NYSGA 1979
JOINT ANNUAL MEETING OF NEW YORK STATE GEOLOGICAL ASSOCIATION
51st Annual Meeting
and
NEW ENGLAND INTERCOLLEGIATE GEOLOGICAL CONFERENCE
71st Annual Meeting
TROY, NEW YORK
October 5, 6, and 7, 1979
GUIDEBOOK
Gerald M. Friedman, editor
Hosts:
Department of Geology
Rensselaer Polytechnic Institute
Troy, New York 12181
New York State Geological Survey
Cultural Education Center
Empire State Plaza
Albany, New York 12230
PREFACE AND ACKNOWLEDGEMENTS
It is a pleasure to welcome all of you to the joint annual meeting of the New York State Geological Association and the New England Intercollegiate Geological Conference. A fine program has been arranged for you. Two overlapping sessions have been planned for October 5, a full day Symposium on Sedimentary Strata and Tectonic Movements and concurrent workshops for earth-science teachers. Field trips have been scheduled for October 6 and 7 to classical sites of eastern New York State and adjoining New England. Have fun on your field trips.
I wish to extend my thanks to the authors and field-trip leaders for their contributions. Students and staff of the Department of Geology of Rensselaer Polytechnic Institute have given time and effort in preparing for this meeting. Credit for the success of this meeting goes likewise to the New York State Geological Survey, especially to R.H. Fakundiny.
Gerald M. Friedman, President
New York State Geological Association

A1: DEVONIAN STRATIGRAPHY AND PALEOECOLOGY IN THE CHERRY VALLEY, NEW YORK REGION
Donald W. Fisher
State Paleontologist
N.Y. Geological Survey
N.Y. State Museum, State Education Department,
Albany, N. Y. 12234
PROLOG
In the northern parts of Otsego and Schoharie Counties, New York and bordering the southern margin of the Mohawk Lowlands and the northern margin of the Allegheny Uplands, is an exceptionally well exposed Early and Medial Devonian (400-365 million years old) sequence. These flat-lying sedimentary rocks record a broad spectrum of paleoenvironments. It is my intention to introduce you to the physical and organic makeup of these Devonian strata and to show how their combined characteristics enable a reconstruction of past environments and their associated role in the events of geologic history.

A1: DEVONIAN STRATIGRAPHY AND PALEOECOLOGY IN THE CHERRY VALLEY, NEW YORK REGION

Deformed Taconic Sequence rocks
Deformed Taconic Sequence rocks at bend of hill on right.

Crossing "Emmon's or Logan's Line"
Crossing "Emmon's or Logan's Line", the western limit of major Taconic gravity slides.

Guilderland; former site of glass manufacturing
Guilderland; former site of glass manufacturing, using sand from dunes atop Lake Albany clays.

Helderberg Escarpment in view to S (left)
Note terraces caused by differing horizontal limestone formations.

Climbing hill of eroded fault scarp
Southern extension of easternmost of Mohawk Valley normal faults.

Middle Ordovician Schenectady sandstone and shale
Middle Ordovician Schenectady sandstone and shale exposures scattered and small from here to Sloansville.

Crossing Schoharie Creek

Schoharie Creek parallels US 20 on S(left).

Schenectady sandstone and shale on hill
Several exposures of Schenectady sandstone and shale on hill at west end of Sloansville.

Region now underlain by Silurian and Devonian strata.
Passing from region underlain by Middle Ordovician strata to region underlain by Silurian and Devonian strata.

Karst topography
Karst topography; sink holes on N & S of US 20 in Lower Devonian Manlius and Coeymans Limestones.

Long exposure of Onondaga Limestone
Long exposure of Onondaga Limestone on S(left), showing Moorehouse Member with 2 m of Nedrow Member at W end.

Roadcuts in Kalkberg Limestone
Roadcuts on both sides of US 20 in Kalkberg Limestone; about 2m of New Scotland argillaceous limestone at top of exposure.

Kalkberg Limestone forms conspicuous terrace
Roadcuts on both sides of US 20 in Kalkberg Limestone; forms conspicuous terrace.

Roadcut on S(left) of Esopus Shale
Roadcut on S(left) of Esopus Shale, deformed by glacial shoving(?).

Cherry Valley hills to S(left).

Exceptional landscape view to N(right)
Exceptional landscape view to N(right) across Mohawk Valley farmland floored with Ordovician and Upper Cambrian strata; Proterozoic gneisses of Adirondack Mountains in distance.

STOP 1. Chittenango, Cherry Valley ls, Union Springs shale
Parking area on right shoulder beyond W end of exposure. Roadcut on S (left) of road.
Three Middle Devonian units of Marcellus Formation of the Hamilton Group are well displayed here: Chittenango Shale (topmost), Cherry Valley Limestone, Union Springs Shale.
The dark gray-black Chittenango Shale contains the small, needle-like fossil Styliolina fissurella believed to have been pelagic in habit. No proven benthonic fossils have been found in the Chittenango. The hard, massive Cherry Valley limestone has yielded several species (Rickard, 1952) but they are scarce and exceedingly difficult to extract. Nautiloid and goniatite cephalopods are diagnostic, chief of which are Striacoceras and Agoniatites vanuxemi. The Union Springs Shale has a few thin limestone beds in its upper few feet which contain horn corals, trilobites, ostracodes, pelecypods, lingulid brachiopods, and the small goniatite Werneroceras plebeiforme, extremely useful for correlation purposes.
Of especial interest here are some unexplainable structural oddities in the Union Springs. One is the "pseudocleavage" and the other is the disrupted limestone concretions. These features may be manifestations of a large westward decollement, created during the Acadian Orogeny in Early Erian (Early Cazenovian) time as continental plate overriding (or underriding) produced a temporary basin on the site of the Devonian carbonate shelf in which black muds accumulated. Whatever their causes, these are anomalous structures in otherwise virtually structureless strata.

Roadcut in Otsego Shale on N (right) side of road.
Cherry Valley hills capped by younger Solsville sandstone and shale whereas Otsego forms slopes and Chittenango floors the intervening valleys.

Onondaga (Moorehouse) Limestone on S(left) of road.

Road ditch on W(left) shows Nedrow shaley limestone.

STOP 2. Moorhouse Member of Onondaga Limestone
The roadcut on the E(right) shows the Moorehouse Member of the Onondaga Limestone; the Nedrow Member may be examined by walking back to the ditch exposure on the west side of NY 166.
A little over 60' of medium to thick bedded, dark to medium gray, fine to medium grained limestone with bedded and nodular dark gray to black chert is well shown. The unit is not overly fossiliferous although brachiopods, bryozoans, and pelmatozoan debris may be collected.
By contrast, the Nedrow is a thin to medium bedded, shaley, argillaceous limestone which weathers lighter. Platyceratid gastropods are diagnostic.

STOP 3 (30 minutes)- Park off highway on right shoulder.
The roadcut on the E(right) shows the Edgecliff Member of the Onondaga Limestone resting with sharp lithologic contact on the Carlisle Center calcareous, silty mudstone.
About 15' of massive, irregular bedded, light to medium gray, medium to coarse grained Edgecliff Limestone with tan to light gray nodular to bedded chert and with prolific corals (often silicified ) and crinoidal debris is splendidly exhibited here. The lower 4' is non-cherty and finer grained and the basal few inches contains angular shale fragments. The contact with the subjacant Carlisle Center is abrupt and a marked lithologic change.

Carlisle Center in sharp contact with Esopus Shale on E(right).

Kalkberg Limestone on E(right).

Kalkberg limestone, chert, and shale on S (right).

Long, high roadcut on S (right) -
Will be visited later as Stop 6.

STOP 4. LUNCH (40 minutes )
Slope underlain by Union Springs Shale capped by terrace of Cherry Valley Limestone (now completely grassed over); excellent view to N across Mohawk Valley to Adirondack Mountains in distance.

Roadcut on N (right) in Onondaga (Moorehouse) Limestone.

Good view to N(right).

28' of Upper Coeymans (Deansboro) Limestone
Roadcut on E(right) shows about 28' of Upper Coeymans (Deansboro) Limestone with great profusion of gypidulid brachiopods, often silicified, and crinoid debris. Few chert nodules signify stratigraphic nearness of overlying Kalkberg Limestone.

16' of upper Manlius Limestone.
Roadcut on E (right), now largely concealed, of about 16' of upper Manlius Limestone.

STOP 5 (40 minutes) - Park on E(right) shoulder.
Long, high roadcut on E (right) in Lower Coeymans (Dayville), Manlius (Thacher), and Rondout (Chrysler). Thicknesses of each are 50', 44' and 12', respectively. Orange paint mark shows Coeymans/Manlius contact. Note that there is no reef rock in the uppermost Manlius nor Tentaculites- bearing ribbon limestones in lowermost Manlius in this section (compare with more easterly Manlius at Stop 7).
Coeymans and Manlius are distinguished in that the former is lighter gray, thicker or irregularly bedded, coarser grained, and breaks with an irregular fracture; here, it is more fossiliferous than the underlying Manlius and has crinoidal debris and larger brachiopods. There is a 4' dolomitic shaley zone 25' from the base of the Manlius which is somewhat gradational into the subjacent Rondout Dolostone.
The Manlius here is less fossiliferous than to the east and its environment may have been somewhat more saline so as to be less conducive to normal marine invertebrates.

Roadcuts on both sides of NY 166 in Kalkberg Limestone.

STOP 6. (40 minutes) Park off highway on right shoulder.
Long, high roadcut on S (right) in Kalkberg, Oriskany, Esopus, Carlisle Center, and Onondaga Formations. - Park off highway on right shoulder. Beginning at the overpass for the abandoned Cherry Valley Railroad, and midway within the Kalkberg Limestone, is a 1-3 cm sticky clay bentonite (volcanic ash) which has been radiometrically dated (Miller and Senechal, 1965), using Rb-Sr isotopes, as 39S million years old. Note the regularity of the thin to medium bedded siliceous limestones, the shale intercalations, and the dark gray to black chert beds and nodules, as well as the great profusion and diversity of brachiopods and bryozoans.
The next overlying unit is a famous one in New York stratigraphy -- the Oriskany Sandstone. Its fame as a gas producer has long been known in central and western New York. Here, however, it is a quartzose limestone with large, rounded, sand grains of quartz in a calcite matrix. The contact with the Kalkberg is a "welded " one.
Seventeen feet of chertified argillite, chert, and dark gray shale make up the overlying Esopus Formation, here. Eastward, in the Hudson Valley, the Esopus reaches a thickness of over 300'. In sharp contact is the next overlying Carlisle Center Formation. This is a curious unit lithologically and paleontologically. Physically, it consists of about 45-55% clay minerals, 25-30% quartz of silt size, and 25-30% calcium carbonate. Organically, it is replete with only one trace fossil, the worm feeding trail, Zoophycos (Taonurus) caudagalli. Its environment of deposition is a puzzle!
The Edgecliff Member of the Onondaga Limestone rests with a marked lithologic and paleontologic change on the Carlisle Center mudstone. This and other units of the Onondaga have been previously described and observed at Stops 2 and 3. Note the green mineral staining, attributed as glauconite, along the contact.

Seneca Ls Mbr of Onondaga on N (left).
Roadcut in Seneca Limestone Member of Onondaga on N (left).

Roadcut in Seneca Limestone on S(right).
During highway construction, this showed an abrupt lithologic contact with the overlying Union Springs black shale. Note the Cherry Valley Limestone terrace above.

Seneca Limestone and Tioga Bentonite
Roadcut on S(right) in massive, dark gray Seneca Limestone with re-entrant at base showing 8-13 cm of sticky, light gray clay,--the Tioga Bentonite.

Chittenango-Cherry Valley-Union Springs Members
Long roadcut in Chittenango-Cherry Valley-Union Springs Members of the Marcellus Formation (STOP 1)

Karst topography region
Sink holes on W (left) about 400' from road.

Coeymans and upper Manlius limestones
Continuous ledge of lower Coeymans and upper Manlius limestones parallels road on S (right).

STOP 7. (45 minutes) -
Buses will unload passengers on left shoulder opposite roadcut and load at right bend, 0.1 mile to the SE.
Roadcut in Manlius (Thacher Member) Limestone on S (right) side. Thin-bedded (ribbon) limestone, fine grained, dark gray to black, weathers very light gray. Rock breaks with a "ringing" sound and conchoidal fracture. Numerous shale intercalations. Bedding planes covered with the extinct mollusk, the narrow conical Tentaculites gyracanthus, the ostracode Hermannina alta, and the small spiriferid brachiopod Howellella Vanuxemi. Bryozoans and gastropods are occasionally found. In 1954 I was fortunate in discovering an horizon covered with the rare edrioasteroid Postibula n. sp.
Walk SE past abandoned farmhouse to next limestone ledge. Here, crossbedded coarse grained limestone occurs in the upper 18" of the ledge; this is a rare sedimentary feature in the Helderberg Group. Proceed W across field to next limestone ledge. This is a stromatoporoid reef, marking the summit of the Manlius Formation. The "cabbage-looking" unbedded limestone rests on regular bedded Thacher Limestone. These stromatoporoids acted as barriers blankets, and baffles and caused waves to break offshore creating differing environments of quite protected areas and agitated open areas.

Spectacular view ahead to the east
Spectacular view ahead to the east, looking across Hudson River Valley to Taconic and Berkshire Mountains in distance. Albany's Empire State Plaza is visible in the Valley.

Another excellent view to the east
Another excellent view to the east, in case you missed the earlier one!

A2: SEDIMENTARY ENVIRONMENTS AND THEIR PRODUCTS: SHELF, SLOPE, AND RISE OF PROTO-ATLANTIC (IAPETUS) OCEAN, CAMBRIAN AND ORDOVICIAN PERIODS, EASTERN NEW YORK STATE
Gerald M. Friedman
Department of Geology
Rensselaer Polytechnic Institute
Troy, New York 12181
My thanks are extended to my student, friend, and colleague Brian D. Keith with whom I enjoyed collaboration in the study of the rocks of the Taoonic Sequence. Parts of this guide are an abbreviated version of our papers Keith and Friedman (1977, 1978).
INTRODUCTION
On this field trip, instead of tracing formations, we shall study sedimentary facies. We plan to hop from the products of one environment to those of another. At each exposure we shall study the rocks in terms of lithology, geometry, sedimentary structures, and fossils, and concentrate on the pattern of deposition which created the facies that we shall examine. Remember that the various exposures of Cambrian and Ordovician rocks to be visited are not time correlative. Each field stop will stand on its own; facies analysis will proceed within the boundary conditions of a single exposure. On this field trip the name of the formation becomes secondary; hence this field trip has been designed irreverently; it pays no heed to formation boundaries.
The fascination of the area around R.P.I. is its diversity of sedimentary geology: in one day of field trips we can examine sedimentary facies of Cambrian-Ordovician age which originated in shallow as well as in deep marine waters. Few other areas can match this diversity of sedinentary facies. The geologic coincidence for this diversity of sedimentary environments in the area of the R.P.I. Campus is its unique location: from Early Cambrian through Early Ordovician R.P.I. would have been on a carbonate shelf. Between Early Cambrian and Early Ordovician times the shelf to basin transition was east of Rutland, Vermont. Tectonic movements shoved Cambrian and Ordovician rocks of slope, rise, and basin facies across the shelf facies so that today the exposures on and near the campus of R.P.I. are basin or basin margin (rise) facies with shelf facies of Cambrian and Ordovician age occurring to the west (Friedman, 1972) (Fig. 1).
During Cambrian-Ordovician time, most of the North American continent was a shallow epeiric shelf sea, like the present-day Bahama Bank. At the eastern edge of this shallow sea, i.e. at the eastern edge of this continent, a relatively steep slope existed down which carbonate sediment moved by slides, slumps, turbidity currents, mud flows, and sandfalls to oceanic depths to come to rest at the deep-water basin margin (rise), where a shale facies was deposited (Sanders and Friedman, 1967, p. 240-248; Friedman, 1972, p. 3; Keith and Friedman, 1977, 1978; Friedman and Sanders, 1978, p. 389, 392). Shale also formed much of the basinal facies in the deep water beyond. Because allochthonous transport has been inferred for large blocks of rocks presently exposed on and near the R.P.I. Campus, the evidence on the ground shows that the campus is the site of Cambrian and Early Ordovician rocks of basin margin (rise ) and deep basin facies (shales deposited in the Middle Ordovician (Schenectady ) west of Campus are autochthonous basin facies). Thus deep-water basin margin (rise) and basinal facies can be visited on and near the R.P.I. Campus, whereas to the west carbonate shelf facies are exposed that are analogous to those of the west shore of Andros Island on the Great Bahama Bank (Fig. 1). The paleoslope was probably an active hinge line between the continent to the west and the deep ocean to the east, similar to the Jurassic hinge line of the eastern Mediterranean between carbonate shelf facies and deep-water shales (Friedman, Barzel, and Derin, 1971). Such hinge lines in the early geosynclinal history of mountain belts are fixed by contemporaneous down-to-basin normal faulting (Rodgers, 1968, quoting Truempy, 1960), as probably occurred with the rocks of the area near R.P.I. Later thrusting to lift the deep-water facies across the shelf facies along hinge-line faults resulted in the contiguity of the two facies. This later displacement was so great that the Cambrian and Early Ordovician deep-water sediments were shifted far west of their basin margin.
This field trip has been divided into two parts, each part corresponding to half a day. In the morning and early afternoon we shall study facies of deep-water origin and in the late afternoon those of shallow epeiric origin. Each of the two depositional settings will now be explained.

A2: SEDIMENTARY ENVIRONMENTS AND THEIR PRODUCTS: SHELF, SLOPE, AND RISE OF PROTO-ATLANTIC (IAPETUS) OCEAN, CAMBRIAN AND ORDOVICIAN PERIODS, EASTERN NEW YORK STATE

STOP 1. EXPOSURE ON EAST SIDE OF U.S.9
(across from a white house) (SECTION SOUTH OF HUDSON)
Figure 12 shows and describes the lithofacies exposed at this stop, and interpretes its depositional setting. The rocks are of deep-water mid-fan origin (Figs. 1 and 10), Note especially the interesting "hemipelagic" interbeds of fine-grained limestone (micrite) and dark shale (Fig. 8) and the carbonate-clast conglomerate (Fig. 4). Read carefully the material covered under the heading of "Deep-Water Setting: a Slope-Fan-Basin-Plain Model" so that you understand the objective of making this stop.

STOP 2. JUDSON POINT
Figure 13 illustrates the section seen at this stop and describes the lithofacies; it also provides an interpretation of the depositional setting. The rocks are of inner- to mid-fan origin (Figs. 1 and 10). The section is dominated by turbidite beds, and several massive coarse sandstone beds. The presence of several AE beds of the Bouma Sequence is characteristic of proximal turbidites. The occurrence of thick massive sands and local conglomerates and thin-bedded laminated sands suggests channel and levee deposits of the inner fan area. Two of the conglomerates are somewhat lenticular and truncate an underlying bed, suggesting channel deposition. Again review the section entitled "Deep-Water Setting: a Slope-Fan-Basin-Plain Model" for a better understanding of the features observed at this stop.

STOP 3. NUTTEN HOOK
Figure 14 gives details on this section, including an interpretation of depositional environment.

STOP 4. EXPOSURES SOUTH OF SCHODACK LANDING
Bus parks on dirt road east of highway. 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 more fine exposures.
Figure 15 describes and illustrates the section seen and provides interpretation of the depositional setting. Note exposures of bedded micrite with shale partings. This micrite represents lime mud which was derived from the shelf and probably settled from suspension. The conglarerate overlying the bedded micrite is probably the result of slumping, since the clasts appear to be derived from the underlying limestone beds. The strata at this stop show mid-fan developrent and possibly an inner fan channel as well. Again review the earlier section entitled "Deep-Water Setting: a Slope-Fan-Basin-Plain Model" for additional interpretation of depositional setting.

