Folded and faulted flysch of Vischer Ferry Zone
Outcrop along north shore of Mohawk River near Vischer Ferry power plant/Lock 7
The rocks here form part of the Vischer Ferry Zone of folded and faulted flysch (Figures 1 and 2). Thin-bedded greywackes and shales, with subvertical dip, are exposed in the discontinuous roadcut going down the paved road and branching off onto the dirt track down to the shore of the river. At the shore, similar thin-bedded flysch and shale comprises the outcrop extending west from the path to the abutment of the power plant (Figure 3). This outcrop displays asymmetrical folds and small faults connected with east-over-west thrusting. A detailed description of this outcrop appears in Bosworth (1989), who pointed out the incipient development of a melange-type fabric in the fault zone (Figure 3), mainly through fracture development and incremental slip on the fracture surfaces. Farther down the dirt track to the south-east, a small hillock and its shoreline on the river under the power transmission line exposes more subvertical, west-younging thin to medium-bedded greywackes and shales.
While the strata here are in part shale-dominated, enough arenaceous greywacke occurs here and in the surrounding areas for the Vischer Ferry Zone to be mapped as Austin Glen Formation across the Mohawk River. To the north, however, near Round Lake (Figure 2), the Zone changes to largely shale, lacking significant arenaceous wackes, and there it is specified to consist of Stillwater Shale. This change is gradational, and thinning and fining of the arenaceous component of the flysch is occurring, within the Zone, across the Mohawk River; we choose for consistency to include anything containing arenaceous greywackes within the Austin Glen Formation.

STOP 3. Thick-bedded Austin Glen Formation flysch
Thick-bedded Austin Glen Formation flysch of Halfmoon Greywacke Zone, folded, with melange on small thrust fault- road cut on north side of Route 146 east of Clifton Park
This outcrop (Figure 4) mostly exposes structurally intact medium to thick-bedded greywackes and lesser shales in a broadly antiformal structure, hence the popular name for this locality, Clifton Park Anticline. However, in the center of the outcrop there is a thrust fault, which can be identified from the zone of overturned steeply-dipping thinner greywackes and shales that form the lower limb of a close fold in the immediate hanging wall of the fault.
This fold might be a tightened hanging wall ramp anticline. To the west [structurally below] this fold structure, there is an approximately 3 meter wide zone consisting of broken blocks of greywacke in a disrupted shale matrix, which is melange derived from the adjacent materials, and defines the fault zone. We think that this fault is an excellent example that shows in miniature how the larger zones of melange formed.
This outcrop is part of a large structural slice, which we term Halfmoon Greywacke Zone (HGZ), that consists of relatively intact, medium-thick bedded greywackes like these, surrounded both to east and west by highly disrupted melange, including some materials exotic to the immediate greywacke-shale association. This HGZ slice consists along the Mohawk River of a disrupted large-scale synform; however we do not favor the klippen interpretation shown for it on the New York State Geological Survey maps since 1970; in particular there is no evidence for a westerly dipping, nor a relatively west-downthrown fault/fault zone on its eastern side.
Excellent sedimentary structure assemblages may be seen in the greywackes in this outcrop indicating deposition by turbidity currents, and local reworking by bottom currents [beds completely occupied by climbing cross-laminations], perhaps the tails of turbidity current events. Claims of the existence of shallow water sedimentary structures, particularly mudcracks, have occasionally been made for the Schenectady Formation, and for greywackes of the same structural slice as this outcrop near the Mohawk river (Rickard and Fisher, 1973); we think that these reports are mistaken, and the structures are probably either syneresis cracks, or tectonic structural features. All greywacke-bearing outcrops we have seen in the Hudson Valley and in the Schenectady Formation have turbidite characteristics, certainly deposited below wave base, and likely in substantially deep marine water given the analogy with modern arc-passive margin collisions, such as Timor-Australia.

STOP 4. Cohoes Melange outcrop
Cohoes Melange outcrop [eastern Mohawk River Central Melange Zone], cliff on Waterford side of Mohawk River below Cohoes Falls
This outcrop and its continuation up and downstream constitutes the best, and most continuous section through the melange of the Hudson Valley. Structural features seen here, and elsewhere in this belt indicate a "hard-rock" origin for the melange, particularly the striations visible on many of the characteristic "phacoidal" or lenticular splinters of the shale, and the polished nature of these surfaces in places when freshly exposed. Clear evidence of olistostromal origin of units with blocks in matrix is found in a few places, but the large majority of the melange in the region does not show features that require a surficial mass-wasting origin. As long as shear strains were high, imbrication and mixing of materials could be achieved in large ductile thrust fault zones, as long as some of these were out-of-sequence thrusts, in order to introduce originally overthrust materials [from the Taconic Allochthon] among the medial Ordovician flysch-derived melange matrix. The latest structures here and elsewhere in the melanges consist of quartz veins, some fibrous, and slickensided, which in many places, including here, show a consistent 120° plunge; this orientation is known to be associated with the Champlain Thrust in Vermont, which is an along-strike continuation of the faults defined by the Hudson Valley melange zones. This fault displacement direction contrasts with the ∼090° plunge of thrust-related slickensides in the Devonian Helderberg Group to the south between Ravena and Catskill.
The section here consists (Figure 5) of alternating zones of exotic-containing and less- to non-exotic- bearing melange. A large isolated wacke block is seen part-way down the cliff path; lower down, several large carbonate breccia blocks are exposed, possibly derived from a Taconic Allochthon source, or from normal fault scarps in the outer trench slope prior to arrival of thrusting and melange formation. Just east of the bottom of the path is a large block of black argillite, which is in our opinion derived from the allochthonous strata of the Taconic Allochthon, specifically from the upper Mt. Merino-basal Pawlet Fm. interval, which contains, regionally, black graptolitic argillites with Nemagraptus gracilis faunas like the one collected and identified by Riva [pers. comm., 1981] from this block. Smaller blocks of chert, also originally from the Mt. Merino Fm. of the Taconic Allochthon, occur at the base of, and above Cohoes Falls. The remaining materials in this part of the section consist dominantly of greywacke and shale [flysch], although there is also a persistent occurrence of greenish shale seams and films in all areas where the exotic melange occurs, as well as scattered small blocks of sideritic mudstone whose stratigraphic source is unidentified, and both of which are not seen in areas just containing greywacke and shale and their melange derivatives. Farther east in this outcrop than the black argillites, there are a few occurrences of blocks/lenses of a fossiliferous wacke, very similar to that exposed in a partly-disrupted bedded section at Snake Hill on Saratoga Lake.
This brachiopod/trilobite fauna contains Cryptolithus tesselatus [Riva, pers. comm, 1981]. Because of its local occurrence, we suggest that this lithology represents input to the flysch trough from a local across-axis source, unlike the majority of the flysch, which clearly has a southerly derivation and along axis transport, from the paleocurrent evidence.
If the water level is very low, excellent exposures of incipiently to strongly disrupted shales and silty wackes of the Waterford Flysch Zone may be seen just below the dam located east of the Waterford-Cohoes road bridge; these represent a discontinuous belt of in part less-deformed rocks forming a slice, or set of imbricate slices, on the eastern margin of the Mohawk River Central Melange. Access to this outcrop, at low water, may be obtained from either the north or south side of the Mohawk River, east of the bridge.

STOP 5. Poestenkill Gorge
Taconic Frontal Fault and Troy Frontal Melange Zone
This is one of the few exposures, and certainly the best (Figure 6), of the Taconic Frontal Fault anywhere along its ∼200 km length. Green arenites and silty wackes and slates of the Bomoseen Formation are in fault contact here with greywacke block-rich grey shale melange of the Troy Frontal Melange Zone. The original (presumed thrust) fault contact has been cut and displaced by a later steep strike-slip fault at this locality, so that most of the exposed length is of the latter; the thrust may be seen under and to the south of the waterfall. It dips quite steeply [∼55°], as is also the case at the few other exposures of this fault; a possible reason for this includes [back] rotation by later thrust ramps. It is the case that outcrop evidence of thrust sense of shear for this fault, here and at the few other localities where it is exposed, is not overwhelmingly convincing. An alternative explanation for the steep dip, also lacking convincing outcrop evidence, is that the fault is extensional, or has a component of late normal displacement, and formed late in, or long after, the Taconic orogenic event. Even if extensional, this in no way contradicts the regional relationships demonstrating the overthrust origin for the Taconic Allochthon and the belt of melange and deformed flysch.

STOP 6a - Troy Frontal Melange Zone
This cut (for location, Figure 7) exposes in all the north side and most of its length on the south side a similar greywacke block-rich shale matrix melange as seen at stop 5, the Troy Frontal Melange Zone. The exposure lies a few hundred meters west of the [here unexposed] trace of the Taconic Frontal Fault. It is close to a unique locality first investigated by Ruedemann (1901 b), the carbonate conglomerate of Rysedorph Hill [see below, Stop 6b] which is the main reason for stopping here in addition to stop 5.
Within the greywacke-shale melange here, late quartz veins like those seen earlier cut all other structures. One block of wacke about 20 meters from the east end of the cut on the north side shows a slate with cleavage oblique to bedding on part of one margin, and this cleavage is clearly cut by the lenticular phacoidal melange matrix fabric. Some of the wacke blocks in this cut have angular, fracture-controlled margins, others have a more rounded and smoothed appearance, possibly indicating they were not fully consolidated upon incorporation. The westernmost outcrop along the south side of Rt. 151 here shows a quite different assemblage, with both dark grey/black and green shale melange matrix, and only modest-sized [∼10-40 cm] sideritic mudstone blocks; it is identical to parts of the exposure in Cohoes Gorge, seen at stop 4. The contact with the greywacke block-rich melange to the east is not exposed, but is inferred to be a significant fault. This melange type forms the matrix on the west side of the exposure of the Rysedorph Hill conglomerate, located a few hundred meters to the north.

STOP 6b. Rysedorph Hill Conglomerate.
ASK PERMISSION at the house on the west side of Olcutt Lane BEFORE entering this property. Please DO NOT hammer this outcrop.
A limestone conglomerate, from which Ruedemann obtained a fauna ranging in age from the Cambrian through the medial Ordovician, forms a unique exposure on part of this hill. Walk up the slope within the woods from the unsurfaced Olcutt Lane, starting before the first bend to the east (Figure 7). Dark and green shale melange with small sideritic mudstone blocks is found, mostly as loose shale chips and fragments, on the slope. The limestone conglomerate and breccia is found forming a knoll, and also as loose fragments, near the top of the first slope. Much written about this famous [notorious?] locality presumes it to be in stratigraphic arrangement with the surrounding shales and greywackes. As you have seen from the roadcut, this is an untenable hypothesis, and the conglomerate/breccia must form a large block, in the exotic matrix melange, or on the contact of this melange with the block-rich greywacke melange to the east. Nonetheless, the large age range of the fauna in this small occurrence of limestone conglomerate needs explanation, even though it is now contained in a block within melange. We suggest that the limestone conglomerate/breccia may be explained by talus accumulation below a normal fault scarp produced by flexural extension in the outer trench slope of the Taconic foredeep basin [Bradley and Kidd, 1991], and the subsequent picking up of a sample of this breccia into the advancing accretionary thrust wedge bordering the Taconic Allochthon. Strata containing physically similar carbonate conglomerates/breccias do occur within the intact stratigraphic sequence in the Taconic Allochthon, but they nowhere have extended faunal age ranges, and none are known with ages younger than early Ordovician.
2016: GE images from 2015 suggest that this outcrop may have been removed.

STOP 7, Ruedemann's "type" section
Outcrops of melange and flysch in old railroad cut and bed of Normanskill [Ruedemann's "type" section]
These outcrops form the "type locality" of Ruedemann for the "Normanskill Formation", mainly because of the fauna he obtained here at Kenwood, and "nearby", including Stop 8 at South Glenmont. As you can see, structural disruption is prominent, and the bedded sections seen between faults have no defined, or definable, top or base. In addition, the use and abuse of the term Normanskill since Ruedemann, especially as a time-stratigraphic term, makes it inappropriate to use it for the general lithic assemblage of flysch greywacke and shale, which is, despite the structural disruption, quite well exposed here. In the creek bed, if the water level is not too high, a downward-younging bed in the crest of an antiform may be seen (Figure 8), with the turbidite sole structures exposed on a surface defining the fold hinge. This structural complexity is unusual for the bedded greywacke-shale sections in the Hudson Valley; Vollmer suggested that the stratigraphic inversion represented by the downward-facing nature of this fold may have been produced by slumping, with the fold being the regional set later superimposed on the already inverted section. This outcrop maps near the eastern margin of the Mohawk River Central Melange Zone (Figure 2).

STOP 8. South Glenmont locality of allochthonous Mt. Merino Cherts
Outcrop in road cut, by road and to east of bridge up to power line, [and along railroad tracks].
Black, grey, and green cherts, some with burrow mottling, as seen in this set of exposures, are characteristic small and large blocks in the exotic melanges. However, they are always blocks, or fault bounded slices, in this context. Identical chert lithologies are found in stratigraphic sequence with other rock types only within the Taconic Allochthon. There they occur only at one position in the stratigraphic succession, at the top of varied continental rise-deposited sediments derived from the Cambro-Ordovician passive margin of North America, and immediately below black graptolitic shales with N. gracilis graptolite faunas, which are in turn overlain by greywacke-shale turbidites of the Pawlet Formation. This locality yielded to Ruedemann the most abundant fauna found in the greywacke-shale area of the "Normanskill", and has as a result strongly influenced the presumed age of the flysch of the Hudson Valley. We are of the opinion that all occurrences of these cherts are highly allochthonous, representing tectonically separated, and perhaps erosionally isolated, pieces originally emplaced as integral parts of the Taconic Allochthon. We think that all ages derived from the faunas in the cherts, and the related black graptolitic slates, are therefore older, by at least some small amount, than any of the greywacke-shale flysch of the Hudson Valley. Prominent down-dip plunging folds (Figure 9) are seen in several parts of this set of outcrops; these probably represent rotation of originally shallow-plunging folds by heterogeneous simple shear associated with thrusting, as indicated by Vollmer and Bosworth (1984) for the more strongly deformed flysch and melange generally. This locality maps close to the eastern boundary of the Mohawk River Central Melange Zone (Figure 1).

STOP 9. Normanskill melange and broken formation.
This outcrop in the north bank of the Normanskill exposes shaly rocks with greywackes that can be demonstrated to be in part a broken formation (Figure 10), with partly traceable sedimentary layering , rather than a melange with completely disrupted layering. Additionally, this locality contains some folded quartz veins. The outcrop also maps within the Central Melange Zone.

STOP 10 - Feuri Spruyt and Callanan Quarry
Unconformity with Helderberg Limestones overlying melange. PERMISSION REQUIRED- request permission in advance by calling 518-767-2222, or writing Callanan Industries Inc, Corporate Headquarters, South Street, South Bethlehem, NY 12161
This locality (Figure 11) shows carbonates of the basal Helderberg Group [early Devonian] unconformably overlying the folded greywackes and shales, and melange of the Ordovician.The boundary between the Ravena Greywacke Zone and the eastern side of the Mohawk River Central Melange Zone passes beneath the unconformity just west of the quarry (Figures 1, and 11). In particular, the unconformable relation to the melange demonstrates that the fault zone which created the melange is an Ordovician structure, and predates entirely, at this position, the Acadian structures that fold the overlying Devonian strata south of this place (Bosworth and Vollmer, 1981). The map relationships, and unfaulted structural condition of the Helderberg Group, west of this locality, shows that all the width of the melange belt comprising the western and eastern exotic melange, which goes beneath this unconformity, must also be an Ordovician, and Taconic-age structure.

A5:GEOMORPHOLOGY, PALEOCLIMATOLOGY AND LAND USE CONSIDERATIONS OF A GLACIATED KARST TERRAIN; ALBANY COUNTY, NEW YORK
Paul A. Rubin
909 County Rt. 2
Accord, NY 12404
Thorn Engel
7D West St.
Voorheesville, NY 12186
Michael Nardacci
Point of Woods
19 Briarwood Terrace
Albany, NY 12203
ABSTRACT
Karstified terrains in Albany County, New York provide evidence of paleoclimatic conditions during Pleistocene glaciation. Caves and the areas surrounding them preserve important clues that can be interpreted to reconstruct portions of the geomorphic and paleoclimatic history of a region. Knowledge gained from these investigations is of increasing importance as development pressures extend into these forested, agricultural and rural areas. This paper focuses on the geology, karst hydrology, and glacial features of two areas not previously described. As a result of karst processes and anthropogenic diversion of the headwaters of the Onesquethaw Creek, the Hollyhock carbonate aquifer and its receiving stream (i.e., Onesquethaw Creek) are extremely sensitive to contaminant inputs. Thus, we have incorporated a section specific to land use considerations and concerns. This ongoing work is an extension of previous work addressing the interaction between karst and glaciation (Rubin, 1991 b; Palmer et al., 1991a, 1991b).
Two karst areas will be visited on this field trip. The first stop, at the Hollyhock Hollow Sanctuary, will feature a cave system that 1) developed prior to the advance of the late Wisconsinan (Woodfordian) Laurentide ice sheet; 2) was enlarged by meltwater invasion; and 3) remains active today. The second stop will be at Joralemon Park, where active and relict caves are used to interpret the interaction between caves and glacial processes. Solutionally enlarged fractures and relict caves and swallow holes in the groundwater basin are integral, functioning components of the epikarst, funneling runoff and infiltrating meteoric waters to deeper conduit flow routes.

GEOMORPHOLOGY, PALEOCLIMATOLOGY AND LAND USE CONSIDERATIONS OF A GLACIATED KARST TERRAIN; ALBANY COUNTY, NEW YORK

Cross Vlomankill

Exposure of Snake Hill shale behind house on right.

Feura Bush Quarry uphill and on right.

Roadcut through Coeymans Limestone.

STOP 1. HOLLYHOCK HOLLOW SANCTUARY
The Hollyhock Hollow Sanctuary and surrounding area represent a unique geologic and hydrologic setting. The Hollyhock carbonate aquifer supports no surface drainage today, except for the Onesquethaw Creek which is seasonally pirated underground for ∼1 km (0.7 mi). All drainage is subsurface in limestone bedding planes, joints, faults and conduits, largely within the Manlius and Coeymans Limestones. Structural deformation here within the Hudson Valley Fold Thrust belt has folded and faulted these limestone units. This deformation is locally responsible for orienting subsurface flow paths and was in place prior to Wisconsinan glaciations. During glaciation, subglacial meltwater carved shallow bedrock channels in the Coeymans Limestone. Several relict caves and perhaps the only known meltwater-carved limestone pedestals in such a setting attest to the unique geology of this karst basin. Scallops (solutional pockmarks in cave walls) in swallow holes document former rapid surface and groundwater flow here. Some of this meltwater was pirated into now relict swallow holes over many thousands of years. This same flow created or enlarged limestone cave conduits which today still drain the carbonate groundwater basin that extends to the north and northwest. These enlarged joints and conduits provide a route for possible rapid transport of contaminants.
Location stops for this field trip are organized sequentially for walking tours.

Cross the Onesquethaw Creek.

Cross Feuri Spruyt Creek

Esopus Shale outcrop on right side of road.

Large rock of Onondaga Limestone on right.

Joralemon Park tennis courts on right.

STOP 2. JORALEMON PARK
At Joralemon Park and vicinity, entrances to active (Hannacroix Maze and Merritt's Cave) and relict (Joralemon's) caves will be visited. Damming of a former surface drainage route by glacial sediment, as well as erosional derangement of surface streams, have resulted in the enlargement of the Hannacroix Maze floodwater cave. All surface flow from throughout the basin is deranged from an earlier flow route and is now pirated through Hannacroix Maze. Prior to deposition of the sediment dam that now forces surface water from throughout the basin to be pirated through Hannacroix Maze, surface flow occurred through Joralemon's Cave. Nardacci (1994) has documented much of the karst hydrology of this stop.

A6:FLYSCH AND MOLASSE OF THE CLASSICAL TACONIC AND ACADIAN
OROGENIES: MODELS FOR SUBSURFACE RESERVOIR SETTINGS
GERALD M. FRIEDMAN
Brooklyn College and Graduate School of the City University of NY
Brooklyn, NY 11210
and
Northeastern Science Foundation affiliated with Brooklyn College, CUNY,
ABSTRACT
This field trip will examine classical sections of the Appalachians including Cambro-Ordovician basin-margin and basin-slope facies (flysch) of the Taconics and braided and meandering stream deposits (molasse) of the Catskills. The deepwater settings are part of the Taconic sequence. These rocks include massive sandstones of excellent reservoir quality that serve as models for oil and gas exploration. With their feet, participants may straddle the classical Logan's (or Emmon 's) line thrust plane. The stream deposits are Middle to Upper Devonian rocks of the Catskill Mountains which resulted from the Acadian Orogeny, where the world's oldest and largest freshwater clams can be found in the world's oldest back-swamp fluvial facies. These fluvial deposits make excellent models for comparable subsurface reservoir settings.
This trip will be in two parts: (1) a field study of deep-water facies (flysch) of the Taconics, and (2) a field study of braided- and meandering-stream deposits (molasse) of the Catskills. The rocks of the Taconics have been debated for more than 150 years and need to be explained in detail before the field stops make sense to the uninitiated. Therefore several pages of background on these deposits precede the itinerary. The Catskills, however, do not need this kind of orientation, hence after the Taconics (flysch) itinerary, the field stops for the Catskills follow immediately without an insertion of background information.

A6:FLYSCH AND MOLASSE OF THE CLASSICAL TACONIC AND ACADIAN
OROGENIES: MODELS FOR SUBSURFACE RESERVOIR SETTINGS

Rensselaer Center of Applied Geology
We shall stop at the Rensselaer Center of Applied Geology, headquarters of the Northeastern Science Foundation affiliated with Brooklyn College of the City University of New York, for a brief review of the geology.

STOP 1. R.P.I. , '87 Gym
Exposure behind fence adjacent to gym.
Ruedemann (1930, p. 114; also Fig. 64) described and photographed this exposure as a good example of a "cliff of mylonite," one of the "excellent exposures of a fault breccia" on the campus of Rensselaer Polytechnic Institute. According to Ruedemann and reconfirmed by Elam (1960) a thrust fault follows part of this street (Sage Ave.) and Ruedemann mistook this conglomerate for a fault breccia. Perhaps the presence of criss-crossing veins in this exposure led to his interpretation of a "cliff of mylonite." Jack G. Elam (1960; unpublished Ph.D. thesis at Rensselaer Polytechnic Institute) assigned the rocks at this exposure to the Schodack lithofacies of Early Cambrian age. Cushing and Ruedemann (1914) had introduced the "Schodack Formation". Zen (1964) has renamed this formation the West Castleton Formation. As already explained, this formation is now assigned to the Hatch Hill Formation (Fig. 1).
Lowman (1961) recognized that the boulders are a conglomerate and not a breccia, and following Kuenen and Migliorini (1950), he introduced the term brecciolas for these rocks.
The limestone, sandstone, and chert boulders which are embedded in shales at this exposure range from angular to rounded and show considerable variation in size (Fig. 9). Some boulders are coarse-grained fossiliferous limestone fragments with a micritic dolomite matrix. The rocks above the brecciolas are greenish-gray shale.

STOP 2. TROY HIGH SCHOOL QUARRY
Walk to the running track and on track proceed left (north) to exposure below RPI housing units.
The spectacular brecciolas at this exposure consist of three members with eleven sub-members (Lowman, 1961); some of the deposits that Lowman studied have since been destroyed. For details of the rocks, refer to Lowman's descriptions (1961). The brecciolas are lithofacies of the Hatch Hill Formation, as at Stop 1.
A thin-section study shows the limestone clasts to consist of biomicrites, biointramicrites, and micrites with varying terrigenous quartz and clay-minerals. The intraclasts are of pelmicrite. Shell fragments have been selectively dolomitized. The carbonate sediments must have lithified before their displacement downslope.
The brecciola bed is steeply dipping (80°) and is approximately 3 m thick. It is interbedded within a fissile shale. The basal contact of the bed is at the top of the exposure, and the top of the bed is at the base of the exposure. The matrix between the clasts ranges from sand at the base of the bed (top of the exposure) to clay at top of the bed (base of the exposure). This change in the texture of the matrix is typical graded bedding.
Although some clasts are rounded, most of them are angular and slab-shaped (Fig. 10). Some slabs experienced multiple bending reflecting high-energy impact (Fig. 10). Sporadic slabs 0.5 m to 1 m long appear to have been in the process of breaking up, with clay wedged into the fractures of the separating clasts. The clasts are sub-parallel to the boundaries of the bed.

STOP 3. RUSHOR'S QUARRY, TROY
Walk old wagon road uphill to ruins of former buildings (now only the floor of the buildings is preserved), site of former abandoned quarry. Look at exposure in old quarry (Rushor's Quarry)
The rocks at this exposure are part of the Austin Glen Member of the Normanskill Formation of Middle Ordovician age. In contrast to the Cambrian (Hatch Hill Formation) deep-water rocks which were tectonically emplaced in the Troy area, the Normanskill Deep-water suite formed in situ after deep submergence of the Cambrian-Early Ordovician carbonate shelf. The sediment composing the rocks at this site were derived from what is now east (Fig. 3), but was north during the Paleozoic. At this stop we see basin-margin sediments devoid of brecciolas. The clue to the presence of a paleoslope are sole marks on the undersides of sandstone beds (Fig. 14). These marks are infillings (molds) of depressions that formed in the soft bottom clays (now shales) as particles in turbidity current flows or sand falls scoured or gouged the bottom. They are also known as impact marks or tool marks. The following sole marks can be seen (definitions modified from Pettijohn and Potter, 1964): flute molds - a raised sub-conical structure, the up current end of which is rounded or bulbous, the other end flaring out and merging with the bedding plane; groove molds - rounded or sharp-crested rectilinear ridges produced by filling of grooves; brush marks - essentially a bounce cast with a crescentic depression on the down-current end; prod molds - a short ridge, parallel to the current, which unlike flute molds, rises down-current, and ends abruptly; frondescent marks -a type of load-flow structure that covers some soles with crowded lobate molds overlapping in the down-current direction.
The rocks in this quarry consist of interbedded sandstone and shale (Fig.l5) which show the characteristics of distal turbidites (Walker, 1967): cross laminae, convoluted laminae, sole marks, graded beds, parallel sides and regular beds, thin beds, fine grain size; individual sandstone beds rarely amalgamate.
The exposure in this quarry is that of a typical flysch composed of alternating sandstones and shales (Fig. 15 ). Most sandstone beds are composed of two units: an underlying finely laminated sandstone and an overlying ripple cross-laminated sandstone (Figs. 16, 17). The ripple cross-laminated sandstone may scour into the underlying finely laminated sandstone. These two sandstone units correspond to the B and C units of a Bouma sequence; the shale would be a Bouma E unit. Please look carefully at the two sandstone units, keep a mental image of their appearance, and carry this image to the next stop where you will need it for interpreting the geological history.

STOP 4. RYSEDORPH HILL
This roadcut is on the southern flanks of an unnamed peak of Rysedorph Hill which is topographically part of a ridge composed of two hills (Rysedorph Hill and Olcott Hill)(Fig. 18). At and near the peak of Rysedorph Hill Ruedemann (1930) discovered spectacular conglomerates and faunas which are now obscured by vegetation; only small sporadic blocks or pebbles of limestone are now found dispersed in shale. This spectacular deposit is known as Rysedorph Hill Conglomerate and, as Ruedemann described, consisted for the most part of limestone conglomerate (see Sanders, 1995).
The rocks at this roadcut are quite different from those which Ruedemann described. Large and small blocks of sandstone and carbonate rock are set in a dark-colored deep-water shale. One of the blocks on the east side of the road is of particular interest. This block consists of Austin Glen/Normanskill sandstone lithology. In fact, it reveals the typical two kinds of sandstone units that we have seen at STOP 3 (Rushor's Quarry in Troy): an underlying finely laminated sandstone and overlying ripple cross-laminated sandstone which correspond to the B and C units of a Bouma sequence (Fig.19). One wonders how this one block traveled from Rushor's Quarry in Troy to this site!
The kind of lithology exposed at this stop has been designated wildflysch, a term applied to a spectacular deposit consisting of small- to enormous blocks of sedimentary, igneous, and metamorphic rocks set in a matrix of fine-grained, typically dark-colored marine shale, siltstone, or mudstone (Fig.12). In modern terms, we would designate the wildflysch as one kind of diamictite (Friedman et al., 1992).
Study of sandstone blocks show them to be fine- to medium-grained and for the most part composed of quartz. Authigenic quartz overgrowth is in places so intense that the original texture is obscured. Plagioclase feldspar and microcline are common. They are commonly sericitized and calcitized. Fragments of sedimentary, igneous, and metamorphic rock are abundant, especially those of sedimentary rocks. Particles of carbonate rock include micrite, oolitic and pseudo-oolitic limestone, peloidal limestone, dolomitic limestone, and crinoidal limestone. These fragments of carbonate rock contain authigenic feldspars which are diagnostic of pre-Knox unconformity (Beekmantown or Sauk) deposits (Buyce and Friedman, 1975 ). Other kinds of rock fragments are composed of siltstones and shales, especially bituminous shales. Metamorphic rock fragments are those of sericite-chlorite schists and quartzites. Igneous rock fragments have porphyritic-ophitic texture. Finely crystallized rock-fragment particles are those of recrystallized volcanic glasses or volcanic rocks, and contain chalcedony and chlorite.
Table 1 shows the petrographic composition of the sandstone blocks. They do not qualify to be called graywacke, despite such usage for these rocks in the literature (Potter, 1979). According to the classification of Friedman et al. (1992) the sandstones are classified as quartz-feldspar-rock fragment sandstones.
Carbonate blocks are for the most part composed of dolostone. The provenance of these blocks includes Cambro-Lower Ordovician platform carbonates (oolitic and peloidal carbonates and authigenic feldspar) and deep-water Austin Glen/Normanskill sandstone. Hence these conglomerates are younger than Normanskill which would make them Upper Ordovician Snake Hill Formation which is the only Ordovician unit younger than Normanskill present in New York (Fig. 1b)(Fisher, 1977). Because of age uncertainties I prefer to label these rocks Tippecanoe-correlative conglomerates and call them Rensselaer Conglomerate since they occur in the town and county of Rensselaer.
To recycle deep-water Austin Glen/Normanskill deposits an initial uplift is necessary. As Sanders (1995) points out "because eastern New York is part of the Appalachian orogenic belt ... 'uplift' means thrust faults". This mechanism displaced deep-water Normanskill deposits into a setting of shallow water or emergence from which erosion detached the blocks and recycled them downslope, once again into deep water. This view is at variance with that of those who feel that these conglomerates resulted from tectonic emplacement (Potter, 1979). However, these deposits are incoherent subaqueous slumps (debris flow) of deep-water setting which were part of a slumped mass that moved by gravity downslope (Friedman et al., 1992, p.). Some of the boulders form a nearly perfect sphere (Fig.12) implying erosional rather than tectonic forces. The blocks are related to erosion on the front of the thrusts which contained rocks from each of the three sequences: Taconic, Sauk, and Tippecanoe (Normanskill) (see Fig. 1a). The presence of Sauk material indicates that some thrusts broke loose inboard of the former shelf edge and transported the carbonate-sequence material over the foreland-basin shales of the Tippecanoe Sequence (see also Sanders, 1995; DeAngelis, 1995).