STOP 5. RPI '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 Elarn (1960) a thrust fault follows part of this street (Sage Avenue) 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. Elarn (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, p. 69) had introduced the "Schodack Formation" which according to Fisher (1961, p. D8) has now fallen victim to a nomenclatorial "snafu." Zen (1964) has renamed this formation the West Castleton Formation.
Lowman (1961) recognized that the boulders are a conglomerate and not a breccia, and following Kuenen and Migliorini (1950), he introduced the term brecciolas. The term brecciolas refers to graded limestone breccia beds that alternate with dark-colored shales (Lowman, 1961, p. B6; Sanders and Friedman, 1967, p. 242; Friedman, 1972, p. 25; Friedman and Sanders, 1978, p. 390, 395).
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. 5). Some boulders are coarse-grained fossiliferous limestone fragments with a micritic dolomite matrix. The rocks above the brecciolas are greenish-gray shales.
The boulders are those of rocks that formed under shallow shelf conditions. Their emplacement as boulders into shales, which are considered to be offshore deep-water sediment, indicates that the boulders moved downslope. The environment of deposition inferred for the brecciolas at this stop is that of the lower slope or base of slope (Fig. 1). Although the boulders came from the west down the slope, shelf carbonates (their source) extend many miles east of Troy (and presumably underlie Troy at depth).
Brecciolas which formed along the original east edge of the carbonate shelf parallel to the depositional strike for hundreds of miles define the site of the basin margin (rise) in Cambrian-Ordovician time. This Cambrian-Ordovician basin margin was located east of Troy near the present site of the Green Mountain axis. A relatively steep slope must have existed between the shelf edge and the basin margin with resultant instability that helped initiate slides, slumps, turbidity currents, mud flows, and sand falls.

STOP 6. TROY HIGH SCHOOL QUARRY
The spectacular brecciolas at this exposure consist of three members with eleven sub-members (Lowman, 1961). For details of the rocks, refer to Lowman's descriptions (1961, p. Bll-Bl2). The brecciolas are Schodack lithofacies of the West Castleton Formation of Early Cambrian age, as at Stop 5. Note that the carbonate shelf west of Troy contains no rocks older than Late cambrian; somewhere between west of Troy and the present Green Mountains the Middle Cambrian (?) and Lower Cambrian strata wedge in.
A thin-section study shows the limestones 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 observation that the limestone boulders are mostly micrites indicates that before removal downslope from their site of deposition the limestones were deposited under low-energy conditions on the shallow shelf to their original west, but at a place now still far to the east of Troy. The abundant fauna shows that the shallow waters were well aerated. The carbonate sediments must have lithified before their displacement downslope.

STOP 7. TROY JEWISH COMMUNITY CENTER
One large block of orthoquartzite, approximately 30 feet by 15 feet, probably settled in deep-water shale. Although limonitic, this orthoquartzite is devoid of rock fragments, hence is a second-cycle or multicycle rock. Note that the exposed shales surrounding this erratic block show that this block occurs singly. This exposure occurs along strike of the brecciolas and many more exposures of the brecciolas occur north of here in Frear Park. In a pit about 100 feet or so north of this block we exhumed from the shale a block of dark gray, fractured and veined micritic dolomitic limestone.
The size and shape of the block of orthoquartzite suggests more than a steep slope. To detach a block of this dimension required considerable instability near the shelf edge, such as severe shakes as occur during earthquakes. This block of rock differs in litho logy from the brecciolas which we have seen at the previous two stops. In contrast to the flat limestone boulders of the previous stop this huge block with its irregular outline suggests that solid bedrock of sandstone was forcibly detached from the shelf edge or basin slope. By analogy with modern events, turbidity currents, slumps, mud flows, and slides are usually funneled through submarine canyons. Could it be that this block was part of the wall of a submarine canyon which became detached during one of the slides and was moved by gravity into the basin or basin margin?
The alternative interpretation would be to consider this block to have been caught up in fault movement. Indeed slickensides are present on this block. However, the lower exposed contact with the shale is depositional and not faulted. Because the orthoquartzite block occurs along strike with the other brecciolas, and a limestone block has been found about 100 feet away, the evidence suggests that emplacement was by gravity rather than by faulting.
Convince yourself that this block is not a glacial erratic.
The shales at this stop have been assigned to the Schodack lithofacies of the west Castleton Formation of Early Cambrian age; the displaced orthoquartzite block may be as old as Precambrian.

Exposures of westernmost deep-water sedimentary facies
Note two exposures of westernmost deep-water sedimentary facies, consisting of Middle Ordovician Normanskill graywacke and shale, in roadcut on right (northbound lane). West of here and underneath the Normanskill at a depth of several thousand feet are Cambrian-ordovician rocks of shelf facies.

This beautifully designed bridge won an award in 1958.

STOP 8. LESTER PARK
This locality is the site of one of the finest domed algal mats to be seen anywhere preserved in ancient rocks. On the east side of the road in Lester Park a glaciated surface exposes horizontal sections of the cabbage-shaped heads c0mposed of vertically stacked, hemispherical stromatolites. These structures, known as Cryptozoons, have been classically described by James Hall (1847, 1883), CUshing and Ruederoann (1914), and Goldring (1938); an even earlier study drew attention to the presence of ooids as the first reported ooid occurrence in North America (Steele, 1825). Interest in these rocks has been revived as they are useful environmental indicators (Logan, 1961; Fisher, 1965; Halley, 1971). The algal heads are composed of discrete club-shaped or columnar structures built of hemispheroidal stromatolites expanding upward from a base, although continued expansion may result in the fusion of neighboring colonies into a Collendia-type structure (Logan, Rezak and Ginsburg, 1964). The stromatolites are part of the Hoyt Limestone of Late Cambrian (Trempealeauan) age. An intertidal origin has been inferred for these stromatolites.
The evidence for deposition under tidal conditions for the Hoyt Limestone at Lrster Park includes: (1) mud cracks, (2) flat-pebble conglomerate, (3) small channels, (4) cross-beds, (5) birdseye structures, (6) syngenetic dolomite, and (7) stromatolites (for characteristics on recognition of tidal limestones, see Friedman, 1969).
At Lester Park the heads which are circular in horizontal section range in diameter from one inch to three feet; many are compound heads. The size of the larger heads suggests that they formed in highly turbulent waters.
The line of depositional strike along which the domed stranatolites occur was probably where the waves were breaking as they came across the deeper ocean from the east and impinged on the shallow shelf.
Several petrographic observations in these rocks permit an analogy with modern algal mats in hypersaline pools of the Red Sea Coast (Friedman and others, 1973). Mat-forming algae precipitate radial ooids, oncolites, and grapestones which occur in these rocks; interlaminated calcite and dolomite which in part compose the stromatolites of the Hoyt Limestone correspond to alternating aragonite and high-magnesian calcite laminites which modern blue-green algae precipitate. In modern algal mats the high-magnesian calcite laminites contain abundant organic matter in which magnesium has been concentrated to form a magnesium organic complex. Between the magnesium concentration of the high-magnesian calcite and that of the organic matter sufficient magnesium exists in modern algal laminites to form dolomite. Hence the observation in ancient algal mats, such as observed in the Hoyt Limestone, that calcite and dolomite are interlaminated, with calcite probably forming at the expense of aragonite and dolomite forming from high magnesian calcite.

Pass basal Paleozoic quartz-cobble conglomerate
Pass basal Paleozoic quartz-cobble conglomerate (a possible talus deposit) on weathered Precambrian gneiss

STOP 9. FORT HUNTER QUARRY
Stromatolites in the Fort Hunter Quarry consist almost entirely of dolomite in the form of irregularly bedded, finely-laminated, undulating structures (Figure 9). The rocks in this quarry are part of the Tribes Hill Formation of earliest Ordovician age (Fisher, 1954). The lithofacies of the Tribes Hill formation have been studied in detail by Braun and Friedman (1969) within the stratigraphic framework established by Fisher (1954). Figure 10 is a columnar section showing the relationship of ten lithofacies to four members of the Tribes Hill Formation. At Fort Hunter we will study the lowermost two lithofacies of the Fort Johnson Member (see column at right (east) end of section, in Fig. 10).
Two lithofacies are observed: (1) lithofacies 1, mottled feldspathic dolomite (Figure 10), and (2) lithofacies 2,. laminated feldspathic dolomite. Lithofacies 1 is at the bottom of the quarry, and lithofacies 2 is approximately halfway up.
Lithofacies 1
This facies occurs as thin dolostone beds, 2 cm to 25 cm but locally more than 50 cm thick, with a few thin interbeds of black argillaceous dolostone which are up to 5 cm thick. In the field, the dolomite shows gray-black mottling and in places birdseye structures. In one sample, the infilling of the birdseyes shows a black bituminous rim which may be anthraxolite. In the field, trace fossils are abundant, but fossils were not noted. Authigenic alkali feldspar (microcline) is ubiquitous throughout this lithofacies; its identity as alkali feldspar was determined by Xray analysis and staining of thin sections with sodium cobaltinitrite. The insoluble residue makes up 22 to 54% by weight of the sediment in samples studied with most of the residue composed of authigenic feldspar. An iron-poor yellow sphalerite may be occasionally found in the rocks of this lithofacies.
Lithofacies 2
This lithofacies is mineralogically identical to the previous facies but differs from it texturally and structurally in being, irregularly bedded and in containing abundant undulating stromatolitic structures ("pseudo-ripples"), as well as disturbed and discontinuous laminae. In places there are a few thin interbeds of black argillaceous dolostone. The thickness of the laminites of this facies ranges from 1/2 mm to 2 or 3 mm; on freshly broken surfaces the color of the thinner laminae is black and that of the thicker ones is gray. The insoluble residue, for the most part composed of authigenic feldspar, constitutes between 35% and 67% by weight in samples studied.
These two lithofacies which form the basal unit of the Ordovician, were formed on a broad shallow shelf. Stromatolites, birdseye structures, scarcity of fossils, bituminous material, syngenetic dolomite, authigenic feldspar, and mottling suggest that these rocks were deposited in a tidal environment (Friedman, 1969). Based on analogy with the carbonate sediments in the modern Bahamas, Braun and Friedman (1969) concluded that these two lithofacies formed under supratidal conditions. However, in the Persian Gulf flat algal mats prefer the uppermost intertidal environment and along the Red Sea coast they flourish where entirely immersed in seawater, provided hypersaline conditions keep away burrowers and grazers (Friedman and others 1973). Hence on this field trip we may conclude that the stromatolites indicate tidal conditions without distinguishing between intertidal and supratidal. For more details on these lithofacies refer to Braun and Friedman (1969).

Cross original Erie Canal, built in 1822.
Amos Eaton surveyed this route at the request of Stephen Van Rensselaer; after this survey Amos Eaton and Van Rensselaer decided to found a school for surveying, geological and agricultural training which became Rensselaer Polytechnic Institute.

Fulton-Montgomery Community College

STOP 10. TRIBES HILL QUARRY
Route of Walk
Take the trail toward old abandoned crusher, but instead of heading toward the quarry move uphill to the first rock exposures. The rocks to be examined are near the edge of steep cliff.
Description and Discussion
In the rocks at this exposure the field relationships show typical channels truncated at their bases. Lodged within the channels are limestone blocks of variable shape ranging in diameter from about one to three feet. These blocks resemble similar blocks in tidal channels of the Bahamas which are derived by undercutting of the banks of the tidal channels. The blocks at this exposure are rounded, suggesting that they have undergone some transport.
The rocks composing the channel (the channel fill) and the blocks of rock within the channels have been described as lithofacies 8 (channel fill) and lithofacies 7 (blocks) of the Wolf Hollow Member of the Tribes Hill Formation (lowermost Ordovician) (see columnar section of Fig. 16); column at right end of the section) (Braun and Friedman, 1969). The channel fill (lithofacies 8) consists of intrasparite and biointrasparite with sporadic ooids, a high-energy facies, whereas the blocks (lithofacies 7) consist of mottled dolomitic micrite and biomicrite, a low-energy facies of the undercut bank. The micrite blocks which foundered in the channels must have been indurated penecontemporaneously.
Hence during earliest Ordovician time high--energy tidal channels crisscrossed tidal flats at this site. In them water coming from the deep ocean to the east rose and fell with the changing tides.

A3: SEDIMENTARY ENVIRONMENTS IN GLACIAL LAKE ALBANY IN THE ALBANY SECTION OF THE HUDSON - CHAMPLAIN LOWLANDS
Introduction
Robert J. Dineen and William B. Rogers*
New York State Geological Survey
The history of Lake Albany has intrigued glacial geologists since the turn of the century. The simple, single-stage lake of Peet (1904) soon was modified by Woodworth (1905) to a two-stage model where varved Lake Albany clay is overlain by sand of Lake Quaker Springs. Later workers, up to the present time, have defined more lake stages using the elevations of beaches, deltas, and terraces and by the character of the deposits of each lake stage. Stratigraphic sections revealed in new exposures and test borings have permitted the definition of sedimentary packages associated with each stage of Lake Albany. This field guide is a preliminary description of this new stratigraphy and provides the student with selected field stops that allow examination of the sediments.
The study area is in the mid-Hudson section of the Hudson-Champlain Lowlands (Fenneman, 1938). It lies between the Adirondack Mountains on the northwest, the Taconic Mountains on the east, and the Helderberg Plateau on the southwest (Fig. 1). The lowlands were deeply dissected by a southward drainage system prior to the Wisconsinan glaciation (Davis and Dineen, 1969). This drainage system consisted of the Colonie Channel and its tributaries - the Mohawk, Ballston, and Hudson-Battenkill Channels (Fig. 1). Only the Hudson-Battenkill channel is occupied by major drainage at present.
The Hudson Lobe of the Laurentide ice sheet occupied the lowlands during the Wisconsinan Glacial Stage. As the Hudson Lobe retreated, proglacial Lake Albany developed on the south. Lake Albany occupied the area from 15,000 to 12,600 y.b.p. (Connally and Sirkin, 1973). Drainage from the Great Lakes Basins entered this lake via the Mohawk River Valley (Stoller, 1911). The lake expanded from south to north as the Hudson Lobe retreated with the ice margin as the north shore of the lake (LaFleur, 1965b). The initial lake deposits were ice-contact sand and gravel that grade up into varved silt and clay (LaFleur, 1969, Dineen, 1979). Kame deltas developed when the ice margin hesitated during its retreat. Lake Albany extended 225 km from Newburgh to Glens Falls (Peet, 1904). Several large ice blocks were left behind by the retreating glacial lobe. The locations of the five ice blocks in the Albany area were the Hudson-Battenkill Channel near Selkirk (Dineen, in prep.), the Colonie Channel between Schenectady and Troy, at Round Lake, at Saratoga Lake (Hanson, 1977), and the Mohawk Channel at Schenectady (LaFleur, this volume). These ice blocks impeded sediment transport and controlled glacial and post-glacial drainage.

A3: SEDIMENTARY ENVIRONMENTS IN GLACIAL LAKE ALBANY IN THE ALBANY SECTION OF THE HUDSON - CHAMPLAIN LOWLANDS

The bluff to the east of the field house is a beach
The bluff to the east of the field house is a beach of +330 ft. Lake Albany (LaFleur, 1965a).

Cross the Hudson River on the NY 7 bridge.
We have driven down the east wall of the preglacial Hudson-Battenkill Channel. Test borings for the bridge and its approaches indicate that a - 20 ft. terrace underlies the floodplain in this area. A +40 ft. bedrock terrace underlies Watervliet to the west. The test borings indicated that only a thin layer of till underlies the floodplain silty sands (J. Rumsey, N.Y.S. Dept. of Transportation, personal communication). The-20ft. bedrock terrace can be traced 12 miles south as far as Castleton and 3 miles north as far as Waterford.

Proceed up the west wall of the Hudson-Battenkill channel.

We have been driving along the interfluve
We have been driving along the interfluve between the Colonie Channel (west) and the Hudson-Battenkill Channel (east). Proceed down the hill into the Dephuskill Valley.

STOP 1. Wunderlich Pit (Fig. 5a)
This pit is in the Pollock Road kame delta. The ice margin was to the north. Meltwater built a kame delta into Glacial Lake Albany at the end of an esker complex, which lies north of the kame delta. Some clay lies draped over the eskers to the north, implying that the ice had melted away by the time of Lake Quaker Springs. The Section exposed in the pit is:
Top to 4m | Grayish brown sandy, silty, boulder till.
4 to 24m | Gravity and thrust-faulted, yellow- brown, planar cross-bedded, gravelly sand, with ripple laminae at the base and contorted laminae at the top.
24 to 30m | Trough cross-bedded, gravity faulted, sandy gravel
The basal gravel was deposited by southward-flowing water in an esker channel, the gravelly sand, in a kame delta. These beds grade southward into trough cross-bedded, silty sand. They are partially overlain by varved clay to the south. The till at the top was deposited during the Delmar Readvance.

We have crossed the east wall of the Colonie Channel.
A test boring in the channel along strike with the Loudonville esker contains large quantities of ground water under artesian pressure. Roger Waller measured a 12 m artesian head in that well (Dineen, Waller, and Hanson, in prep.).

We are now crossing dune sand
We are now crossing dune sand that mantles Lake Albany clay (Hanson, 1977). We are also crossing the west wall of the Colonie Channel.

Crossing Ballston Channel
We are on (and in) the Schenectady delta that the Mohawk River built into Lake Albany (Stoller, 1911). A test boring for I-890 penetrated 174 ft. of silty sand and 20 ft. of till without hitting bedrock.
Dunes are well developed in this area. Gastropods occur locally in sand just below the dune sand - lake sand contact.

The Schenectady well field is to the west.

STOP 2. DICKERSHAIDS PIT (Fig. 5b)
This pit is cut into the Schenectady delta. Its section consists of;
Top to 7.6m | light brown, trough cross-bedded, medium to fine sand with some gravel
7.6 to 20m | light brown, ripple-laminated, fine sand. Concretions are common in this zone
20 to 23m | yellow brown, varved silt and clay
Test borings to the east indicate that the clay extends to a depth of 230 ft. (Winslow and others, 1965).
The gravelly sands at the top of the pit are topset/fluvial beds that prograded eastward across the delta front sand, which in turn had prograded eastward across bottomset clay and silt. The sand is the source beds for the dunes that lie to the east (Dineen, Rogers, and Buyce, 1978).

We are traveling across the topset beds of the Schenectady delta.

Dunes are just starting to appear in this area.

Notice the small dunes to the left (northeast).
We are proceeding along a series of dune ridges.

STOP 3. SCICCHITANO PIT (Fig. 6a)
This pit shows dune, beach, and lake sediments (Dineen, 1977). The hill to the east is a dune-sand mantled drumlin. A compound dune cluster built up around the drumlin. Bedrock lies approximately 60 ft. below the surface, the Ballston Channel lies to the west. The drumlin stood as an island in Lake Albany, as the Schenectady delta built out into this area. A +330 ft. beach is exposed on the east side of the pit. It consists of a wave-cut platform, cut into till, overlain by a lag concentration of boulders and trough crossbedded, gravelly sand. Horizontal to ripple-laminated sand and silt were deposited offshore. Planar cross-laminated dune sand overlies the lacustrine deposits .
Parallel ridges with a NW-SE trend are the dominant form of dune crests in the Pine Bush sand plain, the name of the pine and oak brush covered sandy area between Albany and Schenectady. A secondary mode of dune form comprises crescentric ridges that are convex to the southeast. Ridges of this concentric type commonly join adjacent parallel ridges or form hooks curving to the southwest from the southeast end of a ridge. In the past, these crescentric dunes have been interpreted either as barchans (which suggests a southeast wind direction) or as parabolic dunes (which suggests a northwest wind). These interpretations were based on shape, directions of steeper slopes and linear trends. Recently, we have been able to settle this controversy with cross-bedding data, gathered from deep cuts made in the dunes during a recent flurry of construction projects throughout the Pine Bush area (Dineen, Rogers, and Buyce, 1978). Weathering and bioturbation have destroyed the primary sedimentary structures in the top three meters of the dune sand, so that a substantial excavation is required to expose undisturbed deposits that contain directional features. Measurements of over 200 cross-beds at 35 localities in the Pine Bush dunes give down dip modes to the northeast, southeast, and south. These data combined with the NW-SE trend of the linear ridges and the southeast convexity of the arcuate ridges indicate that the dominant dune-forming winds were northwesterly, hence the crescentic dunes are parabolic.
That southwest winds were also important is indicated by a prominent northeast mode in the dip directions. Fig. 6 of the dune crests shows the characteristic dune ridge pattern. Careful analysis of dune morphology, especially on aerial photos, shows the northeast side of linear ridges to have steeper slopes than the southwest side, and the southwest limbs of parabolic dunes to be atrophied. These observations corroborate the evidence for wind directions given by cross beds.
Only one measurement was recorded of a crossbed dipping toward the northwest quadrant, which indicates a nearly complete absence of dune-forming winds from the southeast during the post-glacial period.
The parabolic dunes have a relatively gentle convex upwind slope of <10° and a steeper concave downwind slope of >15°. They are transverse forms as opposed to the longitudinal ridge-forms.
The dune ridges in the Pine Bush are sinuous, generally parallel, and as much as two kilometers long. They are generally lower than the parabolic dunes.