STOP 5. POESTENKILL FALLS AND GORGE
We are back in Troy from where we initially set out; in fact we passed this site on our way between stops 2 and 3. You may ask why has a visit to this remarkable site been postponed till now, and why did we have to backtrack this circuitous route between Rysedorph Hill and Poestenkill Falls? The answer is that the experience of Rushor's Quarry (Stop 3) and Rysedorph Hill (Stop 4) is essential to an understanding of the geology of Poestenkill Falls and Gorge.
At this classical site Ruedemann (1930) shows "Logan's Line" (now known as Emmons' Line; Rodgers, 1970), the thrust plane which places Cambrian over Ordovician rocks surfacing at this site. Elam (1960) concurs and places Lower Cambrian rocks (his Poesten lithofacies, later West Castleton Formation; Zen, 1961) in contact with Middle Ordovician rocks (the Austin Glen Member of the Normanskill Formation). As already explained, the Cambrian strata, a typical flysch, have now been assigned to the Hatch Hill Formation (Fig. 1a). The Ordovician rocks are wildflysch, as at Rysedorph Hill, and hence I prefer to label them Tippecanoe-correlative strata and call them Rensselaer conglomerate (Hatch Hill Formation) as at Rysedorph Hill. As at Rysedorph Hill, the boulders and blocks consist of sandstones, shales, and limestones (Fig 20). Among the sandstones, blocks of Normanskill rocks can be identified. At this site Cambrian flysch has been thrust over Ordovician wildflysch. In places interbedded with the Ordovician wildflysch are strata of bedded flysch of Normanskill lithology which remind us of Rushor's quarry. Hence although consisting for the most part of debris-flow deposits the Ordovician strata are in part of turbidite origin.
This overthrust (Fig. 21) is interpreted as a segment that extends from Canada through Vermont, New York, and farther south. The fault line is well exposed in the south wall of Poestenkill Gorge. Cambrian shales occur above (east of) the fault, and Ordovician strata below (west of) the fault The Ordovician strata have been described as a fault breccia or mylonite in which blocks of large size have been incorporated in shaly matrix. The matrix shows an anastomosing cleavage pattern that does not penetrate the boulders and blocks. Although described as a fault breccia or mylonite (Ruedemann, 1930; Elam, 1960) this rock is a wildflysch. The blocks are interpreted as having moved down a steep slope from near a shelf edge to a basin or basin margin.
The Ordovician rocks are highly tectonized, especially towards the thrust. Antithetic post-thrust faulting is noted on the north side of the thrust sheet with an approximately 2m displacement seen on the steep slope above the thrust. At and below the thrust sheet in the south wall of Poestenkill Gorge a dense black material may be pseudotachylite, a rock produced in the compression and shear related to intense fault movement, involving extreme mylonitization. My own professor Dr. S. James Shand introduced this term (Shand, 1916) for mylonites he encountered in the Orange Free State of South Africa. As Shand (1947) points out, this kind of "mylonites ... proved most puzzling to field geologists meeting them for the first time".
The Cambrian rocks contain abundant black particles which may be phosphatic.
During the Industrial Revolution numerous factories, clustered on the north slope of Poestenkill Gorge, were making cotton cloth, and curry combs, barbed wire, and buckwheat flour machines, and much more. The first mills were developed in the lower section of the gorge as early as 1791. Their full potential was realized when Benjamin Marshall constructed a brick cotton mill on the north side. Water power began its decline with the popularity of steam power at the turn of the century. Today obscure, moldering industrial ruins testify to this former busy activity. The last of the abandoned mill buildings tumbled into the stream in the fierce flood of 1938.

STOP 6. OLISTOLITHS
At this site "exotic" boulders of various kinds are scattered through shale. Of these one large well-rounded boulder of white limestone demands particular attention (Fig. 22). Smaller angular blocks include those of sandstone and limestone. These olistoliths recall those of Rysedorph Hill and Poestenkill Falls and Gorge and are considered Tippecanoe correlative Snake Hill Formation which at the other two sites have been designated Rensselaer Conglomerate and deserve the same label here. Fisher (1977) applied the term Poughkeepsie Melange to this deposit. However, for a deposit to be called a melange it should be incorporated within a unit "that was moving as an overthrust or as a gravity-gliding mass"(Friedman et al., 1992). The deposit at this site is composed of olistoliths and is not a melange, as Rowley and Kidd (1982) likewise observed.

STOP 7. EXPOSURES SOUTH OF SCHODACK LANDING
We shall first examine the road cut on the east side of the highway and then walk on dirt road across the railroad tracks to view mere fine exposures.
Figure 23 describes and illustrates the section seen. Note exposures of bedded micrite. Micrite is overlain by distinctive lenticular brecciolas. Many of the clasts in these conglomerates/brecciolas evidently were derived from the digging up and local transport of nodular bodies of carbonate that may have become segregated as isolated "nodules" during early marine diagenesis of these deep-water carbonates. The conglomerates form convex-up lenses up to 2 m thick and at least 10 m across. Their bases are flat surfaces or fillings of local channels cut a decimeter or so into the underlying nodular zone. Siltstone strata lacking carbonates drape over the convex-up lenses (Friedman and Sanders, 1995, in press).
These lenses are analogous to hummocky strata, which have been ascribed to combined effects on shelf sediments of waves and currents. The waves involved in the origin of these deep-water, off-shelf brecciolas probably were tsunami (see previous discussion).
At the top of the slope on the east side of the railroad track an exposure shows a graded layer (2 m thick) of shingled clasts that may have been dumped in a manner of hours (Fig.11 ). The comparable thicknesses of the overlying strata may have accumulated over thousands of years.

STOP 8. JUDSON POINT
Figure 24 illustrates the section seen at this stop and describes lithofacies. The section is dominated by massive coarse sandstone beds of excellent reservoir quality which display high porosity and excellent sorting. They are analogous to sandstones forming deep-water reservoirs in California and elsewhere. Those not knowing the regional geology may mistake them for high-energy shallow-water deposits. In places the beds contain micrite pebbles.

STOP 9. EXPOSURE ON EAST SIDE OF ROUTE 9
(across from a white house)(SECTION SOUTH OF HUDSON)
Figure 25 shows and describes the lithofacies exposed at this stop and located across from white house. Note especially the interesting interbeds of fine-grained limestone (micrite) and dark shale (Fig. 7) and the carbonate-clast conglomerate (Fig. 8). The cycles consist of alternating thin-bedded micrite and calcareous shale (Fig. 7). The thickness of the micrite beds is about 1 to 5 cm and that of the calcareous shale varies between 3 and 20 cm. Table 2 and figure 26 provide data on the mineralogic and isotopic compositions of the alternating beds of micrite and calcareous shale. The micrite is pure calcite and encloses particles of quartz. The calcareous shale is composed of clay minerals and feldspar particles; its carbonate concentration is about 10% (calcite, dolomite, siderite) (Table 2). The stable carbon isotopic composition of the carbonate of the two interbedded lithologies is almost identical; the oxygen isotopic composition reflects deep-burial diagenesis (Table 2). The carbon isotopic composition of the brecciola overlying the micrite-calcareous shale cycles is enriched in 13C. Although the range of carbon isotopic composition of total dissolved carbon in seawater is relatively narrow, a consistent decrease in ä13C occurs with depth of water (around 2.6 per mil) (Berger and Vincent, 1986). Thin-section study of the brecciola confirms its shallow-water origin: radial ooids, echinoderm fragments, and intraclasts of oolitic facies. An approximately 2.6 per mil increase in ä13C is shown by comparing the shallow-water brecciola facies with the deep-water micrite. The brecciola facies at this stop represents a shelf-edge facies that a tsunami broke loose and transported to great depth.
The strontium isotopic composition requires discussion (table 2). The principal sources of marine Sr with distinctive 87Sr/86Sr ratios are (1) old granitic basement rocks of the continental crust (high Rb/Sr, high 87Sr/86Sr); (2) young volcanic rocks (low Rb/Sr; low 87Sr/86Sr); and (3) marine carbonate rocks on the continents (low Rb/Sr, intermediate 87Sr/86Sr)(Faure, 1991, p.359). Because young volcanic rocks are not relevant in a discussion of the Lower Paleozoic, only granitic basement rocks and marine platform carbonates determine strontium isotopic composition. The 87Sr/86Sr compositions of the carbonate in micrite and calcareous shale (0.711110 and 0.715163) are higher than in Lower Paleozoic seawater (0.7090-0.7095)(Burke et al., 1982) (Fig. 27) and consistent with precipitation from waters containing significant proportions of continent-derived fluids enriched in 87Sr as a result of basement weathering or percolation through soils or sediment on the continental platform.
Weathering of Precambrian terrain causes enrichment of radiogenic 87Sr (87Sr/86Sr 0.716±0.004) within river and lake waters (Faure et al., 1963). Waters originating from a granitic continental source have a high 87Sr/86Sr ratio relative to those derived from a platform of marine carbonates (Fig. 27). Even though the 87Sr/86Sr composition of the carbonate in both the micrite and calcareous shale is higher than in Paleozoic sea water, the difference between the two compositions is remarkable. The strontium isotopic composition of the carbonate in the calcareous shale almost overlaps that of the granitic basement crust, whereas that of the micrite is much lower and closer to that of Paleozoic sea water (Fig. 27). What determines these drastic changes in isotopic composition of such closely interbedded units? The highly radiogenic isotopic ratios of the carbonate of the calcareous shale reflect supply of radiogenic strontium from the decomposition of the detrital particles, such as feldspar and clay minerals which are present in this rock. By contrast, because the calcite of the micrite is essentially devoid of such detrital particles, its strontium isotopic composition is closer to that of Lower Paleozoic seawater.
Because strontium isotopes are not subject to significant mass fractionation during precipitation (Faure, 1986), the waters responsible for precipitating the carbonate of the calcareous shale must have derived from a granitic continental source. The only such source would be the Precambrian shield which must have been exposed during Early Cambrian times. The 87Sr/86Sr ratio of the micrite, though much lower, still indicates enrichment of radiogenic strontium from the granitic continental terrain, but its signature is considerably closer to that of marine platform carbonates.
The strontium isotopic evidence indicates that the calcareous shales were derived from exposed granitic basement. Sea level must have been low so that weathering and erosion of the granitic continental terrain generated the fine-textured particles. Rivers then distributed the debris across the emergent continental platform and down the slope, probably through submarine canyons. As pointed out earlier, a large block of quartzite in this formation has been tentatively identified as derived from part of the wall of a submarine canyon (Friedman, 1972; Friedman Sanders and Manini, 1982). By contrast, the strontium isotopic evidence for the micrite suggests mixing of waters originating from granitic continental terrain with waters from the epeiric marine carbonate platform under conditions of high stand of sea level. Thus the calcareous shale beds represent low-stand sea-level facies tracts, whereas the micrites are high-stand sea-level facies tracts.
The alternating thin-bedded micrite and calcareous shale beds reflect rapid changes in sea level. To produce such closely interbedded lithologies, the sea level must have moved up and down like a piston. Such cycles have been explained as astronomical rhythms (de Boer, 1991). For low latitudes, the precession of the Earth's axis has been assumed the cause of such rhythms. Precession cycles last about 19,000 and 23,000 years. At this time no dates are available to determine the rate of sea-level changes, but 19,000 to 23,000 years are possible time frames for micrite-calcareous shale couplets to accumulate.

STOP 10. SOUTHWEST CORNER OF BECRAFT MOUNTAIN (Fig. 28)
At the base of this exposure rocks of the Mount Merino Formation of the Taconic Sequence (Fig. 1) consist of highly deformed cherty dolomite. A low-angle, irregular unconformity separates this Ordovician formation from the overlying Silurian Rondout Formation, a silty dolomite. The lower part of the Rondout Formation is undeformed, however, a bedding thrust through this formation has deformed the Rondout Formation above this thrust (Fig. 28). Undeformed, laminated, whitish limestones of the Manlius Formation overlie the Rondout Formation. Within the Manlius Formation a bedding thrust folded the upper part of this formation (Fig. 28).
X-ray study of the rock of the bedding thrust within the Manlius Formation shows it to consist of calcite (96%) and quartz (4%). Its isotopic signatures are in ä13CPDB +2.4, ä18OPDB -9.9, and 87Sr/86Sr 0.715096 (10) (&plsmn;2 S.D.) (The Sr analyses are normalized to 86Sr/88Sr = 0.11940. Analyses of NBS 987 averaged 0.710241 (09) (n = 39) during the period of these analyses. Errors on 87Sr/86Sr are given as 2 sigma (95 %) in the last two digits). The carbon and oxygen isotopes tag a hot heavy-carbon enriched fluid and the strontium isotopes a radiogenic strontium of composition close to that of the continental crust
The thrusts at this exposure are post-Taconic and resulted from Acadian or Alleghanian orogenesis.

Note Catskill front from distance as you approach bridge.

STOP 11. BRAIDED AND MEANDERING STREAM FACIES SEEN FROM A DISTANCE
From the vantage point of this stop we see to the west the classical fluvial sequence of the Middle and Upper Devonian rocks of the Catskill front. Note continuous ledges near the top of the front which reflect the presence of laterally continuous, coarse-grained sandstones and conglomerates deposited in braided streams (Buttner, 1968). Below the continuous ledges are discontinuous cliffs which reflect laterally interfingering channel sandstones and overbank shales deposited in meandering streams.
Infrared photography of the Catskill front from this stop brings out amazing details (Mutch, Head, and Saunders, 1968).

STOP 12. TRESTLE TO MOUNTAIN HOUSE
Walk approximately 300 feet uphill to first sandstone body.
Meandering-Stream Facies
This grayish green, medium-grained graywacke of the Hamilton Group of Middle Devonian age displays abundant truncations resulting from lateral cutting; the sandstones within the channels are crossbedded and display abundant reactivation surfaces. This channel complex is about 15 feet thick and is sandwiched between overbank shale which is well exposed in the hangover at the lower sandstone contact. Note sporadic pebbles, wood fragments, and wood casts as well as onlap and toplap. Looking uphill along the clearing of the old trestle to Mountain House between cliffs of similar sandstone bodies the slopes mark the sites of interbedded shale. The interbedded sandstones and shales represent interfingering channel and overbank deposits of meandering-stream facies. The lateral relationship between channel and overbank will be apparent at stop 15. The green color of the graywacke reflects the abundance of chlorite in the rocks. This chlorite was derived from the source terrain to the east which consisted of metamorphic rocks of the greenschist facies.
A similar sandstone body occurs about 300 feet below which is underlain by gray, red, and green shales.

STOP 13. TWILIGHT PARK
Twilight Park is a private residential section and permission is needed to park here which may be obtained from the Superintendent Hillard Hommel or Justine L. Hommel, Box 129. Haines Falls, NY 12436 (phone 518-589-6191).
The site at this bridge was one of the preferred views of the Hudson River School of Landscape Paintings. Asher Durand (1786-1886) in his painting Kindred Spirits illustrated this site, including the crossbedding developed within the point bars of the meandering stream facies visible below this bridge (Jordan, 1995).

STOP 14. BRAIDED-STREAM FACIES, HUNTER
At this site polymictic conglomerate of braided-stream facies overlies sandstone of meandering-stream facies (Friedman, Sanders, and Kopaska-Merkel, Fig. 4-17). Small channels of conglomerate also cut through sandstone. The pebbles in this conglomerate range in diameter between 3 and 10 cm. The pebbles and sand particles are composed of quartz, including vein quartz, and various sedimentary and metamorphic rock fragments.
Streams of high energy must have been at work to transport these large pebbles. As we have seen from stop 11 these streams were laterally continuous channel complexes devoid of intervening overbank deposits. The coarse particle size of the conglomerates and the absence of overbank shales or siltstones suggest a braided-stream deposit This complex stream system developed on a slope of steep gradient, most probably in association with a series of coalescing alluvial fans that spread westward from the high, tectonically active source terrain to the east

STOP 15: MEANDERING-STREAM POINT-BAR FACIES
MEANDERING-STREAM POINT-BAR FACIES: CHANNELS, OVERBANK, AND SWAMP
This exposure shows a point-bar sequence in Tully-clastic correlative strata of the Gilboa Formation (Upper Givetian, Uppermost Middle Devonian). Two channels are exposed in this road cut, a lower channel and an upper channel (Fig. 29). The lower channel truncates overbank siltstone, whereas the upper channel truncates the lower channel and laterally adjacent overbank siltstone. A shale-pebble conglomerate, as a lag concentrate, overlies the truncation surface of the lower channel; in part this conglomerate is now hidden by fallen debris. This point-bar sequence at this site represents an abandoned meander which became an oxbow lake.
In rocks of the overbank facies, dark gray to black interbeds and lenses containing abundant coarse plant remains, consisting of what appear to be stems and branches primarily, and locally developed coaly material, represent a back-swamp environment located on the slip- off slope side of the lower channel. The back-swamp facies appears to overlie crevasse-splay deposits. These beds, which occur in red overbank siltstone and contain very abundant plant material, some of which has been altered to a coaly substance, are some 5 feet thick and measure well over 60 feet in lateral extent
The woody cells of the plant debris were in part converted to anthracite and in part replaced by pyrite. Replacement occurred at an early stage as evidenced by the lack of deformation of the replaced woody cells. Most of the pyrite has now been oxidized to hematite and limonite, probably by surface weathering. Even the anthracite, which usually resists oxidation, shows evidence of undergoing oxidation in this material. Surface oxidation was probably intensified by sulfate-bearing water derived from pyrite. The vitrinite reflectance of samples of this plant debris is 2.2% to 2.3%. The mean reflectivity of the vitrinites in oil using light with wavelength of 546 nm is 2.5%. This indicates that the vitrinite contains 93% to 94% fixed carbon, about 3.5% hydrogen, and other volatile matter. Locally the coalified plant chambers contain anhedral pyrite and galena: the paragenetic sequence is pyrite and then galena. The vitrinite (coalified woody tissue) contains micron-sized pyrite cubes. Outside the plant tissues, small amounts of chalcopyrite and possibly sphalerite are present (Friedman, 1987a,b; Friedman and Sanders, 1982 ). The deposits observed at this site were buried to a depth of 6.5 km for a duration of about 200 million years (Friedman and Sanders, 1982).
The steep cut-bank on the right of the lower channel may initially have extended upward for many more tens of feet and tapped sand from an earlier upper channel. Sand, now sandstone, moved down the cut-bank as a liquefied cohesion-less particle flow or grain flow and is now preserved as an inclined sand body paralleling the cut bank.
Bivalves of the Species Archanodon (= Amnigenia, Hall 1874) catskillensis (Heteroconchia, Archanodontacea) inhabited the back-swamp facies on the slip-off slope margin of the lower channel. These bivalves (up to 22 cm x 6 cm) are among the largest known fossil fresh-water pelecypods in geologic history. Unfettered, opportunistic growth in this swamp environment marked by rich organic matter and devoid of competition with other pelecypods, and possibly other benthic fauna of any kind, resulted in the unusually large sizes of these clams (Friedman and Chamberlain, 1995).
To the left of the point-bar sequence note on lap of stream facies on to an interpreted soil horizon.
Johnson and Friedman (1969, p. 463-468, including Figs. 7-17) provide a detailed description of this stop (their section 53); Figure 29 is a modified version of Figure 7 of Johnson and Friedman.

A7: TRAVERSE ACROSS THE TACONIAN OROGEN
KURT HOLLOCHER
Geology Department
Union College
Schenectady, NY 12308
In Early Ordovician time the rifted and submerged eastern edge of the North American continent (current coordinates) was located approximately at the present location of the Connecticut River in western New England (Figures 1A and 2). To the east, across a narrow ocean basin, lay an island arc. Subduction of oceanic crust beneath the arc allowed the arc to advance toward North America, colliding in Middle to Late Ordovician time. The remnants of the island arc itself are present in western New England as a sequence of Ordovician sediments (e.g., Bradley and Kidd, 1991) and bimodal volcanic and plutonic rocks (e.g., Leo et al., 1984; Leo, 1985, 1991; Schumacher, 1988; Hollocher, 1993, 1994). The remnants of the island arc are found in four different forms: 1) unmetamorphosed sediments derived from the arc and fore-arc regions that were deposited west of the arc on North American crust; 2) variously metamorphosed continental shelf, continental slope, trench, and fore-arc rocks that became part of the arc's accretionary wedge and were thrust westward onto North America during subduction and collision; 3) interbedded sediments and volcanics associated with arc, and possibly fore-arc and back arc volcanics; and 4) the plutonic roots to the arc. This trip examines all four of these.

A7: TRAVERSE ACROSS THE TACONIAN OROGEN

STOP 1. Rexford Bridge.
No hammers!
On the cliff across the Mohawk River you can see an excellent exposure of undeformed autochthonous Schenectady Formation, which is composed of interbedded gray shale and gray sandstone (graywacke). The sandstones are turbidite beds that are made of sediment derived from erosion of the Taconian island arc, and possibly associated emergent accretionary wedge and fore arc material (see Kidd et al., this volume). Flute casts and other current indicators in eastern New York State indicate a generally northward turbidity current transport direction, suggesting deposition in a north-south trending, northward-deepening sedimentary basin. Garver et al. (in press) has shown that there is a dramatic increase in Cr and Ni concentrations part way up the stratigraphic section in these rocks in New York State and similar rocks in Quebec and Newfoundland. They interpret this increase as resulting from erosional unroofing of mafic and ultramafic ophiolitic rocks that were exposed in the fore-arc region during the arc-continent collision. Ophiolites are still exposed in western Newfoundland and eastern Quebec, but, except for small ultramafic pods, have been eroded away in western New England. Unstable mineral grains and rock fragments in these gray sandstones have decomposed to form illite, chlorite, and other diagenetic minerals. The mineralogy of these rocks is dominated by quartz, illite, chlorite, and kaolinite.

STOP 2. Lock 7 access road.
This small roadcut has allochthonous "Schenectady Formation" that has been deformed. The thrust zone along which these rocks have been transported extends approximately 500 m to the west. Notice that these are still sedimentary rocks and have not been metamorphosed significantly. Graded beds and sole marks in some sandstones indicate topping direction. Note that this outcrop is about 6 km west of a klippe of Austin Glen Formation, the westernmost mapped klippe in the Schenectady area (Figure 1). This and surrounding outcrops probably represent a poorly exposed thrust slice that was transported a relatively short distance.

Ordovician Austin Glen Formation
Outcrops to left and right are Ordovician Austin Glen Formation. These weakly metamorphosed rocks have a strong east-dipping foliation, contain numerous small thrust faults, and is quite inhomogeneous, giving the outcrop a melange-like appearance.

Low Taconics visible in the distance ahead.

High Taconics visible on the skyline ahead.

STOP 3. Taconic crest.
These highly deformed rocks of the Nassau Formation had a shaley deep water facies protolith. Now they are chloritoid-grade phyllites with abundant deformed quartz veins (I have not found chloritoid in this outcrop). The quartz veins occur in several generations, as can be discerned by different degrees of deformation and crosscutting relationships. The phyllites contain the mineral assemblage quartz-white mica (muscovite and paragonite)-chlorite-carbonate (probably ankerite). The large rusty cavities in the quartz veins are weathered carbonate. Although two or three fold generations are apparent in the outcrop, the general dip of the schistosity is east, typical of the entire Taconian accretionary wedge system. Shear sense indicators suggest a top-to-the-west transport direction. Notice that the dominant foliation has been folded by a steeply east-dipping crenulation cleavage.

STOP 4. Pine Cobble.
Turn left into little the parking lot and park. This hike will be to Pine Cobble Long Trail. The hike is 3.2 miles round trip and 800' of climbing. It will take about 2.5 hours. Bring water, a snack, and appropriate clothing.
No hammers! This outcrop of Cheshire Quartzite is located on the southern tip of the Green Mountains, and is equivalent to the Potsdam Formation in New York State. This is the basal Cambrian clastic unit that overlies older rocks, including Grenville age metamorphic basement rocks, of the Green Mountains and Berkshires. The quartzite has a weak foliation defined by muscovite that dips gently east. A set of steeply east-dipping joints may be a fracture cleavage, because the joints have an orientation similar to the crenulation cleavage evident in the more ductile rocks at Stops 3 and 7, and are approximately parallel to the antiformal axial surface of the Green Mountains. The Taconic Mountains are visible to the west, Mt. Greylock to the south, and the Berkshires to the east. The mountains are held up by allochthonous metamorphic rocks that were thrust-transported westward in the Taconian accretionary wedge. The valley is floored by Cambrian and Lower Ordovician carbonate and clastic continental shelf rocks that stratigraphically overly the Cheshire Quartzite of this stop. The Cheshire and underlying rocks, which is part of a broad anticlinal structure that makes up the Green Mountains, plunges southward beneath the valley. The rocks in the valley floor are also allochthonous, having been transported piggyback-style on the Precambrian-based block of the Green Mountains. Hike back down, leave the parking lot and backtrack down Pine Cobble Rd.

Highlands to the left (north) are the southern end of the Green
Mtns.

STOP 5. Natural Bridge State Park.
No hammers!
These are rocks of the Cambrian to Ordovician Stockbridge Formation. This unit represents North American Cambrian or Lower Ordovician continental shelf carbonate rocks that were deformed and transported westward along Taconian thrusts. These have themselves been overridden by Taconian thrust sheets, including the Berkshire block immediately to the east.

STOP 6. Road cut on Rt. 8.
This rock is composed of relatively low-grade metamorphosed calcareous sandstone in the Ordovician Walloomsac Formation. This unit was also deposited on the North American continental margin. Although the rock is folded, sedimentary structures such as cross bedding can still be found in some places. The folds are best outlined by carbonate-rich layers in which the carbonate weathers out to form rusty pits.

STOP 7. Berkshires "western summit".
Excellent views of the Williamstown-North Adams valley with the Taconics, Mt. Greylock massif, Green Mtns., and the carbonate-floored valley.
This outcrop of Hoosac Formation contains biotite grade metamorphosed clastic sediments similar in composition to those seen at the Taconic crest. At these higher grades, biotite is the dominant mafic mineral rather than chlorite. Gray albite porphyroblasts up to 3 mm across are very common, and have grown to replace paragonite as the principal Na-bearing phase. Although the foliation generally dips east, there are numerous folds visible. Most are late, broad, open, folds having a prominent steeply east-dipping crenulation cleavage similar to that at Stop 3. More rare are isoclinal folds that indicate a top-to-the-west shear sense in the plane of the dominant foliation. This rock overlies Precambrian rocks in the Berkshire massif, and so it is part of a block of North American basement that has been transported westward over the shelf sediments seen at Stops 5 and 6.

STOP 8. Eastern Summit Gift Shop.
No hammers!
Excellent view of the eastern slope of the Berkshires, and the Bear Swamp pumped storage hydroelectric reservoir.
This glacially striated pavement outcrop of Rowe Formation contains garnet grade phyllite (but no garnets) that has a composition richer in Fe and Mg and poorer in K, Na, and Si than the schists and phyllites of Stops 3 and 6. This more mafic composition is probably caused by a large volcaniclastic component in the sediments, presumably derived from erosion of volcanics from the Taconian island arc. The dominant minerals are chlorite, white mica, quartz, and octahedral crystals of magnetite. The patchy appearance of the outcrop is caused by mechanical mixing of a variety of slightly different sedimentary lithologies, probably when the rock was a soft sediment. On a large scale, the Rowe Formation has been characterized as a melange, and includes basaltic and ultramafic rocks. Leave the parking lot and turn left (south) down the hill on Rt. 2 east. Units passed on the steep, winding descent of the Berkshires include the Rowe and Hoosac Formations.

Outcrops on right are Hawley Formation.

STOP 9. Hawley Formation.
The Hawley Formation contains large quantities of volcanic and intrusive rocks along with the volcaniclastic sediments. The igneous rocks include mafic and felsic varieties. The mafic rocks have compositions similar to basalts, and seem to include mid-ocean ridge, back-arc basin, and boninitic, and calc-alkaline varieties. These metamorphosed igneous rocks are related to the Taconian island arc, but their diverse lithology, compositions, and ages indicate a complex history for the island arc system in which they were emplaced. The rocks at this outcrop are amphibolite grade carbonate- and hornblende-bearing chlorite-muscovite schists. They contain abundant acicular hornblende up to 20 cm long in some areas, although they are typically 1 to 3 cm long in this outcrop. Euhedral carbonate rhombs (ankerite?) can be seen weathering out on outcrop surfaces to form rhombohedral pits. On the steep slope on the river side of the road there are some nice exposures of coticule (fine-grained pink garnet quartzite). This unusual rock type is thought to represent metamorphosed Mn- or Fe-rich chert that formed from silica derived from the weathering or hydrothermal alteration of volcanic rocks.

Devonian Goshen Formation
Good outcrops of garnet-rich Devonian Goshen Formation schist on the north shore of
the Deerfield River to the right (south).

Core rocks of the Shelburn Falls dome
Outcrops are calc-alkaline felsic gneisses and related amphibolites in core rocks of the Shelburn Falls dome (roots of the Taconian island arc).

STOP 10. Shelburn Falls.
Small access road to the right (south) soon after the bridge. Do not drive down this road, but find a place to park after the bridge. On foot, follow signs on the small access road to "glacial potholes". Find the steps going down to the river behind the gift shop. Do not go down to the rocks if the gate is locked, or if water is flowing strongly over the rocks.
This exposure is an excellent example of the core gneisses of the Shelburn Falls dome. This is an Acadian (Devonian) structural dome that exposes a variety of plutonic-looking calc-alkaline gneisses and amphibolites. These rocks have generally been interpreted to be part of the plutonic roots to the Taconian island arc. Igneous features that can be seen in this outcrop include crosscutting relationships, dikes, xenoliths, intrusion breccia, and late-stage quartz veins and faults. These rocks are similar to, but less deformed than, the Ordovician gneisses exposed in the cores of domes in the Bronson Hill anticlinorium, farther to the east. The precise relationship of the Shelburn Falls rocks to those in the Bronson Hill anticlinorium is somewhat problematic. Although the two are lithologically and chemically similar, a preliminary age date on the Shelburn Falls rocks is substantially older (Paul Karabinos, oral communication, 1993) than the 443-453 MY age of the calc-alkaline gneisses in the Bronson Hill anticlinorium (Tucker and Robinson, 1990). Other features that can be seen here include wonderful large potholes that were formed by the Deerfield River when it was swollen with glacial melt water.

Road climbs out of the topographic depression
Road climbs out of the topographic depression of the Shelburn Falls dome. Hills bounding the dome here are kyanite-staurolite grade Goshen Formation schists that are more resistant to erosion than the calc-alkaline gneisses in the dome interior.

Excellent view of the Deerfield basin
Excellent view of the Deerfield basin, the northernmost sizable portion of the Mesozoic rocks of the Connecticut River Valley. The N-S trending ridge in the middle of the basin is held up by the Deerfield Diabase, probably correlative with the Holyoke Basalt farther south. The large mountain to the southeast is Mt. Toby.

Excellent exposures of fluvial facies
Excellent exposures of fluvial facies of the Mesozoic red beds of the Connecticut Valley basin.

STOP 11. Turner's Falls.
Although it has little to do with the Taconian orogen, this wonderful set of outcrops has excellent exposures of Mesozoic basaltic lava and terrestrial sediments that formed in a rift valley. The outcrops near the parking lot are of tholeiitic Deerfield basalt. The flow base, in contact with red beds, is accessible on the south side of the road to the west of the parking lot. The flow base has pillow lavas that formed as the lava flowed into a saline rift valley lake. The flow top and overlying red beds are visible in the roadcut across the road from the eastern end of the parking lot. Several faint, coarse-grained layers sub-parallel to the flow top are visible in the central part of the roadcut. These are sill-like segregations of residual magmatic liquid that separated from the crystal mush of the compacting, solidifying flow (described for a different locality by McHone and Philpotts, 1995; Philpotts et al., 1995). The outcrops near the river, accessible by foot path from the parking lot, have excellent exposures of the vesicular lava flow top, and one of the coarse-grained sill-like layers. The flow is overlain by fluvial conglomerate, arkose, siltstone, and shale. The fluvial sediments have excellent depositional and soft sediment features including bed forms, mud cracks, trace fossils, raindrop imprints, shale rip up clasts, and filled channels. Near the dam the sediments grade into finer-grained gray and black lake sediments in which fish and plant fossils can be found. Leave the parking lot and turn right to continue on Rt. 2 east. For excellent introductions to the geology of the Connecticut Valley basin, see Hubert eta!. (1978) and Home et al. (1995).

Very coarse-grained matrix-supported conglomerate.
Small road cuts on both sides of the road are composed of very coarse-grained matrix-supported conglomerate. This outcrop represents the alluvial fan facies of the Mesozoic red beds of the Connecticut River Valley. The alluvial fans were principally built on the east side of the basin, below the mountains on the east side of the border fault along which the basin subsided.

Cross the French King Bridge over the Connecticut River.
This is the approximate location of the normal fault that forms the eastern margin to the Connecticut River Valley rift basin.

STOP 12. Millers Falls.
This large roadcut is in the biotite member of the Dry Hill Gneiss, a Late Precambrian (Tucker and Robinson, 1990) unit exposed in the core of the Pelham dome, one of the structural domes in the Bronson Hill anticlinorium. This unit is interpreted to be a thick series of metamorphosed alkalic volcanics that probably erupted in a continental rifting environment (Hodgkins, 1985). The relationship of these rocks to surrounding rocks is unclear, but they are unrelated to the Taconian island arc except to the extent that they are exposed in this dome in the Bronson Hill anticlinorium. The Dry Hill Gneiss is overlain, perhaps along a fault, by felsic Fourmile Gneiss, which is part of the Taconian igneous suite. The Dry Hill Gneiss is a moderately well foliated, layered granitic gneiss that contains the assemblage quartz-plagioclase-microcline-biotite±amphibole (hornblende or hastingsite), with accessory sphene, magnetite, apatite, zircon, and allanite. The allanite crystals are large and are visible as dull tan-colored crystals in hand specimen. The large K-feldspar megacrysts in the gneiss were probably derived from severely deformed and dismembered pegmatites. This texture indicates the great strength of feldspar compared to the quartz- and biotite-rich matrix during extreme solid-state deformation.

STOP 13. Crag Mountain.
Pull off to the right at the top of the hill and park. Follow white blazes along the private driveway. At the double blaze, turn right into the woods. Follow the trail to the quartzite ledges after about 1/4 mile.
This prominence is composed of thickened (by folding) Silurian Clough Quartzite. In this locality it is a quartz pebble and cobble conglomerate metamorphosed to kyanite-staurolite grade. Pelitic schists in the area can contain the assemblage The Clough Quartzite was deposited on an extensive Silurian erosion surface in western New England, and it rests on a variety of Ordovician and older rocks. The quartzite has been deformed so that quartz cobbles and pebbles have been flattened and extended to different degrees, visible in outcrop. The milky quartz is full of fluid inclusions, suggesting that it was originally metamorphic vein quartz. Silurian erosion of Taconian low- and medium-grade metamorphic rocks in the Taconics, Green Mountains, and Berkshires may have been the source for the necessary large quantities of high-purity vein quartz. End of trip!

A8: DEVONIAN CARBONATES AND ECONOMIC RESOURCES: THE BLUE CIRCLE AND CALLANAN QUARRIES
DEAN HERRICK
Continental Placer
26 Computer Drive West
WILLIAM KELLY
New York State Geological Survey
Room 3140 CEC
DON DRAZAN
Division of Mineral Resources
New York State Department of Environmental Conservation
50 Wolf Road, Albany, NY 12233
CRUSHED STONE AND CEMENT PRODUCTION - GENERAL CONSIDERATIONS
The production of crushed stone in New York was 33,500,000 tons 1994 with a value of $196 million. Most of the crushed stone produced in New York is limestone and dolostone with traprock (diabase) and various metamorphic rocks making up the bulk of the remainder. Cement manufacturing amounted to 2,925,000 tons valued at slightly over $149 million. Taken together, crushed stone and cement account for 40% of the value of mineral produced in New York. There is an order of magnitude difference in the price of these two commodities with crushed stone trading for an average of $5.85/ton and cement valued at an average of $50.94/ton. This price difference leads directly to the contrast in mining operations that will be examined. On this field trip, we will visit two quarries operating in the rocks of the Helderbergs. One of these produces crushed stone for construction aggregate and the other produces cement. Although both companies are working in the same stratigraphic section with similar equipment and mining plans, the end use of the rock drives the companies to use very different geologic units within the overall stratigraphic framework. The following brief discussion outlines the processes and constraints on the construction aggregate and cement industries.

A8: DEVONIAN CARBONATES AND ECONOMIC RESOURCES: THE BLUE CIRCLE AND CALLANAN QUARRIES

STOP 1. Callanan Quarry
SITE GEOLOGY
The Callanan Quarry is located primarily in the Town of Coeymans, south of NY Route 396 and the village of South Bethlehem (Fig. 1). The location can be found on the Delmar 7.5' quadrangle. The quarry is owned and operated by Callanan Industries, Inc. All correspondence concerning access should be directed to Mr. Charles A. Stokes, Senior Vice-President, Callanan Industries, One South Street, South Bethlehem, NY 12161. The Blue Circle Quarry is located in the town of Coeymans, east of NY Route 9W (Fig. 1 ). The location can be found on the Ravena 7.5' quadrangle. Correspondence concerning quarry access should be directed to Mr. Kevin Riley, Quarry Superintendent, Blue Circle Industries, Ravena, NY 12143.
The two quarries described herein are separated from each other by nine miles. Consequently the geology at the two sites is quite similar. Both quarries are developed in the lower and middle units of the Helderberg Group rocks. Here, the Manlius is 54 feet thick and subdivided as described above. Units M1, M3, and M6 are dark-gray, fine-grained to sublithographic, fine to medium bedded, subtidal limestone. Units M2 and M5 are light-gray, fine-grained, thin-bedded, super-tidal dolomitic limestone. Unit M4 is medium to dark-gray, massive, intertidal, stromatoporoid limestone. The Coeymans is 27 feet thick, light-gray, medium-grained, massive, non-argillaceous, fossiliferous limestone. It is homogeneous and lacks marker beds.
The Kalkberg is 66 feet in total thickness. The Lower Hannacroix is 11-18 feet thick, medium-gray, medium-bedded limestone with interbedded dark gray to black chert nodules and chert beds one to four inches thick. The Upper Hannacroix is 10 feet thick, fine- to medium-grained limestone. This unit is similar to the Coeymans except that it is less fossiliferous and the fossils are somewhat smaller. The Lower and Upper Broncks Lake total 45 feet in thickness. They are fine- to medium-grained, medium-bedded, argillaceous limestones.
The New Scotland is 100 feet thick and is composed of medium to thick-bedded, argillaceous limestone similar in appearance to the Kalkberg Formation. The uppermost part of the New Scotland is transitional into the overlying Becraft. The Becraft is 40 feet thick, tan to grayish-white with greenish-gray shaly partings. It is a coarse-grained and highly fossiliferous limestone.
Several marker beds and stratigraphic horizons are visible in the quarries and can be used for stratigraphic location. The Coeymans-Kalkberg contact is a key horizon. This contact can be identified by the following characteristics: (1) on a weathered surface, the Coeymans is light-gray to buff and the Kalkberg is medium-gray and is less resistant to weathering; (2) a black, shaly layer, two to six inches thick, commonly occurs between the formations; (3) the Lower Hannacroix of the Kalkberg contains discontinuous bedded black chert.
The contact between the Kalkberg and New Scotland is marked by an increase in siliceous material in the New Scotland giving it a shaly appearance relative to the more massive Upper Broncks Lake Member of the Kalkberg.
The top of the New Scotland contains a transitional zone into the overlying Becraft Formation characterized by alternating beds of crystalline (Becraft lithology) and shaly beds (New Scotland lithology). Also notable at the contact are green shale bands of the Becraft as opposed to the black shale of the New Scotland.
PRODUCTION
The majority of the aggregate produced from the Callanan Quarry in South Bethlehem is used for New York State Department of Transportation (NYSDOT) road construction. Therefore, NYSDOT specifications are most crucial to Callanan's mining. High-friction aggregate, material with greater than 20% non-carbonate content, is used in top-coarse paving material in New York State. High-fiction material commands the highest price, and, for this reason, is the most valuable to producers. Of the five formations mined at Callanan's quarry, only the New Scotland and Kalkberg are approved for high-friction use. As Callanan excavates the New Scotland and Kalkberg, most of the Manlius, Coeymans and Becraft is left behind. These formations are, however, mined for non-friction products, which include commercial uses.

STOP 2. Blue Circle Quarry
A few miles south, the situation is startlingly different. Blue Circle is discarding in waste piles approximately 85% of the Kalkberg and nearly 100% of the New Scotland that is mined. Callanan's low-valued Manlius, Coeymans and Becraft formations command high value at Blue Circle's quarry. These three formations have a high carbonate content which is extremely important in cement production. So much so that Blue Circle strips up to 160 feet of waste rock (rock which is valuable to Callanan) to get to the Manlius and Coeymans formations. A comparison of the cost per ton of aggregate versus cement in New York, cited above, illustrates the difference in value and explains Blue Circle's mining strategy. The much higher cost (and value) of cement is attributed to a number of factors including processing costs, cost of raw materials (limestone, iron, silica, alumina, gypsum) and market demand.

A9: THE PALEOFLUVIAL RECORD OF GLACIAL LAKE IROQUOIS IN THE EASTERN MOHAWK VALLEY, NEW YORK
Gary R. Wall & Robert G. LaFleur
Rensselaer Polytechnic Institute
Department of Earth and Environmental Sciences
West Hall
Troy, NY 12180
ABSTRACT
During the final retreat of Laurentide ice from New York State, the Mohawk Valley played a major role in the routing of glacial meltwater. The Mohawk Valley contained the Iromohawk River, which drained Glacial Lake Iroquois, in the Ontario Basin, into Hudson Valley glacial lakes Albany II, Quaker Springs, Coveville and Fort Ann. Iromohawk drainage occurred for a period of approximately 500 years while the St. Lawrence Lowland remained glaciated and the Mohawk Valley was ice free.
Iromohawk drainage developed a network of distributary channels across the Hudson-Mohawk Lowland, as well as carving the modern Mohawk channel between Schenectady and Cohoes. Progradation of these channels occurred as the Iromohawk drained toward lowering Hudson Valley glacial lake levels. Depositional and erosional surfaces associated with distributary and modern channels have been used to establish a chronology of channel development and usage relative to Hudson Valley glacial lakes. This chronology constrains the timing and duration of later Hudson Valley lake phases between -12,500 and 12,000 years BP.
Sedimentologic evidence in the Scotia Gravel at Scotia, one of the principle Iromohawk deposits in the valley, indicates Iromohawk drainage was a long-term, high-discharge event with cyclic (probably seasonal) variation in flow.

A9: THE PALEOFLUVIAL RECORD OF GLACIAL LAKE IROQUOIS IN THE EASTERN MOHAWK VALLEY, NEW YORK

Schoharie Bridge
The original Thruway crossing of Schoharie Creek catastrophically failed in 1987 due to Schoharie Creek high flow and scour of bridge supports.

Approximate Iromohawk River channel bottom
Mohawk River floodplain and approximate Iromohawk River channel bottom. Iromohawk depth in this location was approximately 50 feet.

Mohawk River and Barge Canal on right.

Middle Ord. Canajoharie Shale exposed on left.

STOP 1. Randall Expansion Bar overview.
Uplifted land associated with the Noses fault is visible to the west. At the base of the hill is the Iromohawk channel bottom, and beyond that the Randall expansion bar. The bar measures 7,000 feet in length and 1,800 feet at its maximum width. Thickness of the deposit is approximately 60 feet. One well log from the deposit indicates the bottom of the bar is approximately at the elevation of the modern floodplain (U.S. Geological Survey, Open File). The height of the bar above the floodplain therefore represents a minimum water depth (60 feet) for bar deposition.

Road descends to Iromohawk channel bottom.
Randall bar is straight ahead and to the right

Road climbs along Randall bar long axis.

STOP 2. Randall Expansion Bar.
Pit owned by Santos Construction Company (SCC) - our access to the pit is under consideration by SCC.
Contact: Dave Santos (owner) (518) 842-6201
Large-scale east--dipping (downvalley) cross-bedding is visible throughout the exposed pit, confirming the eastward flow direction inferred from the deposits east-pointing tapered tail. Exposures in contact with the deposit surface show bedding that mimics external morphology. Overall, the Randall deposit is very poorly sorted with individual clasts ranging from small boulders to coarse sand.

Road descends along eastern tail of Randall bar.

Road crosses top of Rotterdam Jct. portion of Scotia Gravel

Cross Mohawk River and Barge Canal Lock 9

Glenville Channel visible on left
Glenville Channel visible on left- one of four minor channels to incise the Scotia deposit of Scotia Gravel.

Partially cemented blocks of Scotia Gravel
Partially cemented blocks of Scotia Gravel visible in old pit on left

STOP 3. Scotia Gravel and Mohawk River overlook.
If water level is low and interest high, hike from here to exposure of graded gravel foresets.
This exposure is marked by numerous east dipping graded gravel foreset beds. Dozens of these foresets are visible across the exposure, each grading from cobble to coarse sand and pebble gravel, and measuring approximately 3 feet in thickness. The cyclic nature of the graded foresets is more typical of a long term rather than catastrophic depositional event; furthermore, the cyclically suggests a seasonal variation transport energy, essentially gravel varves.

Top of Scotia Gravel (-300' asl).
Deposit continues to the northern (left) valley wall (3000+ feet)

Giant point bar
This stretch of Rt. 5 runs along the top of a giant point bar extending to the south (right) into Schenectady Basin.

Road climbs to top of Scotia Gravel.

STOP 4. Scotia Gravel overlook and paleodischarge discussion.
Another Scotia Gravel overlook, this one into a semi-active gravel pit.

Road parallels Harding Channel on left.

Schenectady County Airport on right.
The airport sits atop a sand plain deposited in Lake Albany by the Glaciomohawk (pre-Iromohawk) and/or Alplaus Kill.

Road descends into Ballston Channel.

Bottom of Ballston Channel.

Road climbs out of channel.

STOP 5. Mohawk Gorge
Directly across the gorge, a 1,200 foot wide bedrock bench stands at ∼270 feet elevation. This bench descends and narrows to 260+ feet elevation some 6,000 feet downvalley where it pinches out at the narrowest gorge reach. A lower bedrock bench stands at 220+ feet.

Village of Vischers Ferry
Village of Vischers Ferry is built on the floor of Niskayuna Basin, the southernmost of three giant kettles in the Hudson Mohawk Lowland. Niskayuna Basin is roughly 4 miles (E-W) by 2 miles (N-S). All three basins lie along the N-S trending preglacial Colonie Channel.

Original Erie Canal visible on right.

Road leaves Niskayuna Basin

Mohawk River on right.

STOP 6. Cohoes Falls
The falls are dry throughout most of the year due to a diversion of flow for the Barge Canal and the hydroelectric plant immediately to the west.
Cohoes Falls has eroded back some 2000+ feet in post-glacial time. Inferences from bedrock islands at the Hudson-Mohawk confluence immediately downvalley suggest much of this erosion may have occurred during Iromohawk drainage. Iromohawk flow exposed and eroded the top of bedrock on both sides of the gorge.

Cross Mohawk River
Bedrock islands visible to right.

Barge Canal locks 2 and 3
Barge Canal locks 2 and 3 visible to right and left respectively

Enter Anthony Kill Channel
This channel developed as Round Lake Basin waters drained toward falling Hudson Valley glacial lake levels.

Willow Glen channel expansion (on right).
Anthony Kill Channel dramatically expands to the north. This feature was likely carved out by eddying flow through Anthony Kill Channel, eroding the less resistant Willow Glen kame delta (the majority of the channel walls are composed of till and bedrock).

STOP 7. Anthony Kill Channel.
A classic example of a misfit stream.

Enter Round Lake Basin
Enter Round Lake Basin, the middle of three giant kettles aligned with the preglacial Colonie Channel. Round Lake Basin is nearly circular with a diameter of apx. 2.5 miles

Road crosses top of small delta at mouth of Round Lake Channel.

Cross Round Lake Channel.
Flow was from left to right into Round Lake Basin.

STOP 8. Round Lake Channel
Visible in this portion of Round Lake Channel are two bedrock erosional surfaces which grade to Round Lake Basin water levels correlative with lakes Coveville and Fort Ann in the Hudson Valley. The upper Coveville surface is distinguished from the lower Fort Ann by the bedrock channel wall flanking Rhule Rd. No. The opposite channel wall is visible below the power lines crossing the channel.

Malta Sand Plain
Road runs across the Malta Sand Plain, a Glaciomohawk deposit into Lake Albany II.

Road descends into Saratoga Lake Basin
Road descends into Saratoga Lake Basin, the northernmost of three giant kettles aligned with the preglacial Colonie Channel. Saratoga Lake Basin has approximate dimensions of 2 miles (E-W) by 6 miles (N-S).

Saratoga Lake is visible straight ahead.

Ascend back onto Malta Sand Plain.

Road descends into Ballston Channel.
Ballston Channel is the middle of three distributary channels branching from the northern end of Ballston Channel at East Line. Drummond Channel connects with Saratoga Lake Basin to the northeast (right).

Road ascends out of channel onto Malta Ridge
Road ascends out of channel onto Malta Ridge, an erosional remnant between distributary channels (Drummond and Mourning) equivalent with the Malta Sand Plain.

Road parallels Mourning Channel (to right).

East Line
Point at which Ballston Channel splits into the distributary Mourning, Drummond, and Round Lake Channels.

STOP 9. Northern end of Ballston Lake
Northern end of Ballston Lake in Ballston Channel.

A10: GEOCHRONOLOGY AND PETROGENESIS OF ADIRONDACK IGNEOUS AND METAMORPHIC ROCKS
James M. McLelland
Department of Geology
Colgate University
Hamilton, NY 13346
INTRODUCTION AND GEOCHRONOLOGY
The Adirondacks form a southwestern extension of the Grenville Province and are physiographically divided into the Adirondack Highlands (granulite facies) and Lowlands (amphibolite facies) by a broad zone of high strain referred to as the Carthage-Colton Mylonite Zone which is continuous with the Chibougamau-Gatineau line, or Labelle shear zone, in Canada. Together these two zones separate the Grenville Province into two major blocks with the Central Granulite Terrane (CGT) lying east of AB and the Central Metasedimentary Belt (CMB) and Central Gneiss Belt (CGB) lying to the west. Within the southwestern portion of the Grenville Province further subdivisions exist and are shown in figure 3. As demonstrated by recent U-Pb zircon and Sm-Nd geochronology summarized by McLelland and Chiarenzelli (1990) and McLelland et al. (1993), the Adirondack-CMB sector of the Grenville Province contains large volumes of metaigneous rocks that represent recent (i.e., ca. 1400-1200 Ma) additions of juvenile continental crust. These results indicate that the Adirondack-CMB region experienced wide-spread calcalkaline magmatism ca. 1300-1220 Ma. Associated high grade metamorphism has been fixed at 1226±10 Ma by Aleinikoff (pers. comm.) who dated dust air abraded from metamorphic rims on 1300 Ma zircons. Identical rocks, with identical ages, have been described from the Green Mts. of Vermont by Ratcliffe et al. (1991), in northern Ireland by Menuge and Daly (1991), in the Llano uplift of Texas (Walker, 1993) and in the Texas-Mexico belt of Grenville rocks by Patchett and Ruiz (1990). It appears, therefore, that a major collisional-magmatic belt was operative along the present southern flank of the Grenville Province during the interval 1300-1220 Ma and may have been related to the assembly of a supercontinent. More locally, this magmatism and associated metamorphism, represents the Elzevirian Orogeny of the Grenville Orogenic Cycle as defined by Moore and Thompson (1980). Within the Adirondacks, Elzevirian rocks are represented by 1300-1220 Ma tonalites and alaskites whose distribution is shown in figure 5. The apparent absence of this suite from the central Highlands is believed to be the combined result of later magmatic intrusion and recent doming along a NNE axis. Within the Frontenac-Adirondack region, the Elzevirian Orogeny was followed by 40-50 Ma of quiescence terminated at 1170- 1130 Ma by voluminous anorogenic magmatism referred to as the anorthosite-mangerite-charnockite-granite (AMCG) suite. The older ages are characteristic of AMCG magmatism in the Frontenac Terrane (including the Lowlands) while the Highlands commonly exhibit ages of 1150-1130 Ma. The large Marcy anorthosite massif and its associated granitoid envelope were emplaced at ca. 1135 Ma (McLelland and Chiarenzelli, 1990). These ages are similar to those determined (Emslie and Hunt, 1990) for the Morin, Lac St. Jean, and several other large massifs farther northeast in the Grenville Province. Rocks of similar age and chemistry (i.e., Storm King Granite) have been described within the Hudson Highlands (Grauch and Aleinikoff, 1985). The extremely large dimensions of the AMCG magmatic terrane emphasize its global-scale nature corresponding, perhaps, to supercontinent rifting with the rifting axis located farther to the east. Valley et al. (1990) and McLelland et al. (1991) have provided evidence that contact, and perhaps also regional, metamorphism accompanied emplacement of hot (1100°C), hypersolvus AMCG magmas. Wollastonite and monticellite occurrences related to thermal pulses from AMCG intrusions occur in proximity to AMCG intrusions (Valley et al., 1990). In the Lowlands and the Canadian sector of the Frontenac Terrane, monazite (table 1., no. 28), titanite, and garnet ages (Mezger et al., 1992) all indicate high temperatures (600-8OO°C) at ca. 1150 Ma. Rutile ages and Rb/Sr whole rock isochron ages document temperatures not exceeding 400°C at ca. 1050-1000 Ma.
Following approximately 30 Ma of quiescence, the Adirondacks, along with the entire Grenville Province, experienced the onset of the Ottawan Orogeny of the Grenville Orogenic Cycle. Initially the Ottawan Orogeny was represented by 1090-1100 Ma hornblende granites in the northwest Highlands. These rather sparse granites were followed by deformation, high grade metamorphism, and the emplacement of trondhjemitic to alaskitic magnetite-rich rocks (Lyon Mt. Gneiss of Whitney and Olmsted, 1988) in the northern and eastern Adirondacks. The zircon ages of these rocks fall into an interval of 1050-1080 Ma which corresponds to the peak of granulite facies metamorphism when crust, currently at the surface, was at 25 km. Accordingly, the alaskitic to trondhjemitic rocks are interpreted as synorogenic to late-orogenic intrusives. They were followed by the emplacement of small bodies of fayalite granite (ca. 1050 Ma) at Wanakena and Ausable Forks.
Sm-Nd analysis (Daly and McLelland, 1991) demonstrates that the emplacement ages of the ca. 1300 Ma tonalitic rocks of the Highlands correspond closely to their neodymium model ages indicating that these represent juvenile crustal additions. As seen in figure 6, εNd evolution curves for AMCG and younger granite suites pass within error of the tonalitic rocks and suggest that the tonalites, together with coeval granitoids, served as source rocks for succeeding magmatic pulses. Remarkably, none of these igneous suites gives evidence for any pre-1600 Ma crust in the Adirondack region and the entire terrain appears to have come into existence in the Middle to Late Proterozoic. Significantly, Sm-Nd analysis for the ca. 1230-1300 Ma tonalitic to alaskitic Hyde School Gneiss at the Lowlands demonstrates that it has model neodymium ages and εNd values similar to Highland tonalites (McLelland et al., 1993). These results are interpreted to reflect the contiguity of the Highlands and Lowlands at ca. 1300 Ma. Given this, the Carthage-Colton Mylonite Zone is interpreted as a west-dipping extensional normal fault that formed during the Ottawan Orogeny in response to crustal thickening by thrust stacking (McLelland et al., 1993). East dipping extensional faults of this sort and age have been described by van der Pluijm and Carlson (1989) in the Central Metasedimentary Belt. Motion of this sort along the Carthage-Colton Mylonite Zone would help to explain the juxtaposition of amphibolite and granulite facies assemblages across the zone. A downward displacement of 3-4 km would satisfactorily explain the somewhat lower grade of the Lowlands terrane.

A10: GEOCHRONOLOGY AND PETROGENESIS OF ADIRONDACK IGNEOUS AND METAMORPHIC ROCKS

STOP 1. Peck Lake Fm.
This exposure along Rt. 29A just north of Peck Lake is the type locality of the sillimanite-garnet-biotite-quartz-feldspar gneisses (kinzigites) of the Peck Lake Fm. in addition, there are exposed excellent minor folds of several generations. Note that the F1 folds rotate an earlier foliation. The white quartzo-feldspathic layers in the kinzigites consist of quartz, two feldspars,and garnet and are believed to be anatectic and have been folded by F1 indicating pre-F1 metamorphic events. Typical whole rock compositions are shown below. Spinel has been found enclosed in garnets at this outcrop. The similarity of the Peck Lake Fm. to the Major Paragneiss of the Lowlands suggests that the Adirondacks were contiguous at the time of deposition of the rocks.

STOP 2. Irving Pond Fm., .5 mile north of Nick Stoner's Inn, Canada Lake .
.5 mile north of Nick Stoner's Inn, Canada Lake. Very near hinge line of F1 Canada Lake isocline.
The outer portion of the Irving Pond Fm. is exposed in low cuts along the east side of Rt. 29A just prior to the crest in the road heading north.
At the southern end of the cut typical, massive quartzites of the Irving Pond are seen. Proceeding north the quartzites become "dirtier" until they develop sillimanite-garnet-biotite feldspar (kinzigites) layers along with quartzite.
At the northern end of the cut, and approximately on the Irving Pond/Canada Lake Fm. contact there occurs an excellent set of F1 minor folds. Polished slabs and thin sections demonstrate that these fold an earlier foliation defined by biotite flakes and flattened quartz grains.
At the southern end of the outcrop dark, fine grained metadiabase sheets crosscut the quartzite. Near the telephone pole erosional remnants of diabase appear to truncate approximately horizontal foliation in the quartzite suggesting that the diabase was emplaced after an early metamorphism. At the north end of the cut a diabase sheet of variable thickness is folded in the F1 fold. The folding is interpreted as Ottawan, the diabase as AMCG in origin, and the early foliation as Elzevirian. This is consistent with the presence of quartzite xenoliths in the ca. 1300 Ma tonalites.
The Irving Pond Fm. is the uppermost unit in the lithotectonic sequence of the southern Adirondacks. Its present thickness is close to 1000 meters, and it is exposed across strike for approximately 4000 meters. Throughout this section massive quartzites dominate.

STOP 3. Canada Lake Charnockite
Large roadcuts expose the type section of the Canada Lake charnockite. Lithologically the charnockite consists of 20-30% quartz, 40-50% mesoperthite, 20-30% oligoclase, and 5-10% mafics. The occurrence of orthopyroxene is sporadic. These exposures exhibit the olive-drab coloration that is typical of charnockites. Note the strong foliation in the rock. Farther north along the highway there are exposed pink leucogranitic variants of this unit. The chemical composition of these is given in table 3 (ab-6). The whole rock chemistry of the charnockitic phase is similar to AM-86- I 7 in table 3. The lateral continuity of the Canada Lake is striking (fig. 2) but the presence of xenoliths reveals an intrusive origin.