STOP 4 OLD STATE AND NY 155 PITS (Fig. 6b)
Cross NY 155 and follow the dirt road eastward for approximately 0.3 mile: We have walked along the northeast limb of a parabolic dune. The blow-out hollow lies to the right. Sand blown from this hollow was deposited at the dune crest. Migration of these two features leave the limbs trailing, and produces the parabolic dune form. The southwest limb of this dune is subdued. The slipface of another dune lies to the right (south). Several small hollows can be seen along the inside of the limb that we are on. These are blowouts that formed recently due to tree throw or denudation of vegetation by fire. The taller trees are pitch pine, the low scrubs are dwarf or scrub oaks.
The pits to the northwest and west show aeolian cross-bedding in dune sand that disconformably overlies the lake sand. This dune is part of a large compound dune cluster. The dunes of the cluster are connected on their northeast limbs, which can be seen to the east of this dune crest. The connected northeast limbs form a continuous ridge that can be traced for over 3km.

Notice the till overlain by dune sand in the road cuts.

Some "dunes" are erosional forms
A sand pit just northeast of here showed trough crossbedded, gravelly, coarse sand. This gravelly sand underlies dune-shaped hills, implying that some "dunes" are erosional forms that have been wind-sculpted. The gravelly sand was probably deposited in a kame delta of the Delmar Readvance.

We are crossing the buried preglacial Mohawk Channel.
A drumlin field buried by lake sediment cuts across the channel (Dineen, 1975). The drumlin field is flanked on the west by a thick gravel blanket. The drumlins act as underground dams by impeding the west-to-east movement of ground water in the gravel blanket.

Crossing the Normanskill.
Climbing the south wall of the Mohawk Channel.

STOP 5. TOWN PIT (Fig. 7)
This pit is cut into the distal, kame delta portion of the Guilderland kame terrace. This stop, and stops 6, 7, 8 will illustrate the distal-to-proximal increase in labile (shale) lithic clasts, in angularity of clasts, and in clast size, that accompanies the decrease in sorting typical in a kame terrace. The Guilderland kame terrace was first mentioned by Woodworth (1905) when he observed the existence of a large gravel terrace northwest of Guilderland Center. He considered the terrace to be an ice marginal kame. LaFleur (1965b) called attention to glacial lake beaches that are cut along the northern margin of the kame. LaFleur also reported southwest dipping gravel and irregular beds of rhythmic clay in the kame. Woodworth (1905) and LaFleur (1965b) interpreted the kame as having been deposited by meltwater streams in an elongate hole in the ice. LaFleur (1965b) suggested that the streams were the outflow of Lake Amsterdam in the Mohawk Valley. Dineen (1975) found that the kame is continuous with a buried gravel blanket which extends north to Schenectady. The kame consists of well-sorted, sub-rounded, ice-contact sand and gravel to the east, and poorly-sorted, subangular, silty, bouldery sand and gravel to the west. The number of shale clasts and the overall grain size decrease from west to east. The surface of the kame slopes to the southeast, from +360 ft. at Stop 8 to +330 ft. at Stop 5. Stop 5 is in a kame delta that was built into Lake Albany, and shows planar cross-bedded, rhythmic silt and sand overlying trough cross-bedded, ice-contact sand and gravel. The rhythmites are overlain unconformably by planar-bedded, silty, cobbly sand that grades into clay to the southeast. These upper beds are delta foresets, and dip S20°E.

STOP 6. LEDO PIT (Figure 7)
Stop at entrance to pit and walk in. This pit contains large-scale, trough cross-bedded, cobbly, gravelly sand, dipping N20°E and overlying ripple trough cross-bedded, coarse sand. The cobbly sand grades upward into channels filled with rhythmic silt and clay. The channels trend N20°W. They are overlain by cobbly, silty gravel that is overlain by varved clay to the north.

STOP 7. OLIVER PIT (Fig. 7)
This pit contains planar cross-bedded, cobbly, sandy gravel that dips N80°E, and which overlies ripple-laminated coarse sand. These beds are overlain by pebbly, silty cobble gravel with channels filled with rhythmic silt and clay. Varved clay overlies the sequence to the north.
The lower gravel layers extend north of the kame, where they partially fill the Mohawk Channel; and they are overlain by lake deposits northward. They can be traced to Schenectady. This gravel probably was deposited on the ice block that occupied the Schenectady area during the early Lake Albany time (see LaFleur, this volume).
The channels that cut into the top of the gravel slope northeastward, perpendicular to the axis of the kame terrace .

STOP 8. WEST PIT (Fig. 7)
This pit contains poorly bedded, poorly sorted, shale-rich, silty, bouldery gravel, overlain by varved clay that fill erosional channels cut into the top of the gravel.

STOP 9 COLONIE COUNTRY CLUB PIT (Fig. 5a)
This is the Voorheesville delta. The access road runs along the foreset slope of the delta. The delta was deposited into early Lake Albany, and is at the distal end of the Meadowdale kame and outwash complex that was deposited by meltwater from a stagnant ice block in the Guilderland Center-Voorheesville area (Dineen, 1977). The section in the pit consists of planar bedded, ice-contact gravel and sand at the base, overlain by planar cross-bedded, foreset sand and gravel, which are overlain by topsets of trough cross-bedded, silty, gravelly sand. The Town of Voorheesville derives its water supply from the delta.

We are travelling up the foreset slope of the South Bethlehem delta.

STOP 10 TOWN PIT (Fig. 8b)
Park at the entrance to the access road and walk down into the gravel pit. The South Bethlehem deltas lie at +340, +300, +220, +190, and +170 ft. The +340 ft. delta is wholly contained within the Onesquethaw Creek Valley, and lies approximately 1 mile (1.6 km) west of Stop 10. The +300 ft. delta is the largest and best developed delta. The lower deltas prograde eastward across varved silt and clay. The +300 ft. delta was described as an ice- marginal kame delta by Woodworth (1905) and Cook (1930). Woodworth (1905) noted that the +300 ft. delta had a boulder and till covered, raised outer margin, with a southwest gradient. These features imply that the delta was deposited in the ice- contact environment. Airphoto and field observations suggest that the +300 ft. delta's outer margin is not raised more than 2m (5 ft.). Exposures in gravel pits and along the Onesquethaw Creek reveal a predominance of fining-upward beds of coarse sand and gravel, and some lenses of boulders. These beds dip to the northeast at Stop 10, and to the southeast at Stops 11, 12, and 13. No till has been observed in the pits, but gravity faults are common west of a rock ridge in Stop 10, and in ice-contact gravel that is exposed in Stops 10, 12, and 13 . Boulders mantle the northeast slope of the delta along Rupert Road. Several channels cut southeastward across the delta's surface in the areas of Stops 10 and 12. Rhythmic silts and clays overlie the southeast and east margins of the delta (Stops 11 and 12). No kettle-holes were observed. A test boring 3500 ft. (1.3km) east of the delta showed a 70m (200 ft.) section of deltaic gravels interbedded with varved clay (Dineen, Waller, and Hanson, in prep.). The delta had been deposited in open ice-free water when the Onesquethaw Creek was carrying large quantities of very coarse sediment. The sediment was probably derived from a rapidly melting ice block that lay in the upper Onesquethaw Valley. The lower deltas were deposited in lower lakes by the Onesquethaw recycling the upper deltas. This stop (Stop 10) is at the apex of the +300 ft. Lake Albany delta. This pit shows normal-faulted, ice-contact, gravelly, coarse sand at the base. The sand is overlain by trough crossbedded, bouldery sandy gravel foreset beds. The foreset beds are overlain by trough crossbedded to structureless, silty gravel topset beds. The bouldery cross-beds indicate that this is the proximal section of delta.

STOP 11 SPAWN HOLLOW PIT (Fig. 8)
This pit is within planar cross-bedded, foreset beds of the central part of the delta. A thin section of topset beds is at the top of the pit. The exposed face shows the break in slope between the topset and foreset beds.

STOP 12. MALLOY PIT (Fig. 8b)
Notice that the delta foreset beds here are finer grained, and tend to be trough crossbedded rather than planar cross-bedded as they are at Stop 11. The topset beds are siltier and thicker than to the west.

STOP 13. CALLANAN PIT (Fig. 8b)
This pit is on the prodelta slope of the +300 ft. delta. Ice-contact sandy gravel lies at the base of the pit. This is covered by bottomset beds of trough cross-bedded, coarse sand. The bottomset beds are overlain by foresets of planar cross-bedded, coarse sand and gravel. Very silty, trough cross-bedded, topset gravels and varved clays cap the sequence.

STOP 14. WRIGHT PIT (Fig. 9a)
This stop shows lake silt and sand layers that were folded and faulted by ice shove during the Delmar Readvance. The section at this site consists of:
Top to 2.0m | yellow brown, varved clay and silt with laminae of fining upward, very fine sand. Layering is 6 cm thick. The sand is ripple to planar-laminated, the planar-laminae are at the base of the beds over fine lag gravel and a truncation surface.
2.0 to 3.3m | yellow brown, compact, ripple to planar-laminated, very fine sand with 0.5 cm laminae of clay. The sand fines upward. Bedding is faulted and folded, the fold axes trend Nl5°E and N80°E. The faulting is thrust up to the S40°W, soft sediment deformation is common.
3.3 to 3.7m | yellow brown, very fine sand with silt laminae. The varves fine-upward, and are 0.5cm thick. The varve sequence coarsens-upward to ripple-laminated sand, which fines-upward to varved silt.
3.7 to 4.7m | yellow brown, structureless, very fine sand, with contorted fragments of clay. Concretions are common at the base.
4.7 to 6.3m
gray brown, folded, very fine silt, clay, and fine sand in 5 to 20 cm thick coarsening-upward folded layers. The fold axes trend N60°E to N70°E. The tops of the folds are truncated and are covered by fining-upward, ripple cross-laminated, very fine sand.
6.3 to 13.3m | light gray, laminated silt.
Base of pit. | Test boring log:
13.3 to 32.5m | pinkish gray to light gray, varved silty clay.
32.5 to 35.4m | light gray, varved, slightly silty clay
35.4 to 39.0m | light gray, varved, sandy, silty clay
39.0 to 63.0m | gray, varved clay
63.0 to 79.2m | light gray, varved clay
79.2 to 82.0m
gray, soft, varved clay with a
trace (<5%) fine sand grading
down to sandy clay with subrounded
shale and quartzite
clasts
82.0 to 87.2m | Black shale.
The upper silty beds are folded parallel to the interfluve ridges that are present throughout the Delmar area. The upper part of the section was probably folded by the Delmar Readvance.

STOP 15. Kleinke Pit (Fig. 9a)
This pit is also developed in folded lacustrine silts and sands. The fold axes trend N40°E.
The section is:
Top to 0.8m | very light yellow brown, planar-laminated, very fine sand. A truncation surface is at 0.8m.
0.8 to 3.8m | yellow brown silt to medium sand that coarsens-upward. This unit is mostly ripple cross- laminated with climbing ripples at its base and top. Ripples climb to the S80°S and N80°W.
3.8 to 5.0m | yellow brown, structureless silt.
5.0 to 11.0m | yellow brown, folded and convoluted silt to very fine sand. Dewatering structures are common. The fold trends N40°E.
11.0 to 11.5m | yellow brown, contorted, varved sand, silt and clay.
11.5 to 13.5m | yellow brown, ripple-laminated, fining-upwardt fine sand to silt. Truncated and cemented at 11.5m.
This area was probably folded by the Delmar Readvance.

STOP 16. (Malloy) Loudonville Pits (Fig. 10b)
These pits are on the axis of the Loudonville esker complex. The Loudonville esker complex was described by Peet (1904) as a moraine-kame-delta complex that extended from North Albany to Newtonville. It is bounded on the north by a "boulder strewn" moraine ridge with elongate kettles (Woodworth, 1905). The esker system slopes to the south, with coarser gravels and cobbles to the north and finer gravel and sand to the south (Woodworth, 1905). Kettle holes are common, with faulted bedding near the kettles, and unfaulted bedding dominating to the south. The lenticular gravel at the north grades southward into horizontally bedded, finegrained sediments (Woodworth, 1905). The eskers are overlain by cross bedded, gray and yellow sand (Cook, 1905). The esker complex grades southward into the Schodack kame terrace (Woodworth, 1905, Cook, 1930, LaFleur, 1965a, 1965b). Woodworth (1905) interpreted the Loudonville complex as being built by south-flowing, inglacial streams. Cook initially interpreted the complex as a crevasse filling (Cook 1930), but later re-interpreted it as being deposited in a blind, lake water-filled, ice-walled tunnel (Cook, 1946). He misinterpreted the rounded bluffs surrounding the complex as being molded by over-hanging ice walls (Cook, 1946), rather than as beach-cliffs cut by Lake Albany waves (Fairchild, 1918, LaFleur, 196lb, 1965b). Stop 16 shows a 16m fining-upward sequence of poorly-to well-sorted, ice-contact sand and gravel. The lower gravel contains boulders, silt, and cobbles in planar cross-beds which interfinger with cobble lenses. These lower beds are overlain by ripple-laminated sand that is overlain by lenticular, fining-upward, trough cross-bedded gravel and ripple-laminated sand. This sequence is overlain to the south by planar cross-bedded, ripple-laminated, deltaic fine silt and sand. The entire sequence is cut by gravity-faults that bound basins which filled with varved clay. The varved clay reaches an elevation of +400 ft. The +400 ft. varved clay and delta complex at Stop 16 was deposited in a lake that existed up-stream (north) from Lake Albany. The western edge of the esker complex was exposed in a building excavation at the corner of Osborne and Shaker Roads in 1976. This excavation contained a fining-upward sequence of trough cross-bedded gravel and sand. The gravelly sand beds were planed off, and were overlain by horizontally laminated, yellow brown sand. The entire sequence contained numerous gravity faults. The lower trough cross-bedded, gravelly sand was deposited in the esker. The upper, laminated sand was deposited in a Lake Albany beach. Stagnant ice lay in the area until after the lake dropped below the +330 ft. level, as indicated by the gravity faults. The area of this pit is probably the recharge of the Loudonville eskers' artesian groundwater system.

A4: THE STRUCTURAL FRAMEWORK OF THE SOUTHERN ADIRONDACKS
James McLelland
Department of Geology
Colgate University
Hamilton, NY
INTRODUCTION
The area referred to as the southern Adirondacks is shown in Figure 1. Within this region, the Precambrian is bounded approximately by the towns of Lowville and Little Falls on the west and Saratoga Springs and Glens Falls on the east.
Mapping in the southern Adirondacks was done first by Miller (1911, 1916, 1920, 1923), Cushing and Ruedemann (1914), Krieger (1937), and Cannon (1937); more recent investigations were undertaken by Bartholomew (1956), Thompson (1959), Nelson (1968), and Lettney (1969). At approximately the same time Walton (1961) began extensive field studies in the eastern portion of the area (Paradox Lake, etc.), de Waard (1962) began his studies in the west (Little Moose Mt. Syncline). Subsequently de Waard was joined by Romey (de Waard and Romey, 1969).
Separately and together, Walton and de Waard (1963) demonstrated that the Adirondacks are made up of polydeformational structures, the earliest of which consist of isoclinal, recumbent folds. Their elucidation of Adirondack geology set the tone for future workers in the area. In this regard one of their most important contributions to the regional picture was that the stratigraphy of the west-central Adirondacks is correlative with that of the eastern Adirondacks.
Beginning in 1967 McLelland (1969, 1972) initiated mapping in the southernmost Adirondacks just to the west of Sacandaga Reservoir. This work was extended subsequently north and east to connect with that of Walton and de Waard. Geraghty (1973) and Farrar (1976) undertook detailed mapping in the eastern half of the North Creek 15' quadrangle. This tied into investigations in the Brandt Lake region by Turner (1971). Recently, Geraghty (1978) completed a detailed study of the structure and petrology in the Blue Mt. Lake area. The foregoing investigations have increased our knowledge of the southern Adirondacks, and this field trip is designed to show as many examples of the region's structure, lithology, and petrology as time allows.
2011: This following trips are identical:

A4: THE STRUCTURAL FRAMEWORK OF THE SOUTHERN ADIRONDACKS

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 F2 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. Note that fish-hook terminations on some of these suggest that they have been transposed. It is also clear that these anatectites have been folded by F2 indicating a pre-F2 metamorphic event(s). In a similar fashion some garnets in the rock appear to be flattened while others do not. It is believed that the anatectites formed at the muscovite-quartz reaction and are essentially in situ melts. Further anatexis did not take place due to absence of vapor.

STOP 2. Irving Pond Fm., .5 mile north of Nick Stoner's Inn, Canada Lake .
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 are essentially quartzose sillimanite-garnet-biotite-feldspar gneisses (kinzigites).
At the northern end of the cut, and approximately on the Irving Pond/Canada Lake Fm. contact there occurs an excellent set of F2 minor folds. Polished slabs and thin sections demonstrate that these fold an earlier foliation defined by biotite flakes and flattened quartz grains.
The Irving Pond Fm. is the uppermost unit in the stratigraphy 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
These 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.
Although no protolith is known with certainty for these rocks a metavolcanic history is suggested by their homogeneity and lateral continuity. Their bulk chemistry corresponds to dacites.

Canada Lake Store. Good exposures of Royal Mt. member of Green Lake Fill.

STOP 4. Rooster Hill megacrystic gneiss at the north end of Stoner Lake.
This distinctive unit is believed to be, in part, correlative with the Little Moose Mt. Fm. 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 as well as elongated in an E-W direction with concomitant developed of tails of grain-size reduced tails asymmetric to foliation. However, a few megacrysts are situated at high angles to the foliation. The groundmass consists of quartz, oligoclase, biotite, hornblende, garnet, and occasional orthopyroxene. An igneous rock analogue would be quartz-monzonite or granodiorite depending on concentration of K-feldspar.
The origin of the Rooster Hill is obscure. Its homogeneity over a thickness approaching 2.5 km suggests an igneous parentage. This conclusion gains support from the presence of localities where megacrysts appear to retain a random orientation, and from the occasional presence of what may be drawn out xenoliths of biotitic or amphibolitic gneisses. However, these features may be explained by other models. The contacts of the Rooster Hill are always conformable with enclosing units, and this suggests a metastratified (metavolcanic?) origin. However, the anorthosites of the region also show conformable contacts, and this may, in part, be due to tectonic flattening.
Recently Eckelmann (pers. comm.) has studied zircon population morphologies in the Rooster Hill and similar lithologies. His results strongly suggest an igneous plutonic origin. This would be consistent with the igneous origin assigned the Hermon granite of the northwest Adirondacks - a rock that is markedly similar to the Rooster Hill.

Low roadcut in kinzigites of Tomany Mt. Fm.

Long roadcuts of quartzo-feldspathic gneisses and metasediments
Long roadcuts of quartzo-feldspathic gneisses and metasediments of Lake Durant Fm. intruded by metagabbro and anorthositic metagabbro.

Roadcut of anorthositic metagabbro and metanorite.

Excellent examples of anorthositic gabbros
Roadcut on west side of highway shows excellent examples of anorthositic gabbros intrusive into layered pink and light green quartzo-feldspathic gneisses. The presence of pegmatites and cross-cutting granitic veins is attributed to anatexis of the quartzo-feldspathic gneisses by the anorthositic rocks.