STOP 4. Royal Mt. Tonalite
(>1301 Ma, table I, sample AM-86-12, now fixed at 1307±2 Ma).
Steep roadcuts, exposed across from the Canada Lake Store, expose typical examples of the early tonalitic rocks that occur within the southern and eastern Adirondacks and that manifest the presence, throughout the region, of collisional magmatic arcs of calcalkaline chemistry that existed along the eastern margin of Laurentia from ca. 1400-1200 Ma. Amalgamation of these arcs culminated in the Elzevirian Orogeny at ca. 1250-1220 Ma.
The whole rock chemistry of the tonalitic rocks is given in table 3. Figure 7 shows the εNd characteristics of these rocks and emphasizes their petrologically juvenile character, i.e., they are not derived from any crustal rocks with long-term crustal residence but are essentially mantle derived (including derivation from melting of basaltic rock derived from the mantle at ca. 1300-1400 Ma). The εNd characteristics are compared with those from Lowland tonalites and granitoids of similar age, and the similarity suggests that they are essentially the same, strongly suggesting contiguity across the entire Adirondacks at that time (∼1300 Ma).
A disrupted layer of amphibolitic material runs down the outcrop to road level at the east end of the outcrop. This, and other mafic sheets in the outcrop, are interpreted as dikes and sheets coeval with the tonalite. In the eastern Adirondacks it has been possible to document mutually crosscutting relationships between these rock types. Also documented there are xenoliths of kinzigitic rock in the tonalites. Within the southern Adirondacks xenoliths of quartzite similar to the Irving Pond Fm. have been found in the tonalite.

STOP 5. Rooster Hill megacrystic gneiss at the north end of Stoner Lake.
This distinctive unit belongs to the AMCG suite and is widespread in the southern Adirondacks. Here the unit consists of a monotonous series of unlayered to poorly layered gneisses characterized by large (1-4") megacrysts of perthite and microcline perthite. For the most part these megacrysts have been flattened in the plane of foliation, however, a few megacrysts are situated at high angles to the foliation and show tails. The groundmass consists of quartz, oligoclase, biotite, hornblende, garnet, and occasional orthopyroxene. An igneous rock analogue would be monzonite to quartz-monzonite and the presence of orthopyroxene makes the rock mangeritic to charnockitic.
The contacts of the Rooster Hill megacrystic gneiss are everywhere conformable, but the presence of xenoliths of kinzigite indicate its intrusive nature. Rocks such as the Rooster Hill are interpreted as derived from melting of ca. 1300 Ma tonalitic and lower crustal granitoid rocks with heat derived from large AMCG gabbroic intrusions that would ultimately differentiate to anorthosite. This suggestion is consistent with the εNd trends of AMCG and tonalitic rocks in figure 6a and with the REE distributions shown in figure 14, where it appears that melting of tonalite so as to leave a plagioclase-rich residue can give the AMCG REE-trends.

Low roadcut in kinzigites of Tomany Mt. Fm.

Long roadcuts of quartzo-feldspathic gneisses and metasediments
Long roadcuts of pink quartzofeldspathic gneisses and metasediments of intruded metagabbro and anorthosite metagabbro. The igneous rocks are believed to belong to the AMCG suite.

Roadcut of anorthositic metagabbro and metanorite of AMCG suite.

Excellent examples of anorthositic gabbros
Roadcut on west side of highway shows excellent examples of anorthositic gabbros intrusive into layered pink and light green quartzofeldspathic gneisses.

Pink granitic gneiss of AMCG suite
Pink granitic gneiss of AMCG suite intruded by anorthositic AMCG gabbros and gabbroic anorthosites. Large boudin of calcsilicate in granite.

Roadcuts of Sacandaga Fm 1154 mya
Roadcuts of quartzites and other metasediments of the Sacandaga Fm. Mezger (1990) obtained a U-Pb garnet age of ca. 1154 from these rocks.

Red-stained AMCG quartzofeldspathic gneisses that have been faulted along NNE fractures.

Stop 6. Core rocks of the Piseco anticline.
This stop lies along the hinge line of the F2 Piseco anticline near its domical culmination at Piseco Lake. The rocks here are typical of the granitic facies of quartzofeldspathic gneisses such as occur in the Piseco anticline and in other large anticlinal structures, for example Snowy Mt. dome, Oregon dome.
The pink "granitic" gneisses of the Piseco anticline do not exhibit marked lithologic variation. Locally grain size is variable and in places megacrysts seem to have been largely grain size reduced and only a few small remnants of cores are seen. The open folds at this locality are minor folds of the F2 event. Their axes trend N70W and plunge 10-15° SE parallel to the axis of the Piseco anticline.
The most striking aspect of the gneisses in the Piseco anticline is their well-developed lineation. This is expressed by rod, or pencil-like, structures which are clearly the result of ductile extension of quartz and feldspar grains in a granitic protolith. The high temperature, grain size reduction that has occurred results in a mylonite. Where recognizable, early F4 isoclinal fold axes parallel the lineation.
These rocks are similar in age and chemistry to other AMCG granites and are considered to be part of that suite.
Smooth outcrops of Piseco Core rocks showing exceptionally strong mylonitic ribbon lineations.

STOP 7. Typical Adirondack marble is exposed in roadcuts on both sides of the highway.
Northern intersection of old Rt. NY 30 and new Rt. NY 30, 3.3 miles east of Speculator, New York.
Typical Adirondack marble is exposed in roadcuts on both sides of the highway. These exposures show examples of the extreme ductility of the carbonate-rich units. The south wall of the roadcut is particularly striking, for here relatively brittle layers of garnetiferous amphibolite have been intensely boudinaged and broken. The marbles, on the other hand, have yielded plastically and flowed extensively during the deformation. As a result, the marble-amphibolite and marble-charnockite relationships are similar to those that would be expected between magma and country rock. Numerous rotated, angular blocks of amphibolite and charnockite are scattered throughout the marble in the fashion of xenoliths in igneous intrusions. At the eastern end of the outcrop tight isoclinal folds of amphibolite and metapelitic gneisses have been broken apart and rotated. The isolated fold noses that remain "floating" in the marble have been aptly termed "tectonic fish". The early, isoclinal folds rotate on earlier foliation. The garnetiferous amphibolites have typical igneous compositions and are interpreted as flows or sills.
Near the west end of the outcrop a boudin of charnockite is well exposed. McLelland and others (1987) have presented evidence that boudin represents a local example of charnockitization by carbonic metamorphism. However, granites of similar composition outside the marble do not develop orthopyroxene, demonstrating the local nature of the process and the limited permeation of the fluid phase.
Exposed at several places in the roadcut are crosscutting veins of tourmaline and quartz displaying a symplectic type of intergrowth. Other veins include hornblende- and sphene-bearing pegmatites.
Almost certainly these marbles are of inorganic origin. No calcium carbonate secreting organisms appear to have existed during the time in which these carbonates were deposited (>1200 Ma ago). Presumably the graphite represents remains of stromatolite-like binding algae that operated in shallow water, intertidal zones. This is consistent with the presence of evaporitic minerals, such as gypsum, in Lowland marbles.
At the eastern end of the outcrop coarse diopside and tremolite are developed in almost monomineralic layers. Valley et al. (1983) showed that the breakdown of almost Mg-pure tremolite to enstatite, diopside, and quartz in these rocks requires low water activity at the regional P,T conditions. Similarly, the local presence of wollastine requires lowering of CO2 activity, presumably by H2O. These contrasts demonstrate the highly variable composition of the fluid phase and are consistent with a channelized fluid phase within a largely fluid-absent region.

Extensive roadcuts in lower part of marble.
Quartzites, kinzigites, and leucogneisses dominate. Minor marble and calcsilicate rock is present.

Large roadcuts in well-layered, pink quartzofeldspathic gneisses
Large roadcuts in well-layered, pink quartzofeldspathic gneisses with subordinate amphibolite and calcsilicate rock. The layering here is believed to be tectonic in origin, and the granitic layers represent an intensely deformed granite. The calcsilicate layers may be deformed xenoliths.

STOP 8. Anorthositic rocks on the SW margin of the Oregon Dome.
One half mile south of southern intersection of old Rt. 30 and with new Rt. 30.
On the west side of the highway a small roadcut exposes typical Adirondack anorthosite and related phases.
The glacially smoothed upper surface of the roadcut reveals the presence of three major igneous phases: 1) a dark, pyroxene-rich dike that crosscuts the anorthosite, contains anorthosite xenoliths, and contains a large irregular, disrupted mass of sulfidic calcsilicate; 2) a coarse grained, Marcy type anorthosite facies with andesine crystals 6-8" across; and 3) a fine grained anorthositic phase. Some of the coarse grained facies has been crushed and these portions bear some resemblance to the finer grained phase (note, for example, those places where fractures cross large andesine grains and produce finer grained material). However, close inspection of the finer grained material reveals the presence of ophitic texture with pyroxenes of approximately the same size as the plagioclase, and this texture and association are much better explained as igneous in origin. Therefore, the texture of the fine grained phase is interpreted as igneous in origin and may be due to chilling near the contact of the Oregon Dome massif. By contrast, large (3-4 cm) rafts of coarse grained, ophitic gabbroic anorthosite seem to be "flat" in the fine grained phase. Analyses of typical anorthositic rocks are shown in Table 5.
The pyroxene-rich ferrogabbro dike shows "soft" contacts with the anorthosite and is interpreted as essentially coeval. Zircons from it give a minimum age of 1087 Ma and, by comparison with other Adirondack anorthosites, its emplacement age is set at ca. 1135 Ma. The composition of the ferrogabbro is shown in table 5 where it is seen to be rich in TiO2 and P2O5. Similar rocks occur together with other Adirondack anorthosites and are interpreted as late, Fe enriched differentiates of a Fenner-type fractionation trend. It is suggested that further differentiation within these rocks can result in liquid immiscibility and the production of magnetite-ilmenite liquids.
The upper, weathered surface of the outcrop affords the best vantage point for studying the textures and mineralogy of the anorthositic rocks. In several places there can be seen excellent examples of garnet coronas of the type that are common throughout Adirondack anorthosites. These coronas are characterized by garnet rims developed around iron - titanium oxides and pyroxenes. Recently McLelland and Whitney (1977) have succeeded in describing the development of these coronas according to the following generalized reaction:
Orthopyroxene+ Plagioclase + Fe- bearing oxide + quartz= Garnet + clinopyroxene.
This reaction is similar to one proposed by de Waard (1965) but includes Fe-oxide and quartz as necessary reactant phases. The products are typomorphic of the garnet-clinopyroxene subfacies of the granulite facies (de Waard 1965). The application of various geothermometers to the phases present suggests that the P,T conditions of metamorphism were approximately 8 kb and 700±50°C respectively.

Minor marble, amphibolite, and calcsilicate rock.
Predominantly very light colored sillimanite-garnet-quartzfeldspar leucogneisses interpreted as minimum-melt granitic due to anatexis of kinzigite near Oregon dome anorthosite. Enclaves of spinel- and sillimanite-bearing metapelite are present

Roadcuts in garnetiferous metasediment.
To the west of the intersection are roadcuts in garnetiferous metasediment. A large NNE normal fault passes through here and fault breccias may be found in the roadcut and the woods beyond.

Entering granitic-charnockitic gneiss
Entering granitic-charnockitic gneiss on northern limb of the Glens Falls syncline. Note that dips of foliation are to the south.

Downdropped block of lower Paleozoic sediments.
Entering town of Wells which is situated on a downdropped block of lower Paleozoic sediments. The minimum displacement along the NNE border faults has been determined to be at least 1000 meters.

Silver Bells ski area to the east.
The slopes of the ski hill are underlain by coarse anorthositic gabbro that continues to the west and forms the large sheet just south of Speculator.

Entrance to Sacandaga public campsite.
On the north side. of NY Rt. 30 are quartzo-feldspathic gneisses and calcsilicates. An F1 recumbent fold trends sub-parallel to the outcrop and along its hinge line dips become vertical.

Gabbro and anorthositic gabbro.

Stop 9. Pumpkin Hollow.
Large roadcuts on the east side of Rt. 30 expose excellent samples of the Sacandaga Fm. At the northern end of the outcrop typical two pyroxene-plagioclase granulites can be seen. The central part of the outcrop contains good light-colored garnet-microcline-quartz gneisses (leucogneisses). Although the weathered surfaces of these rocks are often dark due to staining, fresh samples display the typical white vs. grey color of the Sacandaga Fm. The characteristic and excellent layering of the Sacandaga Fm. is clearly developed. Note the strong flattening parallel to layering. Towards the southern end of the outcrop calc-silicates and marbles make their entrance into the section. At one fresh surface a thin layer of diopsidic marble is exposed.
At the far southern end of the roadcut there exists an exposure of the contact between the quartzo-feldspathic gneisses of the Piseco anticline and the overlying Sacandaga Fm. The hills to the south are composed of homogenous quartzo-feldspathic gneisses coring the Piseco anticline (note how ruggedly this massive unit weathers). The Sacandaga Fm. here has a northerly dip off the northern flank of the Piseco anticline and begins its descent into the southern limb of the Glens Falls syncline.
The pronounced flaggy layering in the Sacandaga Fm. is not of primary sedimentary or volcanic origin. Instead it is tectonic layering within a "straight" gneiss. Hand specimen and microscopic inspection of the light layers, particularly, reveals the existence of extreme grain size reduction and ductile flow. Long quartz rods consist of rectangular compartments of recovered quart and annealed feldspar grains occur throughout. The rock is clearly a mylonite with its mylonitic fabric parallel to compositional layering.
The chemistry of the light colored layers in the Sacandaga Fro. indicates that they are minimum melt granites. As one proceeds away from the core of the Piseco anticline, these granitic layers can be traced into less deformed sheets arid veins of coarse granite and pegmatite. In the most illustrative cases the granitic material forms anastomosing sheets that get grain size reduced and drawn into parallelism as high strain zones are approached. The Sacandaga Fm. is interpreted as an end result of this process and represents a mylonitized migmatite envelope developed in metapelites where they were intruded by AMCG granites at ca. 1150 Ma and then intensely strained during the Ottawan Orogeny at ca. 1050 Ma. This interpretation is consistent with field relationships, the presence of spinel and sillimanite restites in the leucosomes, and with the fact that similar metapelitic rocks are crosscut by ca. 1300 Ma tonalites. The latter observation makes the Sacandaga Fm. protoliths older than the ca. 1150 Ma granitic rocks in the Piseco anticline and makes an intrusive relationship obligatory despite the conformable contact at the south end of the road cut.

Core of the Piseco anticline.
All exposures are within the basal quartzo-feldspathic gneisses at the core of the Piseco anticline.

Re-enter the Sacandaga Fm. Dips are now southerly.

Southerly dipping pink, quartzofeldspathic gneisses with tectonic layering
In long roadcuts of southerly dipping pink, quartzofeldspathic gneisses with tectonic layering. The coarse grain size of the gneissic precursors can be seen in many layers.

A11: MIDDLE DEVONIAN TEMPERATE WATER BIOHERMS OF WESTERN NEW YORK STATE (EDGECLIFF MEMBER, ONONDAGA FORMATION)
THOMAS H. WOLOSZ
Center for Earth & Environmental Sciences
SUNY College at Plattsburgh
Plattsburgh, N.Y. 12901
DOUGLAS E. PAQUETTE
Safety and Environmental Protection Division
Brookhaven National Laboratory, Building 535A
Upton, Long Island, N.Y. 11973
The bioherms of the Edgecliff member of the Onondaga Formation are a well known feature of the geology of New York State and the Niagara Peninsula in Ontario, Canada. Over the past thirty to forty years, the Onondaga and its bioherms have been the subject of a number of studies which have greatly increased our understanding of this unit (see Bren and Ver Straeten (1994) for references).
As is the case with "reefy" limestones in general, the Edgecliff has been assumed to represent a warm, tropical, shallow water environment. However stromatoporoids and calcareous algae are rare in the Edgecliff which is unusual for Devonian reefal limestones. The absence of these organisms lead Kissling and his students (Kissling and Coughlin, 1979; Cassa and Kissling, 1982; Kissling, 1987) to interpret these bioherms as deep water structures. The absence of an obvious peritidal facies in the Onondaga was also cited as supportive of a deep water interpretation, suggesting that the shallow water facies which rimmed the basin have since been removed by erosion. More recently Wolosz (1990, 1991) has argued that shallow water facies are present, but have gone un-noticed since they do not fit the standard model for tropical carbonate peritidal facies. However, over the past fifteen years there has been increasing paleontological evidence that the "reefy" Edgecliff Member of the Onondaga Formation represents an example of Devonian temperate water deposition (Koch and Boucot, 1982; Blodgett, et al., 1988). Stromatoporoid biogeographic data and isotopic analyses which further support the temperate water hypothesis are included in this field trip guide.
The field trip will examine a series of Edgecliff bioherms, which are interpreted as representing an onshore to off-shore trend in biohermal development for this temperate water Devonian limestone.

STOP 1. Roberts Hill Reef.
NOTE: Private Property. DO NOT enter without first obtaining permission at house on north side of hill.
Roberts Hill Reef is the best known example of a Successional Mound in the Edgecliff, and has been described in detail by Wolosz (1985). This exposure allows for examination of the typical Edgecliff bioherm growth pattern of interbedded Colonial Rugosan and Favositid/crinoidal Sand Paleocommunities.
The outer edge of a central rugosan mound is exposed along the east side of a small valley which runs southwards across the hill, while the west side of the valley exposes bedded packstone flank beds with large favositid colonies. Further to the east, south and southeast a second stage of rugosan growth (Recolonization Stage of Wolosz (1985)) can be observed to cap the flank beds. This cyclic intergrowth of paleocommunities was controlled by sea-level fluctuation. Evidence for changing turbulence levels during reef growth can be directly observed at the outcrop and includes the following: 1) development of rubble apron along the northeast side of the hill which wedges out into the flank beds between the two stages of rugosan growth. This facies is dominated by the small solitary rugosan Cystiphylloides, and is interpreted as the result of an extreme shallow water stage during which the top of the mound was covered by a meadow of these small solitary rugosans. Interpretation of water depth is based on the similarity of this facies with the shallow water Cystiphylloides biostromes at Thompson's Lake Bioherm and in the Port Colbome area. 2) A rubble ring surrounding the central rugosan core and large overturned favositids in the adjoining flank beds. 3) Pods of colonial rugosan rubble at the toe of the Rugosan Recolonization Zone at the southernmost edge of the reef along the east cliff face of the hill. The large colony fragments in these rubble pods indicate elevated turbulence levels during the demise of the reef.
This reef is also tightly cemented with little observable porosity as is common for the eastern reefs of the Edgecliff.

STOP 2. Albrights Reef
NOTE: Private Property. DO NOT enter without first obtaining permission at house on north side of hill.
This exposure is a small erosional remnant of a large successional mound similar to Roberts Hill (Wolosz, 1985). It is an important exposure because it offers an excellent cross-section through the rugosan mound itself, exposes the basal contact of the mound with the underlying Edgecliff C1 facies, and allows direct observation of the successional patterns among the rugosan fauna during development of the mound.

STOP 3. North Coxsackie Reef
NOTE: Private Property. DO NOT enter without first obtaining permission at house on north-west side of intersection of Route 102 and 106 (approx. 0.7 mile south).
The North Coxsackie reef (Figures 11 and 12) is rooted in Edgecliff crinoidal grainstone/packstone- the C1 unit is absent. The main mass of the reef is a Composite Thicket/Bank reef roughly 280 meters long (north-south)by 220 meters wide (east-west) with an estimated thickness of 15 meters. Volumetrically, the Favositid/Crinoidal Sand Paleocommunity dominates this reef, having formed a bank, with beds dipping gently (5 to 12 degrees) away from the center of the structure. Interbedded with the favositid/crinoidal sand facies are two roughly 0.3 meter thick horizons of the Phaceloid Colonial Rugosan Paleocommunity - each representing a single thickening event which covered the entire mound. These thickets are dominated by Cyathocylindrium, although Cylindrophyllum and Acinophyllum are common.
A cliff along the northwestern edge of the reef exposes an approximately 6 meters thick by approximately 60 meters long Acinophyllum mound, underlain by crinoidal grainstone/-packstone. This small structure is located to the west of, and stratigraphically just above, a well defined rubble horizon exposed along the northeastern edge of the main reef, indicating that it grew on the down-current side of the mound. This mound is similar to the early Acinophyllum stage of reef growth exposed at Albrights reef, with the exception that the calci-silt-packstone matrix surrounding the corallites is more finely bioclastic, containing debris transported from the larger mound to the south.

STOP 4. Thompson's Lake Bioherm
NOTE: Private Property. DO NOT enter without first obtaining permission at house to the southwest of hill on Route 157.
This exposure has been described by Williams (1980), who divided the exposure into eleven different micro-facies, discussion of which is beyond the scope of this report. Simply put, most of the small elongate hill is made up of packstone with abundant favositid colonies. Along the roadcut two small rugosan mounds can be observed (Figure 13), underlain by roughly 2.6 meters of Edgecliff biostromal deposits, including a well developed Cystiphylloides biostrome which can be followed around the entire hill as a recessive bed. These facies are analogous to the shallow water deposits found near Port Colbome, Ontario, Canada as described in the text.
The underlying contact with the Schoharie Formation is easily observable, and represents initial shallow water deposition with grainstone as the basal Edgecliff facies.

STOP 5. Mt. Tom Reef.
The reef makes up the large hill to the south of the road.
NOTE: Private Property. DO NOTenter without first obtaining permission at house at intersection of Koenig and Mt.Tom roads. Examination of Mt.Tom #6 requires permission from farm on Koenig Road to the north of hill. Examination of Mt.Tom #2 requires permission from Mercy Hill Farm.
Paquette and Wolosz (1987) argued that three reef exposures- the Mt.Tom, Mt. Tom #2, and Mt. Tom #6 - represent the extensively eroded remains of a single large mound/bank reef. The .6 by .8 km. areal extent of this structure would make Mt. Tom both the largest exposed Edgecliff reef and the only known surface exposure of this reef type (these reefs are commonly referred to as pinnacle reefs in the subsurface).
The mound\bank nature of Mt. Tom #1 is displayed in the cliff face along the southeast side of the hill. The reef is underlain by the basal Edgecliff calcisiltite, with the base of the reef marked by thickets of Acinophyllum. Small phaceloid colonial rugosan mounds (again, mainly Acinophyllum) can be observed along the cliff near the base of the reef. These small mounds and thickets coalesced to begin the formation of the larger structure. Dominance of the initial large mound shifted between Acinophyllum and Cylindrophyllum prior to onlapping by the crinoidal sands of the favositid/crinoidal sand paleocommunity. A second mound stage made up of Cylindrophyllum thickets overlies these grainstones and packstones. In turn, the second mound stage is itself onlapped and eventually swamped by the favositid/crinoidal sand paleocommunity (exposed further back on the top of the hill, not shown in Figure 2). Overall, Mt. Tom #1 is roughly 18 m thick as preserved.
Wolosz and Paquette (1988) have interpreted this mound\bank\mound\bank pattern as catch-up\fall back cycles controlled by fluctuations in water depth above the top of the reef. It is important to note that the second mound building stage at Mt. Tom #1 does not drape the entire pre-existing structure, but is instead restricted to the top of that structure. In effect, during bank stage, the reef was a high relief platform on the sea-floor with its top within the ecologic mound building zone of the colonial rugosans. Upward growth of the reef is mainly due to the repetitive establishment of new mounds on the top of the platform. As sea-level was approached, the mound building colonial rugosans were overwhelmed by increased turbulence conditions and the mounds onlapped by encroaching crinoidal sands producing a bank stage; but with sea-level rise the mounds became re-established. This shifting between rugosan mound/thicket construction and the favositid/crinoidal sand paleocommunity has been attributed to a water turbulence controlled community succession (Wolosz, 1992b).
Following the initial mound building stage, lateral growth of Mt. Tom appears to have been due mainly to deposition of crinoidal debris flanks with occasional small mound structures (satellite mounds) growing in those flanks (see discussion of Mt. Tom #2).
Diagenetic patterns in Mt. Tom are similar to those in subsurface pinnacle reefs. The initial mound facies (base of reef) is tightly cemented, as is Mt. Tom #2; while the upper parts of the reef and Mt. Tom #6 exhibit a small primary porosity.

STOP 6. Mt. Tom #6
Mt. Tom #6 forms the low, wooded ridge to the southwest of Mt.Tom Road.
Mt. Tom #6 is a small ridge which consists mainly of bedded crinoidal grainstone/packstone. Randomly distributed small overturned favositids are common as are both solitary and phaceloid rugosans, but no evidence of mound formation is present. Topographically, Mt. Tom #6 is at the same elevation as the present top of Mt. Tom. Since the regional southwest dip of about 18 meters/kilometer (Rickard and Zenger, 1964, p.5) would not greatly alter this topographic relationship, the elevations of the Mt. Tom #6 exposure and the top of Mt. Tom were probably also equivalent at the time of deposition. However, when one observes Mt. Tom #6 from Collins Road (see map, Figure 14), the questa-like nature of this small ridge is evident, with the dip slope pointing to the north-northwest, directly away from the main mass of Mt. Tom.
Paquette and Wolosz (1987) cited this as evidence that the two exposures are parts of one reef, with Mt. Tom #6 consisting of distal flank beds. Mt. Tom reef would then be at least 0.8km. long on an northwest axis from Mt. Tom #1 to Mt. Tom #6.

STOP 7. Mt. Tom #2 Reef.
Leave cars and proceed east from the intersection. Mt. Tom #2 forms the low hill to the south of the small creek, and numerous small outcrops may be examined along the south side of the creek valley or on the hill itself. A small quarry on the northwest edge of the hillside exposes bedded Edgecliff facies, while a small rugosan mound is located just to the southeast of the quarry among the trees. In contrast to Mt. Tom #2 lies to the west of Mt. Tom #1 and is topographically roughly 18 meters below #6. Stratigraphically older beds can be examined here, with the Edgecliff/Carlisle Center contact marked by the appearance of a spring just east of the intersection of Collins and Geywittz Roads. A small quarry visible from the road exposes bedded Edgecliff with overturned colonial coral. To the southeast of this quarry is an exposure of a small colonial rugosan mound roughly 17 meters across and of indeterminate thickness. East from the quarry, along the south side of the creek, there are numerous outcrops of bedded crinoidal grainstone/packstone with abundant favositids. Small patches or lenses of colonial rugosans within the bedded packstones are common, and represent small satellite thickets or mounds which appear to range stratigraphically from near the C1/C2 contact (roughly the point at which growth of Mt. Tom #1 began), upwards to about 6 meters above that contact. The packstones surrounding these upper mounds dip away from Mt. Tom #1 at roughly 15 degrees.

B1:THE GEOLOGY OF CLARKSVILLE CAVE, ALBANY COUNTY, NEW YORK
Paul A. Rubin
909 County Rt. 2
Accord, NY 12404
SECTION A: Modification of Pre-Woodfordian Caves by Glacial Meltwater Invasion in East-Central New York
Periods of high glacial meltwater have altered some preglacial cave-passage configurations. Floodwater and fossil karst features, whose formation cannot be explained based on available water from the surrounding watershed, are found superposed on actively forming cave passages. These features may be recognized through correlation of watershed boundaries, peak-runoff observations through a cave system, the presence of anomalous in-cave and surface features, and the geomorphic interpretation of the area in question. Knowledge of minimum rates of karstification may be used to infer climatic conditions, making possible the reconstruction of the hydrology associated with deglaciation.
Clarksville Cave, situated in the hamlet of Clarksville, New York, provides an excellent example of invasion by Wisconsinan meltwater on a pre-Woodfordian cave system. Vadose development of a major part of the explored cave has occurred preferentially aslant a thrust-fault ramp, often along a calcite bed/limestone contact created by pressure solution. Other fault-related features include slickensides, extension veins, fault-bend folds, stylolites and the repeated basal Onondaga Limestone and impermeable Schoharie Formation thrust below the Onondaga Limestone stratigraphic column. An imbricate thrust east of the cave has up thrown the Esopus Shale against the Onondaga Limestone, forcing the development of an inefficient resurgence at the base level Mill Pond.
During the Wisconsinan glacial stage, subglacial meltwater formed a series of now abandoned bedrock channels and paleo-gorges that, due in part to topographic controls, found outlets along and over the flank of the Helderberg Escarpment. Some of this meltwater was pirated into Clarksville Cave where inefficient outlets resulted in the formation of higher in-cave "intermittent phreatic" levels not controlled by the thrust fault. These levels abruptly truncate and grade to lower vadose passages. The character of these upper levels, the paleo-gorge and related caves, and elevated paleo-insurgence points correlate with described alpine karst settings.
SECTION B: Flow Characteristics and Scallop-Forming Hydraulics within the Mill Pond Karst Basin, East-Central New York
This is a study of the hydrology of Clarksville Cave and the headwaters of the Onesquethaw Creek, situated in the hamlet of Clarksville, New York, specifically the Mill Pond karst basin. During most of the hydrologic year, water entering that pan of the watershed that is downstream of the Wolf Hill Dam is pirated into the Onondaga Limestone. Tracer tests and in-cave stream gaging indicate that extreme conduit conditions are present in the aquifer, with a maximum water velocity on the order of 5.3 km/hr.
It has been hypothesized that a submerged conduit must lie covered by breakdown blocks at the cave's northern terminus. Having established a known peak flow, a modified version of the Darcy-Weisbach equation was used to accurately calculate the minimum diameter of this conduit. Knowledge of the structural geology throughout the watershed, coupled with a detailed leveling survey in the cave, permitted reasonable estimates to be made for the two unknowns in the equation. A submerged conduit was subsequently opened and explored.
Scalloped cave walls are present in Perry Avenue (Fig. 3) at a key stream gaging location. Backflooding occurs behind inefficient passage constrictions a short distance downstream of, but not up to, this station. Evidence exists that documents that only long return-interval flood stages cause backflooding to this station. This situation permits a reasonable estimate of the maximum discharge and flow velocity responsible for scallop formation. Scallop wavelengths were measured below the elevation of peak floodwaters. By inputting measured values for discharge and flow velocity into published equations, it was possible to back calculate scallop Reynold's numbers that favorably correlate with measured flow velocities and discharges. A possible revision of the scallop Reynold's number is suggested when it is utilized in the determination of paleoflow velocities. It also appears that scallop wavelength is partially determined by the properties of the rock comprising the walls of the conduit.