Stop 5. Lake Durant and Sacandaga Fms.
Stop 5. Lake Durant and Sacandaga Fms. intruded by anorthositic gabbros and gabbroic anorthosites. These roadcuts are located on Rt. NY 10 just south of Shaker Place.
The northernmost roadcut consists of a variety of metasedimentary rocks. These lie directly above the Piseco anticline and are believed to be stratigraphically equivalent to the Sacandaga Formation. The outcrop displays at least two phases of folding and their related fabric elements. These are believed to be F2 and F3. A pre-F2 foliation is thought to be present. Both axial plane foliations are well developed here. Several examples of folded F2 closures are present and F2 foliations (parallel to layering) can be seen being folded about upright F3 axial planes.
Farther to the south, and overlooking a bend in the west branch of the Sacandaga River, there occurs a long roadcut consisting principally of pink and light green quartz-perthite gneiss belonging to the Lake Durant Fm. About half-way down this roadcut there occurs a large boudin of actinolitic and diopsidic gneiss. To the north of the boudin the quartzo-feldspathic gneisses are intruded pervasively by anorthositic gabbros, gabbroic anorthosites, and various other related igneous varieties. At the north end of the cut and prior to the metastratified sequences these intrusives can be seen folded by upright fold axes. They are crosscut by quartzo-feldspathic material.
Within this general region the Lake Durant Fm. and other quartzofeldspathic gneisses seem to have undergone substantial anatexis. This is suggested by the "nebular" aspect of the rocks. Good examples of this are seen in the manner in which green and pink portions of the quartzo-feldspathic gneisses mix. Note also the clearly cross-cutting relationships between quartzofeldspathic gneiss and mafic layers at the south end of the roadcut. Here it seems that mobilized Lake Durant is cross-cutting its own internal stratigraphy. Also note that the quantity of pegmatitic material is greater than usual. This increase in anatectic phenomena correlates closely with the appearance of extensive metagabbroic and metanorthositic rocks in this area. It is believed that these provided a substantial portion of the heat that resulted in partial fusion of the quartzo-feldspathic country rock.

Red-stained basal quartzo-feldspathic gneisses that have been faulted along NNE fractures.

Stop 6. Core rocks of the Piseco anticline.
Hinge line of Piseco anticline near domical culmination at Piseco Lake. The rocks here are typical basal quartzo-feldspathic 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 grain size reduced and only a few small remnants of cores are seen. The open folds at this locality are minor folds of the F3 event. Their axes trend N70W and plunge 10-15° SE parallel to the Piseco anticline. Co-axial F2 isoclines are also present.
The most striking aspect of the gneisses in the Piseco anticline is their well-developed lineation. This is expressed by rodding and ribbon fabrics. These may consist of alternating ribbons of quartz, quartzo-feldspathic gneiss, and biotite-rich layers. In some instances the rods represent transposed layering on the highly attenuated limbs of early, isoclinal minor folds. Near the northeast end of the roadcut such minor folds are easily seen due to the presence of more massive layers in the rock. Slabbed and polished specimens from this and similar outcrops demonstrates that these early folds are exceedingly abundant in the Piseco anticline. Examination of these folds shows that the dominant foliation in the rock is axial planar to them.
The lineation in these outcrops is shown in Fig. 8a while slabbed sections are shown in Figs. 8b,c. Fig. 8b is cut perpendicular to foliation and both parallel to (left face) and perpendicular to (right face) lineation. As can be seen K-feldspar augen have been elongated in the direction of lineation. Together with elongated quartz aggregates, these grain size reduced minerals form the prominent mineral lineation that characterizes foliation surfaces (Fig. 8a). Note that the K-feldspar augen exhibit shapes closer to equant on the right hand face at perpendicular to lineation. This strongly suggests that the rock fabric is the result of rotational strain in the direction parallel to lineation, i.e., the lineation is an elongation, or stretching type. Fig. 9 shows a less deformed sample slabbed perpendicular to foliation and parallel to lineation. The development of tails on K-feldspar augen are clearly visible. These are the result of grain size reduction during ductile rotational strain. A sinistral (east over west) sense of motion is indicated. At more extreme conditions of strain the K-feldspar augen and quartz aggregates are drawn into ribbons as in the present outcrop. Long dimensions of 40-60 cm are common along with thicknesses of a millimeter, or less. Clearly strain has been extreme and elongations of 30-40 times are not unusual.
Ribbon gneiss origin by rotational strain is also suggested by the parallelism between lineation and F2, F3 fold axes. It is believed that these fold axes were drawn into parallelism with the lineation by ductile, rotational strain directed from east to west. The most satisfactory mechanism for this configuration is the stacking of thrust sheets and thrust nappes during plate collision. Thrusts have been recognized to the east of Lake George (Fig. 4) and others probably exist although the intense, ductile nature of the deformation has resulted in extremely subtle truncations that are difficult to recognize. Sheath folds (Fig. 10) with tube axes parallel to lineation are consistent with this model. Presumably crustal thickening during the Grenville Orogeny was caused by the stacking of these thrusts.

Stop 7. Blue Mt. Lake Fm. exposed in roadcuts on both sides of highway.
The Blue Mt. Lake Fm. is exposed in roadcuts on both sides of the highway. These exposures show typical 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 with ease during the deformation. As a result the marble-amphibolite relationships are similar to those that would be expected between magma and country rock. Numerous rotated, angular blocks of amphibolite are scattered throughout the marble in the fashion of xenolith, 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 rema in "floating" in the marble have been aptly termed "tectonic fish." The early, isoclinal folds rotate on earlier fo1iation.
Near the west end of the outcrop a deformed layer of charnockite is well exposed. In other places the charnockite-marble interlayering occurs on the scale of one to two inches.
Exposed at several places in the roadcut are cross-cutting veins of tourmaline and quartz displaying a symplectic type of intergrowth. Other veins include hornblende and sphene bearing pegmatites.
Commonly included in the Blue Mt. lake Fm., but not exposed here, are quartzites, kinzigites; sillimanite rich, garnetiferous quartz-microcline gneisses; and fine grained garnetiferous leucogneisses identical to those characterizing the Sacandaga Fm. These lithologies may be seen in roadcuts .5 mile to the south.
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 (> 1 b.y. ago). Presumably the graphite represents remains of stromatolite-like binding algae that operated in shallow water, intertidal zones. If so, the other roadcut lithologies formed in this environment as well. This seems reasonable enough for the clearly metasedimentary units such as the quartzites and kinzigites. The shallow water environment is much more interesting when applied to the charnockitic and amphibolite layers. The fine scale layering, and ubiquitous conformity of these, strongly suggests that they do not have an intrusive origin. Perhaps they represent the metamorphosed products of volcanic material in a shelf like environment. Such intercalation is now occurring in many island arc areas where shallow water sediments cover, and in turn are covered by, ash and lava. Alternatively they may represent metasediments. A large lumber of minerals are developed within these outcrops. Both calcite and minor dolomite are present in the carbonate horizons. These are accompanied by green diopside and serpentinized forsterite as well as by tourmaline, graphite, and various sulfides. In calcsilicate horizons phlogopite, diopside (white), and tremolite occur. Wollastonite is locally present. The presence of tremolite and wollastonite is believed to be a function of the relative concentration of CO2 and H2O in the vapor phase Valley et al., 1983).

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

Large roadcuts in lower Lake Durant Fm.
Pink, well-layered quartzo-feldspathic gneisses with subordinate amphibolite and calcsilicate rock.

Stop 8. Intermediate Adirondack anorthositic gneiss
On the west side of the road small roadcut exposes an excellent example of Adirondack anorthositic gneiss intermediate in character between the so-called Marcy type (coarse) and the Whiteface type (fine grained). About 50% of the rock consists of fine grained crystals of andesine plagioclase. Some of these crystals appear to have measured from 6-8" prior to grain size reduction. Excellent moonstone sheen can be seen in most crystals. In places ophitic to subophitic texture has been preserved with the mafic phase being represented by orthopyroxene.
In addition to the anorthosite there exists a clearly crosscutting set of late iron-rich orthopyroxene rich dikes containing xenoliths of coarse grained anorthosite. The latter may represent a late mafic differentiate related to cotectic liquids responsible for the ophitic intracrystalline rest magma. This would be consistent with the iron enrichment trend characteristic of Adirondack igneous differentiation.
Near road level there can be found several inclusions of calcsilicate within the anorthositic rocks. These are believed to have been derived from the Cedar River Fm. and are consistent with a non-basement status for the anorthosite.
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.

Cedar River Fm. Minor marble, amphibolite, and calcsilicate rock.
Predominantly very light colored sillimanite-garnet-quartz-K-feldspar leucogneisses.

Leucogneisses of the Blue Mt. Lake Fm.
To the west of the intersection are roadcuts in leucogneisses of the Blue Mt. Lake Fm. A large NNE normal fault passes through here and fault breccias may be found in the roadcut and the woods beyond.

Entering Little Moose Mt. Fm.
Entering Little Moose Mt. Fm. 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 intrusive into the Blue Mt. Lake Fm.

Lake Durant Fm
On the north side of NY Rt. 30 are quartzo-feldspathic gneisses and calcsilicate rocks of the Lake Durant Fm. An F1 recumbent fold trends subparallel 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 examples 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 sillimanite-garnet-microcline-quartz gneisses (leucogneisses). Although the weathered surface of these rocks are often dark due to staining, fresh samples display the typical light color of the Sacandaga Fm. The characteristic excellent layering of the Sacandaga Fm. is clearly developed. Note the strong flattening parallel to layering and the lineation developed on many foliation surfaces. These gneisses are similar to so-called straight gneisses found in proximity to ductile shear zones. The Sacandaga Fm. may represent mylonitic rocks of this type and its layering may, in fact, be tectonic.
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. NO HAMMERING PLEASE. Many "punky" weathering layers in the outcrop contain calc-silicates and carbonates.
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 homogeneous quartzofeldspathic 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.
No angular discordance or other indications of unconformity can be discerned at the base of the Sacandaga Fm. However, this does not preclude the prior existence of an angular discordance which may have been swept into pseudo-conformity by tectonism.
Along most of the roadcut there can be found excellent examples of faults and associated pegmatite veins. Note that the drag on several of the faults gives conflicting senses of displacement. The cause of this is not known to the author. Also note the drag folds which indicate tectonic transport towards the hinge line of the Piseco anticline.

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 quartzo-feldspathic gneisses of Lake Durant Fm.
In long roadcuts of southerly dipping quartzo-feldspathic gneisses of Lake Durant Fm.

A5: MICROSTRUCTURE OF A VERMONT SLATE, AN ADIRONDACK GNEISS, AND SOME LABORATORY SPECIMENS
W. D. Means
Department of Geological Sciences
State University of New York at Albany
M. B. Bayly
Rensselaer Polytechnic Institute
The aim of this trip is to examine the microstructure of some naturally and experimentally deformed materials and to discuss the relationships between the observed structures and the deformations they represent. The microstructures at each stop will be described using hand-out photomicrographs. The trip is therefore not very suitable for future use by independent field parties. These notes will accordingly be brief.

A5: MICROSTRUCTURE OF A VERMONT SLATE, AN ADIRONDACK GNEISS, AND SOME LABORATORY SPECIMENS

STOP 2. Quartzo-feldspathic gneiss
Exposure is mainly west side of new Route 4. Two smallscale features of interest occur here. The first is a quartz ribbon lineation trending east in the plane of the main southeast-dipping foliation. This is a common type of lineation in Adirondack gneisses, of obscure kinematic significance. The nature of this lineation will be discussed -- is it transposed quartz layering? stretched quartz aggregates or grains? synkinematic secretion ? or .... ?
The second microstructure of interest consists of partial feldspar rims, in preferred orientation, around feldspar grains. The hypothesis that these are in-fillings of potential voids between rigid grains in relative motion will be discussed.

STOP 3. Cedar Mountain Slate Quarry.
The quarry displays many structural features of interest, including variously shaped green spots and a large recumbent synform. The synform closes to the east (hinge-line subhorizontal, trending north); a folded surface is exposed on the west wall of the quarry and fold profiles are exposed in the north wall. The main cleavage that provides the slate is subhorizontal, axial-planar to this fold. On this trip, attention will be focussed on the crenulation cleavages which overprint the main slaty cleavage.
The crenulation cleavage is mostly an antithetic kink-like variety; it may be seen in places in two conjugate orientations consistent with shortening parallel to the (shallow) dip direction of the slaty cleavage. Puzzling features which will be illustrated and discussed are the less frequent occurrence of synthetic crenulation cleavage (perhaps suggesting extension in the dip direction of the slaty cleavage), and some dark layers enriched in "insoluble" material. In a few places these layers coincide with crenulation cleavage planes, but in many places the crenulations and the dark layers seem to be independent of each other --- not parallel and not genetically related although close together in the rock.

A6: CLEAVAGE IN THE COSSAYUNA AREA, AS SEEN AT THE OUTCROP
Lucian B. Platt
Bryn Mawr College
ABSTRACT
This trip crosses the Taconic allochthonous sheets in Washington County, N.Y., eastward on Saturday and westward on Sunday. The purpose is to look at various structures visible at outcrop and with a hand lens and to consider how much of the deformation can be attributed to dissolution. I believe that much rock has moved through solution, but many features seen at outcrop are not easily interpreted. At the west edge of the klippe rocks, the underlying carbonates are remarkably undeformed, and the Taconic Sequence, though folded and cleaved, does not show obviously massive rock loss. Eastward the situation becomes more complicated, and at the easternmost stop, extension fibers have formed in fanning "cleavage." I hope those taking the trip will share their observations and thoughts at the outcrop so that we all learn.

STOP 1. Bald Mountain, near Middle Falls, N.Y.
Re-enter the bus 1 hour after getting out.
Enter the quarry on the west side and walk around the southwest side of the hill along the old ro'ad. The quarry existed to produce lime, and some evidence of kilns remain. The geologic relations at Bald Mountain have been examined by scores of geologists for over a century. Published mapping by Ruedemann (Cushing and Ruedemann, 1914) shows Lower Or~dovician limestone overlain by a thrust plate of Lower Cambrian shale. In fact, a screen of Middle Ordovician shale intervenes between, and the best explanation of the geology in this vicinity is that the carbonate floats as a tectonic fish in the Ordovician shale which is overlain by the thrust plate of Taconic rocks. Our interest in the locality is that we can see shale with pebbles of carbonate, and we can see some dissolution features adjacent to some of the carbonate. One point to note is how LITTLE deformation there is in the Ordovician carbonate, even in small pieces, in contrast to the cleaved shale.

STOP 2. One mile southeast of Argyle, NW quadrant of intersection.
Re-enter the bus after no more than an hour.
Some small folds in these Lower Cambrian carbonate, silt, and shale beds can be seen in the southwest part of the corner field. The chevron folds do not show much cleavage, but other parts of the pasture do. Dale (1899) found trilobites in both the pebbles and the matrix, but the conglomeratic look to the carbonate beds is probably due to insoluble residue concentrated along dissolution surfaces. The main point of this stop is to examine the styles of deformation in this more or less carbonate-rich part of the Taconic Sequence.

STOP 3. 1000' west of the south end of Cossayuna Lake.
Re-enter the bus in one hour.
At the road cut it is easy to see conglomerate of carbonate pebbles in shale and some beds of limestone in shale. Walk up to the outcrops of this rock on the slope north of the road cut. In several places the glacially scraped rock shows solution features in the carbonate. Seeing this requires getting down on hands and knees and using a hand lens in many cases; hence if it is raining, we will abandon this stop. One aspect of the solution of these rocks is that many solution features do not continue very far in the rock; they are approximately parallel to tight fold axes in the area. How much change in thickness of beds around tight folds, particularly in area of "similar" folds, is due to removal of rock? In nearly isoclinal folds, it is possible to show that dissolution could cause virtually all of it.

STOP 4. BM564
Re-enter bus after 30 minutes.
Folds in Lower Cambrian Mettawee and West Castleton Formations . This small outcrop is rich in deformation features. Chevron folds and kinks. Microboudins. "Slip" both ways on vertical cleavage. It is not clear to me how slip both ways could occur on parallel cleavage surfaces; hence I conclude that during folding a substantial part of the rock went into solution, and the plane along which material was removed only appears to be a line of slip. Years ago, Donath (1961) showed that slip occurs along surfaces of mechanical anisotropy; here we can infer that the cleavage we see was not a place of particular anisotropy before or during the early stages of its formation. Flattening by selective dissolution seems a better way to me. But where does the material go? What is the reservoir rock for this source rock?

STOP 5. Intersection of NYRoute 313 and County 61
Re-enter bus after about an hour and a half.
Quite a variety of wonderful things are visible at this roadcut. I suggest that you walk east along the outcrop before you get down to the details. The paucity of veins at previous outcrops is in sharp contrast to this spot. I doubt it is merely a matter of metamorphic grade, though this rock is obviously more metamorphosed than the first stops. These rocks are folded and veined (calcite before quartz?) but the cleavage is not particularly impressive. Nevertheless, small crenulations show concentrations of micaceous minerals along limbs quite like the drawings of Gray (1979, Fig.3), and I infer, as he does, that solution of quartz is a major factor in the wrinkling. A thin section of sandstone from this outcrop shows extensively twinned calcite vein material, some sutured sand grain boundaries, and very little but nevertheless some dark submicroscopic material in strings along some grain boundaries and in sutured grain contacts. In one vein it appears that the calcite twin lamellae are bent. In the thin section, only two sand grains other than quartz were found, so this particular section was not ideal rock to see mica beards, etc., as shown by Means (1975, Fig. 1 ).

STOP 6. Across from 1852 covered bridge over Battenkill in Vermont
Re-enter bus after 1 hour.
These carbonates are so-to-speak out from under the east side of the Taconic rocks we have been looking at between here and Bald Mountain (stop 1). As we have moved east and southeast across the Taconic Sequence, the metamorphism has increased, as was clear at the last stop. How does this affect the carbonates? Things to look at here include the following:
a. Crinoid stems in coarse beds. Although the crinoid is dead, the ossicle is in good condition.
b. Some calcite layers look schistose. Are these beds?
c. The difference in ductility between different layers is apparent.
d. Where are the stylolites in these strongly deformed rocks? Or are there just no insoluble residues?
e. Near the west end of the outcrop folded layers have fanning "cleavage" but the feature that is fanning has calcite fibers.
f. Some curved veins have fibers. Did the fibers survive folding, or did the fibers form after the folding of the veins, or did the veins from with their present curvature? This would seem to imply that the fibers are related to something different from compressional dissolution cleavage fanning the fold .