B1:THE GEOLOGY OF CLARKSVILLE CAVE, ALBANY COUNTY, NEW YORK

STOP 1. Clarksville Cave
Turn right into parking area for June's Place restaurant. Proceed to upper parking area behind June's. Clarksville Cave is a popular caving location in the Albany area. Always cave with experienced cavers, dress warmly, wear a hardhat with a chin strap, and carry three sources of light (one preferably mounted on your helmet to free your hands for climbing). Do not attempt to pass through Brinley's Sump when there is little or no air. Under these flow conditions, the Gregory Entrance is sumped shut and a through trip is not possible. Failure to follow standard safety procedures has resulted in numerous rescues, mobilization of multiple rescue teams, ambulances, and the press.

B2: BUILDING STONES OF SCHENECTADY, NEW YORK
JANET B. HOLLOCHER
2208 Barcelona Rd.
Schenectady, NY 12309
KURT HOLLOCHER
Geology Department
Union College
Schenectady, NY 12308
Introduction
The building stones of downtown Schenectady contain some of the best examples of rock types and medium- and small-scale geologic features that the general public can readily view. Within easy walking or driving distance are high-quality rocks of many types, some of them carefully polished and beautifully displayed. There are buildings made with igneous, sedimentary, and metamorphic rocks that include oxide rich gabbro, porphyritic granite, crossbedded sandstone, fossiliferous limestone, marble, gneiss, and partially melted migmatite. During this half-day trip, we will tour the downtown area to view the most interesting building stones, to see what minerals, fossils and other features they contain, to infer the geologic processes that formed them.
The aim of this trip is to help people to learn more about geology, just by spending a few hours in downtown Schenectady (Figure 1). Anyone who is interested in geology can observe rock types and features on his own, without a guide, and without traveling miles on rural roads, bushwhacking through woods and swamps, or stopping next to busy highways. Those who examine urban building stones can sharpen their powers of observation and learn to recognize a wide variety of rock types, minerals, features, and fossils. BRING HAND LENSES!
Each block of building stone, or each panel of facing stone, is one small window into the past. However, there are some important things to remember when looking at building stones. First, remember that all of the rocks you are looking at came from somewhere else. The geologic history that they record within them happened in another place. Second, many buildings contain rocks of several types, so as to juxtapose geologic events from different places and different times. No matter how closely adjacent stones may seem to match one another, we can not, in a strict sense, prove that they were ever connected in their original positions. However, it is a reasonable assumption that similar stones from the same building came from the same formation or body of rock, and possibly came from the same quarry. While the overall arrangement of the stones in a building has no geological meaning, we can gain knowledge about the original rock as the sum of observations made on individual stones.

B2: BUILDING STONES OF SCHENECTADY, NEW YORK

STOP 1. Nott Memorial.
Note the various building materials that comprise this structure, from foundation to roof. The foundation appears to be made of gray granodiorite. The abundant wall stones are gray lithic sandstone that may be Devonian in age, from the Catskill Delta, or Ordovician, from the Schenectady Formation. The columns are of pink granite and gray granodiorite. The light-colored cross bedded quartz sandstone on the steps is probably the Berea sandstone from Ohio.

STOP 2. Memorial Chapel.
This building, constructed after World War I, has been here long enough to demonstrate the effects of weathering on rock. The columns in front of the building are made of calcite marble. Notice that the surfaces of the marble facing the building are smooth with sharp edges. The surfaces facing away from the building are rougher and the edges more rounded, a result of chemical and mechanical weathering on the side exposed to the elements. The steps are gray granitic rock, made of quartz, biotite, and feldspar.

STOP 3. Webster House, SW comer of Union campus.
This building was once the library for the City of Schenectady. The steps and foundation are made of muscovite granite with at least one inclusion of foliated muscovite granite. The sides of the steps are made of a fossil hash limestone, composed of broken pieces of shells, crinoids, and bryozoans. The kinds of fossils and the relatively uniform grain size suggest that they were deposited in a shallow marine environment by relatively uniform currents. The columns on the front of the building are pink granite similar to that quarried on Deer Isle, Maine. The granite has a "rapakivi" texture, which consists of pink microcline phenocrysts with rims of white albite. rapakivi is a Finnish name meaning approximately "mud rock", after the crystal-bearing soil that commonly develops on rapakivi granite. Other minerals include black biotite and quartz.

STOP 4. 600 Liberty Street
This building has decorative facing stones of muscovite quartzite. This is a metamorphic rock composed mostly of quartz, and with some muscovite, tourmaline, and pyrite. Rocks similar to these are found in the Adirondacks and in New England. The original rock, or protolith, was most likely a quartz-rich sandstone or quartz conglomerate that contained some clay, iron sulfide, and probably organic matter. During metamorphism, under the influence of heat and pressure, the quartz grains in the sand recrystallized into quartzite, while the clays and associated sulfides were transformed into layers composed of muscovite, tourmaline, and pyrite.
Thanks to the varying placement of the stones, one can observe the layers from the side and also face-on. Most of the stones have been placed with the layering horizontal, so that you see contrasting layers that are relatively rich in quartz or in muscovite. Some stones are oriented with the layering vertical and parallel to the building face, so that the stones look sparkly and the long, black tourmaline crystals are easily visible on the surface.
Some of the quartzite is colored pinkish red by weathering pyrite, which leaves cube-shaped cavities behind. One can still see pyrite cubes in some of the stones. Into other cavities, quartz crystals have grown and their prismatic shapes are visible. On the southernmost section of quartzite facing, quartz veins can be seen, some containing quartz boudins - strong quartz layers around which other, weaker rock has deformed.

STOP 5. 600 Franklin Street.
This one-story modern building has a facade of sandstone that is stunningly fossiliferous. Probably from a Paleozoic shoreline environment, where rich shell beds lay near a sandy beach, this rock is full of fossils. Look for large and whole brachiopods, pelecypods, and gastropods (up to 6 cm across). Note that many of the blocks are darker (browner or redder) and more porous near their periphery. This "weathering rind" probably formed along joint surfaces through which ground water flowed. The ground water gradually dissolved away some calcite, making the rock porous with abundant fossil molds. The joints also broke the rock into slabs, which were later subdivided into blocks for building.

STOP 6. Schenectady County Office Building,
The facade of this modern building contains three types of building stone. At the Veeder Avenue entrance, the steps and low enclosing wall are made of coarse, gray granite which contains white plagioclase, pink K-feldspar, hornblende, and gray quartz.
The red facing stone around the Veeder Avenue entrance is an oxidized granite. The oxidized iron, as hematite, gives it a red color. Look closely at the quartz to see its bluish cast, an effect that is commonly produced by the presence of sub-microscopic rutile crystals that scatter blue light. The presence of blue quartz suggests a special temperature history for the rock. Titanium, in the original magma, was included as a minor dissolved impurity in quartz as it crystallized. If the pluton had cooled relatively quickly, over tens of thousands of years, titanium would have remained dissolved in the quartz. However, this pluton either cooled much more slowly, or the pluton was reheated to moderate temperatures and slowly cooled long after the pluton was solid. Over this long time at moderate temperatures (∼400°C), titanium dissolved in the quartz nucleated and grew as tiny rutile crystals.
The retaining wall and the low walls parallel to Veeder Avenue and enclosing the Albany Street entrance are made of gray diorite, a plutonic igneous rock that contains much less quartz and K-feldspar than granite, and more sodium- and calcium-rich plagioclase. This diorite contains fine-grained xenoliths, which look like dark blobs. They may be "auto-inclusions", inclusions of finer-grained (more rapidly cooled) portions of the same magma, which was later fractured and mixed with adjacent magma.

STOP 7.County Courthouse, Albany Street.
The walls next to the sidewalk are biotite granite. The dark, sparkly flecks are the mica biotite, which are the next most abundant mineral after feldspar and quartz. The steps of the Courthouse are muscovite granite, which is similar to the biotite granite but it also has shiny flakes of colorless muscovite.
The columns and pediments of the Courthouse are made of limestone. First, look at the middle pediment on the left as you face the Courthouse. Notice the layers in this rock. In the lower half of this pediment, the layers are slanted; in the upper half, the layers are horizontal. The slanted layers are called cross-beds. Inspection of the rock with a hand lens shows that it is made largely of small fossil fragments. Many of the fossil fragments are rounded, suggesting abrasion during transport in water. The fact that most of the particles are of similar size suggests deposition by relatively even currents water. These observations might lead us to interpret that this rock originated as deposits in tidal channels or deltas on a carbonate bank, such as might be found in the present day Bahamas.

TOP 8. St. Joseph's Church, Albany Street.
This brick church has four types of building stone. The lowest foundation stone is a gray-green sandstone. Notice the pattern of closely spaced horizontal lines made by cutting tools on many of the block surfaces. Notice, too, that some of the blocks have another, less regular pattern of horizontal lines or grooves, thicker than the tool-cut pattern. These are "plane beds", horizontal layers made when sand is deposited in fast-moving streams or currents. These may be Devonian sandstones from the Catskill Delta.
Capping the lower foundation stone is a lighter-colored fossiliferous limestone that contains bryozoans. The steps of the church are made of coarse-grained, gray, biotite granite. Atop the stones that flank the steps are blocks of fossil hash limestone.

STOP 9. 504 State Street.
The large panels of facing stone that cover the entryway are made of marble. Look for panels that contain large and dramatic folds that are highlighted by gray patches and layers in the white rock. The black specks and gray areas are graphite, formed by the metamorphism of organic matter that was present in the original limestone. The sparkly mineral is the brown mica, phlogopite, a magnesium-rich biotite. The elongate, colorless to light brown crystals in the marble are the mineral actinolite, an amphibole similar to hornblende. Its presence indicates that high temperatures were reached during metamorphism.
Outside the entryway, note the foundation stones composed of fossil hash limestone. Notice that this limestone is coarser - the fossil fragments are larger - than in fossil hash limestones at previous stops. Notice, too, the shapes of the fragments. Many of them are rounded, indicating that the fragments have been abraded during transport.
Around the corner on Clinton Street, look at the blocks of limestone and the orientations of the layers within them. Notice that some blocks contain slanted cross-beds. In one block, a flat-lying fossiliferous layer truncates, or cuts off, the cross-beds in a lower layer. This sedimentary feature is typical of channel fills - channels that have cut into underlying layers that are then filled in with sediment.

STOP 10. Key Bank, 436 State St.
The foundation stones on the outside of this building are made of rapakivi granite. Look closely and you will see large crystals of feldspar, much larger than the other crystals in the rock. These large crystals are called phenocrysts, and they crystallized from the slowly-cooling magma. Later, more rapid cooling caused crystallization of the smaller crystals that make up the matrix to the phenocrysts.

STOP 11. 340 State Street.
The facing stone on this building is made of a granitic migmatite that contains the minerals K-feldspar, quartz, plagioclase, and biotite. This rock is composed of two parts: a metamorphic component and an igneous component that are closely associated. The metamorphic component is a layered gneiss that is separated into blocks by dikes and other small bodies of unlayered granite and granitic pegmatite. The gneiss has the same mineralogy as the granite, and it contains fine-grained dark inclusions that look like igneous xenoliths. This evidence suggests that the gneiss was once a granite, was then metamorphosed to form the gneiss, and metamorphism reached high enough temperatures so that the rock partially melted (∼800°C). Deformation while the rock was partly liquid caused segregation of the liquid into fractures, which became the granite and pegmatite dikes when they crystallized during cooling.
Buildings were replaced after 1995.

STOP 12. 332 State St.
The base of this building is made of a fine-grained biotite granite, over which is a fossil hash limestone.
Buildings were replaced after 1995.

STOP 13. TrustCo Bank, 320 State St.
This building has columns of pink biotite granite and slabs of polished red granite. The latter is particularly interesting. It contains large, gray to white plagioclase crystals that contain concentric layers within them having slightly different appearance. The layers formed as the crystals grew while suspended in the granite liquid. Some of the pink K-feldspar crystals have rims of white albite, which is the rapakivi texture described above. The zoning and rapakivi textures indicate physical changes in the magma during growth of these crystals, changes that may have included temperature, pressure, water content, or the chemical composition of the liquid during mixing with other magma or during crystallization of the liquid.

STOP 14. Rudnick's, 308 State St.
This storefront is faced with a granitic gneiss: a metamorphosed light-pink or tan granite. If you look carefully, you will see that the rock has a weak foliation that is defined by the parallel orientation of elongated crystals, including feldspar augen. Augen formed during deformation from pre-existing large crystals in the granite protolith.

STOP 15. Fleet Bank, 306 State Street.
Although the source of this rock is unknown, it looks just like the Whiteface Mountain facies of anorthosite from the high peaks region of the Adirondacks. Anorthosite is an igneous rock composed mostly of dark- to light-gray plagioclase with small quantities of black pyroxene and perhaps a few other minerals. Undeformed Adirondack anorthosite contains large dark-gray plagioclase crystals up to 30 cm long, and commonly 10 cm long. The dark color is caused by dust-sized ilmenite that formed in the plagioclase during cooling. When the original anorthosite was deformed, the edges of the gray plagioclase, and sometimes whole crystals, recrystallized into smaller light-gray or white plagioclase crystals that are free of ilmenite dust. In some of the less deformed parts of this rock you can see nice, big dark-gray igneous plagioclase crystals, and interlocking plagioclase and pyroxene crystals that have the original igneous texture. If you look closely at the dark-gray plagioclase crystals, you may see the blue iridescence that this variety of plagioclase is famous for.

STOP 16. Olender Furniture, 260 State Street.
The front of this building is made of polished muscovite-biotite granite. The interesting thing about this rock is that, if you look closely with a hand lens, you will see occasional dull pinkish-tan crystals up to 2 mm long. These are crystals of allanite, a member of the epidote family that is extremely rich in rare earth elements and the radioactive elements uranium and thorium. Over geologic time, the uranium and thorium cause sufficient radiation damage to the allanite crystal lattice to destroy it. The result is a glass that weathers easily to the pink material you see. Fresh allanite is dark brown and shiny. This granite is probably no more radioactive than the other rocks you have seen today, it just has larger (but fewer) crystals that contain these ubiquitous radioactive elements. This rock also contains small xenoliths, or perhaps auto-inclusions, and big, white K-feldspar phenocrysts.

STOP 17. 224 State Street.
The face of this building is composed of pink biotite granite that contains several xenoliths. Besides these and the zoned feldspars, the most interesting aspect of this rock is that it contains numerous, brownish-red crystals of sphene up to 3 mm long that are shaped like elongated diamonds. The name sphene is derived from the Latin word for wedge, which these pointy crystals resemble. Sphene is useful for radiometric dating, and is one of the second author's favorite minerals.

STOP 18. Fleet Bank, 216 State St.
The facing stone of this entryway is composed of an almost black gabbro, an iron- and magnesium-rich rock that is rare as a building stone. The bulk of the rock is composed of dark-gray plagioclase, up to 5 cm long, and black clinopyroxene. These form an interlocking, igneous texture. If you look at a low angle at the highly polished surface, you will see that some patches of crystals are very shiny, like metal. If you look closely at these metallic patches, you will see that there are two different minerals present. One is more shiny and better polished. This is ilmenite which, in large concentrations, is the principle ore mineral of titanium. The other is somewhat duller and more poorly polished. This mineral is magnetite, and its poor polish is caused by its four good cleavage planes. The intersecting cleavages make numerous tiny triangular pits on the surface that are difficult to polish away. Ilmenite and magnetite both crystallized from the magma, are both oxide minerals, and are both natural semiconductors. This building also has fossil hash limestone and biotite granodiorite. The granodiorite contains phenocrysts of white feldspar.

STOP 19. Curb stone at the intersection of Mill Lane and State St.
This rock is a granitic gneiss that has a peculiar texture. Most of the mineral grains are rather small and form closely-spaced layers. The most obvious grains, however, are white feldspars that have angular or broken shapes. This is a particular kind of gneiss known as a mylonite. Mylonites are fault rocks in which fault deformation was by slow ductile flow instead of by brittle fracture. This rock was deformed enough to recrystallize the quartz and micas, but the large, strong feldspars remain intact enough to give an indication of the original grain size of the granite.

STOP 20. YMCA, on the south side facing State St.
The lower part of the building is made of highly fossiliferous limestone, in which can be seen bryozoans, crinoids, brachiopods, and gastropods. Some of the stones have layering, both horizontal plane beds and cross beds. These indicate that this rock was deposited in a near shore carbonate bank environment in which currents, possibly driven by the tides, transported and deposited the fossils.

STOP 21. Washington St. at Rotondo Park.
The stone wall at this Mohawk River overlook is composed mostly of fine-grained dolomitic limestone. The limestone is made of fine-grained, gray calcite mud, with irregular layers and patches of coarser-grained, brownish dolomite. The dolomite fills ancient worm burrows and bioturbated horizons in the rock.
In addition, the lower part of the wall on the west side contains some blocks of fossil-rich limestone that contain large brachiopods and tabulate coral. There are also some blocks of gray Schenectady Formation lithic sandstone, one of which has exposed flute casts that were formed by the swift turbidity currents that deposited the sandstones.

STOP 22. 21 Front St.
This house contains an excellent example of a red sandstone. With a hand lens you will be able to see that the rock contains abundant translucent white and pink feldspars in addition to gray glassy quartz and mica. The abundant feldspars mean that this sandstone is classified as an arkose (Figure 2), the grains for which were derived from coarse-grained igneous or metamorphic rocks, and were transported a relatively short distance prior to final sedimentation and lithification into rock. The red color strongly indicates that this sediment was originally deposited on land, which allowed oxidation of the iron to form the red hematite pigment. This rock was probably quarried from Mesozoic red beds in the Connecticut River basin or in the NewarkDelaware basin farther south.

STOP 23. First Reformed Church
This church was originally built in 1862, but was damaged by fire and rebuilt in 1948. The foundation to this church is made of highly fossiliferous limestone that contains abundant bryozoans, brachiopods, tabulate and rugose corals, crinoids, and cephalopods.
The front of the church has steps made of slate, probably from the Taconics in New York or Vermont. The pillars are made of pink granite, containing pink K-feldspar, white albite, clear gray quartz, and black mafic minerals. Several xenoliths can be seen. The coarse-grained red sandstone surrounding the doors is feldspar-rich arkose similar to that at Stop 22. The brown sandstone, which is carved into the forms of corn, grapes, wheat, pine, and oak, is a quartz sandstone in which most of the grains are glassy quartz. In both sandstones the coloring agent is hematite.
The step below the doorway on the east side near the front of the church is a different fossiliferous limestone that contains abundant gastropods up to 4 cm across. This rock also contains thin, black fragments of trilobite shells and sub-spherical ostracods (?).

STOP 24. St. Georges Episcopal Church.
In the cemetery next to this church one can see the results of differential weathering. Compare in particular the weathering of marble and red sandstone of stones of similar age.
The stone around the front door is made of fossiliferous limestone that includes beautiful examples of brachiopods, rugose coral, bryozoans, trilobite fragments, crinoids, and fine-grained rip-up clasts that were probably broken up and transported during storms. Some of the rip-up clasts contain thin layers that were probably deposited by algal mats on the floors of quiet lagoons. Most of the church is made of gray sandstone that weathers brown.

STOP 25. First Presbyterian Church, 209 Union St.
This building contains red quartz sandstone and blocks of gray sandstone, probably from the Schenectady Formation. The building next door is the Turnbull House. It is made of a red quartz sandstone that has numerous peculiar pockmarks up to 4 mm across. Many of the pockmarks have a rhombic (diamond) shape that is reminiscent of the crystal form of calcite. Calcite was probably the first cement in this rock, which was then followed by a more durable cement such as quartz. When the sandstone blocks were exposed to the weather, the soluble calcite gradually dissolved, and the sand grains which the calcite held in place fell out, leaving the pits.
The steps of this building are made of red arkose, in which can be seen numerous black grains which are sand-size grains of the fine-grained metamorphic rocks slate and phyllite. The presence of both feldspars and low-grade metamorphic rock fragments indicates a nearby source area for the sand that was made up of igneous and low-grade metamorphic rock.

STOP 26. 220 Union St., Van Antwerp house
This old house has a variety of different kinds of slate on its roof. The colors of the slates include black, red, gray, green, and purple. The different shapes, thicknesses, and edge treatments clearly show that the slates had different sources, and were probably periodically replaced to make repairs. The rusty-weathering slates are probably from Pennsylvania, whereas the others are probably from the Taconics in Vermont or New York.

STOP 27. 108 Union, the old Schenectady Court House.
The steps are made of gray sandstone that has interesting parallel grooves on their sides. These grooves are formed as the plane beds in the sandstone weather out at different rates because of different grain sizes or different cements in alternating layers. The blocks to the sides of the steps are made of fossiliferous limestone that contains tabulate and rugose corals, brachiopods, and other fossils. An excellent tabulate coral can be seen to the left of the steps, and a large cephalopod fragment can be seen just to the right of the steps.

The facing stone beneath the windows is marble. This marble is particularly interesting because it contains stylolites- very wiggly, sub-parallel sets of black lines in the rock. Stylolites form as fractures or other surfaces in the rock, along which water flowed during burial or low-grade metamorphism. The water dissolved some of the calcite, and left the dark insoluble material behind. Dissolution does not form a flat surface, but rather develops interdigitating calcite fingers on either side of the solution surface. This is what makes the stylolites so irregular. The fingers point in the direction of the maximum compressive stress that was acting on the rock during stylolite formation. This building also has muscovite-biotite granite facing some portions, and blocks of very fine-grained fossil hash limestone with visible bedding.

STOP 29. 225 State St.
The facing below the windows of this building is black slate. The surface of the slate is the natural texture that formed when the slate was split along its excellent cleavage. The cleavage of slate is caused by the parallel alignment of muscovite and chlorite, which themselves have an excellent mineral cleavage. The sections of the building between the windows are faced with biotite granite, which contains rare, large feldspar phenocrysts.

STOP 30. Mr. James Salon, 249 State St.
The beautiful polished green stone on the outside of this building is a chlorite schist, rare in building stone because it is quite soft and hard to polish. If you look closely, you will see dark red garnets up to 4 mm across in this lovely rock. The most striking thing about this rock is its wavy "grain". The principal grain is a strong foliation of parallel-aligned chlorite crystals. This foliation was developed by deformation during metamorphism. At the time it was formed, this foliation was probably quite planar. The rock was later deformed twice to form two sets of small "crenulation" folds that are similar in size, shape, and appearance to the corrugated paper of a cardboard box. This rock therefore gives clear evidence of three episodes of deformation during metamorphism. Different episodes of deformation probably indicate different episodes of the mountain building event that caused the metamorphism.

STOP 31. Schenectady Federal Savings, 251 State St.
This entryway is faced with slabs of spectacular red granitic migmatite. The visible minerals include pink K-feldspar, white plagioclase, glassy-clear gray quartz, and black biotite. As described above, migmatite means "mixed rock" in which some parts appear to be metamorphic rock and others appear to be igneous. The layered portions of this rock are gneisses that have been highly metamorphosed and deformed. The igneous rocks include the entire range from fine grained granite to granitic pegmatite (very coarse-grained). In some places gneissic layers or granitic dikes have been offset by small shear zones (very local and short faults), that formed when the rock was hot, ductile, and probably partly liquid. Some of the granite dikes are obviously intrusive and crosscut layering or other dikes, but some appear to have formed in place by the partial melting of the metamorphic portions. On the polished surface one can see metallic gray and metallic yellow minerals, which are iron oxides and pyrite, respectively.

This building has polished facing stone that looks identical to the dark gabbro at Stop 18, only more fine-grained. The Photo Lab, at 273 State St. has a few small slabs of gray quartz monzonite porphyry on the lower part of the foundation.

STOP 33. Wall Street
At the intersection of State Street and Erie Boulevard. The lower part of the wall facing Erie Boulevard is composed of fossiliferous limestone. Many of the features that can be seen here are illustrated and explained in Figure 4. Some layers in the rock are composed of very fine-grained carbonate mud that contains few fossils. This may have been deposited in a quiet, possibly hypersaline lagoon environment. The coarse-grained layers that are interbedded with the carbonate mud are made mostly of whole and broken fossils and chunks of rock that look like the carbonate mud. These were probably formed by masses of water that were forced over the beach area into the lagoon during severe storms. The fast-moving, turbulent water carried fossils from the near offshore and beach environments into the lagoon where they were deposited as the currents slowed. In some cases the storm surge currents broke up lithified sediments into smaller stones, which were transported and deposited with the fossils as "rip-up clasts". The storm surge deposits are typically coarse-grained on the bottom and grade to finer-grained on top. Using this rule, you can see that some of the blocks are upside-down from their original orientation. Fossils visible here include gastropods, brachiopods, and corals. Red sandstone and fine-grained fossil hash are also present in this wall.

STOP 34. 401 State St.
The facing stone on the outside of this building is an almost black diabase, a rock of basaltic composition having a grain size and texture intermediate between that of gabbro and basalt, but having a similar chemical and mineral composition. It is formed in small plutons that cool relatively quickly (in ˜1 to 100 years), and in the centers of thick lava flows and lava lakes. This rock contains long, lath-shaped plagioclase crystals that enclose black pyroxenes and metallic iron-titanium oxides. The textures are best seen by looking at a low angle at light reflected off the polished surface.

STOP 35. Center City and CVS, 433 State St.
The facing stone here is composed of a "hypersolvus" granite. The granites we have seen previously have had discrete crystals of K-feldspar (pink or white) and plagioclase (usually white in granite, with twinning). This granite has only one feldspar with a composition intermediate between plagioclase and K-feldspar. During cooling, this intermediate feldspar composition became unstable and unmixed into very thin, alternating layers of K-feldspar and plagioclase. The unmixed feldspar is known as perthite. If you look closely with a hand lens you will see the alternating, irregular layers of unmixed plagioclase and K-feldspar in the feldspar crystals. Perthite only forms in slowly cooled rocks. If the rock had cooled quickly, it would still have only a single feldspar.

STOP 36. Jay Street pedestrian mall.
Some stores have very antique, green serpentinite, and green to maroon to brown altered serpentinite. The original material for both was probably ultramafic rock, such as a dunite or peridotite, which may have been part of the deep oceanic crust or upper mantle. During metamorphism, the rock was infiltrated by aqueous fluids that turned anhydrous olivine and pyroxene into water-bearing serpentine, talc, and amphiboles, and deposited silica and white calcite. Deformation during metamorphism shattered the rock mass, forming irregular blocks and veins. The altered serpentinite formed when later circulation of oxygen-rich water through the rock caused some of the iron in the silicates to turn to hematite, staining parts of the rock red.

STOP 37. City Hall.
This building is among the most splendid in downtown Schenectady, and is a fitting location for the end of the trip. The steps are made out of gray muscovite granite, similar to that found in many other buildings we have seen.
The columns are made of white Vermont marble. These columns show especially well the effects of weathering, similar to that seen on the columns of Memorial Hall on the Union College campus (Stop 2). The side of the columns facing the elements are rather rough and worn-looking. The side of the columns facing the building is contrastingly smooth with sharp edges to the carved flutes. The softness, excellent cleavage, and solubility of calcite in the marble is what makes it so susceptible to weathering.
The historical placards on the front of the building are made of altered serpentinite, similar to that seen along Jay St. at Stop 36.

B3: FLUVIAL GEOMORPHOLOGY OF THE PLOTTERKILL PRESERVE
Donald T. Rodbell and Paul S. Hays
Union college
Introduction
The stability of hill slopes reflects a delicate balance between the driving and resisting forces on a landscape (Ritter et al., 1995). Driving forces on a hill slope are those that increase shear stress and promote mass wasting whereas resisting forces are those that contribute to the shear strength of the materials that compose a hill slope (Table 1). Because the factors listed in Table 1 change with time, the degree of hill slope stability is transient and episodes of pronounced hill slope instability have been recognized in the geologic record (e.g. Reneau et al., 1990). For example, rapid fluvial downcutting in response to climate change and/or a lowering of local base level may destabilize hill slopes by eroding the toes of slopes and thereby removing their lateral support. This example of linked geomorphic systems is well illustrated in the Plotterkill Preserve. The Plotterkill Preserve is located ca. 10 km northwest of Schenectady, NY. The Preserve is underlain by the Schenectady Formation (Ordovician), which is composed of shale and beds of sandstone (greywacke) and represents flysch deposition derived from erosion of the Taconic island arc (see Hollocher, this volume; Kidd et al., this volume). Surficial deposits include glacial drift, talus and colluvium, and fluvial sand and gravel. The Plotterkill, which heads in the Helderburg Hills, is a tributary to the Mohawk River and has deeply incised into the Schenectady Formation and the overlying mantle of glacial drift. Where the Plotterkill incised into the Schenectady Formation, near-vertical escarpments of up to ca. 25 m occur. In contrast, in at least one locality where the Plotterkill has cut through a locally thick deposit of glacial drift, a large (5600 m2) complex rotational slump-earth flow occurred and remains active today.