A7: THRUST SHEETS OF THE CENTRAL TACONIC REGION
Donald B. Potter
Hamilton College
Clinton, New York
INTRODUCTION
This field trip is based on mapping in the Berlin, Hancock, and Williamstown Quadrangles during the summers of 1976, 77, and 78. This work was done for the U.S.G.S. and in conjunction with Nicholas M. Ratcliffe in preparation for the new geologic map of Massachusetts. The field trip concentrates on key exposures in the valleys of the Hoosic and Little Hoosic Rivers. In addition to the recent field mapping, the author has made some important reinterpretations of faults mapped earlier (Potter, 1972) in the Hoosick Falls area. Three major thrust sheets and a group of ·minor thrust slices are recognized in the central Taconic region. Their relative age of emplacement (oldest at bottom), correlation with previously named thrust sheets, and probable times of deformation are as follows:
Former Designations
(Potter 1972)
Present Designation
Stage of Deformation
| | F3
Not recognized as separate sheet. | IV. Berlin Mountain Thrust Sheet |
| | F2
Rensselaer Plateau Thrust Sheet | III. Rensselaer Plateau Thrust Sheet |
Not Named | II. Butternut Hill thrust slices |
| | F1
North Petersburg Thrust Sheet | Giddings Brook Thrust Sheet |
I. The Giddings Brook thrust sheet, a name from the northern Taconics and worthy of perpetuating in the central Taconic region, consists of very distinctive stratigraphic units (Figure 3.) several of which are fossiliferous. The dominant thrust sheet in the Taconic allochthon, it was emplaced in Mid-Ordovician time as a gravity slide. Beneath it in the central Taconic region is Mid-Ordovician Walloomsac slate with its Whipstock Breccia member, a wildflysch type of block and shale unit. The Giddings Brook thrust fault is recumbently folded, and the internal structure of the sheet itself is commonly that of a major recumbent anticline opening east with youngest formations at the base of the sheet.
II. The Butternut Hill thrust slices are small lenticular masses consisting of limestones and dolostones of the Stockbridge Formation with infaulted lenses of Rennselaer Graywacke. Near Berlin Village one of these slices truncates the trace of the Giddings Brook thrust fault and is, itself, truncated by the trace of the Rensselaer Plateau thrust fault. The Butternut Hill slices are envisioned as hard dry slices of rock dragged along the base of the advancing Rensselaer Plateau thrust sheet.
III. The Rensselaer Plateau thrust sheet consists dominantly of RensseJaer Graywacke with interbeds of maroon and green-gray slate. Near its base the Rensselaer sheet contains metavolcanic rocks. The position of the Rensselaer Plateau sheet structurally above the Giddings Brook is clearly indicated by numerous excellent exposures many of which have limestone or dolostone slices (Stockbridge Formation) at the thrust contact. This relationship is seen at Stop 2.
IV. Berlin Mountain thrust sheet. This name is given for the. greeni'sh and purple chloritoid-bearing slates and phyllites with few distinctive marker beds that make up the bulk of the Taconic Range. Berlin Mountain is a major crest in this range. That this is a separate thrust sheet is suggested by the following evidence: north of the Hoosic River (Stop 1) the chloritoid phyllites in question are separated from distinctive formations of the Giddings Brook thrust sheet by slices and slivers of Stockbridge carbonate rocks. The Giddings Brook sheet is isoclinally folded (F2) with the Rensselaer Plateau sheet and both lie beneath the Berlin Mountain thrust fault. Also, the position of the Rensselaer Graywacke in the Taconic Range (Figure 2.) casts doubt on an earlier working hypothesis in this region which states that the Rensselaer Graywacke was a basal stratigraphic unit in the thrust sheet that formed the range. The graywacke is seen to be limited to the north and south ends of the range and does not occur along the east or west edges nor in the center. Had that Rensselaer Graywacke been present as a stratigraphic unit at the base of the chloritoid phyllites it seems highly likely that it would now be found infolded with them. An alternate hypothesis is proposed: the Rensselaer Graywacke in the Taconic Range belongs to the Rensselaer Plateau thrust sheet; over the top of this was emplaced sheet IV, Berlin Mountain thrust sheet. Both sheets were subsequently cupped into a broad F3 synform whose axis trends northwest - southeast. Subsequent erosion has exposed the.· older, Rensselaer Plateau thrust sheet, albeit patchily, at the north and south noses of the synform. Elsewhere the Rensselaer sheet is covered by the Berlin Mountain (IV) thrust sheet.
At least three stages of deformation are recorded. Initial large and small scale recumbent folding (F1) occurred during the emplacement of the Giddings Brook sheet;· the axial plane cleavage (S1) that formed at this time has been subsequently rotated to a moderately steep southeast dip and has generally been overwhelmed by the development of a pronounced slip cleavage (S2). This slip cleavage is co-planar with the axial planes of F2 folds, isoclinal to asytmJetrical with axial planes dipping east or southeast. F2 -folds are seen in the outcrop pattern at Stop 3; and a large south-plunging isoclinal anticline involving the Giddings Brook and Rensselaer Plateau thrust sheets is interpreted to be an F2 fold at Stop 1. F3 folds have northwest-trending axes. At Stop 3 they bring to the present surface the south-plunging Giddings Brook thrust fault and account for the northwest-southeast outcrop pattern superposed on a large F1 recumbent fold there; also, F3 folding accounts for a major fishook pattern on the east side of the Taconic Range. The doubly plunging synform of the Berlin Mountain and Rensselaer Plateau thrust sheets in the Taconic Range probably is an F3 fold, and the Hoosick Falls embayment (west of Bennington, Figure 1.) is probably produced by erosion of an F3 anticlinal warp.

A7: THRUST SHEETS OF THE CENTRAL TACONIC REGION

STOP 1.
The aim of this traverse is to demonstrate the anticlinally folded Giddings Brook (I) thrust sheet with Stockbridge Formation beneath the thrust fault to the west, and chloritoid schists of the Berlin Mountain (IV) thrust sheet above the Giddings Brook to the east. The latter contact is marked by long slivers of limestones and dolostones (Stockbridge Formation). A large F2 anticline is indicated by the exposure, half-way through this traverse, of autochthonous formations - Whipstock Breccia and Austin Glen Graywacke members of the Walloomsac - beneath the folded Giddings Brook thrust fault.
In the fields above the parking location are limestones and dolostones of the Stockbridge Formation (probably units F and G). One layer in this sequence yields early Ordovician brachiopods. Other layers in these fields carry Post-Canadian brachiopods, ostracods, trilobites, bryozoa and are mapped as Walloomsac limestone (Owl).
Crossing the Giddings Brook Thrust Fault at the saddle, we encounter various formations of the G. B. thrust sheet: medium-light gray, some dolomitic slates (Poultney); dark gray and black slates (Hatch Hill) enclosing the Eagle Bridge Quartzite; green-gray slate (Mettawee) and Zion Hill Quartzite. At the 1027 crest we cross the Giddings Brook thrust and see autochthonous rocks of the Walloomsac Formation. The dominant lithology here is the Whipstock Breccia, a dark gray slaty rock crowded with rusty and white-weathering chips of siltstone and sandstone. The Whipstock encloses lenses of sheared limestone and dolostone (Stockbridge Fm.) and lenses and beds of Austin Glen Graywacke. The Whipstock is interpreted to be a submarine slide breccia facies of the Walloomsac, deposited in front of the advancing Giddings Brook thrust sheet and containing blocks and lenses of the Taconic Sequence as well as of the Stockbridge Formation and the co-deposited Austin Glen Graywacke.
From crest 1027 to crest 1294 we cross the Giddings Brook thrust again and then traverse across variably foliated olive-weathering siltstone (Bomoseen), and dark gray slates containing limestone lenses (West Castleton); east of crest 1294 we encounter a large sliver (2000 feet long and up to 200 hundred feet wide) of sheared limestones and dolostones (Stockbridge Formation) which marks the sole of the highest thrust sheet (Berlin Mountain (IV) Thrust Sheet). The dominant lithology of the Berlin Mountain sheet is green and purple chloritoid schist, with coarsest chloritoid commonly near the thrust fault.
Return to parking area by traversing along the trace of the Berlin Mountain thrust sheet marked by slivers of carbonate rocks.

Folded Stockbridge and Walloomsac Limestone
Large exposures of recumbently folded Stockbridge (unit G) and Walloomsac limestone on right (west) side of highway.

Cross trace of (Giddings Brook) thrust fault
Cross trace of (Giddings Brook) thrust fault, and proceed south on Taconic Sequence formations near base of G. B. thrust sheet.

Bold cliffs on Taconic Mountains to east
Barn on east side highway, house on west. Bold cliffs on Taconic Mountains to east are Rensselaer Graywacke near base of Rensselaer Plateau thrust sheet.

Bomoseen Graywacke on right side of highway.

Massive exposures of Mettawee slate on west side of highway.
These slates are at the core of the Giddings Brook nappe.

STOP 2. Exposure of the Rensselaer Plateau thrust fault
Exposure of the Rensselaer Plateau thrust fault north of Prosser Hollow. Below the thrust fault is an apparently normal sequence of Bomoseen, Mettawee, and Hatch Hill (with Eagle Bridge Quartzite) - all part of the Giddings Brook thrust sheet. The Rensselaer Plateau (III) thrust fault is marked by slivers of limestone and dolostone (Stockbridge Formation) that have been tectonically dragged to their present positions. Immediately above the Rensselaer Plateau thrust is the Rensselaer Graywacke, perhaps several hundreds of feet thick and intensely sheared. The Graywacke is faulted against chloritoid schist 0.3 miles east of this stop, at the trace of the Berlin Mountain thrust fault.
The following details of the Rensselaer Plateau fault zone are noted. First, the Rensselaer Graywacke above the thrust is mylonitic through a zone approximately 150 feet thick (measured perpendicular to foliation), and the mylonitic foliation is concordant with normal foliation above and below the thrust zone. Second, the thrust plane truncates the mylonitic foliation. Third, a well-developed foliation parallel to the thrust plane occurs in the uppermost 2-3 feet of the limestone. Numerous other structural features may be observed. Widely spaced fractures, parallel to the thrust plane, also truncate the foliation and show a similar sense of movement to that on the thrust. Several warps in the thrust plane apparently represent areas where (later) movement on the thrust has locally followed the foliation instead of cutting across it. Near the upper (western) end of the outcrop, a sliver of mylonitic graywacke about 5' X 5' is completely enclosed within the limestone. West of this, the thrust plane steepens and follows the trend of the foliation in the graywacke for an indefinite distance.
The earliest structural event well-represented at this stop is the formation of the pervasive axial plane foliation, S2, and the accompanying regional metamorphism. Emplacement of the graywacke along the Rensselaer Plateau Thrust may have occurred prior to the formation of S2. Evidence for this is the occurrence in several places along the thrust of tectonic slivers of autochthonous carbonates around which S2 has been refracted.
The mylonites either were pre S2 and rotated into their present orientation during the formation of S2, or else formed at the same time as the foliation. The latter explanation is preferred.
Following S2, minor movement occurred between the Graywacke and the slates beneath. This movement caused the presently observed thrust plane, the thin zone of well-developed foliation in the upper few feet of the limestone, and the low angle fractures in the rocks immediately above and below the thrust. Perhaps we are seeing the results of a stick/slide phenomena of thrust faulting and not discrete periods of foliation formation followed by minor movement.

Bomoseen and Mattawee members on west side of Route 22.
From here to Petersburg we are in the lower part of the Giddings Brook thrust sheet which has a recumbent anticline structure. Formations exposed in the channel of the Little Hoosic, or near road level, are typically younger formations of the Taconic Sequence on the inverted limb of the recumbent anticline; higher on the east and west slopes of the Little Hoosick Valley are older formations of the nappe, and above these is the Rensselaer Plateau thrust sheet.

Mettawee on right.

STOP 3. Jones Hollow-Satterlee Hollow refolded recumbent
The southward plunge of the Giddings Brook thrust is interupted here by F3 cross-folds bringing the sole of the Giddings Brook thrust and underlying Walloomsac to the surface. Walloomsac floors the valley of the Little Hoosic River southward from this point.
The JH-SH recumbent covers an area about two miles long and one mile wide. Its outcrop pattern and small scale structures indicate three stages of deformation. The core of the large recumbent fold is marked by Walloomsac slate, and by Stockbridge units F and G.; its upper limb consists of slates of the Mettawee and Poultney formations; its lower limb consists of Mettawee slates, Mudd Pond Quartzite, Hatch Hill Formation. The stages of deformation can best be understood by referring to the map pattern and section. On the map the upper limb has the pattern of a 2 mile-long ram charging northeast. The ram's back gives the northeast trace of the axis of the recumbent fold (F1); the axial plane cleavage (S1) associated with this recumbent fold has been rotated from its presumed low angle of dip and it is not as easily seen as is S2. The second stage of deformation resulted in a northeast - striking slip cleavage (S2) which dips 35-50 degrees southeast and is co-planar with axial planes of F2 folds. The ram's head and chest are produced by F2 folds and the northeast - trending fault that truncates the ram's nose is parallel to S2. Northwest - trending F3 folds form the pointed foreleg and the ram's tail.
We will visit outcrops of Walloomsac and Stockbridge units F and G in the core of the recumbent fold, and the Poultney and Mettawee formations on the upper limb. Of particular interest are the long splinters of Poultney slate formed by S1-S2 intersection.

Jones Hollow-Satterlee Hollow recumbent
Jones Hollow-Satterlee Hollow recumbent forms prominent hills at 10-11:00 o'clock.

Outcrops on both sides of road of green Mettawee slate

Mettawee slate on right in woods.
Outcrops above this on east slope on Sugarloaf Hill show pronounced development of S1 and S2 cleavages.

Mettawee slate on right

Large outcrops of Stockbridge limestones and dolostones
On the right (west) side of road, large outcrops of Stockbridge limestones and dolostones (units D and E) which are part of the Butternut Hill thrust slice.

Walloomsac slate on right.

Walloomsac slate on left.

Walloomsac slate on both sides of road

STOP 4. Butternut Hill.
We will traverse 3/4 mile east over the top of Butternut Hill to East Road where we will be picked up by busses. The purpose of this stop is to see one of the smaller thrust slices in this part of the Taconic allochthon: the Butternut Hill (II) thrust slice. The age of its emplacement relative to other thrust sheets cannot be demonstrated here for it is simply floating in Walloomsac. However, one-half mile south of the village of Berlin, an identical thrust slice cuts the trace of the Giddings Brook thrust fault and is, itself, truncated by the Rensselaer thrust fault, thus establishing the Butternut Hill slice as number II in a series of IV sheets or slices.
The Butternut Hill slices (they are not connected) consist of various members of the Stockbridge Formation with in-faulted Rensselaer Graywacke. This distinctive combination of autochthonous carbonate formations and massive allochthonous turbidite can be found as scores of slices ranging from 2 miles2 in area (Berlin Village locality) down to slices a few a few feet in length. The slices are generally tucked up under the Rensselaer Plateau thrust fault and may simply represent slabs of Stockbridge carbonate formations into which the Rensselaer Graywacke was kneaded as the Rensselaer thrust sheet advanced. Some features of the Butternut Hill slices still remain a puzzle: Why wasn't Walloomsac drawn up with the Stockbridge in these slices? Why do we see only one lithology of the Taconic Sequence (Rensselaer Graywacke) in these slices?
Our traverse will take us across Walloomsac which displays S1 and S2 cleavages; a thin mylonite zone; units G and F of the Stockbridge; Rensselaer Graywacke and associated green phyllite.

Gentle slopes on your left (east) underlain by Walloomsac and Stockbridge
Gentle slopes on your left (east) underlain by Walloomsac and Stockbridge formations; above these on the steep slopes is a thin wedge of the Rensselaer Plateau (III) thrust sheet and above that the Berlin Mountain (IV) thrust sheet.

Stockbridge (unit D) thin platy gray limestone on left.

STOP 5. Volcanic rocks and Rensselaer Graywacke
Volcanic rocks and Rensselaer Graywacke at the base of the Rensselaer Plateau Thrust sheet. Here, as at many localities along the east edge of the Rensselaer Plateau and to the southeast, tbe base of the Rensselaer Plateau thrust sheet is marked by a dark green hard metavolcanic unit rich in epidote and chlorite. At one locality within the graywacke terrain on the plateau a similar volcanic unit displays pillow structure. Elsewhere, as at the present locality, the metavolcanic rock appears banded to massive and is characteristically highly deformed. The parent rock was probably a mafic tuff or flow.
We will examine the outcrops of deformed metavolcanic rock and then traverse about l/4 mile north to see the overlying Rensselaer Graywacke.

A8: DETAILED STRATIGRAPHIC AND STRUCTURAL FEATURES OF THE GIDDINGS BROOK SLICE OF THE TACONIC ALLOCHTHON IN THE GRANVILLE AREA
Rowley, D.B., Kidd, W.S.F. and Delano, L.L.
Department of Geological Sciences
State University of New York at Albany
Albany, New York 12222
SUMMARY
The trip will visit localities in the "Giddings Brook Slice" of the lower Taconic allochthon in the vicinity of Middle Granville, New York. Eight localities will be visited, at each the stratigraphy and structure of the lower Taconic allochthon will be described and investigated in detail. Stratigraphically, the stops will emphasize our recognition of a more detailed stratigraphy than previously defined, specifically, the presence of two Cambrian black-green lithologic boundaries, abundant sedimentologic evidence for deep water North American continental rise depositional environment and the need for a Taconic reference section with well defined stratigraphy and known stratigraphic contacts. Structurally, the trips will focus on the nature of the continental rise sediments at the time of emplacement on the continental shelf and the nature of the deformation associated with emplacement. Particular emphasis will be placed on evidence suggesting that the low Taconics were emplaced as coherent tectonic slices and not as soupy soft sediment slides as all previous tectonic interpretations have suggested. Instructions to Participants Participants must bring their own pack lunch. There will be no opportunity to obtain it during the trip. This trip involves 1 1/4 hours travel before the first stop but compensates for that by having little distance between stops in the field area. Good outcrops in the Taconics are rare -- PLEASE DO NOT HAMMER OR DEFACE OR OTHERWISE DESTROY OUTCROPS -- Please take samples only if you will be doing bona fide research with them.

A8: DETAILED STRATIGRAPHIC AND STRUCTURAL FEATURES OF THE GIDDINGS BROOK SLICE OF THE TACONIC ALLOCHTHON IN THE GRANVILLE AREA

Route 40 follows closely the western edge of the Taconic Allochthon
Lowlands to the west are mostly underlain by autochthonous and parautochthonous shales and lesser greywackes (Normanskill/Snake Hill). Road cuts on right of deformed (shelf) carbonates that are at the sole of the Taconic allochthon.

Sole of the Taconic allochthon.
Road cuts on right of deformed (shelf) carbonates that are at the sole of the Taconic allochthon.

Road runs within the Taconic allochthon for next 9 miles

Optional STOP (a) 1.5 to 2.5 miles west of the junction of 22 and 40
Road cuts show gently east-dipping autochthonous carbonates whose unfolded, undeformed structural condition contrasts markedly with that of rocks in the Taconic Allochthon only 2 miles to the east.

OPTIONAL STOP (b) 1.2 miles north of the junction
Go straight across 22 from Rte. 40 and follow dirt road to dirt parking area on right above Metawee River. Go over stile and follow path down slope to river. Gently east-dipping (10- 15°) carbonates (autochthonous or parautochthonous) extend ot north along west bank of river and also illustrate little deformed nature of platform rocks, in this case less than 1/2 mile from the western edge of the Allochthon. Dark shales on east bank have lenticular cleavage and may be part of melange terrane bordering Taconic Allochthon.

STOP 1. Roadcut and stream outcrop on NY Rte. 22 near Truthville
Walk east along Rte. 22 (N side) past road cut and angle left down to stream at east end of cut.
PLEASE DO NOT WANDER IN THE ROAD OR OBSTRUCT TRAFFIC - IT TRAVELS AT LETHAL SPEEDS HERE.
The lowest lithounits exposed in the area. The glacially polished outcrop by the stream and the roadcut expose typical lithology in atypically good outcrop.
This outcrop shows typical Bomoseen lithologies in atypically clean outcrop. The dominant rock type is a poorly and lenticularly-cleaved green silty wacke. Where a polished surface is seen, as in the stream outcrop, this lithology is in part internally finely laminated and bedded, although it is not possible to detect this in the road cut or weathered outcrops. A subordinate lithology, which is almost always present in outcrops of Bomoseen, consists of rather diffusely bounded thin (cm) beds of fine sandy green quartzite. These always contain narrow extension gashes perpendicular to bedding.
The etched polished surface of the stream outcrop shows the fine bedding and some cross-lamination in the wacke, disturbed in places by sediment loading/injection structures. Folds in this outcrop are probably due originally to soft sediment deformation and slumping, as is the disruption of the quartzites seen here and locally in the northern roadcut.
At the western end of both roadcuts, about 2 meters of thicker and well-defined planar-bedded green medium-grained quartzites from a contrasting member, which would be identified as "Zion Hill quartzite." It is not common in this area. The Bomoseen is structurally underlain and stratigraphically overlain at the western end of the outcrop by green silty micaceous slates of the Truthville Formation.
The gently to moderately east-dipping bedding and near-parallel slaty cleavage are characteristic of almost all outcrops in the Giddings Brook Slice, and imply the presence of very tight folds. A mesoscopic, tight antiformal fold with a gently south-plunging hinge is seen in the center of the northern cut. Although this example may owe its existence to disorientation of layering during soft-sediment deformation, its geometry and orientation are representative of the larger-scale folds. Bedding/cleavage orientations at the Truthville Slate-Bomoseen contact in the southern cut imply (correctly) that the succession is inverted in this outcrop. Many post-cleavage, slickensided faults with small offsets are seen.

STOP 2: Quarry adjacent to Holcombville Road
Mettawee Slate Formation and contacts.
The basal contact of the Mettawee Slate Formation is exposed on the east side of this quarry (the strata are inverted) next to the track leading to the water's edge (bear slightly left past the ruined shed). The stratigraphically lowest beds exposed consist of 1 to 5 cm nodular micritic limestones in dark grey slate, assigned to the top of the Browns Pond Formation, as is the single 30 cm bed of laminated calcarenite, which can be seen in the northwall of the quarry in a thicker development. The rest of the rocks exposed in the quarry, stratigraphically above this calcarenite are assigned to the Mettawee Slate Formation (sensu stricto- see stratigraphic discussion). Some diagenetically dissolved nodular micritic limestones occur in the basal few meters of green slate, together with a limestone breccia less than a meter thick which is only exposed along the base of the east wall of the quarry (water level usually prevents easy access to this bed). Several meters of purple slate with diffuse boundaries occur within green slate on the north wall of the quarry (we will not examine this; purple slate may be seen in loose pieces near the quarry). The rock then turns from green to shades of grey slate, exposed on the west wall.
Fissile, sooty, black, pyritiferous slate of the basal Hatch Hill Formation lie not more than 5 meters, stratigraphically above (structurally below) this porcellanous gray slate. At least two beds of coarse dolomitic arenite occur not more than 10m above the slate in the west wall of the quarry. These exposures which will not be visited on the formal field trip, may be found by walking south on Holcombville Road from the quarry entrance to the dirt track that runs around the south end of the quarry. Follow this track until it comes to an open space in front of a large slate heap. Outcrops are in the track and to the west in the bushes.