B3: FLUVIAL GEOMORPHOLOGY OF THE PLOTTERKILL PRESERVE

STOP 1. Plotterkill Preserve
From here we will spend several hours walking along the Plotterkill; the trails are well marked but some are quite steep.
We will begin by walking down the trail to the Plotterkill (Fig. 4). As you approach the valley floor (ca. 8 minutes) and before you reach the alluvial fan (Fig. 4) you will notice the curved trunks of some trees on the hillside to your left. Tilted trunks are a good indication that soil creep is active on the hillside
When you reach the relatively flat valley floor, you will be standing on an alluvial fan (Fig. 4) which is graded to a level that is much higher than the modem Plotterkill. As you continue down the axis of the fan you will cross two scarps, which demarcate distinct terrace levels cut onto the toe of the alluvial fan by the Plotterkill. The trail turns to follow the south side of the Plotterkill and enters the downvalley end of an abandoned channel of the Plotterkill. Well preserved terraces can be seen on either side of this paleochannel. At the downvalley end of the abandoned channel, there is a good exposure into one of the prominent terraces in this part of the valley. This exposure reveals ca. 1-2 m of a very poorly sorted deposit of sand, gravel, and angular boulders up to 70 cm long. Clasts in these deposits are angular and were derived locally from the sandstone units of the Schenectady Formation. These clasts show a pronounced imbrication in which their a-b planes are inclined upstream, reflecting fluvial transport. In addition, one can observe that the modem Plotterkill flows on a beveled surface of Schenectady Formation shale. In places this surface is mantled by ca. 1 m or more of coarse and poorly sorted alluvium, which is very similar to the material that makes up the deposits that underlie the terrace surface.
Follow the paleochannel until the trail crosses the Plotterkill. You will see the large landslide to your left (south). The upvalley end of the paleochannel corresponds precisely with the downvalley end of the landslide. It is likely that initial movement of the slide forced the course of the Plotterkill to the north until it avulsed its channel, thus forming the paleochannel. Subsequent fluvial incision into the slide material and southward migration of the cut bank of the Plotterkill has isolated the inlet to the paleochannel.
Continue up the bed of the Plotterkill. Watch your step! On the south side of the Plotterkill, approximately 75 m upstream from the landslide is an excellent example of a flight of fluvial terraces (Fig. 2). Here, three distinct terraces can be differentiated on the basis of elevation. In addition, exposures into the alluvium that underlies the terrace surface can be seen. In several locations one can see clearly that the alluvium rests unconformably on a beveled surface which has been cut onto the shales of the Schenectady Formation. This surface is a rock cut terrace or a strath (Ritter et al., 1995) and is overlain by alluvium. The observation of a planar erosional surface that mirrors the terrace tread and which is overlain by alluvium the thickness of which does not exceed the normal scouring depth of the river meets the criteria for designating a terrace an erosional or strath terrace (Mackin, 1937). The presence of strath terraces suggests that the Plotterkill has been incising its channel progressively and that this incision was punctuated by periods of stream equilibrium during which time the Plotterkill laterally eroded the underlying Schenectady Formation. Step-wise incision may have been caused by episodic increases in stream power, decreases in sediment yield to the stream, decreases in local base level, or a combination of these three factors.
Return to the base of the landslide. Standing here, one can clearly see the abundant exotic lithologies that make up the material composing the landslide (Table 2). This material is till and its prevalence in this part of the valley suggests that hill slope instability at this particular point in the valley is due, in part, to the influence of lithology on hill slope stability.
Walk up the slide. The slide surface can be divided into an upper and lower half (Fig. 3). The lower part of the slide is devoid of vegetation except for several small tree islands; these may be remnants of a continuous vegetated surface. Tree ring studies suggest that this surface is more than 30 years old. This part of the slide is continuously eroding into the Plotterkill and during times of high water tables, springs develop in the uppermost part of the lower half of the slide. These springs probably reflect ground water flow along shear planes that underlie the upper half of the slide. Saturation of the lower half of the slide is responsible for this nearly continuous earth flow. The upper half of the slide is probably dominated by rotational slide (slump) activity as is evidenced by transverse tensional cracks, minor scarps and rotated segments. The uppermost part of this part of the slide is characterized by a prominent near-vertical scarp.
An array of stakes (steel rebars) have been placed on the surface of the landslide and surveyed precisely using an electronic distance meter in April, 1995. We plan to monitor the movement of the landslide annually.

STOP 2. Gravel pit on north side of road
(pit is owned by Scotia Sand and Stone Company- 518-346-5749)
This gravel pit provides excellent exposures of the Scotia Delta (see Wall and LaFleur, this volume) that prograded eastward into Glacial Lake Albany. We are stopping here to briefly see the unequivocal evidence that these exposures reveal for higher local base levels ca. 12-13 ka. The elevation of the foreset-topset transition here (88 m) can be used to estimate of the surface of Glacial Lake Albany ca. 12.5 ka (see Wall and LaFleur, this volume) and hence of local base level at that time. Progressive and step-wise lowering of local base level to the modern elevation of the Mohawk River at this point of the Mohawk Valley (67 m) may have been responsible for episodic incision by the Plotterkill and other creeks in the region (e.g., Washout Creek, Fig. 1).

STOP 3. Scotia Delta
Here we can see a lower level of the Scotia delta to the right (south) of Rt. 5N. There are at least 3 levels of the Scotia delta in this part of the Mohawk Valley. The elevations of these levels are 90 m, 85 m, and 70 m.

B4: SEQUENCE STRATIGRAPHY OF PLATFORM CARBONATES: DEVONIAN LIMESTONES OF JOHN BOYD THACHER STATE PARK, SOUTHWEST OF ALBANY, NY
GERALD M. FRIEDMAN
Brooklyn College and Graduate School of the City University of New York,
Brooklyn, NY 11210
and
Northeastern Science Foundation affiliated with Brooklyn College
Rensselaer Center of Applied Geology,
15 Third Street, P.O. Box 746, Troy, NY 12181-0746
The Lower Devonian strata that crop out on the Helderberg Escarpment illustrate the characteristics of marine platform parasequences in carbonate rocks. In the hierarchy of stratigraphic units, parasequences are a relatively conformable succession of genetically related strata bounded by surfaces of erosion. The parasequences exposed in this escarpment, which include stromatoporoid reefs, stromatolites, and lithified lime mud (micrite) show regressive facies separated by unconformities representing transgressive episodes. The lowermost part of the section exhibits classical karst-generated solution collapse breccia of the kind that hosts oils and gas in the subsurface. The Middle Devonian Onondaga facies at this site are full of coral-reef debris. In the subsurface, Onondaga reefs form gas reservoirs and now serve as reservoirs for gas storage. Sir Charles Lyell visited this classic site, part of the Helderberg Mountains, in 1841 and a monument commemorates his visit and that of Sir William Logan, James Hall, Amos Eaton, and others of the heroic age of Geology.
No road log, only the one stop at Indian Ladder

B5: LOWER AND MIDDLE DEVONIAN FORELAND BASIN FILL IN THE CATSKILL FRONT - STRATIGRAPHIC SYNTHESIS, SEQUENCE STRATIGRAPHY, AND THE ACADIAN OROGENY
CHARLES A. VER STRAETEN AND CARLTON E. BRETT
Department of Earth and Environmental Sciences
University of Rochester
Rochester, New York 14627
Modern stratigraphic study has come to be increasingly based on high resolution subdivision of the sedimentary record through detailed event and cyclic analysis. The recognition and correlation of unique single event horizons (e.g., altered volcanic ashes, shell marker beds, faunal epiboles and immigration events) and genetically-related depositional sequences permits microstratigraphic subdivision of the rock record at a finer scale than is possible through classical methods of bio- and lithostratigraphy. "Layer cake" stratigraphy, once the bane of stratigraphic thought, has again emerged in modified form through the application of "Event" (Kauffinan., 1988) and "Sequence Stratigraphic" (Van Wagoner et al., 1988) methods.
The construction of a refined microstratigraphic framework of strata permits detailed analysis of the timing and nature of events in the rock record. Short term dynamics in the history of a basin are recorded by: sharp transitions between intrabasinal and extra-basinal sedimentation; clustered volcanogenic strata; condensed beds and minor unconformities; abrupt changes in faunas and short-term incursions of exotic faunas; cyclic sedimentation; and eustatic- and tectonic-controlled changes in relative sea level. A detailed, correlatable framework of large and small scale events helps unravel the history of a sedimentary basin.
The late Early and Middle Devonian was a very dynamic time on the margin of the Eastern Interior of North America. A continent-continent collision, subsequent subsidence and infilling of an adjacent sedimentary foreland basin, and the evolution and migration of major faunas are recorded in the rocks of the Catskill Front in eastern New York State. The interaction of tectonically-induced flexure of the foreland basin and changes in eustatic sea level had a profound influence on the Northern Appalachian Basin at that time. Alternating tectonically active and quiescent stages of the Acadian Orogen (Acadian "Tectophases" of Ettensohn, 1985) resulted in major periodic alterations of subsidence and uplift, sedimentary style, faunas, and paleoecology. Superimposed over the tectonic influences are apparent changes in eustatic sea level (e.g., Johnson et al., 1985). As a result, the upper Lower and Middle Devonian foreland basin fill of New York is a complex succession of tabular to distinctly wedge-shaped bodies of carbonates and siliciclastics, shifting depocenters and basin centers, and marked unconformities.
This paper and field trip will examine the sedimentary record of the upper Lower and Middle Devonian rocks in the Catskill Front (see Figure 1). In addition to a review of member- and formation-level stratigraphy, the authors will present: 1) important new details and interpretations of strata of the Tristates Group, the Onondaga Formation, and the lower part of the Hamilton Group; 2) a discussion of the major and minor unconformities within the study interval; 3) the sequence stratigraphic framework for the upper Lower and Middle Devonian in New York State; and 4) stratigraphic trends and their implications for the evolution of the Northern Appalachian Basin and the Acadian Orogeny.

B5: LOWER AND MIDDLE DEVONIAN FORELAND BASIN FILL IN THE CATSKILL FRONT - STRATIGRAPHIC SYNTHESIS, SEQUENCE STRATIGRAPHY, AND THE ACADIAN OROGENY

Observe west wall of Mohawk Valley in distance on right

View of Helderberg Escarpment
View of Helderberg Escarpment, capped by Lower and Middle Devonian strata. straight
ahead.

Proceed through the Albany Pine Plain
Proceed through the Albany Pine Plain, on late-glacial windblown sand dunes near the northwest shore of glacial Lake Albany.

Highway continues through the Albany Pine Plain
Note vegetated sand dunes along Thruway.

Taconic Mountains visible in distance ahead
Remnants of Ordovician overthrusted highlands of the Taconic Orogeny.

Cross over Normanskill Gorge
Cross over Normanskill Gorge, near type section of Ordovician Normanskill Group.

Views of Helderberg Escarpment to right for next 17.5 mi.

Roadcuts in flysch-type sediments
Roadcuts in flysch-type sediments of Ordovician Austin Glen Formation (Normanskill Group) along NYS Thruway for next 15 mi.

Catskill Mountains visible ahead
Catskill Mountains, middle to Upper Devonian strata, visible ahead. Helderberg Escarpment on right, with limestone outcropping near crest of ridge.

Classic outcrop of "Dinosaur Leather" sole marks
Classic outcrop of "Dinosaur Leather", sole marks on base of Austin Glen Fm. turbidite bed visible 1.0 mi. north of Coxsackie exit along west side of N.Y. Rt. 9W.

Outcrops of Lower Devonian Kalkberg Limestone
Outcrops of Lower Devonian Kalkberg Limestone (Helderberg Group) visible on both sides of Thruway as you rise up onto the Helderberg-Kalkberg Escarpment. Exposures of Helderberg Group (Manlius, Coeymans, Kalkberg, New Scotland, and Becraft. Fms., in ascending order) for next 2.5 mi.

Lower Devonian Esopus Formation
Long outcrop of middle part of Lower Devonian Esopus Formation (dark shale; Tristates Group) on right

Strongly-dipping outcrop on left
Strongly-dipping outcrop of Lower Devonian Glenerie Formation? (Tristates Group) on left.

New Scotland and Becraft Formations on left.

Esopus Shale on left.

Schoharie Formation on right; note dark band.

Low anticline on right.

Cherty Onondaga Formation (limestone)
Cherty Onondaga Formation (limestone) on both sides of I-87 for next 0.4 mi.

Cuts in Helderberg Group
Cuts in Helderberg Group (Kalkberg, New Scotland, and Becraft Fms.) for next 3.0 mi.

New Scotland and Becraft Limestones along exit.
Note additional outcrops of New Scotland and Becraft Limestones along exit.

View of Catskill Mountains/Catskill Escarpment
View of Catskill Mountains/Catskill Escarpment in the distance to right.

New Scotland Limestone to left.

New Scotland, then Kalkberg Formations on right.

Bear right onto entrance ramp for NY Rt. 23 West
Exit ramp to left (east) shows angular unconformity of Ordovician Austin Glen Formation with uppermost Silurian Rondout Group; outcrop continues through Lower Devonian Manlius, Coeymans, Kalkberg, and lower part of the New Scotland formations. Faulted section along right side of entrance ramp repeats Manlius, Coeymans, and Kalkberg Formations.

Helderberg Group Limestones
Merge with Rte, 23; observe outcrops of Helderberg Group Limestones to right and left. For detailed discussion of structure of rocks along Rt. 23, see Marshak, 1990.

Crest of anticlinal structure in road cuts.

Esopus Shale on right.
Bridge over Catskill Creek; note high outcrop of Esopus Shale on right.

STOP 1A (Optional). Wallbridge Unconformity in Catskill Creek at Austin Glen.
To get to Optional Stop 1, walk back along Rt. 23 to bridge and walk down to creek along side of bridge. Turn right at bank of Catskill Creek and follow around to the natural dam in creek south of the bridge.
The natural dam at the mouth of Austin Glen is formed by the resistant base of the Lower Devonian Glenerie Limestone, underlain successively by limestones of the Port Ewen and Alsen Formations at the top of the Lower Devonian Helderberg Group. The basal bed of the Glenerie Formation is sand-rich, and features a prominent zone of reworked phosphate pebbles at its base. This phosphatic lag immediately overlies a prominent disconformity, the Wallbridge Unconformity (Sloss, 1963), which is one of six major unconformities in the Phanerozoic of North America. To the north and west, into central to western New York, this unconformity overlies progressively older rocks, as old as Late Silurian in western New York. South of Catskill the unconformity overlies progressively younger rocks in the upper part of the Port Ewen and Port Jervis Formations. In the Tristates area of southeastern New York, near Port Jervis, the succession from the Port Jervis Formation into the overlying Glenerie Formation is continuous and conformable (Rickard, 1975).
Downstream of the natural dam Catskill Creek runs through a gorge (Austin Glen) of the New Scotland and lower limestones of the Helderberg Group. The lower part of the gorge is the type section for the Ordovician Austin Glen Formation, seen previously on this trip in outcrops along the New York State Thruway. Upstream of the natural dam and the Rt. 23 bridge a high cliff of Esopus Shale is visible. Return to the anticlinal outcrop adjacent to the vehicles.

STOP 1B. Esopus, Schoharie, and Onondaga Formations.
Cuts on north side of N.Y. Rt. 23, west of bridge over Catskill Creek.
Highway cuts along Rt. 23 expose the upper part of the Esopus Formation, a complete section of the Schoharie Formation (unnamed lower, Aquetuck, and Saugerties Members), and the base of the Edgecliff Member of the Onondaga Formation in an antiformal fold west of Catskill Creek. The lower part of the exposure displays dark, rust-spotted, blocky-weathering silty shales of the Esopus Formation (Upper part of Depositional Sequence 2 of this paper). Along Rt. 23 the Esopus Shale is capped by a distinctive, 6.8 m-thick laminated unit that forms a distinctive marker at the base of the upper member of the formation. At Catskill the laminated unit is abruptly overlain by the Schoharie Formation; at Kingston, however, the top of the laminated unit underlies the Esopus-Schoharie contact by 22.5 m. The Esopus and Schoharie Formations thin laterally between Kingston and Catskill; however, the absence of upper Esopus strata above the laminated unit at Catskill appears dominantly to be associated with erosional truncation at a sequence-bounding unconformity below the Schoharie Formation (= base of Depositional Sequence 2 of this paper).
The sub-Schoharie unconformity at the base of Depositional Sequence 2 is marked by a sharp lithologic change and abundant glauconite, phosphate pebbles, fish bone material, and scattered white vein quartz pebbles. Five meters of calcareous, bioturbated argillaceous siltstone to silty mudstone of the lower unnamed member (formerly Carlisle Center Formation) overlie the contact. This contrasts sharply with up to 44 m of the unnamed member at Kingston. A 60 cm-thick, dark to black, rusty weathering, calcareous to cherty bed ("black bed" of Oliver et al., 1962) occurs near the middle of the member at both Catskill and Kingston. Glauconite and scattered quartz pebbles, apparently mixed downward from above by burrowing organisms, occur again in the upper part of the unnamed member at and below a lesser unconformity (= surface of maximum starvation in sequence stratigraphy terminology) at the base of the Aquetuck Member.
The Aquetuck Member along Rt. 23 (∼12.7 m-thick) is characterized by fine-grained, buff- to olive-banded, cherty and siliceous to calcareous shales. An interval of interbedded olive and dark gray strata 2.6-5.2 m above the member base represent the most basinal conditions in the Schoharie Formation. This interval at Kingston is represented by ∼3.25 m of dark, blocky-weathering, calcareous shale and is correlative with a widespread interval of dark gray to black shale in the middle of the Needmore Formation in central Pennsylvania (see body of paper). Carbonate content increases and the siliceous aspect of the strata decreases through the upper part of the Aquetuck Member at Catskill. The lower part of the member is unfossiliferous; small brachiopods and other forms appear in the upper part of the member, and diversify and increase in abundance upward through the overlying Saugerties Member.
The contact with the Saugerties Member is gradational and is placed at the lowest continuous, light-weathering limestone band. Nine meters of fossiliferous, interbedded buff calcareous shales and light-colored limestones comprise the Saugerties Member at Catskill. The lowest strata of the Onondaga Formation (Edgecliff Member) are exposed near the west end of the outcrop.

Outcrops of Union Springs and Mount Marion Formations on the Hoogeberg Ridge to right.

Outcrops of Esopus to left along Thruway.

Outcrops of Schoharie FormationPlacemark
Outcrops of Schoharie Formation on left and right; note prominent cleavage.

Fine brown glacial sands exposed on right
Fine brown glacial sands exposed on right (possible shoreline sands of glacial Lake Albany?).

Bridge over Kaaterskill Creek
Falls over Ordovician Austin Glen Formation on left.

Steeply-dipping Onondaga Formation on right.

Moorehouse, Nedrow and Edgecliff Members
Outcrop of Moorehouse and underlying Nedrow and Edgecliff Members of the Onondaga Limestone on left.

STOP 2. Port Ewen, Glenerie, and Esopus Formations
Port Ewen, Glenerie, and Esopus Formations, including the Wallbridge Unconformity.
Abandoned exit of New York State Thruway at N.Y. Rt. 23A. The lower and middle parts of the outcrop are accessible; the upper part of the outcrop is along the New York State Thruway and can only be observed with written permission of the Thruway Authority.
This Lower Devonian outcrop exposes uppermost strata of the Helderberg Group, the Wallbridge Unconformity, the Oriskany-equivalent Glenerie Limestone, and the lower part of the Esopus Shale. The exposure extends southward ∼300 m along the New York State Thruway, where middle and upper Esopus strata are overlain by more calcareous strata of the Schoharie Formation.
The Wallbridge Unconformity, one of six major North American Phanerozoic unconformities (Sloss, 1963) caps argillaceous limestones of the Port Ewen Formation as seen at Optional Stop 1A. The unconformity is marked by a thin ( ∼10 cm-thick) phosphate pebble-rich conglomeratic lag at the base of the Glenerie Formation. This bed lies at the base of Sloss' (1963) Kaskaskia Supersequence, which extends from the upper Lower Devonian through the Mississippian Period, and marks the base of Depositional Sequence 1 of this paper. The Glenerie Formation at Rt. 23A (3.5 m-thick) consists of relatively fine-grained, fossiliferous, drab brown limestones and dark gray cherts. Oriskany-age brachiopods are visible in cross-section in some limestone beds; the highly diverse and abundant fauna known from the Glenerie Limestone locally, however, appears absent at this outcrop.
The limestones and cherts of the Glenerie Formation are gradationally overlain by strata of the Esopus Formation at Stop 2. The lower member of the Esopus, as defined herein, consist of a tripartite subdivision of strata: 1) a lower interval of interbedded, thin siltstones, cherts, shales, and K-bentonites. This interval includes the Sprout Brook Bentonites of Ver Straeten (1992b, in review; also Ver Straeten et al., 1993), which at this outcrop consist of up to 15 thin, altered volcanic ash layers; 2) a middle subunit of dark gray to black, banded shale with scattered medium-size (∼ 10-20 cm), dark blue-gray calcareous-phosphatic concretions; and 3) an overlying coarsening-up interval of medium dark gray silty shales to buff-gray- weathering, slightly calcareous siltstones. Small brachiopods (Atlanticocoelia and/or Leptocoelia) and other uncommon fossils occur in the upper subunit, with scattered glauconite.
The lower submember (∼6.6m-thick) of the member is highly deformed at this outcrop; disharmonic folds, shear zones, and prominent fractures and cleavage are associated by Marshak (1990) with movement of a detachment fault between the Glenerie and Esopus Formations. Bentonite beds along the outcrop pinch and swell between more resistant beds and form horizons along which faults slide. The overlying middle dark gray-black shale subunit (2.0 m-thick) in the upper part of the cliff shows prominent slaty cleavage. Subunit 3 of the lower member of the Esopus Formation along Rt. 23A totals 4.0 m in thickness; its capping buff-gray siltstone bed forms a prominent ledge around the corner from the anticlinal exposure.
The overlying middle and upper members of the Esopus Formation extend southward along the outcrop and consist of rusty, dark gray silty mudstones to argillaceous siltstones that total over 40 m in thickness. The upper member of the Esopus, unlike the previous stop, consists of the laminated unit and ∼2.9 m of strongly Zoophycos-churned siltstones to fine sandstones. The base of the Schoharie Formation is marked by a prominent glauconite-rich bed with quartz pebbles. The overlying unnamed member of the Schoharie Formation is 9.2 m-thick along the Thruway cut and shows distinctive banding, as does the overlying Aquetuck Member (10.7+ m exposed; thicknesses for the Schoharie Formation reinterpreted from Johnsen, 1957). This banding may be related to Milankovitch cycles similar to those reported from Cretaceous and other age rocks (see discussion of Sequence DS3 in main body of paper).
The basal Glenerie phosphate pebble bed marks initial transgression during deposition of the first post-Wallbridge depositional sequence (=Sequence DS1 of this paper). Continued transgression coupled with the onset of tectonically-induced foreland basin subsidence (Acadian Tectophase I) marks the change into the overlying Esopus Formation. Shallowing and siliciclastic progradation through the upper part of the Esopus Formation is truncated by apparent erosion of upper Esopus strata (see discussion above) below an unconformity at the base of the Schoharie Formation (=base of Sequence DS2 of this paper).

STOP 3A. Schoharie and Onondaga Formations.
Walk carefully back along Rt. 23A to bridge over the Thruway. Highway cuts along NYS Thruway and NY Rt. 23A visible from Rt. 23A bridge. Access to exposures along thruway only through written permission of the Thruway Authority.
Highway cuts along Rt. 23 and the Thruway show extensive exposures of the Lower Devonian Schoharie and lower part of the Middle Devonian Onondaga Formations. Buff-orange, brown, and gray colors characterize the Schoharie Formation along the exposure. Light-weathering limestones, with common yellowish-weathering cherts, are typical of the Onondaga Formation. Very long exposures of the Schoharie are visible along the Thruway to the north. To the left, immediately north of the bridge, a darker, banded interval is notable in the lower part of the exposure. This interval of siliceous shales in the lower part of the Aquetuck Member (seen at Stop 1) is correlatable to a calcareous shale interval at the same position at Kingston; as previously noted, it is also recognized in the middle part of the Needmore Formation in Pennsylvania (see body of paper). Overlying strata on the northwest side of the bridge belong dominantly to the Aquetuck Member.
On the opposite side of the highway north of the bridge, alternating bands on argillaceous, buff-weathering limestones and purer, more calcareous limestone layers characterize the Saugerties Member of the Schoharie Formation. Overlying coarse, crinoid-rich, non-cherty to chert-rich limestones represent the Edgecliff Member of the Onondaga Formation.
Walk back to intersection of Rt. 23A and Old Kings Rd.

STOP 3B. Schoharie and Onondaga Formations.
Cuts along N.Y. Rte 23A at and near its intersection with Kings Highway, ∼0.0-0.3 mi. west of the bridge over the New York State Thruway.
Outcrops to the east and west of and along Old Kings Road on the south side of Rt. 23A expose argillaceous limestones of the upper part of the Schoharie Formation (Aquetuck and Saugerties Members) and a thick section of limestones of the Onondaga Formation (∼44-m thick; Edgecliff, Nedrow and Moorehouse Members). The Schoharie-Onondaga contact is exposed on the east side of Old Kings Road, south of Rt. 23A. Buff- and light gray-weathering limestones with thin quartz sand stringers (Saugerties Member) are gradationally overlain by light gray, clean limestones of the Onondaga Formation (Edgecliff Member). The lower part of the Onondaga section exposed along Old Kings Road (basal 2.0 m-thick non-cherty interval and overlying chert-rich strata) comprise the EdgecliffMember (ca 16m-thick). The lower 2.0 m of relatively chert-free, coral, brachiopod, and crinoid-rich pack- and grainstones ("Jamesville Quarry facies" of Brett and Ver Straeten, 1994) are capped by a thick section of medium-grained, cherty, crinoidal packstones ("Clarence facies" of Brett and Ver Straeten, 1994). Similar alternations of cherty and chert-free strata characterize the Onondaga Limestone in the Catskill area; chert-dominated facies are predominant locally, however.
The member level subdivisions of the Onondaga Limestone that are well-defined and easily recognized in central New York (see Brett and Ver Straeten, 1994) are less readily detectable in Hudson Valley outcrops. They can tentatively be separated by changes in chert and argillaceous content, and in bedding thickness.
A 6.6 m-thick covered interval, (which is exposed along Cauterskill Road, Mile 49.0 of this trip) at least in part represents the Nedrow Member. Overlying strata to the west along Rt. 23A comprise the Moorehouse Member. The coarse- to medium-grained, chert and crinoid-rich lithology of the Edgecliff Member below is replaced in the Moorehouse Member by finer-grained, cherty, wacke- to packstones characterized by brachiopod-dominated faunas. Calcite slickensides are common along bedding planes through the Moorehouse Member at Stop 3B; faulting, however, appears to be restricted along the bedding planes, associated with slippage of beds over each other during folding and overturn of the section.
The Onondaga Formation totals ∼44 m at Stop 3B; uppermost strata of the formation are covered. Fifty meters of Onondaga strata are reported from outcrops along the NYS Thruway at Saugerties, 8.5 mi. to the south (Feldman, 1985); the top of the Saugerties section is thought to be close to the contact of the Onondaga Limestone and overlying clastics of the Union Springs Member (Stop 4, next locality).
A geologic overview of Localities 1-3 and 5 is summarized here (see Figure 3) Post-Wallbridge deposition of the Glenerie, Esopus, Schoharie, and Onondaga Formations represent a succession of, respectively, intrabasinal carbonates, extra-basinal siliciclastics, mixed siliciclastic and carbonate sediments, and a return to fully intrabasinal carbonates. These trends are associated with initial tectonic quiescence and carbonate-quartz arenite deposition above the Wallbridge Unconformity (Glenerie Formation), followed by: 1) a pulse of active tectonism in the Acadian Orogen, accompanied by volcanism and deposition of the Sprout Brook Bentonites, transport and deposition of fine- to medium grained siliciclastics, and subsidence of the foreland basin (Esopus Formation); 2) decreased tectonic activity and lowering of topographic relief in the mountain belt, associated with a decrease in siliciclastic input into the basin and deposition of calcareous shales and siltstones to argillaceous limestones (Schoharie Formation); and 3) a return to tectonic quiescence, marked by deposition of intrabasinal carbonates (Onondaga Formation). This succession of events 1-3 comprises Acadian Tectophase I as it is recorded in the foreland basin fill of eastern New York State.
Superimposed on these tectonically-related trends are three major depositional sequences (DS-1 to DS-3). These sequences appear to be dominantly controlled by eustatic sea level changes. The first sequence (DS 1) comprises the Glenerie and Esopus Formations. Initial deepening above the Wallbridge Unconformity continues upward through the Glenerie Limestone and lower to middle Esopus Shale (note: deepening during Esopus time is in part due to tectonically-induced subsidence of the basin). Upward shallowing through the upper middle to upper Esopus Formation is truncated by submarine erosion below a sub-Schoharie unconformity at the base of DS-2. Initial deepening through the Schoharie Formation culminates in deposition of widespread dark shaly strata represented at Catskill by an interval of dark, siliceous to cherty shales in the lower part of the Aquetuck Member. Overlying increasingly more calcareous strata are associated with a general shallowing-upward reaches a maximum at or near the Schoharie-Onondaga formational contact. Initial deepening at the base of the Onondaga Limestone marks the base of DS-3; transgression continued upward through the Edgecliff and Nedrow Members. Trends through the overlying Moorehouse Member indicate another major shallowing-upward trend during late highstand of DS-3 . Transgression during the succeeding DS-4, which is dominantly represented by the overlying Union Springs Formation, was initiated during deposition of the upper part of the Moorehouse Member.

Cross over Kaaterskill Creek at Webber Bridge.
Drive through the Bakoven Valley, with deeply eroded black shales of the Bakoven Member (Union Springs Formation) overlain by glacial sediments.

Note outcrop of Stony Hollow Member
Note outcrop of Stony Hollow Member (Union Springs Formation) at intersection; more outcrops of Stony Hollow Member northward along Underhill Rd and at the crest of Rt. 23A to the southwest.