STOP 3: Browns Pond Formation and Mettawee Slate
Stop at or before the place where Browns Pond comes closest to the road. At this point a dirt track can be found leading east from Holcombville Road. Turn vehicles around, park at side of road, and fol low the trace for:
STOP 3A. Lower part of Browns Pond Formation in the type area.
10 m from road along track there is a small outcrop of buff-weathering green Mettawee Slate in the bed of the track. Track turns left and up slope. In bushes on right, thin bedded calcarenites and black slates outcrop that are much better exposed in Stop 3b (below). Track turns right; passing by cabin small outcrops also of dark calcareous slate and thin-bedded limestone are seen. Track passes small pond/swamp on left and turns right (to S). At bend in track is outcrop and loose pieces of distinctive grey-black wacke (Black Patch Grit lithology) containing large rounded quartz grains, and dark slate rip-up clasts. Track turns left (to E) and after 20 m a low ridge occurs. To left (N) of track, exposure of about 7 m thick homogenous pale-weathering coarse quartzite (Mudd Pond Quartzite lithology). Grey-black quartz wacke found at base of outcrop. Rejoin track, finding more wacke in outcrop west of the track just north of where it turns from NE to N-trending opposite a cabin down the slope. North of the cabin, below the track, another thick quartzite is exposed. Black slate can be found in poor exposures stratigraphically below this second quartzite which we will not visit. Beyond the slope is a swamp-filled narrow valley on both sides of which Truthville slate is exposed and beyond which Bomoseen Formation is encountered. Return to Holcombville Road.
Mudd Pond Quartzite lithology may occur in 2 large beds (here-rare), one (e. g., Stop 5), or, more commonly, is not present. These highly lenticular discontinuous quartzites probably occupy channels.
Black Patch Grit lithology is more often present than Mudd Pond, and is a better lithostratigraphic marker (see Stratigraphic discussion). Its extreme mixture of grain sizes, rip-up clasts and, locally, included pebbles and boulders, suggest a slump to debris flow origin.
STOP 3B. Upper part of Browns Pond Formation in the type area.
From dirt track, walk south along Holcombville Road to first roadcut on left (east) side of road on small rise. Thin-bedded, dolomitic, laminated and cross-laminated, dolomitic calcarenite and calcisiltite are interbedded with black calcareous slate. Cross-lamination demonstrates inversion of these beds. This lithologic assemblage, although prominent in this local area, is not common in the Browns Pond Formation.
Walk north on the road to the roadcut on the western side. This mostly consists of a distinctive limestone breccia with close-pakced homogenous grey limestone clasts of irregular but compact shape, set in an orange weathering dolomite-rich matrix, containing some quartz grains, that occupies a small proportion of the whole rock. Probable crack-injection relationships between matrix and clasts can be seen in places. Contacts of this breccia with areas of dark fine-grained thin bedded limestone and calcareous slate are seen, with the bedding truncated and no convincing signs of faulting. At the north end of the outcrop a possible block of breccia 2 m across rests within bedded material. In other places the bedded material seems to be in large clasts within or perhaps forming a matrix to large blocks of the breccia. Thus there seems to be evidence of mutual breakup of breccia and bedded limestones; however, there is no evidence that the breccia itself was formed in situ. Instead we suggest that it was deposited as consolidated blocks.---Theokritoff (1964) reports fossils from this outcrop. This distinctive breccia is only seen, when it occurs, very close to the top of the Browns Pond Formation. A rather similar breccia, seen rarely in the overlying Mettawee Slate Fm. is in a much thinner bed and has a significantly larger proportion of matrix. Debris flow deposits with carbonate blocks and slaty matrix are more common than this type in the Browns Pond Formation and will be seen at Stop 5.
STOP 3C. Go through gate in fence on the western side of the road, north of the roadcut just examined. Walk west to shore of pond across outcrops of distinctively buff-weathering green slate of the Mettawee Slate Formation. These are stratigraphically above the carbonates of the Browns Pond Formation, just seen. At the pond shore, a ledge-like outcrop exposes sooty black pyritiferous slate and some beds of laminated calcarenite and calcisiltite. Inverted cross-lamination can be seen. At the north end of the ledge, a 10 cm bed of pebbly limestone breccia is seen containing a minor amount of dark phosphatic pebbles. This green-black slate change is the upper of the two black-green boundaries in the area and correlates with the one seen in other areas of the Taconics. The locally developed limestone and black slate assemblage can be mapped as West Castleton; however, it is perhaps more easily mapped as a basal member of the Hatch Hill Formation. The limestones in this outcrop, and in 3b are probably turbidites, mostly representing the D and E horizons.

STOP 4. Five units repeated across syncline
Hatch Hill, Poultney, Indian River, Mt. Merino and Pawlet Formations repeated across syncline-Tanner Hill Road.
This stop entails walking for 1.1 miles west along Tanner Hill Road. Start at roadcut on north side on slope of hill. Thin to thick (1 cm-3 m) bedded dolomitic sandstone and quartzite beds; distinctive orange deep weathering rottenstones, interbedded with fissile black pyritiferous slate. Thickest beds are internally massive, very close sandstones and contain rip-ups of finer dolomitic sandstone. Thinner beds are finer grained, parallel laminated, uncommonly cross-laminated and only some show grading. In this outcrop, one side of a channel (proving inversion of this section) can be seen at the base of the thickest bed. The dolomite in these sands (10-50%) was originally clastic although now recrystallized.
The thick beds are either grain flow deposits or traction deposits at the base of large turbidity flows; in either case they fill channels. The thinner laminated beds are more problematic; those showing grading are probably turbidites, but the laminated beds with sharp tops and bottoms are harder to interpret. They are probably too coarse to represent deposits on levees of submarine turbidite channels.
The top of the Hatch Hill Formation at this locality, proceeding up the hill, consists mostly of black slate with a few very rotten weathering sandstones. If limestones occurred in this black slate, as they do in places, they are traditionally (Theokritoff, 1964; Potter, 1972) placed as a basal member of the Poultney -- another instance where the lithostratigraphy might usefully be changed. However, the resulting confusion might be worse than the existing kind.
Just west of the small borrow pit on the north side of the road, the low outcrop shows a rapid gradation from black to green slate with thin subordinate dark slate laminae. This is the base of the Poultney Formation. Opposite the quarry entrance, thin (mm) silty quartzite laminar beds are seen; these are characteristic of the Poultney and may be seen in the low, more or less continuous outcrop on the north side of the road, in varying abundance, throughout this formation. Their universally silty grain size, fine parallel and lesser cross laminations, the absence of associated coarser quartz-rich sands and the abundant indications of burrowing in the associated slightly silty slates, particularly well shown near the top of this section), are suggestive evidence that these silty quartzites were deposited by deep contour currents and that they are contourites.
By a track leading off the road to the north a 1 m section of maroon slate is exposed and two more sections containing maroon slate, one 5 m thick, are exposed to the west, up the hill. This maroon horizon can be traced locally to the north but is not found elsewhere in the area and is regarded as rare. The color of the slate is somewhat different and moderately distinguishable from the purplish Mettawee slate below and the red Indian River slate above.
In the whole of the section thus far up to the Indian River Formation contact, bedding is sensibly parallel with cleavage, reflecting the tightness of the large-scale folds.
The Indian River Slate Formation follows across a 5 m thick zone of interlayered red and green slate. The sea (blue) green porcellanous slate of the interlayered zone contrasts with the olive-green and silty nature of the Poultney slate and sea-green slate of this type is always placed with the Indian River, since red slates within the Indian River can be seen elsewhere to alter to this type. A good illustration of this may be seen at the western contact (top) of the Indian River exposed on the west side of the road about 0.2 mile north of the contact with the Poultney Fm., where relic patches of red slate may be seen diffusing into the sea-green slate. Elsewhere the Indian River may in places be altered to this green slate across its entire thickness.
Rare silty quartzite laminae identical to those in the Poultney occur within the lower part of the Indian River. Pale buff-weathering laminae or layers, pale greyish-white on a fresh surface, are siliceous but well-cleaved and interpreted to have been silicic ash beds, now tuffs. These are slightly better developed in the second occurrence of Indian River, 0.5 mile along the road, but the thickest beds (10-15 cm) can only be seen in exposures not readily shown to large groups. The spotty appearance of many cleavage surfaces in the Indian River, as if coarse sand grains are scattered through it, is due to ellipsoidal, microcrystalline quartz aggregates, probably recrystallized radiolaria.
Beddrug-cleavage obliquities reflecting mesoscopic folds are seen locally within this belt of Indian River Fm.
The source of this notably red clay is proposed (Bird & Dewey, 1970) to be terra rossa soils developed on the karst surface that cuts the sub-Black River and Trenton platform carbonates. The soils provided the clays transported out to the continental rise; the rocks do not seem to provide clues to their last agent of transport, which may have been contour currents.
From the north-south road segment along which Indian River is exposed, the road turns west. On the southwest side there is a small outcrop of greyish cherty slates transitional to the Mt. Merino Formation, whose lower member is seen in a cut on the northeast side of the road. Chalky-weathering dark cherts 1-5 cm thick are interbedded with dark grey and black slates and cherty slates. The upper member of the Mt. Merino Fm. is not seen here or elsewhere on this trip; it consists of a sooty black slate that is commonly graptolite-bearing (Zones 11 and 12 of Berry). The two members can be shown to be a facies of one another, with the variable being the abundance or lack of chert.
To the west of this outcrop, where the road turns back to the north, a small excavated outcrop to the west and southwest of the road exposes fine silty greywackes of the basal Pawlet Formation. A fine development of a spaced cleavage oblique to bedding and bedding-parallel parting produces a well developed pencil-slate.
North and west along the road, the major synclinal axis is crossed and then the stratigraphy is repeated in reverse order. At the top of a gentle hill, an outcrop of the cherts of the Mt. Merino Fm. is seen on the right, followed by red slates of the Indian River down the slope on the left. At the north end of this outcrop the contact with the Poultney Fm. is exposed. Intermittent outcrop of Poultney Fm. occurs as the road turns from N-S to about E-W. Just around this bend, a larger outcrop of Poultney on the left has been reported by Theokritoff (1964) to contain graptolites of Berry's Zone 6. The next outcrop on the left contains black slate and lesser dolomitic arenites of the upper Hatch Hill Formation; Theokritoff (1964) reports dendroid graptolites of Tremadocian age from this cut. More Hatch Hill Fm. outcrop occurs at and south of the intersection with Truthville Road.
All along this road, except locally near the core of the syncline, bedding and cleavage are sensibly parallel and dip 20-40° east. We emphasize that this requires the large-scale folds to be near isoclinal in geometry with axial surfaces dipping at the same attitude as the slaty cleavage.
End of Stop 4.

Poultney / Indian River contact
Contact of green Poultney Formation with red Indian River Formation. Road runs N-S

Mt. Merino cherts on right.
Road curves to left - outcrop of Mt. Merino cherts on right.

Mt. Merino cherts
Road curves to right - outcrop of Mt. Merino cherts on right at top of hill

Indian River red slates exposed on left.
Road runs N-S.

Poultney Formation outcrop on left reported fossiliferous.
Road turns to W.

Optional STOP (c). Old Indian River Slate Quarries
Pass dirt track to left which leads to old Indian River slate quarries (permission required). Follow track, taking left fork when choice encountered. After fork, park when track turns sharply S after tall ridge outcrop (of Mt. Merino cherts) in trees on right (south). Head NE from track; south end of quarry should be encountered after 30 metres. Tight F1 folds well-displayed in south wall of quarry are prominent because of pale-weathering siliceous tuff beds (meta-bentonites) up to 10 cm thick. DO NOT HAMMER, PLEASE.

STOP 5. Bomoseen To Pawlet
Mettawee River section by North Granville
STOP 5A: - Starting at waterfall where Mettawee River bends sharply north and smaller stream joins it from SE. Get to top of falls by going up the bank and around behind the small cliff, in the woods. Typical Bomoseen lithology of green silty wacke and cm thick diffusely bounded, green fine-grained quartzites seen beside falls and in cliff. An M-style fold of D1 generation may be seen at the base of the cliff. Where the cliff curves away from the river into the earth bank, the contact with the Truthville Slate Formation is exposed.
This consists of typical silty mica-spangled olive-green slate: very close to its contact with the Bomoseen, there is a 20 cm thick bed of clean medium-grained quartzite, of Mudd Pond type. Thicker occurrences of Mudd Pond Quartzite in this stratigraphic position exist in several places. A thin lenticular occurrence of green, planar bedded quartzite of "Zion Hill" type is seen in the top of the Bomoseen at the base of the cliff. A few thin (mm) laminae of silty quartzite are present here in the Truthville Slate Fm.
At the first rapids with a large erratic boulder in midstream, the first black-green boundary is exposed, the contact between the Truthville Slate Fm. and the Browns Pond Fm. The slate grades rapidly from green to dark grey and loses its silty nature and mica-flakes. Upward (stratigraphically) there is a debris flow with limestone, laminated micrite and dark slate clasts in a slaty matrix. Above this, at the small promontory, several 30 cm to 4 m thick beds of Mudd Pond-type quartzite occur within dark slate and minor black calcareous wacke. (Black Patch grit lithology). Large load casts can be seen on the base of the quartzite beds and evidence is seen for injection of black slate and wacke into the quartzite. A small fault cuts across the quartzites parallel to the stream.
Small quantities of black quartz wacke are found in black slate for a short distance above the quartzites, as at Stop 3a. Here it is not clear if they are pieces in a debris flow or in lenticular beds. In either case their shapes have been much changed by flattening in the slaty cleavage. Very thin bedded calcareous black slate and slaty limestone occur to the west. Opposite a large erratic block on the south bank, there is 2 m thickness of limestone breccia containing calcarenite to micrite and black slate clasts, in a slaty matrix. Bedded micrites of varying nodularity, 1-10 cm thick, are found in calcareous dark grey to black slate above this breccia. Some thicker micrite lenses in this interval are associated with soft-sediment disruption. At the east end of the stone foundation of an old mill, there is a rapid gradation from dark grey and black to green slates over a meter or two. Micrite, mostly in disconnected nodules, occurs on both sides of this contact in a similar manner to the same one seen at Stop 2, between Browns Pond Fm and Metawee Slate Formation.
If the water is high, it will be necessary to go up the bank and around the outcrop of green slate under the mill foundation. Some thin calcisiltite and a few calcarenite beds occur in the green slate; no purple slate exists here, as is the case in many places, particularly on the western side of the area. The slate becomes greyish in its upper part and just to the west of a small cave in the outcrop, there is a contact with black slate of the overlying unit.
This might be mapped as West Castleton, since laminated calcarenites, calcisiltites and micrites are exposed within the base of this black slate. However, they form a very thin interval and are succeeded, close to another stone wall foundation, by orange-weathering dolomitic sandstone and quartzite beds typical of the Hatch Hill Formation. These can be found in fairly continuous outcrop, with decreasing dips to about 10°E by the parking lot. The thicker arenite beds here are at about the same stratigraphic level as those seen at the beginning of Stop 4 on Tanner Hill Road.
To the west along the river, there is reasonably good exposure along the south bank, exposing Poultney Formation from a short distance west of the parking lot. We will not visit this part of the section. Instead, walk (if on bus trip) or drive back to the road, turn left and cross the bridge. Park cars on the left just across the bridge, and find the footpath down to the river on the west side of the road. STOP 5B. Dark slabby cherts of the Mt. Merino Formation are exposed under the bridge. To the east of the bridge, pale green slates are assigned to the Indian River. The cherts are somewhat disturbed by minor faulting. To the west, across an unexposed interval, outcrops of well-bedded silty and sandy greywacke with interbedded grey slates belong to the Pawlet Formation. These are better exposed on the north bank, where inverted sedimentary structures can be found, but it is not feasible to take a large group there.

STOP 6: Stoddard Road Thrust
Park on left just before pond. Ask Permission at farmhouse on corner.
At this stop we will visit outcrops of Indian River, Poultney, and Pawlet Formations. Indian River and Poultney Fms. lie on the western (lower) limb of a large F1 syncline which is cored by Mount Merino Fm. (not visited). The lower limb of this syncline is thrust westward over Pawlet greywackes which lie in the core of an F1 syncline to the west. This stop is important because here a thurst relationship can be unequivocably demonstrated due to the well constrained stratigraphy and regional structural framework. Equally important is the presence of fault or at least fault-related rocks in outcrop. Mesoscopic and microscopic examination of these fault-related rocks constrain the timing and style of faulting in this area. The stop also demonstrates that caution is necessary in statements concerning the density of faults in regions where stratigraphy is less well constrained.
Indian River; hard, green, well cleaved, porcellanous slates, crop out alongside Stoddard Road and south and immediately adjacent to the pond. The small abandoned quarries to the north of the pond are in the Indian River. To the west of the Indian River are a series of low outcrops of gray-green, less fine grained argillites and slates with interlayered, thin silty quartzites, characteristic of the Poultney Formation. A short distance to the west-northwest is a steep, 1-1.5 m high ledge of medium to dary gray, fine silty, moderately to well cleaved, moderately fissile argillite with thin (0.1-3 cm), silty, often laminated, discontinuous and lensoid quartzites. At the base of the ledge are a series of small outcrops of poorly exposed, though very distinctive, gray weathering, medium to dark gray, medium grained, lithic greywackes of the Pawlet Formation. On the hill to the northwest tne greywackes are well bedded and interlayered with dark gray slate.
The 1-1.5 m high ledge outcrop, containing Poultney lithologies, is interpreted to be fault-related. The mesoscopic character of these fault related rocks is more completely described in the structure section above. Important features to note here are: 1) the mesoscopic foliation in the argillite matrix, 2) sharp, tectonic truncations of laminations in the quartzites, 3) shape preferred orientation of the discontinuous quartzites, 4) presence of isolated fold hinges (none have been noted so far), and 5) lack of mineralization, brecciation or other evidence so commonly cited as evidence against the presence of thrust faults in other parts of the Taconics.