STOP 4. Onondaga Formation and Bakoven Member
Onondaga Formation and Bakoven Member of the Union Springs Formation.
East bank of Kaaterskill Creek, below the N.Y. Rt. 23A bridge. Type section of the Bakoven Member. PRIVATE PROPERTY.
The stream bed and east bank of Kaaterskill Creek expose the upper 0.85 m of the Onondaga Formation and the lower 27 m of the Bakoven Member of the Union Springs Formation. The abrupt change from shallow marine carbonates to basinal black shales seen in the outcrop mark the onset of Acadian Tectophase II.
Light-weathering, relatively fine-grained limestones with atrypid brachiopods, small rugose corals, and other forms characterize the Onondaga Formation at this locality. The upper 35 cm of limestone appears slightly darker in color and overlies a thin (1 -cm-thick) K-bentonite. Key upper Onondaga marker beds (e.g., the Tioga B-OIN bentonite at the base of the Seneca Member) are not seen at this outcrop; it is not known whether the exposed strata belong to the Moorehouse or Seneca Members. A thicker but partially covered outcrop (2.9 m-thick) of upper Onondaga strata occurs immediately north of Rt. 23 east of the bridge.
The Onondaga-Union Springs formational contact is abrupt, and features numerous bored phosphate pebbles and well-defined burrows that are visible in the creek when the water level is low. The contact is overlain by a thin (ca 2-3 cm-thick), highly condensed bed of phosphatized fossil debris (e.g., crinoid ossicles) and fish bone and teeth (NOTE: Please do not collect from the bone bed-this is a classic section and type locality). The bed marks a major sediment-starved flooding surface associated with tectonic subsidence of the Appalachian foreland basin at the onset of Acadian Tectophase II of Ettensohn (1985). For further discussion of this contact, see Ver Straeten et al. (1994) and Lindemann and Feldman ( 1987).
Overlying rusty-weathering, fissile black shales of the Bakoven Member represent deposition of fine-grained, organic-rich sediments in the proximal subsiding trough of the Appalachian foreland basin. Anaerobic conditions on the sea floor prevented colonization by benthic faunas; only rare leiorhynchid brachiopods and pelagic (?) dacryoconariids (Styliolina) and rare cephalopods occur in the shales. Three thin intervals of more calcareous strata (styliolinid packstones) occur upward through the section. The poorly resistant shale features numerous tectonized intervals (small shear zones and mesoscopic folds; Marshak, 1990) and fault surfaces, especially above the Onondaga Limestone in the lower part of the Bakoven Member.
The low valley to the west is floored by the Bakoven Shale, and is partially infilled with Pleistocene sediments. Roadcuts on the west side of the valley exposes the Stony Hollow Member of the Union Springs Formation (not the Mount Marion Formation as reported by Murphy et al., 1980; Marshak, 1990; Cassie, 1990).

Pass overturned to steeply-dipping Onondaga Limestone of Stop 3B

Schoharie Formation on left.

Esopus(?) Formation on right.

Catskill Escarpment and Hoogeberg Ridge
Catskill Escarpment and Hoogeberg Ridge visible in far and middle distance to right.

Road to scenic High Falls on Kaaterskill Creek
Road to scenic High Falls on Kaaterskill Creek, an excellent section of Otsego Member of the Mount Marion Formation.

Catskill Escarpment and Hoogeberg Ridge to right.

Onondaga Formation on right.

Onondaga exposure behind house on left.

Watch for "beefalo" in pasture to left of road.

Excellent view of Catskill Escarpment
Excellent view of Catskill Escarpment, with Kaaterskill Clove visible to right and back a little.

Katsbaan Reformed Dutch Church
Katsbaan Reformed Dutch Church, built 1732. Stone walls dominantly made of blocks of Onondaga Limestone, except front wall (brown-green sandstones of Austin Glen Formation).

Outcrop of Schoharie-Onondaga contact on right
Outcrop of Schoharie-Onondaga contact on right after turn (a left turn at the intersection would pass outcrops of the Onondaga Limestone, the Stony Hollow Member (Union Springs Formation), the Otsego Member and undifferentiated upper Mount Marion Formation, and lowest strata of the Plattekill Formation.

Saugerties Member (Schoharie Formation) on left.

Schoharie-Onondaga formational contact on right.

Onondaga Formation on left.

Site of 1994 Woodstock Festival on right.

Long outcrop of the Saugerties Member (Schoharie Fm.)
Long outcrop of the Saugerties Member (Schoharie Fm.) and most complete section of the Onondaga Formation in the Hudson Valley (along both sides of I-87).

Large quarry of Berne and Otsego Members
Large quarry of dark, shale-dominated Berne and Otsego Members (Mount Marion Fm.) on north shoulder of Mount Marion to right.

Crest of Mount Marion
Crest of Mount Marion, highest hill in the Hoogeberg Ridge. Type section of Mount Marion occurs at south end of the ridge, in a high south bank of Plattekill Creek.

Outcrop of Stony Hollow Member (Union Springs Fm.) on left.

Bridge over Plattekill Creek
Bridge over Plattekill Creek; outcrop of upper Stony Hollow Member (Union Springs Fm.) or Cherry Valley Member (Mount Marion Fm.) in creek bed on right.

Rest Stop

Middle part of Berne Member (Mount Marion Fm.).

Outcrops of Stony Hollow Member
Outcrops of Stony Hollow Member along I-87 for next 1.7 mi.

Long outcrop of Stony Hollow Member, both sides of highway.

Hurley Member and Cherry Valley member
Hurley Member (type section; Union Springs Fm.) and Cherry Valley Member (Mount Marion Fm.) exposed on left.

Lower part of continuous section of Berne Member
(Mount Marion Fm.).

Berne and Otsego Members (Mount Marion Fm.)
Boundary ∼2/3 height up bank on both sides.

Berne and Otsego Members in high bank on right.

Bridge over Esopus Creek.

Outcrops of Esopus and Schoharie Formations
On both sides of highway.

Glenerie, Port Ewen, Alsen, and Becraft Fms.
Outcrops of (in descending order) Glenerie, Port Ewen, Alsen, and Becraft Formations.

New Scotland, Kalkberg, Coeymans, and Manlius Fms.
Outcrops of (in descending order) New Scotland, Kalkberg, Coeymans, and Manlius Formations.

Ordovician Austin Glen Formation
Outcrops of Ordovician Austin Glen Formation on both sides of entrance ramp.

STOP 5. Esopus and Schoharie Formations.
Synclinal exposure on north side of Rtes. 199/209 east of Rt. 9W, north of Kingston.
Outcrops on the north and south side of Rtes. 199-209 expose upper strata of the upper member of the Esopus Formation and the unnamed, Aquetuck, and lower part of the Saugerties Members of the Schoharie Formation. The north outcrop is less weathered, and better displays various features of the strata.
16.3 m of the upper member of the Esopus Formation are exposed at Stop 5. These strata represent siltstones to fine-grained sandstones that cap the formation locally. The laminated unit at the base of the upper member seen in the Catskill region (Stops 1B & 2) is absent at this outcrop, but is partially exposed 0.4 mi. south at the north end of the Hudson Valley Mall (east of Rt. 9W). The contact between the laminated subunit and the overlying bioturbated siltstones to sandstones is sharp at the mall exposure. A continuous, almost complete section of the upper member is exposed along a railroad cut north of O'Reilly Street in southwestern Kingston (Stop #3 of Oliver et al., 1962), where the member totals 27.5+ m in thickness; the contact with the underlying middle member is covered below 5 m of the laminated subunit. The overlying siltstone-fine sandstone subunit totals 22.5 m in thickness, in contrast with 2.9 m at Stop 2 and 0.0 m at Stop 1 in the Catskill area.
The top surface of the Esopus Formation is well exposed on a eastward dipping bedding plane on the outcrop, where well-preserved Zoophycos and other trace fossils are exposed. The contact with the overlying unnamed member of the Schoharie Formation is sharp. Scattered quartz and phosphate pebbles are visible in the succeeding strata. The unnamed member at Kingston consists of bioturbated, calcareous, silty mudstones to argillaceous siltstones that total 32 m in thickness. This contrasts with ∼45 m at the railroad cut in Kingston and 9.2 m (Stop 2) to 5.0 m (Stop 1) in the Catskill area. Subtle banding is visible in the unnamed member along the outcrop. The prominent black, siliceous marker bed of the unnamed member ("black bed" of Oliver et al., 1962; 0.7 m-thick) is visible in the middle of the member along Rtes. 199-209.
The contact with the overlying Aquetuck Member (Schoharie Formation) is gradational. The highest white quartz pebbles in the upper part of the unnamed member were used by Oliver et al. (1962) to define the top of said member. These occur just above the uppermost prominent white band of limestone in the middle of the outcrop.
The siliceous/cherty nature of the overlying Aquetuck Member in the Catskill area and north is replaced by more calcareous strata in the Kingston area. The dark, siliceous, shaly interval near the base of the member is represented by a 3.2+ m-thick interval of blocky-weathering shales and thin limestone bands ∼3 m above the base of the member. Prominent "coffee and cream" banding is well-developed in the Aquetuck Member as well as the other members of the Schoharie Formation along the outcrop. White nodular limestone bands in the Aquetuck Member are replaced upward by more continuous, tabular limestone beds in the overlying Saugerties Member.

STOP 6. Bakoven and Stony Hollow Members of the Union Springs Fm.
Cut along City View Terrace immediately east of N.Y. Rt. 28.
This roadcut and a subjacent cut along Rt. 28 expose the upper 10 m of the Bakoven Member and the lower 23 m of the overlying Stony Hollow Member (Union Springs Formation). The Bakoven Shale at Kingston consists of ∼100 m of fissile black shale (Rickard, 1989, Ver Straeten et al., in prep.). Similar to Stop 4, the member is nearly barren of fossils; styliolinids, cephalopods, and Panenka bivalves comprise the dominant forms found here. The Bakoven Member features numerous deformational structures similar to those at Stop 4, which include several zones of sheared and mesoscopically-folded shales below the overlying resistant strata of the Stony Hollow Member.
The Bakoven-Stony Hollow contact is gradational at Kingston. Calcareous, buff-weathering, thinly laminated to burrow-mottled lower Stony Hollow strata also feature a low diversity, anaerobic to dysaerobic fauna of dacryoconariids and rare, small bivalves and brachiopods. Grain size increases upward through the Stony Hollow Member from laminated claystone-mudstone couplets in the lower part to fine-grained sandstones near the top of the unit. Biofacies upgrade from basinal anaerobic/dysaerobic dacryoconariid-dominated faunas to fully aerobic brachiopod-crinoid-trilobite shallow marine assemblages through the Stony Hollow and Hurley Members. A dysaerobic, dacryoconariid-leiorhynchid brachiopod-cephalopod assemblage in the overlying Cherry Valley Member indicates a return to deeper water conditions associated with transgression. The bottom of the Cherry Valley Member is a sequence boundary at the base of the Mount Marion Formation. The entire Stony Hollow and Hurley Members (type sections) and Cherry Valley Member (eastern clastic facies reference section) are exposed in the immediately adjacent area (see Griffing and Ver Straeten, 1991, p. 247-249).

Cross Sawkill Creek.

Berne Member on left.

Outcrop of Berne Member
Outcrop of Berne Member adjacent to outcrop along I-87/NYS Thruway

STOP 7. Berne and Otsego Members Mount Marion Fm.
Abandoned quarry along Ulster Co. Rte 31, north of Buzzanco's Greenhouses. PRIVATE PROPERTY: contact Mr. Buzzanco at the greenhouses. Locality 3 of Ver Straeten, 1994.
The upper part of the Berne and lower part of the Otsego Members of the Mount Marion Formation (Depositional Sequence 5 of this paper) are exposed in this abandoned shale pit). ∼55 m of dominantly dark gray mudstones and claystones crop out in the quarry. Cyclically-occurring shell beds, generally separated by 3-8 m of unfossiliferous mudstones, feature distinctive brachiopod-dominated faunas that in general increase in diversity upward through the interval exposed. These small-scale cycles represent individual parasequences. The strata are also punctuated by packages of thin sandstone beds; recent work shows that most of the shell beds and clusters of thin sandstones have been successfully correlated along the outcrop belt along much of the eastern New York outcrop belt (> 110 km, Kingston to Schoharie; Ver Straeten, 1994).
The base of the quarry lies ∼85 m above the top of the Union Springs Formation. Regionally the contact of the Berne and Otsego Members is marked by the occurrence of a richly fossiliferous coral-brachiopod biostrome (Halihan Hill Bed of Ver Straeten, 1994). This bed, which occurs ∼12m up in the quarry section, marks the first known occurrence of the classic fauna of the Middle Devonian Hamilton Group. Regional study indicates the bed represents initial flooding after a significant fall in relative sea level within Depositional Sequence 5; an abrupt contact of the Halihan Hill Bed with underlying claystones is due to local to regional submarine erosion of underlying sand-rich strata during sea level lowstand (Ver Straeten, 1994).
Overlying dark shale-dominated strata mark a return to deeper water settings associated with continued transgression. Low diversity shell beds, characterized by leiorhynchid and Mediospirifer-Athyris brachiopod associations characterize a 30 m-thick interval above the Halihan Hill Bed. Shell beds in the upper part of the quarry show an increase in diversity, apparently associated with a decrease in water depth. A package of thin sandstones at the top of the quarry are succeeded locally by a prominent, richly fossiliferous sandstone (up to 2.5 m-thick) that forms the caprock of waterfalls and ridges along the Hoogeberg Escarpment in eastern New York (e.g., High Falls of Kaaterskill Creek, SW of Catskill).

Otsego Member on right.
Exposures of middle Mount Marion strata for next 1.0 mi.

Sawkill Creek

Hill Rd. to flagstone quarries on left.
Hill Rd. on left; road to extensive turn-of-the-century flagstone quarries in upper part of the Mount Marion Formation.

Intricately decorated house
Intricately decorated house on right side of Sawkill Rd.

Road to more abandoned flagstone quarries on left.
Jockey Hill Rd. on left; road to more abandoned flagstone quarries.

Upper Mount Marion Formation
Massive sandstones of upper Mount Marion Formation on right.

Quarry in upper part of Mount Marion
Quarry in upper part of Mount Marion on right behind houses.

Roadside cuts in upper middle part of Mount Marion
Roadside cuts in upper middle part of Mount Marion Formation for next 1.0 mi.

Upper part of Mount Marion Formation for next 0.3 mi.

STOP 8. Upper part of the Mount Marion Formation.
Abandoned flagstone quarry north of N.Y. Rt. 28 and east of Onteora Lake. PRIVATE PROPERTY.
Turn right into entrance to abandoned flagstone quarries; park and walk up roadway past concrete barriers. Extensive exposures throughout the quarries. This stop will concentrate on rocks along the entrance road and in the upper quarry behind abandoned buildings on quarried cliff.
This abandoned quarry features excellent exposures of nearshore marine to non-marine transitional deposits in the upper part of the Middle Devonian Mount Marion Formation. The upper strata of the formation are dominated by cyclic alternations of interbedded mudstone-sandstone facies and flaggy-bedded sandstone bodies on the order of 10 m total thickness. The coarser, sand-dominated strata may feature thin beds to lenses of quartz and chert pebble conglomerate. Normal marine faunas (brachiopods, bivalves, etc.) occur through most of the section; however, apparent plant-root traces in some beds indicate periodic subaerial exposure during deposition.
This locality was originally quarried around the turn of the century for bluestone flags that were used in New York City for sidewalks and curbstones; the quarry was reactivated during the 1970's for production of concrete aggregate (Banino, 1987). Two main levels were worked for quarry stone in the past. The main quarry face of the lower level exposes ∼9 m of section, which is comprised of: a) a lower, 1.4 m-thick sandstone body; b) a middle 5.5 m-thick unit of interbedded dark gray mudstones and thin sandstones, which coarsens toward the top; and c) 2.0 m of flaggy-bedded sandstones at the top.
The upper level of the quarry features extensive lateral exposures of the flaggy-bedded sandstones. The top 0.5 m of the middle mudstone unit of the lower quarry face are exposed in the floor of the upper quarry, where scattered brachiopods (Mucrospirifer and Devonochonetes coronatus) and bivalves can be found. A large area of the upper quarry is floored by a 10 cm-thick quartz-rich sandstone with a symmetrically rippled top and common Cruziana trilobite traces on the underside of the bed.
The mudstone unit is overlain by conglomerate lenses and/or a pebbly, coarse sandstone bed at the base of the quarry face. The overlying interval (∼1 m-thick) is characterized by thin- to medium-bedded sandstones and thin, black, fine-grained, organic- and pyrite-rich beds. These thin (∼1-5 cm-thick), recessed interbeds contain abundant plant material, which include lenses of in situ root traces; yellow to white mineral crusts (Melanterite and Epsornite?) weather out of the crevices, probably associated with the decay of pyrite. Single valve rhynchonellid brachiopod shells also occur in some of the thin sandstones.
Overlying strata (ca 5 m-thick) are dominated by medium-bedded lithic arenites that appear planar to cross-bedded. Pebbly lenses occur scattered through the section. Extensive bedding plane exposures of the flagstone interval are visible in the southern part of the quarries, where several unusual trace fossils have been found. A discontinuous but prominent crevice, ∼halfway up the flaggy sandstone unit, is bounded by two lighter- and more smoothly-weathering sandstone beds. The upper bed (∼40 cm-thick), which forms the cap rock of the east wall, appears in side view to feature in situ plant root traces. Overlying sandstones are darker and flaggy bedded, similar to the beds below.
The top surface of the sandstone body is rippled (symmetric ripples) and is abruptly overlain by olive-gray colored, crumbly-weathering, sandy mudstones and thin sandstones. Relatively large Camarotoechia and Mucrospirifer brachiopods occur in the upper part of the sandstones (as densely packed lenses) and the overlying sandy mudstones. North of the quarry, in the woods, a relatively steeply-dipping body of thin, highly trough cross-bedded sandstones overlies the position of the olive-gray shales. It is not clear at present if this unit represents a submarine or subaerial channel-form deposit.

Upper Mount Marion strata.

Mount Marion in small quarry on right.
Marine shales in uppermost Mount Marion in small quarry on right.

Top of marine section
Top of marine section at quartz-rich sandstone at base of exposure on left hand side(= top of Mount Marion Fm.); overlying thick sandstones are in the succeeding Ashokan Formation.

Exposure of Ashokan Formation on right side.

Outcrops of Plattekill Formation on left and right
Lowest redbed exposures along Rt. 28.

Plattekill Formation on right.

STOP 9. Plattekill Formation.
Cuts along N.Y. Rt. 28, 0.7 mi. west of intersection with N.Y. Rt. 375.
This outcrop of red, green, and olive mudstones (lower part) and medium-gray, cross-bedded sandstones (upper part) of the Plattekill Formation are a gross generalization of facies that characterize the remainder of the Middle and Upper Devonian of the Catskill Front. The lower 5 m of green, green-mottled red, and red mudstones feature calcrete nodules, indicative of development of paleosols on subaerial flood plains. Plant fossils and root traces are visible throughout much of the section; distinctive weathering styles appear to characterize different paleosol units along the outcrop. Overlying olive-weathering mudstones (∼1.5-3.0 m-thick) are erosively capped by -4 m of planar cross-bedded, lithic arenites that represent deposition within a migrating fluvial channel.
Pedersen et al. (1976) reported a zone of deformation in a paleosol horizon - 2.5 above the base of the section. These structures on close examination appear to resemble separate, low angle, basin- or bowl-shaped structures ∼0.5 to 1.0 m in diameter. They are similar to "pedogenic slickensides" described from redbeds of Silurian-, Devonian-, and Pennsylvanian-age by Gray and Nickelsen (1989). Slickenlines on the bottom-side of the structures visibly radiate outward and upward through 180° laterally on the outcrop. Pedogenic slickensides form in modern vertisols associated with seasonal wetting and drying of expansive clays in the B soil horizon (Gray and Nickelsen, 1989; Ciolkosz et al., 1979).
The succession of events for Stops 4 and 6-9 and overlying strata are summarized here (see Figure 4). Six major depositional sequences are recognized above (and including) the top of the Onondaga Limestone in New York State (see body of paper above). These sequences correspond to five formation-level subdivisions of the Hamilton Group (upper Onondaga and Union Springs Fms., Mount Marion/Oatka Creek Fms., Skaneateles Fm., Ludlowville Fm., and the Moscow Fm., Sequences DS4-8, respectively) and the overlying Tully and Geneseo Formations (Sequence DS9). In the Catskill Front, marine rocks of Sequences DS4 and DS5 feature recognizable transgressive and highstand systems tracts (see body of paper). Strata of the overlying Sequences DS6-9 are fully non-marine; no sequence stratigraphic framework for these fluvial-dominated rocks has been proposed (however, see Bridge and Willis, 1994).
A larger-scale set of trends related to Acadian Tectophase II are superimposed onto Depositional Sequences DS4-9. Widespread, intrabasinal carbonate deposition during the late, quiescent stage of Acadian Tectophase I (Onondaga Limestone) is succeeded by a thick, wedge-shaped body of siliciclastics associated with Acadian Tectophase II (Hamilton Group). The progression of Tectophase II is characterized by: l) onset of renewed tectonism accompanied by increased volcanism and deposition of the Tioga Bentonites, subsidence of a proximal foredeep (eastern NY) and uplift of a peripheral bulge (western NY), and transport/deposition of initially fine-grained black shale. This was followed by the onset of progradation of progressively coarser clastic marine sediments into eastern New York (Union Springs and Mount Marion Fms.); 2) decreased tectonism in the Acadian orogen and progradation of non-marine facies into eastern New York (Ashokan, Plattekill, and Manorkill Formations). Decreasing siliciclastic input is indicated by a general upward increase in carbonate content in upper Hamilton Group strata in central to western New York (Ludlowville and Moscow Fms; this trend is analogous to general trends through the Schoharie Formation during Tectophase I); and 3) a return to tectonic quiescence and low relief of tectonic highlands in the late Middle Devonian, indicated by deposition of intrabasinal limestones (Tully Formation). Stages 1-3 comprise Acadian Tectophase II as it is developed in New York State. Onset of black shale deposition in the latest Middle Devonian (Geneseo Formation) marks the onset of Acadian Tectophase III.

B6: ORDOVICIAN ROCKS IN THE MOHAWK VALLEY: GEOLOGIC SITES FOR
EDUCATION OF HIGH SCHOOL AND COLLEGE STUDENTS
JOHN IRWIN GARVER
Schenectady NY 12308-2311
garverj@unvax.union.edu
The Mohawk Valley has outstanding bedrock geology and the stratigraphy of the Middle Ordovician rocks reflects the tectonic events associated with the Taconic orogeny (Figures 1-4). One advantage of teaching in this area is the ability to integrate the local stratigraphic record into classes concerned with stratigraphy, sedimentology, depositional environments, tectonics, and other geologic studies (Garver, 1992). Most of the Mohawk Valley is underlain by Middle Ordovician rocks that were deposited prior to and during the collision of the Taconic arc. This collision is clearly reflected in changes in the stratigraphic record, as well as structural and metamorphic events farther to the east (see Kidd et al. [this volume] for the structural aspects of the frontal thrust; see Hollocher [this volume] for the metamorphic aspects across the Taconic Orogenic belt). These changes include: 1) a deepening upwards trend that reflects tectonic subsidence; 2) lateral facies changes that reflect the basin geometry; and 3) paleocurrent trends that ultimately define the nature of coarse clastic infilling during the orogeny. The immediate focus of this field trip is on the stratigraphic record of the Taconic orogeny in the Mohawk Valley. In our examination we will look at separate pieces of the stratigraphy in ascending stratigraphic order - we will be traveling upward through time. We will examine changes in depositional environments and how these changes can be inferred from the rock record. We will also examine the lateral variation in the stratigraphy to infer changes in the basin geometry. Finally, we will use paleocurrent indicators to infer the shape of the basin and the flow directions of sediment fill during the Taconic orogeny.
This trip has two goals. The first goal is to gain an understanding of how to interpret depositional environments and how the changes in depositional environments can be used to infer tectonic events. The second, and perhaps most important, goal is to discuss how these different geologic sites can be used for the education of students. I have little experience with primary and secondary students on the outcrop, but I do have considerable experience with undergraduate students in the field and some of the challenges encountered in this arena certainly apply to younger students. Of the five sites on this trip, I use four of them in my course "Stratigraphy and depositional environments of New York", which I teach at Union College (for a complete description of the course, see Garver, 1992). These sites are advantageous because they focus on the most dramatic changes in the stratigraphy and they are easily accessible - most are in public parks.

B6: ORDOVICIAN ROCKS IN THE MOHAWK VALLEY: GEOLOGIC SITES FOR
EDUCATION OF HIGH SCHOOL AND COLLEGE STUDENTS

Canal Park and Lock 9 to the left.

Sign tells of the displacement on the Wolf Hollow Fault.
Bear left and continue on Wolf Hollow Rd. Note historic sign telling of the displacement on the Wolf Hollow Fault.

STOP 1: Hoffmans Fault
In Wolf Hollow a high-angle normal fault cuts the Schenectady Formation and older rocks (Figure 1 and Figure 10). This fault, which trends about 030 (north-northeast) is one of a family of high-angle normal faults that were probably active in the Middle Ordovician. Most of these faults dip to the east and the eastern block is downdropped- some notable exceptions occur farther to the west at the "Noses" (Figure 1). At this site one can see slightly tilted rocks of the Schenectady Formation (interbedded sandstone and shale) on the east side of the road. On the west side of the road are exposures of the Beekmantown Group - these are especially easy to see when the leaves are off the trees. Not visible from here are also exposures of the Trenton limestones and the Utica Shale, both resting above the Beekmantown Group. Using stratigraphic mismatch we can determine the apparent throw on the fault. Although the sign at the entrance to Wolf Hollow states that the fault has 1000 feet of displacement, is difficult to calculate the exact displacement because there are no clear stratigraphic markers in the Schenectady Formation. (See Locality 19 in Fisher, 1980). Using simple cross sections and reasonable stratigraphic thicknesses for these units, the apparent displacement is somewhere between 200 and 400 meters.

Schenectady Formation on the east side
Note the excellent exposures of the Schenectady Formation on the east side of the road along the entire length of the Hollow.

Exposures of the very fossiliferous Trenton Group limestones
Exposures of the very fossiliferous Trenton Group limestones (Glens Falls Limestone) on the left (west) side of the road).

Beekmantown Group (Wolf Hollow Limestone)
Several outcrops of carbonates of the Beekmantown Group (Wolf Hollow Limestone which is Lower Ordovician) along the right (north) side of the road.

STOP 2A: Quarry at Manny's Corner
Quarry at Manny's Corner - Beekmantown , Black River, Trenton groups
Pull off in small overgrown drive on left side of road to old abandoned quarry. This is private property. Please call Cranesville Block Company (518-346-5749) for permission to enter the "Manny's Corner quarry".
In this quarry, the Cambrian to Lower Ordovician Beekmantown Group is disconformably overlain by Middle Ordovician carbonates of the Black River and Trenton Groups (see Locality 17 of Fisher, 1980). The floor of the quarry is composed of the Lower Ordovician Wolf Hollow Member of the Tribes Hill Formation. The Tribes Hill Formation is one of the upper units in the Beekmantown Group, a widespread and relatively uniform sequence of carbonates and dolomites found throughout eastern North America (for other stops in this unit see Friedman, 1972). Note that this unit is dolomitic, has algal mounds, and is replete with a single species of gastropod (Ecculiomphalus ). The walls and nearby outcrops (north side of Rt. 67) are composed of the Lowville Limestone, the Amsterdam Limestone, and the Glens Falls Limestone (&tilds;Larrabee Limestone and the overlying Shoreham Limestone) all of which belong to the Black River Group and the Trenton Group (see Fisher, 1965; 1977). At this exposure, the unconformity between the Beekmantown Group and the overlying Middle Ordovician rocks is well displayed, and regional stratigraphic studies indicate that the upper part of the Beekmantown Group (the Lower Ordovician part) is missing. The Lowville Limestone is generally not fossiliferous, but it contains birdseye texture, a few vertical burrows, and mudcracks; locally it is dolomitic. The Amsterdam Limestone is irregularly bedded and the contact between the two units is marked by the first fossiliferous beds. These thin beds are very fossiliferous, with brachiopods, rugose coral, crinoids, and trilobites dominating the fauna. As you examine the outcrop from bottom to top, note the distribution of coral.
For students in "Stratigraphy and depositional environments of New York," this project involves measuring a short (10 m) stratigraphic section, in which they describe the fossil content of the units, and interpret the depositional environments of these shallow marine rocks. As we will see, the interpretation of the depositional environments is aided by carefully noting the sedimentary structures and faunal content of each rock unit. After examining the rock we will have a brief discussion about relative sea level changes and the role of tectonic activity. The change in faunal content upsection indicates deepening through time and most students use their newly acquired knowledge concerning sea level changes and basin subsidence to explain this apparent transgression. As we will discuss, the deepening in the stratigraphic section may be related to tectonic subsidence. The goal of this phase of the project is to relate depositional environments and the unconformity to regional or global events that might have produced this particular sequence.

STOP 2B: Road cut across from Manny's Corner Quarry
Trenton Group Limestone
Exposed in the roadcuts along the north side of Rt. 67 are excellent exposures of the extremely fossiliferous Glens Falls Limestone. Note that these beds contain fossiliferous limestone (locally with scoured bases and graded beds) with interbedded calcareous shale which is also fossiliferous.
These rocks are replete with fossils; brachiopods, bryozoans, trilobites, crinoids, and others. Of particular note are two rather distinct trilobites. A small trilobite, Cryptolithus tesselatus, is common in the resistant limestone beds - they are typically the size of a fingernail. A much larger trilobite, Isotelus gigas, is common (unfortunately as fragments) in both the limestone bed and the calcareous shale. These are important index fossils. As we will see at Canajoharie Creek, geologists generally use fossils for either biostratigraphy or for reconstructing depositional environments. The concepts of biostratigraphic analysis are fundamental and are the basic tenet of the science of stratigraphy. As organisms evolve through time they change and new species eventually become extinct. By carefully studying the vertical distribution of distinct and common species, paleontologists have been able to determine fossil zones that are defined by the occurrence of a particular index fossil(s). Cryptolithus tesselatus is an index fossil for these beds. As we move upsection we will no longer see this fossil because it had become extinct. The distribution of index fossils and other more common and long ranging fossils is very closely related to depositional environments. (Good index fossils are found in many depositional environments). Some fossils can be used to determine the relative water depth. In the Mohawk Valley there have been very detailed studies of fossils with respect to water depth (see Cisnee and Chandlee, 1982; Cisne et al., 1982). As we will discuss at the outcrop, the assemblage of fossils in this outcrop suggests deeper water than does the assemblage in the underlying Amsterdam Limestone. Additionally, the occurrence of fine-grained calcareous shale suggests deposition below the normal wave base (the effective depth to which fair weather waves affect the bottom sediments). In this regard the stratigraphic section is deeper than that at the quarry. A deepening trend such as this is referred to as a transgression.