STOP 7. (Optional) Complex Stratigraphic and Structural Relations
Stop just beyond white house on right at top of hill. Ask permission at white house
This stop illustrates the problems that result in regions of complex stratigraphic and structural relationships. Specifically the problems here include: (1 ) difficulty of assigning lithologies to lithostratigraphic units in areas where stratigraphic succession is disrupted, even in areas with reasonably good exposure, (2) all contacts are unexposed or at best poorly exposed and thus the nature (sedimentary or tectonic) of the contacts is uncertain, (3) local relationships that are not in accord with regional relations, and (4) problems of distinguishing between preD1, syn- to late D1 or D2 structures.
Very brief lithologic descriptions of each of the outcrops (lettered) is provided below. Possible lithostratigraphic unit assignments are given. Participants visiting the outcrops may thus experience for themselves the local complexities and problems. Structures observable in these outcrops include F1, F2, S1, S2 and local late veining.
(A) Dark gray partly silty argillites with thin silty greywackes. Pawlet.
(B) Black argillite, moderately cleaved. Mount Merino.
(C) Pale green to blue-green (sea green) moderately hard, well cleaved slate. Indian River.
(D) Pale green to pale gray, hard, moderately to well cleaved argillite with thin silty quartzites(?) (possibly tuff bands). To the south, red well cleaved slate. Indian River.
(E) Pale gray to pale green to gray argillite. Indian River.
(F) Medium gray argillite with moderate cleavage. Poultney-top of the Indian River.
(G) Gray weathering, medium to dark gray, fine silty argillite. Poultney .
(H) Same as G.
(I) Gray weathering, medium to dark gray, some almost black, slightly fine silty, moderately-cleaved argillite. Also 25 cm layer of brown weathering gray, fine grained, laminated, dolomitic arenite . Poultney (?).
(J) Gray weathering, dark gray, fine to partly silty moderately cleaved argillite. Poultney.
(K) Gray to dark gray, fine to silty argillite, moderately to poorly cleaved, locally highly veined. Poultney.
(L) Medium to dark gray, fine to partly silty argilite, moderately cleaved, with thin (1-15 mm) silty quartzites. Local bioturbated color laminated slate. A few 2-10 cm thick, brown weathering, fine-grained, dolomitic quartz arenites in medium gray argillite. Poultney.
(M) Pale gray-green, argillite with thin (less than 15 mm) silty quartzites . Poultney.
(N) Gray weathering, pyritiferous(?), dark gray to black siliceous argillite.
(0) Brown weathering, calcareous, medium to fine grained greywacke. Pawlet.
(P) Pale green-gray, moderately soft, well cleaved argillite. Indian River. Just to the north (approximately 3 m), sooty black graptoliferous (poorly preserved) argillite. Mount Merino.
(Q) Medium to dark gray moderately to well-cleaved argillite with some dark gray siliceous mudstones. Poultney(?), Mount Merino(?).
(R) Medium gray, moderately hard argillite. Poultney(?), Mount Merino(?).
(S) Brownish weathering greywacke with minor dark gray slate. Pawlet.
{T) Medium to dark gray partly silty argillite with thin, fine siltstone layers. Poultney.
(U) Medium to dark gray partly silty argillite with thin fine siltstone layers and a few silty quartzites. Poultney. On west side of outcrop small amount of pale green to blue green well cleaved argillite. Indian River (?).
(.V) Medium gray partly silty argillite with moderately to well developed cleavage. Poultney(?) Mount Merino(?).
Regional Picture:
To the south along strike, a well defined east-facing sequence from Poultney to Pawlet lies on the upper (eastern) limb of a large F1 anticline. This limb is truncated to the east by the New Boston Thrust, which juxtaposes Poultney over east-facing Pawlet greywackes. To the north and immediately to the west is a small klippe of Pawlet Formation. Thrusting of the klippe probably occurred as a pre- to early D1 event. The overall distribution of lithologies outlined above suggest the presence of a north or west-facing sequence. This is not compatible with the relationships defined both to the north or the south. For this reason we suggest that the area is disected by a series of essentially phacoidal thrust faults which give rise to the apparent reversal in facing.

STOP 8:
Stop just before white house on left. Park at roadside. Dirt track making 150° angle with road on right. Walk up this dirt track for - 0.3 mile past outcrops of Pawlet Fm. to contact with Poultney Fm. Follow contact north into woods for -0.1 mile.
The purpose of this stop is to examine a typical section of Pawlet Formation and the complex character of it's contact with stratigraphically underlying lithostratigraphic units. Most workers, including Zen (1961, 1964) Shumaker (1967) and Potter (1972) have argued that the Pawlet Formation unconformably overlies lower Taconic lithostratigraphic units. Shumaker (1967) interpreted the Pawlet contact at this locality to be sedimentary and unconformable, possibly angular. We interpret this contact to be tectonic. Support for this contention include the following observations: (1) complex interleaving of lithostratigraphic units. (2) East-facing Pawlet greywackes just below (topographically) the overturned contact. (3) Regionally, there is a marked apparent thinning from the lower (west) limb to the overturned upper (east) limb of the F1 syncline defined by the Pawlet Formation, suggesting that part of the upper limb has been tectonically excised.
The outcrops visited at this stop illustrate the extreme difficulty of demonstrating the precise nature of this contact on the outcrop scale. The majority of the outcrops are of Pawlet greywackes and slates. Other lithologies include: (1) Dark gray variably siliceous argillites and slates. (2) Medium gray fine silty argillites with thin, mostly silty quartzites. Poultney. (3) Medium to dark gray finely cleaved slates with a silky sheen on cleavage surfaces. Poultney (?). (4) Green, gray and gray-green fine well cleaved slates. Minor thin calcareous siltstone (silty limestones) and quartzites. Mettawee (sensu lato). Figure shows the distribution of lithologies. Numbers refer to the lithostratigraphic units, following the scheme of Figure lb. Letters refer to the brief descriptions that follow.
Descriptions:
Start at small roadcut on the main road 10 m south of H. & H. Slate Co. quarry access road.
A - Greywackes and slates. Folded by F1, moderately NE plunging fold with an axial surface slaty cleavage. Note cleavage refraction through greywackes. Moderately developed steep spaced crenulation cleavage. Veining and late disruption of the south end of cut.
B - Low outcrops on the east side of access road. Greywackes and slates. East-facing.
C - Bulldozed greywackes at the first turn.
D - Across small stream, south of C. West part of outcrop, east-facing bedded greywackes and slates. Central part of outcrop, deformed, tectonically sliced greywackes and slates. East side of outcrop, bedded, east-facing greywackes and slates in gently south plunging antiform.
E - Bedded greywackes, bounding steep zone of veined and disrupted greywackes.
F - Bedded greywackes and slates. Slates more abundant. Bed thickness varies from a few to 10's of cms. Fresh greywacke exposed at corner. Note medium grain size and lithic component.
G- Very small, mostly covered outcrop of greywackes and slates.
H - More greywackes to the north of access road.
I - Small outcrop of thinner (4-8 cm) greywackes and slates. Possibly west-facing.
J - Another outcrop on the east side of the access road, same as I.
K - Contact. Three lithologies present, from west to east these are: discontinuous, west facing(?), greywackes and slates. Dark gray, variably siliceous argillites and slates, some chert. Interlayered medium gray fine silty argillites and thin, fine grained to silty quartzites, typical Poultney. The thin siliceous lithology is often observed at this contact. Contact appears sedimentary at this outcrop.
L - Predominantly medium gray argillites and slates with thin quartzites. Poultney.
M and N - Bulldozed cut in medium to dark gray slates, thin calcareous siltstone layers, thin quartzites and minor Pawlet-like greywacke. Relationships of lithologies not clear, but probably tectonic. Second generation structures prominent.
O - Small outcrops along jeep track, taking off to the north of the access road. Lithologies include gray to dark gray slates, greywackes, gray, green and gray-green slates, some slates with thin quartzites, some dark gray siliceous slates.
P- Scattered outcrops of finely cleaved medium gray slate (Poultney?). Locally highly veined.
Q - Chalky weathering, medium to dark gray, variably siliceous argillites. Brecciated chert. Greywackes downslope .
R - Graywackes
S - Same as Q. Note greywackes and small amounts of gray slate with thin quartzites 1 m below ledge. Also, in bottom part of ledge of siliceous argillite a 'layer' of greywacke lithology truncates the siliceous lithologies across at least the cleavage. This greywacke 'layer' does not possess bedding characteristics and is not believed to be of primary sedimentary origin. Other possibilities include injection or tectonic slicing.
T - Downslope to the southwest of R, small outcrop of medium gray slates with thin quartzites, typical of the Poultney. Greywackes occur both above and below this exposure.
As you can see simple contacts cannot be drawn in this area.

A9: MARINE AND FLUVIAL DELTA PLATFORM ENVIRONMENTS OF THE TRANSGRESSIVE CLASTIC CORRELATIVES OF THE MIDDLE DEVONIAN (ERIAN) MOTTVILLE LIMESTONE MEMBER OF THE SKANEATELES FORMATION IN EASTERN NEW YORK STATE
Fred Wolff
Assoc. Prof., Geology Dept., Hofstra University, Hempstead, New York, 11550
Peter J.R. Buttner
Director of Environmental Management
New York State Park System
Central Office
INTRODUCTION:
In west-central New York, the base of the Skaneateles Formation is in arenaceous limestone and coquinite designated by Smith (1916) as the Mottville Limestone. When traced eastward toward Kingston, N.Y., this unit and the associated calcareous siltstones thicken and grade into lenses of calcareous, planar crossbedded sandstones and dark gray laminated and bioturbated shales and coquinites, without the diagnostic faunal correlatives (Grasso and Wolff, 1977).
The sequence is interpreted as a zone of carbonate deposition (organic and inorganic) formed on the marine delta platform during a temporary clearing of the Proto-Atlantic seaway. Eastward this clearing produces a short transgression enabling a reworking of the sandy sediments on the marine delta platform to produce a series of offshore and nearshore sand bars and associated embayments. A major embayment located between two nearly-merging lobes of the alluvial delta platform forms an area of practically restricted circulation producing a variety of shallow water environments (nearshore and river mouth bars, sand flats, channels, beaches) and restricted environments (irregular shelf ponds, lagoons, mudflats, interdistributary bays and swamps). These "transgressive" sediments are abruptly truncated by a sequence of gray "channel" sandstones and "overbank" olive-green to maroon silty shales - the return of distributary progradation as the rivers of the classic Catskill Delta Complex once again spill their sediments across the subsiding basin.
This field trip will examine the transgressive and restrictive nature of the marine sediments that are wedged between the initial redbeds of the Catskill delta. Some of these stops and environments described here have also been described elsewhere. (Buttner, 1968; Wolff, 1969 ; Pedersen, Sichko, Wolff, 1976)

A9: MARINE AND FLUVIAL DELTA PLATFORM ENVIRONMENTS OF THE TRANSGRESSIVE CLASTIC CORRELATIVES OF THE MIDDLE DEVONIAN (ERIAN) MOTTVILLE LIMESTONE MEMBER OF THE SKANEATELES FORMATION IN EASTERN NEW YORK STATE

Outcrop of Otsego Shale

STOP 1. Rt. 143 west of Dormansville
Units - Solsville Member; facies - Chemung; depositional environment - nearshore marine delta platform in marginal embayment (Albany Bay)
STOP 1A - Quarry on N. side of road near home of Mr. M. Rossner
Park in wide driveway near crest of hill at home of M. Rossner
Description: While a few 0.2-0.5 meter planar crossbedded sandstones appear somewhat lower in the section, this is the first major lenticular sandstone in the area. The 2-meter sandstone has crossbeds, thin laminations, and local truncation surfaces. It contains a few bivalves (Cypricardella) lateral bioturbation structures, mud clasts, and plant fragments. The planar crossbedding trends N. 70° W - S 60° E, suggesting an onshore-offshore current influence. The sandstones are interpreted as prograding river mouth bars. The section is unique because strata at this interval are red beds in the adjacent quadrangles - the marine Marcellus being nearly 60 meters thicker than sections to the west and south. The area has been termed "Albany Bay" by Goldring (1943) - see Figure 7.
STOP 1B. Quarry on Lobdell Mills Road across Rt. 143.
Drive across Rt. 143 to dirt road opposite driveway (Lobdell Mills Rd.) and park at first quarry on left
Quarry consists of 2 meters of medium-dark gray siltstone and shale with several Mucrospirifer coquinite horizons. Associated fossils include a diverse assemblege consisting of: Camarotoechia, Athyris, Chonetes, and the bivalves Modiomorpha, Paracyclas, and Grammysia. Flatbedded, fine-grained sandstones with coquinites are common in the Dormansville-Westerlo area at an elevation of 1200-1300 feet, suggesting brief periods of strong agitation in relatively shallow water. The abundance of sessile epifaunal filter feeders suggests an abundance of suspended organic matter in deep quiet water. These contrary interpretations may be resolved by considering the embayed marine platform to also contain localized sandy shoals and broad muddy lagoons. A 0.8 meter crossbedded calcareous sandstone occurs on the N. side of Rt. 143 0.3 miles west of here (8 meters higher in the section) and this is believed to represent the clastic correlative to the Mottville in this region (Wolff, 1969).

STOP 2. Rensselaerville Falls. Edmund N. Huycks Preserve
(Walking tour - cameras only; no hammers please)
Units- Solsville, Mottville correlatives, Panther Mt., Plattekill; facies - Chemung and Catskill; depositional environment - marine delta platform, brackish lagoonal (interdistributary), and floodplain - alluvial channel.
Description: The 22 meter section below the roadway bridge consists of flat, thick-bedded to massive sandstones or low-angle planar crossbedded sandstones interbedded with dark gray silty mudstones and shale - lithologically and stratigraphically similar to the Solsville Sandstone section at Stop 1, but without the coquinites. In the park, the section below the falls consists of 1-2 meters of medium-grained sandstones with some sinuous ripples (crests trend N 50° W). These may represent the top of the Solsville, though the presence of Pterinopectin macrodonta suggested the lowest Skaneateles (Mottville?) to Goldring (1943 p. 266 and 268).
The lower falls contain megarippled sandstones capped by a light-gray, bar-like, 1-1.2 meter crossbedded sandstone with cross sets trending S 70° W (3°) and N 70°E (15°). These are unique - the only such sandstones with such an internal and external geometry within either stratigraphic formation - see Figure 8A. They are interpreted as reworked river mouth or nearshore sand deposits formed during the clearing of the seas that produced the Mottville Limestone.
In ascending the falls, note that the bars are overlain by 16 meters of fine-grained, flat-bedded thin sandstone and siltstone with thin seams of black shale. These are non-marine strata, formed by vertical accretion, with the black shales containing small ostracods (Beyrichia) and phyllopods (Estheria) that indicate a brackish water environment (Goldring, 1935, p.l64). There is also a gradual color change from medium-gray to olive-gray to mottled olive green-maroon red to red as one ascends the section. The falls are capped by 2.3 meters of gray, medium-coarse grained sandstones that truncate the red mudstone. These trend S 75° W and contain basal clasts of white micrite and red-green mud.
The section is interpreted as one demonstrating the progressive change from open marine to marginal shoal-lagoon brackish water conditions. The persistence of fine-grained sandstone and shale suggest the continual infilling of a marginal embayment - perhaps the continuation of "Albany Bay". The erosional contact at the base of the channel sandstones, with the encroachment of a deltaic distributary from the northeast indicates the start of alluvial sedimentation on the delta platform.
Climb to the top of the falls, cross over the footbridge, climb a short hill, and then return on the trail that descends on the opposite side of the ravine.

STOP 3. Rt. 143 at Franklinton
Units: Mottville clastic correlatives ; facies - Chemung; depositional environment - shoal on nearshore marine delta platform.
Description: This 6-meter section exhibits the interfingering of two en-echelon "bar-like" sandstones that are overlain by 1 meter of fossiliferous dark gray shales. The medium-grained sandstones are light-gray in color (weathers a dark brown) and calcareous with individual planar crossbeds 2-4 cm thick and trending N 50-70° E at slopes of 4-7° (similar to the section at Stop 2 - see Figure 9 on page 22).
The unit coarsens upward and grades into the overlying marine shales which contain Glyptodesma, Mucrospirifer and Camarotoechia. The entire section is 0.2 miles long and is interpreted as a reworking of marine delta platform deposits into these transgressive sand bars on the outer fringes of the prograding deltaic lobe visited at Stop 2 (see also Figs. 2, 4 and 7).

STOP 4A. Rt. 145 S. of Cairo after the junction with Rt.32.
Alternate Stop 4
Unit: Plattekill of the Catskill Facies on the alluvial delta platform.
Description: This 12-meter section represents two upward-fining fluvial cycles well within the Plattekill Formation and illustrates the major difference between the progradational marine sandstone lenses of the platform (Stops 1 and 2), reworked transgressive coastal marine sandstone bars (Stop 3) and the fluvial sandstone channels.
The sands are dark gray, medium-coarse thick bedded (10-30 cm) and planar-crossbedded depositional units with infrequent scour and fill pockets across a sharply truncated megarippled surface. Plant fragments and olive-red mud clasts are common.
The gradational nature of the massive, irregularly bedded sandstones into gray-red silty mudstone indicate, through channel abandonment, the gradual change from channel to levee to floodplain environment. This rhythmic pattern is prevalent through the next 400 meters of section in the nearby Catskill Mts. The dominance of gray channel sandstone over red floodplain siltstone-mudstone at this interval suggest rapid seaward delta progradation of many distributaries, with relatively little vertical accretion in floodplain and interdistributary bay environments. Gradients were probably low, but the large scale megaripples and scour suggest high current velocities and perhaps gently curved rather than true meandering rivers. In places, channel deposits directly overlay earlier deposits of similar origin, indicating complete lateral and vertical erosion of the overbank red mudstones and a nested sequence of irregular, sub-parallel distributary channels prograding into the basin.

STOP 4. On Catskill Creek off Rt. 145 and Rt. 23B near Leeds
Units: Mottville and Plattekill Members; facies - Chemung and Catskill; depositional environment - marginal fluvial and fluvial .
This section is stratigraphically similar to the one at Stop 2 Rensselaerville Falls) but begins within a 4-meter upward-fining sequence of planar crossbedded channel sandstones overlain by olive gray and dull maroon mudstones and shales as overbank and floodplain deposits. This first fluvial cycle also has the first "redbeds" of the Plattekill Formation. North and south of this area the first fluvial deposits are not red, and the thickness of this non-red alluvial sequence increases to locally form the Ashokan Member. Nearly all of the important flagstone quarries in this region came from the Ashokan. The unit consists of flat-bedded and low angle planar and trough crossbedded sandstones with sharp basal contacts and an abundance of mud clasts and plant fragments. The associated olive and gray shales rarely contain marine fossils.
The Ashokan Member is distinguished from the Plattekill by the lack of redbeds, the dominance of medium-sized (2-4 cm) flat-bedded sandstones (as flagstone) and the dominance of thinly laminated flat-bedded sandstone. These criteria along with current lineation, bioturbation, mottling, load casts, and lateral sediment associations suggest the development of extensive sand flats and marginal channels between the major deltaic lobes (Figures 3 and 7).
Above the initial fluvial sequence are red-green mottled sandstones and some thin seams of black shale with ostracods (Beyrichia). The overlying 3 meter section consists of gray-green flagstone, massive, calcareous sandstone with mud clasts, and interbedded slumped and bioturbated sandstone with an erosional top. This represents a short "upward coarsening" sequence, with some period for reworking and burrowing by organisms before erosion, and is taken to represent a tidal or supertidal sandflat and also the clastic correlatives to the Mottville interval in this area. Above this truncation the next 6 meters consist primarily of light-gray-olive green siltstone mudstone and shale, with abundant plant fragments and believed to represent overbank disposition as marsh deposits above the sandflats. These mudstones are truncated by a 1.6 meter section of planar crossbedded gray sandstones with megaripples, scour and fill pockets, load casts, and some bioturbation - the return to fluvial conditions. It is overlain by the typical sequence of gray to olive-green to maroon-red mudstones and shales - the second fluvial cycle. Figure 9. Planar crossbedded light gray calcareous sandstones of en-echelon "bar-like" Mottville Clastic Correlatives on Rt. 145 at Franklinton (Stop 3).
The correlation of the light gray calcareous crossbedded sandstones as 'Mottville correlatives" is based partly on the unique lithology within the fluvial section but moreso on the position of this unit between the first two fluvial cycles, as will be re-examined at Stops 5 and 6 when we again view this interval within an embayment.

Roadcut between gas stations
Slow down at roadcut between gas stations and stop on roadside

STOP 5A. off Rt. 32 near
Units - Upper Mt . Marion (Solsville), Mottville correlatives, and Ashokan; facies - Chemung; depositional environment - nearshore marine, marginal channel and sandflats. Stop 5A - Along Rt. 32 before junction with County Rd. #36, and at quarry near town garage on Rd. #36.
Description: The top of the section (on Rt. 32) contains extensive flat-bedded and low angle planar crossbedded and laminated gray sandstones (Unit C) - the type used for the flagstone industry that has dominated this region for the past 75 years. These truncate a 1.2 meter section of massive calcareous sandstones and olive mudstone (the Mottville clastic correlatives - Unit B) that are underlain by a 1.8 meter interval of megarippled and planar crossbedded and laminated sandstones with mud clasts and scour and fill pockets, and massive flat-bedded sandstones - Unit A. Here too the clastic correlatives form marginal sandflat or marsh environments between two marginal or fluvial channels (as at Stop 4).
The quarry on County Rd. 36 consists of 2 meters of thin-bedded planar crossbedded gray sandstone (Unit A) overlain by an 0.5-0.8 meter undulatory surface with scour and fill structures, in turn overlain by a 1.3 meter light gray calcareous, crossbedded sandstone (Unit B).
The laminated flat-bedded and cross-bedded sandstones are interpreted as tidal sand flats and beaches fronting the deltaic marshes. The megarippled surface and scour and fill with pockets of olive mud-stone add support to this, the upward fining sequence suggesting the filling in of a shallow embayment behind the tidal sand flats. The overlying laminated and slightly sorted "bar-like" sandstone represents the reworking of the sandflats into a shoal or beach (Unit B). The truncation of this sequence by the next series of gray crossbedded sandstones with basal mud clasts and plant debris suggests the presence of a marginal channel or river mouth bar. The large tree molds (Wolff, 1969) indicate a close proximity to the seed fern forests that inhabited the local coastal swamp.