Dolostone of the Beekmantown Group
Small public park (to left] with very nice exposures of the dolostone of the Beekmantown Group.

Exceptional exposures of the Utica Shale
Note the exceptional exposures of the Utica Shale across the interstate in the exit ramp for the eastbound traffic.

Middle Ordovician Trenton Group in opposite lane
Excellent exposure of limestones of the Middle Ordovician Trenton Group in the opposite lane. Above this exposure (on Rt. 5S) is the conformably overlying Utica shale. At the far end of the road cut on I-90, the uppermost beds of the Beekmantown group are exposed. Once again, the Knox unconformity separates the Trenton Group and the Beekmantown Group.

Cross the Noses fault.
This fault belongs to the family of normal faults that cut Middle Ordovician and older rocks in the Mohawk Valley, and is therefore similar in timing to the Hoffmans Fault. This fault and others to the west bound an upthrown block (horst) that exposes some of the oldest rocks in the Mohawk Valley. Note that this horst was probably a topographic high during the Middle Ordovician- as can be seen from the regional geologic map (Figure 1), the Trenton Group was not deposited on this block. Elevation of the horst above sea level may explain this distribution of rock units.

Precambrian Basement and overlying rocks of Beekmantown Group.
Across 1-90 and along the barely visible Rt 5S are prominent exposures of the Precambrian
Basement and the unconformably overlying rocks of the Beekmantown Group. The contact between
these rocks, which can be seen along Rt 5S, shows evidence of structural disruption, and the
interpretation of the contact is complicated by this disruption. The Precambrian rocks are provisionally
assigned to the Peck Lake Formation, which is a garnet biotite gneiss about 1.1 Ga
(billion years old). Although this contact may be faulted, in this area the Beekmantown Group is
known to unconformably overly the Precambrian Basement. For a discussion of this area see
Locality 12 in Fisher, 1980.

Cliffs of the Upper Cambrian Little Falls Dolostone
For about 0.5 miles there are very steep cliffs of the Upper Cambrian Little Falls Dolostone on the left (south) side of I-90. This unit, which is part of the Beekmantown Group, is stratigraphically lower than all of the other exposures of the Beekmantown Group that we will see on this trip. In places this unit has vugs containing doubly terminated quartz crystals locally known as the "Herkimer Diamond".

STOP 3: Canajoharie Creek (Floral Avenue)
Beekmantown, Black River, Trenton groups
Park at end of Floral Ave in dirt parking lot at the end of the street. Walk toward river and take foot path upriver for several hundred meters.
Similar to the exposures at Manny's Corners, limestone and shale of the Trenton Group disconformably overlie dolostone of the upper part of the Beekmantown Group in the river bed of Canajoharie Creek. This well-exposed and very fossiliferous stratigraphic section records important changes in the depositional history of the Mohawk Valley. Rocks in the Canajoharie Creek river bed include the Chuctanunda Creek Dolostone, which is pan of the Beekmantown Group, and the disconformably overlying limestone and shale of the Trenton Group. Interbedded limestone and shale of the "lower Trenton Group" is conformably overlain by the Utica Shale, which is some 305 meters thick at this locality. All rocks of the Trenton Group were deposited during the Trentonian stage of the Middle- Late Ordovician (circa 448-458 Ma) and the rocks of the Chuctanunda Creek member of the Tribes Hill Formation were deposited during the Gascondian stage of the Early Ordovician (circa 505-488 Ma).

STOP 4: Canajoharie Creek (Wintergreen Park) - Utica Shale
The second stop, which is near the top of the Utica Shale, can be accessed from Wintergreen Park (only open during the summer but it is possible to visit this locality year-round). Here the Utica Shale is a black, laminated and locally fossiliferous shale with minor thin (generally <2-5 cm) seams of light gray and rusty weathering bentonite. The bentonites can be recognized easily because orange-red rusty streaks emanate from them. The rusty streaks are caused by the oxidation of pyrite which is common in the bentonitic seams. We will walk downstream to examine a fossiliferous section containing the trilobites Triarthus and Isotelus, as well as brachiopods and graptolites. Locally, very large nautiloids can be found in this outcrop. For pioneering work on the Utica shale (slightly to the west) see Kay, 1953.
The changes in depositional environments and basin geometry during the deposition of these rocks are well recorded in both the stratigraphy and lateral and vertical distribution of fossils. As you can imagine, individual organisms (fossils) preferred different depositional settings and therefore they commonly are found in only certain facies. For example, a thick-shelled pelecypod may inhabit a high-energy niche in the shoreface while a thin-shelled brachiopod may have found its niche in a deep-water environment. Once preserved in the geologic record, these individuals may serve as useful indicators of the energy level or water depth during deposition of a particular unit. In addition, the distribution of such fossils may provide important information concerning the original configuration and deepening trends within a basin of deposition. (see Cisnee and Chandlee, 1982; Cisne et al., 1982). From the enormous database collected by John Cisne and his co-workers, Ray Gildner has developed a Hypercard stack (Macintosh-based) that shows the distribution and occurrence of 10,000 fossils in the database. In essence, one can see the places where an individual fossil was observed in many stratigraphic sections. The distribution of two depth-sensitive individuals are shown in Figure 5. Here you can see that the distributions of Triarthus and Cerarus are very different; Triarthus is restricted to the eastern (deeper) sections and Cerarus is present only in the western (shallower) sections. From this we can see that the basin deepens to the west.
The occurrence of the bentonite is extremely important (Figure 5). Bentonite is commonly interpreted to represent volcanic ash. Therefore not only can these thin beds serve as chronostratigraphic markers (one bed is the same age everywhere), but they can also tell us that volcanic activity occurred nearby. Although the stratigraphy records this dramatic subsidence, this volcanic ash is the first direct sample of the Taconic arc to the east.

Precambrian Dike across the river
Again the Little Falls Dolostone is exposed to the right (south), but here you can also see a well exposed outcrop of the Precambrian basement across the Mohawk river on Rt. 5N. This exposure is also provisionally assigned to the Peck Lake Formation (circa 1.1 Ga) and is intruded by a dark weathering basaltic dike that has been dated at about 700 Ma (see locality 12 in Fisher, 1980). Dikes of about this age are common in the Adirondacks.

Trenton Group resting unconformably on the Beekmantown Group
Exposure of Trenton Group resting unconformably on the Beekmantown Group. Look closely because
the unconformity is at the very beginning of the outcrop (west side).

Exposures of the Beekmantown Group on the right.

Cross the approximate trace of the Wolf Hollow Fault.

Middle Ordovician Schenectady Formation
Excellent exposures of interbedded medium- to thin-bedded sandstones and shale of the Middle Ordovician Schenectady Formation. If observed from a distance, this turbidite sequence shows low-angle truncations that probably represent channeling on a submarine fan.

Exposures of the Middle Ordovician Schenectady Formation.

STOP 5: Plotterkill Preserve - Schenectady Formation
The Plotterkill Preserve is a private preserve that surrounds the lower reaches of the Plotterkill stream which drains north into the Mohawk River (Figure 12 and 13). The stream cuts into and beautifully exposes sandstone and shale of the Middle Ordovician Schenectady Formation (see Locality 30 in Fisher, 1980). The Schenectady Formation is Mohawkian in age (upper Middle Ordovician). Most of the formation (and the Utica Shale) is restricted to the Nowadagan stage but the lower beds belong to the Canajoharian stage (i.e., the top of the Mohawkian). In general the Schenectady Formation is composed of interbedded light-brown- to buff-weathering, medium- to fine-grained sandstone with interbedded gray to black laminated shale. The sandstones are laminated and rippled and locally graded. They commonly have flutes and grooves on their bases and ripples on the tops. The unit is virtually unfossiliferous with exception of uncommon graptolites. These sandstones are interpreted to have been deposited in very deep water and to have been transported to the site of deposition by turbidity currents.
Although many geologists accept the notion that the clastic material had a source to the east, the paleocurrent data from this unit do not clearly support this contention. Using data collected from the Plotterkill Preserve and data from several other sites in the Mohawk Valley one can reconstruct the paleoflow directions within the basin during deposition. Virtually all of the pareocurents trend to the north-northeast. As exaplained above, these current directions may reflect sedimentation on a submarine fan that formed axial to the principal structural trend of the foreland basin.
For students in Stratigraphy and depositional environments of New York, this project involves measuring, plotting, and interpreting paleocurrents and relating this information to concepts of basin infilling. In the field, students spend several hours measuring flutes, grooves, and ripple marks from relatively flat-lying sandstone beds with a Brunton compass. Measurements are then entered into computer data files and plotted using Macintosh software. In addition to the data set collected by the students (all the data from different groups are merged), they are given two additional data sets from geographically separated outcrops of the same unit.
The Schenectady Formation has very good paleocurrent indicators - mainly flute and grooves. Virtually all of the paleocurrents in rocks of the Schenectady Formation in the Plotterkill preserve indicate flow from the southwest to the northeast (flow direction to about 020 to 030°) (see Figure 14 ). If these sediments were derived from the Taconic Arc to the east, then why do the ancient flow directions tell us that the sandstone flowed from the southwest? The answer lies in a possible interpretation concerning how turbidites flow in a basin and the shape of the basin. Turbidites flow downslope. If they encounter the deepest part of the basin, they tend to turn to flow along the basin axis as opposed to flowing upslope on the other side. In this regard. we recognize that foreland basins can develop two different types of submarine fans. The first, called a lateral fan, is composed of turbidites that accumulate directly off the edge of a large source terrain. In this case, all of the paleocurrents tend to record flow directly away from the source. The second, called an axial fan, records flow parallel to the source and possible parallel to the structures that influenced the source. This part of the Schenectady Formation was most likely deposited as an axial fan with a main feeder canyon somewhere to the south. It is interesting to note that the average paleocurrent direction in the Schenectady Formation is perpendicular to the direction of tectonic transport (thrusting direction) in the western Taconics (about 290 to 300° as determined at five localities). If thrusting in the Taconics was related to basin formation, then one would predict a foreland basin with a trough-like axis oriented at about 020-030° - exactly the orientation of the paleocurrents. A similar trend in sediment dispersal was recognized in correlative rocks in Pennsylvania, where the sandstones of the Martinsburg Formation indicate basin infilling by both lateral and axial submarine fans (McBride, 1962).
In this area, the Schenectady Formation is underlain by the Utica Shale (i.e. Wintergreen Park), and together their thickness is nearly 1000 to 1800 meters. This shale/sandstone package thins gradually to the west and thickens dramatically to the front (east edge, near Troy) of the Taconic Range. The extreme thickness and the composition of these strata is an important sedimentation pattern. The thickness of strata preserved in a basin is generally a reflection of the relative depth or the amount of subsidence that occurred in the basin. This room for sediment is sometimes referred to as "accommodation space" because if there is not room for sediment (a basin), sediment tends to not accumulate. With this in mind, one could postulate that the basin was deepest, or experienced the most subsidence from here (Piotterkill) east to the Troy area where the unit thickens considerably. Shale that filled the basin has no obvious provenance or source area because the particles are so fine-grained. However, recent studies suggest that this shale reflects the changes in the composition of the thrust complex to the east (Garver et al., 1996). Sandstones contain coarse-clastic material that represents identifiable fragments of the source region. Because these and correlative sandstones have a distinct composition, workers have postulated that these sandstones had a source that lay to the east that was composed of mainly sedimentary rocks. Sandstones of the Schenectady Formation contain quartz, feldspar, and sedimentary rock fragments (with minor metamorphic and volcanic rock fragments), and a minor detrital mica.
The Schenectady Formation, therefore, was derived from the Taconic orogenic belt to the east - in this regard it is a synorogenic deposit. Paleocurrents indicate that the flow of sediment was to the north-northeast, which is exactly what we would predict if the structures presently preserved if the Taconic mountains produced a foreland basin. The sandstones and the shales were derived from the thrust complex and are therefore rich in sedimentary detritus and recycled grains - detritus directly from the Taconic arc is rare.

B7: TREATMENT OF SURFACE AND GROUNDWATER: TOUR OF MOHAWK VIEW WATER TREATMENT PLANT
ROBERT J. MASWICK
Chief, MVWTP Operator
Latham Water District
347 Old Niskayuna Road
Latham, NY 12110
PHILLIP D. SNOW, PHD
Civil Engineering Department
The Mohawk View Water Treatment Plant is unique in that it has three different raw water supplies: 1) a surface water reservoir in a suburban housing area with occasional algal blooms; 2) a ground water supply with high amounts of soluble iron and manganese; and, 3) a river supply with varying flows and water quality problems. The tour will show the wide variety of treatment methods used to deal with the water quality problems associated with these various raw water sources.

B7: TREATMENT OF SURFACE AND GROUNDWATER: TOUR OF MOHAWK VIEW WATER TREATMENT PLANT

STOP 1.Overview of Latham Water District Water Supply
Overview of Latham Water District Water Supply
The major components of the Latham Water District Water Supply include the Intake Channel, Raw Water Pump Station, Mohawk View Water Treatment Plant (MVWFP), Clearwell storage tanks, the Mohawk View & River Road High Lift Pump Stations, and Lagoons for settling basin and backwash wastes. The water treatment plant consists of the Aeration Basin, Flocculation and Coagulation Basins, Settling Basins, Rapid Sand Filters, and chemical feed facilities. The well supply, completed in 1965, now consists of 5 wells, with a permitted withdrawal of 7.5 MGD. The well supply receives full treatment at the WTP. Although the RRWTP was abandoned in 1985, the Stony Creek Reservoir today still supplies over 5.1 million gallons of raw water (on an almost daily basis) to the MVWTP.

B8: ENVIRONMENTAL TECHNOLOGY AND PRESERVATION: THE PINE BUSH, LANDFILLS, AND GROUNDWATER INTEGRITY
JACQUELINE A. SMITH
ERIC ESLINGER
Alpha Earth, Inc.
10 Sussex Road
Glenmont, NY 12077
DAVID L. HANSEN
Landfill Technologies, Inc.
P.O. Box 519
West Sand Lake, NY 12196
The active Albany Interim Landfill and the closed Albany City Landfill are located in the City of Albany, New York, in a region of stabilized dunes known as the Pine Bush (Figure 1). Surface deposits in the Pine Bush consist of highly permeable sands originally deposited by the paleo-Mohawk River as delta deposits during the high stand (maximum extent) of glacial Lake Albany. The sands constitute a large unconfined aquifer. Subsurface investigations have shown that the nearby unlined Albany City Landfill, which was opened in 1969, has contributed both organic and inorganic contaminants to the Pine Bush aquifer. The lined Albany Interim Landfill was designed in a manner intended to protect groundwater integrity in the surrounding Pine Bush region. Groundwater contamination on the scale of the area of the Albany City Landfill can be difficult to remediate. Remediation of smaller commercial sites with contaminated groundwater is a somewhat more tractable problem. This field trip provides an opportunity to visit the Pine Bush, the Albany Interim Landfill, the Albany City Landfill, and a small commercial site (Stewart's Shop #182) that is currently undergoing groundwater remediation.

B8: ENVIRONMENTAL TECHNOLOGY AND PRESERVATION: THE PINE BUSH, LANDFILLS, AND GROUNDWATER INTEGRITY

STOP 1: Albany Interim Landfill
Access to the landfill is restricted. Call Landfill Technologies, Inc. (518-674-8694) in West Sand Lake, New York, to arrange a tour of the active and closed landfill areas.
ALBANY INTERIM LANDFILL The Albany Interim Landfill (AIL) covers an area of approximately 12 acres on the west side of Rapp Road in the City of Albany (Hansen, 1995). The AIL was constructed in the early 1990s with a double composite liner. The closed Greater Albany Landfill and the New York State Thruway lie to the south. A residential trailer park is located several hundred feet to the north. The Pine Bush Preserve borders the AIL to the west. Landfill service buildings and Rapp Road lie to the east. Figure 5 shows the approximate location of the AIL relative to the surrounding properties. The AIL is operated by Landfill Technologies, Inc. (LTI) of West Sand Lake, New York. In 1991, a program of biostabilized solid waste placement was proposed at the AIL. The program began with a pilot project in 1989.

STOP 2:Pine Bush Preserve and Albany City Landfill
STOP 2: Albany Pine Bush Preserve The Albany Pine Bush Preserve is open to the public. Sign in at the box near the entrance. We will walk generally east, pausing atop and between dunes to note the morphology and vegetation, eventually ending up at the west end of the closed Albany City Landfill. On the way, we will pass a monitoring well that is most likely GW-lD, the upgradient well installed by Engineering-Science in 1990. After looking at the landfills from this different perspective, we will make our way back through the Pine Bush to the vehicles.
ALBANY CITY LANDFILL
The Albany City Landfill (the landfill) covers approximately 80 acres of the Pine Bush. The landfill is located on the north side of the New York State Thruway between Rapp Road, the Conrail railroad tracks, and the Pine Bush Preserve. The landfill has been capped and permanently closed since 1994.
The landfill is of a relatively simple design: it is unlined, it has no leachate collection system (Malcolm Pirnie, 1988), and it is believed to be a surface waste pile rather than an excavated pit refilled with waste (Engineering-Science, 1992). During its years of operation, the landfill was filled using conventional sanitary landfilling techniques of compaction and daily covering of waste. Methane and leachate were not extracted during operation. Methane extraction wells and automatic burners were installed in 1991 after methane migration toward the south (under the Thruway) was discovered.
The landfill began operations in August 1969. It was operated by a private company under contract to the City of Albany until 1974, when the Albany Department of Public Works assumed operational responsibility. At the time of the transfer of responsibility, weight scales were installed and the City began to keep records of the incoming waste. Until that time, the waste had been largely unrecorded and uninspected. It is suspected that during the 1969-74 period and potentially until the 1980s, numerous area industries had disposed of various amounts of industrial and hazardous wastes at the landfill (Malcolm Pirnie, 1988; Engineering-Science, 1992).
Beginning in 1983, a portion of the waste brought to the landfill was used as fuel for the ANSWERS Refuse-Derived Fuel (RDF) plant located on Sheridan Avenue in Albany. Fly ash from the incinerator at the ANSWERS RDF plant was brought to the landfill for disposal (Malcolm Pirnie, 1988). Between 1983 and 1987, approximately 203,265 tons of fly ash were disposed of at the landfill. In addition, approximately 343,143 tons of municipal and other waste were deposited at the landfill during the same period (Engineering-Science, 1992). The municipal and other wastes brought to the landfill for disposal included bypassed solid waste (waste not used as RDF), excess RDF, petroleum-contaminated soil, picked material (unshreddable material removed during RDF processing), and ferrous material (Malcolm Pirnie, 1988), plus pharmaceutical wastes, iodine/soil wastes, and asbestos (Engineering-Science, 1992). The landfill began accepting petroleum-contaminated soil in 1987 (under the approval and recommendation of the New York State Department of Environmental Conservation, or NYSDEC), primarily for use as daily cover material; the landfill accepted approximately 14,000 tons of petroleum-contaminated soil in 1987 (Malcolm Pirnie, 1988).
Closure of the landfill began in 1982 under a phased approach. In 1985, the City of Albany signed a NYSDEC Order of Consent for the final closure of the landfill. In 1986, the City of Albany proposed an expansion project of the existing landfill to facilitate and expedite the closure process (Malcolm Pirnie, 1988). The expansion was approved by NYSDEC in 1989 (Engineering-Science, 1992), which resulted in the construction of the Albany Interim Landfill during the early 1990s.

STOP 3: Brandywine Stewart's Shop
The site is a convenience store and gas station. The remediation shed is closed to the public. Please do not take up customer parking spaces or block customer access to the store or gas pumps.
STEWART'S SHOP #182
The volatile organic compounds benzene, ethylbenzene, and toluene, which were detected at relatively low concentrations in groundwater at the Albany City Landfill in 1990, are commonly found as groundwater contaminants at sites that have experienced subsurface gasoline spills. The volatile natures of these and many other compounds typically found in gasoline offer a means of remediating, or cleaning up, the contaminated groundwater by encouraging volatilization, or evaporation, of the compounds. One method of encouraging volatilization of compounds is to pump contaminated groundwater through an air stripper. This remediation method is being used at Stewart's Shop #182, a small site on South Brandywine Avenue in Schenectady, New York (Figure 8).
The following information is summarized from Passaretti Geological & Environmental Consultants, Inc. (1991).
Groundwater Study
Stewart's Shop #182, a convenience store and gas station, is located at 100 South Brandywine Avenue in Schenectady, New York. In 1991, three underground gasoline storage tanks and one underground waste oil tank were removed from the site as part of a tank upgrading program. Petroleum-contaminated soil was encountered during the tank removal. Approximately 250 cubic yards of soil were removed from the former tank pit for offsite disposal. New underground storage tanks were installed in a different part of the site. The site had reportedly been a Stop & Go Station prior to being a Stewart's Shop. The contiguous site to the northeast had also reportedly been a gas station. The NYSDEC representative requested completion of a groundwater study at the site.

B9: GEOLOGY AND MINING HISTORY OF BARTON MINES CORPORATION, GORE MOUNTAIN MINE
WILLIAM M. KELLY
Rm. 3140 Cultural Education Center
wkelly@museum.nysed.gov
MARY LOUISE HILL
Department of Geology
Temple University
Philadelphia, PA 19122-2585
mlhill@astro.ocis.temple.edu
This trip proceeds from Union College to the former Barton Garnet Corporation mine near the summit of Gore Mountain, New York. For 105 years, this was the site of the world's oldest continuously operating garnet mine and the country's second oldest continuously operating mine under one management.
The Barton Mines Corporation open pit mine is located at an elevation of about 800 m (2600 ft) on the north side of Gore Mountain (Fig.l ). The community at the mine site is the highest self-sufficient community in New York State. It is 16 km (10 mi) from North Creek and 8 km (5 mi) from NY State Route 28 over a Company-built road that rises 91 m (300ft) per mile. This road, like others in the vicinity, is surfaced with coarse mine tailings. About eleven families can live on the property. The community has its own water, power, and fire protection systems. On the property are the original mine buildings and the Highwinds Inn, built by Mr. C.R. Barton in 1933 as a family residence. The Inn is now privately leased from the Corporation and operates 10 months per year. It offers a four-bedroom lodge, a four star dining room, cross-country skiing and fantastic views of the Siamese Wilderness Area.
The garnet is used in coated abrasives, glass grinding, metal and glass polishing, and even to remove the red hulls from peanuts. Paint manufacturers add garnet to create non-skid surfaces and television makers use it to prepare the glass on the interior of color picture tubes prior to the application of the phosphors. Barton sells between 10,000 and 12,000 tons of technical-grade garnet abrasive annually. About 40% of the company's shipments are to foreign countries. All current U.S. production of technical-grade garnet is limited to the Barton Mines Corporation. The product is shipped world wide for use in coated abrasives and powder applications (Austin, 1993a,b).
Garnet has been designated as the official New York State gemstone. Barton produces no gem material but collectors are still able to find rough material of gem quality. Stones cut from Gore Mountain rough material generally fall into a one to five carat range. A small number of stones displaying asterism have been found. Garnets from this locality are a dark red color with a slight brownish tint. Special cutting schemes have been devised for this material in order to allow sufficient light into the stone.

B9: GEOLOGY AND MINING HISTORY OF BARTON MINES CORPORATION, GORE MOUNTAIN MINE

STOP 1. Barton Garnet Mine
HISTORY
The early history of the Barton garnet mine has been compiled by Moran (1956) and is paraphrased below. Mr. Henry Hudson Barton came to Boston from England in 1846 and worked as an apprentice to a Boston jeweler. While working there in the 1850's, Barton learned of a large supply of garnet located in the Adirondack Mountains. Subsequently, he moved to Philadelphia and married the daughter of a sandpaper manufacturer. Combining his knowledge of gem minerals and abrasives, he concluded that garnet would produce better quality sandpaper than that currently available. He was able to locate the source of the Adirondack garnet stones displayed at the Boston jewelry store years before. Barton procured samples of this garnet which he pulverized and graded. He then produced his first garnet-coated abrasive by hand. The sandpaper was tested in several woodworking shops near Philadelphia. It proved to be a superior product and Barton soon sold all he could produce.
H.H. Barton began mining at Gore Mountain in 1878 and in 1887, bought the entire mountain from the State of New York. Early mining operations were entirely manual. The garnet was hand cobbed (i.e. separated from the waste rock) by small picking hammers and chisels. Due to the obstacles in moving the ore, the garnet was mined during the summer and stored on the mountain until winter. It was then taken by sleds down to the railroad siding at North Creek whence it was shipped to the Barton Sandpaper plant in Philadelphia for processing. The "modern" plant at Gore Mountain was constructed in 1924. Crushing, milling, and coarse grading was done at the mine site. In 1983, the Gore Mountain operation was closed down and mining was relocated to the Ruby Mountain site, approximately 6 km (4 mi) northeast, were it continues at present.

B10: GROUNDWATER AQUIFERS OF THE UPPER MOHAWK VALLEY
PHILIP C. HEWITT
DEPARTMENT OF EARTH SCIENCES
SUNY COLLEGE AT BROCKPORT
BROCKPORT, NY 14420-2936
Much of the groundwater used by the city of Schenectady and the several smaller communities in the near vicinity comes originally from the Mohawk River via gravel aquifers lying just below or at the present surface. In addition to the city itself, the towns of Niskayuna, Rotterdam Junction and the Scotia-Glenville area also use this major primary source (Figure 1). Of course, other smaller sources exist, including the bedrock sandstones and shales (the Middle Ordovician Schenectady Formation) and surficial but small perched sand and gravel deposits adequate for household supplies with volumes that range from 1.5 to perhaps as much as 10 gallons per minute for a reasonable period of time. The Mohawk River, however, provides millions of gallons of clean fresh water each day from gravel aquifers through which the less than desirable river water flows and is, as a result, cleaned to a remarkable degree.
The basic study of the area was done by Simpson (1949) and by Winslow et al. (1965) as well as several other authors. The present study, primarily in the Rotterdam Junction Aquifer (Figure 1), builds upon their work and corrects some basic misconceptions regarding gravel aquifers of this type. It was supported by the Schenectady Chemical Company, now Schenectady International, and was used in litigation designed to protect their own and the town of Rotterdam Junction's water supply. The matter became important because the gravels were being mined and the aquifer was in danger of total removal (Figure 2). The vice-president of the company at that time (Clinton P. Braidwood) provided a drill rig and crew for my exclusive use and hired me as a consultant to study the aquifer fully. Dr. Robert Yunick, the present vice-president, continued the effort and now that litigation has ended successfully, has given me permission to publish the study. The town of Rotterdam Junction now owns the property in question in that area and James Constantino, the present town supervisor, has given permission for our entry to that particular site and has permitted our visit.

B10: GROUNDWATER AQUIFERS OF THE UPPER MOHAWK VALLEY

3.1 STOP 1 at L&M Motel. Discuss aquifer location.
THE SCHENECTADY AQUIFER
These gravel deposits are located in an area known as the Great Flats and are found along the south bank of the Mohawk River over an area a few hundred feet wide and less than one-quarter of a mile in length. The L&M Motel lies on top of the easternmost extent of that aquifer. West of the Schenectady Rotterdam #5 Well Field is Lock #8, but it is Lock #7 which actually controls the level of the water in the River (called the Barge Canal) at that point. As will be shown, the locks on the Mohawk River actually control the flow of water into these gravels.
The quality of the Mohawk River water is dramatically changed after it enters the gravels, which have small amounts of sand and clay in the interstices. As a result, water pumped at the Schenectady and Rotterdam #5 Well Field is cleaned and requires only a small amount of chlorination and relatively minor treatment to make it palatable and highly potable. Of course, it is an area in delicate balance. On an early occasion during the construction of the motel, some contamination did in fact occur but it was rapidly ended and there appears to have been no problem since that time. Any construction or even contamination from the recently built mall on Campbell Rd. (Rotterdam Square Mall), or the recently closed gasoLine station (Mobil) could also endanger these water supplies. Furthermore, the water level in the Mohawk River depends upon the lock levels for each of the aquifer portions of these gravels.

STOP 2. Continue discussion of aquifer location.
This is source of Schenectady City Water. Note Rotterdam Town Wells #5 District is in same well field. Discuss the aquifer itself and probable environmental concerns.

STOP 3 Park. Discuss source of water here.

Note bedrock on this road is Schenectady formation.

STOP 4 Old Kellam-Schaffer pit.
Discuss Rotterdam Junction Aquifer. Note groundwater elevation differences. Note surface till. Note gravel and clay and calcium carbonate blocking pores. Discuss pumping situation and excavation problems.
THE ROTTERDAM JUNCTION AQUIFER
By far the largest and most vulnerable of the gravel aquifers is the one that provides the water supply for the town of Rotterdam Junction and its main industry, Schenectady International. The length of this gravel aquifer is over 11,000 ft. and it varies from a few hundred to over a thousand feet in width. The gravel is typically a clean pea gravel, but also has a reasonable quantity of sand and minor clay. Thicknesses are quite variable but primarily the best gravels are as few as ten to fifteen to over forty feet thick in much of the length. The most interesting part of the problem lies in the fact that this aquifer is also a valuable economic resource. Its first appearance was in the Kellam-Schaffer Pit which we will visit on Stop 4. Here gravel was mined for many years. Two wells in this area tap the aquifer and for years provided water for the function of the Rotterdam Junction Chemical Plant which had (and still has) need for a plentiful supply (at least 2000 gallons per minute) of clean water for its operation. Later, others purchased the pit and expanded the quarrying, leaving a large and deep pit (Figure 2). The question of the value of the gravel versus the value of the water produced nearly thirty years of litigation, mining, periods in which mining was stopped legally, and continual study to learn everything we could about the aquifer in order to do all we could to prove its vulnerability and the probable loss of clean water with the loss of the aquifer to mining. Finally, thanks to Schenectady International, the aquifer area in the now much enlarged pit belongs to the town of Rotterdam

Note Schenectady International Plant at NE location.

STOP 5. Pump House #3 on left side opposite Post Office.
Discuss pumpage of well and the well development. Continue aquifer discussion.

STOP 6. Discuss Lock #9 and Lock System in general.