STOP 5B - On Rt. 32 below junction with County Rd. #36.
This 24-meter outcrop consists of massive marine sandstones and dark gray shales with several horizons of ball and pillow structures (Figure 10). It is known locally as the Mt. Marion Formation and is correlative with the Solsville Member of the Marcellus Formation. Other characteristic features include long, low angle planar foresets, coquinite horizons and the thin but persistent 7 cm Alcove Conglomerate that can be traced to Stop 1 at Dormansville. The section (as at Stop 1) represents the marine delta platform with the ball and pillow structures interpreted as load casts developed from sediment foundering during earthquake activity. The seismic tremors could also create tsunami which extend into the embayments and channels and transport the marginal and fluvial deposits (and the pebble bed) onto the marine platform (Wolff, 1977). A possible Middle Devonian astrobleme may be buried within the Catskill Mountains only 9 kilometers from this outcrop (Isachsen, Y.W. et.al. 1977) suggesting an even more extreme origin for these deposits.

STOP 6. Rt. 212 near Centerville
Units - Mottville Correlatives and Ashokan Member; facies - Chemung; depositional environment - marginal marine and fluvial.
Description - Here the suggested Mottville correlatives are sandwiched between the first two marginal channels or river mouth bars (See Figure 11). The lower 2.2 meter section consists of medium-grained planar crossbedded gray sandstones with basal mud clasts directly overlying marine strata. The unit is overlain by 0.3 meters of dark shale and 1 meter of massive light gray sandstone.
The next 4.5 meters comprise the Mottville correlatives and consist of 2 meters of alternating massive gray calcareous sandstones and dark shales with bioturbation markings and load casts. These are truncated by 2 meters of thinly laminated and crossbedded sandstone, 1.3 meters of massive light gray calcareous sandstone, and 1.2 meters of interbedded fine-grained sandstone and dark shale with flaser bedding. The sequence ends with 1 meter of rippled sandstone and shale with extensive lateral worm burrows. (Figure 12)
The outcrop is capped by an 8 meter sequence of thick beds of gray planar crossbedded sandstone with megarippled surfaces and abundant mud clasts.
The lower sequence shows small scale polymodal trough cross bedding and lamination suggesting the periodic reworking of a marginal channel or river mouth bar. The middle section with the massive, crossbedded and cross laminated calcareous sandstones, ripples, flaser bedding and bioturbation suggests the preservation of intertidal sand flats, and shallow lagoons. The massive crossbedded and burrowed light gray calcareous sands may indicate the pressure of a beach or reworked sand flat environment. This short interval of marine resedimentation is sharply truncated by the overlying fluvial progradation that nearly erodes this transgressive sequence. However, the persistence of these unique reworked deposits both to the north and to the south of this region (Wolff, 1969) and to the west (Grasso and Wolff, 1977) indicates that the extension of the Mottville clastic correlative is possible through these unique lateral sedimentary associations.

A10: STRATIGRAPHY, STRUCTURE, AND THE MINERAL WATERS OF SARATOGA SPRINGS - IMPLICATIONS FOR NEOGENE RIFTING
James R. Young
Dunn Geoscience Corporation
Latham, New York
George W. Putman
State University of New York at Albany
Albany, New York
The carbonated mineral springs of Saratoga have been the object of considerable interest ever since their discovery by colonists in the late eighteenth century. The three major previous studies (Kemp, 1912; Cushing and Ruedemann, 1913; and Colony, 1930) express the crux of the problem as we see it today. Foremost, among these, is the abundant CO2 gas and the difficulty of explaining its presence in such large amounts by known shallow, oxidizing mechanisms of generation, or by hydrolysis reactions involving carbonates, the reasons for which will be partially addressed below and further during the field trip. The only known applicable methods remaining are thermal: 1) either direct degassing of an igneous melt or decarbonization of carbonate rocks adjacent to an intrusion, or 2) decarbonization in water-rock equilibria during metamorphism. Recourse to the former mechanism in terms of cooling Paleozoic plutonism has been taken by all three of these earlier workers because of chemical inconsistencies that are also incompatible with low-temperature methods of CO2 formation; i.e., negligible sulfates, nitrates, and phosphates. This interpretation presents an apparent paradox for all known igneous activity in the Northeastern United States ceased with dike swarms in the middle Mesozoic--about 100 million years ago. Since it is now known that anomalous convective and conductive heat flow from this time should have long since ceased allusions to dying metamorphic or igneous fires from the past are not a really very satisfying explanation; indeed, they have only served to deepen the mystery.
We must ask then, are the waters and gas at Saratoga really thermally generated; and, if so, how can we understand the source of the thermal processes in more definite terms?

A10: STRATIGRAPHY, STRUCTURE, AND THE MINERAL WATERS OF SARATOGA SPRINGS - IMPLICATIONS FOR NEOGENE RIFTING

Pass over pre-glacial Mohawk River Channel

Pass excellent road cut exposure of Utica Shale cap rock.
Stopping not permitted

McGregor Fault scarp on left

Small exposure of Paleozoic carbonates
Small exposure of Paleozoic carbonates in creek bed (Snook Kill) at Junction. Proceed up McGregor Fault Scarp.

STOP 1. Precambrian paragneiss and quartzite
Precambrian paragneiss exposed in roadcut. Note almandine garnet and sillimanite needles parallel to the foliation planes.
Precambrian metasedimentary quartzite unit exposed in streambed .

STOP 2. (one hour)
Pompa crushed stone quarry
Excellent exposures of the Gailor and Galway Formations, a variety of sedimentary features, and several fault zones. Note upper-most Gailor novaculite zone, Hoyt unconformity, vuggy zone with quartz crystal fillings, karst breccia fillings, and fault gouge.

STOP 3. (15 minutes) Lester Park
Well preserved specimens of cryptozoa of the Hoyt formation. Note its position at the lip of another fault scarp.

State Park and Bottling Plant
Saratoga Springs State Park to the east and Saratoga Vichy bottling plant on the west

Hathorn #3 mineral well on the left.

STOP 4. (45 minutes) Walk up Geysers Brook
Disembark and walk up Geysers Brook passing the Polaris, Karista, Hayes, Island Spouter mineral wells. The Ferndell spring on the right is normal surface groundwater. Continue up the brook to the Orenda well and picnic area.

Lunch stop. 12:00 p.m.
Discussion of the chemistry of the waters. pH and temperature measurements of the Orenda well and several others. Note the large tufa mound from the Orenda discharge.

State Bottling Plant on right.
Pass old State Bottling Plant on right. Site of Geyser and State Seal wells.
2015: This is now an auto museum.

Lincoln and Washington baths on the left.

STOP 5. (10 minutes) Grand Union Motel - Rosemary well
Grand Union Motel on the right is the site of the anomalous Rosemary well. pH and temperature measurements of the water and a brief discussion of the signficance of its different chemistry.

Hathorn #1 Mineral Well on corner

STOP 6. (15 minutes) High Rock and Peerless springs
High Rock and Peerless springs are across the road from one another. The natural High Rock is at the base of the Saratoga Fault scarp, a continuation of the McGregor Fault

Old Red Spring

B1: ECONOMIC GEOLOGY OF THE HUDSON RIVER VALLEY
George M. Banino
William E. Cutcliffe
Dunn Geoscience Corporation
Latham, New York
The purpose of this field trip is to examine some of the economic uses of the rock and mineral deposits of the Hudson River Valley, and to discuss the importance of economic geology in helping to bring these commodities to the market. The area we will study has a wide variety of economic deposits and mining operations, all of which are related to the construction industry. This is in part due to the location near major metropolitan markets and the presence of a major transportation route, the Hudson River, but is basically controlled by the nature and location of the geologic deposits.
During this trip four sites will be examined, each producing a different product, and each with a different geologic setting that must be considered in the mining process. The sites to be visited are Norlite Corporation, Cohoes, New York, producing lightweight aggregate; Atlantic Cement Co., Ravena, New York, producing portland cement; Callanan Industries, Port Ewen, New York, producing construction aggregate; and another portion of the Callanan property producing sand for bituminous concrete.
There is a long history of geologic work in the Hudson River Valley, going as far back as Amos Eaton in the first quarter of the 1800's, which has led to a large volume of geologic studies and innumerable field trips. This guidebook draws principally from three previous trips, the 33rd New York Geological Association trip in 1961 (Dunn & Rickard, 1961), the 61st New England Intercollegiate Geologic Conference in 1969 (Brown & Cutcliffe, 1969), and the 14th Annual Forum on the Geology of Industrial Minerals in 1978 (Banino & Brown, 1978).

STOP 1. Norlite Corporation
The Norlite Corporation, a subsidiary of P.J. Keating Co., Lunenburg, Massachusetts, produces expanded shale aggregate, or lightweight aggregate, by a rotary kiln process. The property consists of the deep quarry and manufacturing facility. The Snake Hill shale which is quarried is overlain by glacially derived overburden consisting of clay, silt, and cobbles, which are stripped off prior to drilling and blasting.
Geology
The Snake Hill is a thick sequence of shale with occasional mudstone and sandstone beds. As revealed in the quarry and drill core, the rock is a monotonous sequence of medium dark gray to dark gray, very fine grained shale with occasional thin beds of convoluted mudstone or very fine sandstone. Overall, bedding dips about 50 degrees to the southeast and cleavage dips about 60 degrees to the southeast.
Close inspection of the quarry reveals more detailed structural features. Where bedding is sufficiently apparent, the noses of isoclinal folds can be observed, particularly where the rock is more of a siltstone than a shale.
Along the west wall of the quarry, one of several faults can be observed. This fault cuts the rock at a lower angle than either the bedding or the cleavage. The age of the faulting is not known.
Manufacturing
Norlite lightweight aggregate is a manufactured product in which crushed shale is expanded to produce an aggregate used, normally, for Portland cement concrete. The advantage of this product is its reduction in weight as compared to normal weight aggregate. This allows the production of lightweight concrete, either for small structures to be moved by hand, such as concrete blocks or curbing, or for structural concrete, particularly in tall buildings where there is a considerable savings in reducing the total weight of the building. Typically a cubic foot of Norlite coarse aggregate weighs 45 pounds compared to about 100 pounds for regular weight concrete.
Expanded shale aggregate also has several other properties that make it attractive for specific uses. Because lightweight aggregate contains very small separated air cells, it has enhanced insulatory value. The air cells greatly enhance the thermal resistance (R value) of concrete, so that lightweight aggregate concrete has the capability of providing over twice the thermal insulation of normal weight concrete . Also, because all combustible material has been burned out in the manufacturing process, the fire resistance of lightweight aggregate concrete is greater than that for natural aggregate concrete.
The basic process in expanding shale is the introduction of crushed shale into an oil fired rotary kiln where temperatures in the burning zone are maintained between 2000 and 2100 degrees Fahrenheit. At this temperature the shale reaches what is known as the point of incipient fusion where the shale is in a semiplastic state and gasses are generated by the breakdown of carbonates and oxides. The gasses are generated but contained within the semiplastic mass, expanding the shale and creating individual nonconnecting air cells. As the material is passed out of the kiln, it is air quenched to form a vitreous clinker that is then recrushed and sized to make the final product. Figure 3 is a plant flow diagram of the Norlite process.

STOP 2. ATLANTIC CEMENT COMPANY
Atlantic Cement went into production in 1960 following detailed geological analysis which preceded the investment of $44,000,000. There are three major quarries on the property: the Becraft quarry, the North Coeymans-Manlius quarry, and the South Coeymans-Manlius quarry. Adjacent to these are several other mining faces, including the high face of the Esopus shale and lower benches in the Kalkberg. The Becraft and Coeymans-Manlius quarries provide the high-calcium limestone for cement while the Esopus face provides an alumina additive and the Kalkberg is stripped to gain access to the Coeymans-Manlius.
The Kalkberg is a New York State Department of Transportation-approved coarse aggregate source. However, an aggregate processing plant has never been established here. Because the Kalkberg that is being removed is a future resource, it is placed separately in stockpiles for possible future use. The top of one of these stockpiles is undergoing reclamation, though it is realized that it may be disturbed later.
The Coeymans-Manlius face is excavated from a few feet above the RondoutManlius contact, to avoid incorporating the dolomitic Rondout in the shot, to about ten feet above the Coeymans-Kalkberg contact. Silica from the Kalkberg requires some adjustment of the design mix, but this increases reserves and decreases the amount of Kalkberg that must be removed.
STOP 2a
The walls of the access ramp of the North Coeymans-Manlius quarry expose a complete section from the Rondout to the Lower Hannacroix member of the Kalkberg formation. The contact of the Rondout with the underlying Normanskill shale is at the water level of the sump at the bottom of the ramp. The Rondout can be seen to be about four feet thick, increased over its normal two foot thickness by faulting. The Manlius units and Coeymans are well-exposed along the ramp. Note the gradational contact of the Coeymans and Lower Hannacroix near the top of the ramp where chert can be seen on both sides of the contact.
STOP 2b
The full section of Becraft is exposed in the Becraft quarry. The lower contact is gradational but can be placed about two feet below a discontinuous blue-gray chert horizon that can be found on the face. The high shale face above the Becraft is in the Esopus formation which is used as an alumina and silica source. Below the Esopus, the upper two feet of the Becraft face in places reveal the remnants of the Alsen, Port Ewen, Connelly and Glenerie formations that are fully developed at the Callanan quarry. A high-angle thrust fault, with relatively minor displacement, is located at the north end of the quarry. The area around this quarry has well developed synclinal ridges, with the youngest unit, the Esopus, forming the ridges and the high-carbonate Becraft forming the valleys which occasionally contain wetlands.
STOP 2c
The access into the South Coeymans-Manlius quarry displays a complex local structure. This exposure is at the northern end of a major thrust fault, at the point where the displacement is small enough that the rock has failed by folding rather than by faulting. The black chert bands of the Lower Hannacroix mark the asymmetrical anticlinal fold. However, the bedding is largely obscured by very well developed fracture cleavage. There is marked thickening of the beds along the fold crest as a result of slippage along the cleavage surfaces.
2015: The Ravena plant was originally Atlantic Cement. It later became known as Blue Circle. Lafarge merged with Blue Circle in 2005.

STOP 3 -- Callanan Industries, Inc. Port Ewen
Crushed Stone Quarry
The Port Ewen quarry is owned and operated by Callanan Industries, a subsidiary of Penn Dixie Corporation. The principal product is New York State Department of Transportation approved coarse aggregate (crushed rock). Within the past five years a small fine aggregate (sand) operation was initiated to produce asphatic sand for the company's asphalt plant located on the property.
Two crushed stone products are produced; high friction bituminous concrete aggregate, and portland cement concrete aggregate. The reserves are within the Lower Devonian Helderbergian rock units .
High friction aggregate is specified by the New York State Department of Transportation for use in top coarse asphaltic concrete pavements to obtain an aggregate that does not polish when exposed to heavy traffic. High friction aggregate specification requirements are divided into noncarbonate and carbonate rock types. Most noncarbonate high quality rocks such as granites, diabases, and quartz feldspar gneiss, can be used as high friction aggregate and also as a 20% blend to upgrade high quality aggregate that does not otherwise meet the high friction aggregate specifications.
The second classification, carbonate rocks, which the entire Port Ewen quarry sequence falls within, to meet high friction aggregate requirements either must contain 10 percent material plus 100 mesh insoluble residue in concentrated hydrochloric acid (presumably quartz) or contain 20 percent noncarbonate material (chert).
Ten formations are mined at the Port Ewen operation. They are the upper two units of the Rondent, Manlius, Coeymans, Kalkberg, New Scotland, Becraft, Alsen, Port Ewen, Connally, and Glen Erie formations. With the exception of the Connally formation which is a calcareous sandstone, all of the other formations are either dolomitic limestones (Rondent and Manlius), high calcium pure limestones (Coeymans and Becraft), cherty limestones (Kalkberg, Alsen and Glen Erie) or argillaceous limestones (New Scotland and Port Ewen formations).
Listed below are the formations and their uses:
Formation | Approximate Thickness | Use |
Glen Erie
100
Regular Aggregate - High Friction
Upper High Friction Sequence
Connally | 15 | Regular Aggregate - High Friction
Port Ewen | 100 | Regular Aggregate - High Friction
Alsen | 20 | Regular Aggregate |
Becraft | 40 | Regular Aggregate |
New Scotland | 115 | Regular Aggregate - High Friction | Lower High Friction Sequence
Kalkberg 65
65
Coeymans | 20 | Regular Aggregate |
Manlius | 50 | Regular Aggregate |
Roundot (2 units) | 40 | Regular Aggregate |
The two products must be mined, processed, stockpiled and delivered separately. Plant production demands necessitate maintenance of separate operating faces and loading units for each product. For example, high friction aggregate will be mined from two separate faces for two or more 8-hour shifts followed by regular aggregate production from two additional faces for several shifts or days.
Structure
The Helderbergian limestone formations are intensely folded and faulted. The initial stop at this site will be in the northeastern portion of the quarry where the lower Rondout, Manlius, Coeymans, Kalkberg, and New Scotland vertical beds are forming the east limb of north-south trending syncline which plunges to the north. The Becraft, Alsen and Port Ewen formations are complexly faulted in the northeastern portion of the quarry and challange certain geological interpretations without additional subsurface drill hole information.
The northern face exhibits several moderate angle thrust faults in the Glen Erie, Connally, and Port Ewen formations. The distinctive Connally calcareous sandstone unit makes an excellent marker bed to discern the structural relationships.
In the western portion of the quarry a major thrust fault has been mapped and mined during the past twenty years. The eastward dipping thrust sheet has caused numerous mining stability problems.
Quality of Products
New York State Department of Transportation requirements for high friction aggregate demand that only the approved formations be included in that product. This demands good quality control beginning with well defined geology, ongoing mine planning and regular production control.
Dunn Geoscience Corporation personnel are retained to complete biannual geologic source reports which represent in both map and cross section form the areas of proposed operation for the next two years of both products by formation boundaries. In addition, the boundaries of each product are marked with spray paint on the faces and targets are set on the upper levels to indicate the orientation of the third dimension extension of the contact.
A mine plan has been completed by Dunn Geoscience Corporation to allow annual and monthly planning to be fitted into a long term mining and reclamation plan. Triennial reclamation plans are required and submitted to the New York State Department of Conservation
Market
The large majority of the finished products are barged to New York City via the Rondout Creek and Hudson River. The crushed rock and fine aggregate that is supplied to the Callanan asphalt plant is used within the local region.
Sand
The sand deposit appears to be an upland erosional remnant of a formerly larger deposit. Similar material can be found on the east side of the railroad tracks and to the north along the north valley wall of Rondout Creek at Wilbur, New York.
The source is glacio-lacustrine in origin, displaying a single mode of deposition. The several local deposits exhibit similar structure suggesting that the depositional environment was fairly extensive in the Rondout-Hudson Valley region. Damming by glacial ice in the Hudson River valley is believed to have created a lake both in the Rondout and Wallkill River valleys that extended to the south to within 2.5 miles of New Paltz, New York.
Material composition and bedding configurations suggest that the Port Ewen deposit was laid down in a pro-delta glacio-lacustrine environment. The slight coarsening upward and distinct bedding indicated either a slight shallowing of water or an advance of the sediment source into the lacustrine environment. The aeolian sand probably represents final deposition in the pro-glacial zone as lake waters receded.
The soil layer and the aeolian fine sand is stripped from the proposed area of operation. The sand deposit is removed by front-end loader, into trucks, and hauled to the asphalt plant site where it is stockpiled and blended as needed. The gradation and quality of the deposit is such that no additional processing of aggregate is required.
Material from the source primarily is used to make bituminous concrete aggregate as required.

B6: DEGLACIAL EVENTS IN THE EASTERN MOHAWK - NORTHERN HUDSON LOWLAND
Robert G. LaFleur
Troy, New York 12181
Introduction
The Mohawk Lowland extends some 90 miles east from Rome to the modern Mohawk's junction with the Hudson River at Cohoes (Figure 1). Woodfordian ice advancing south and westward through the Hudson-Mohawk Lowland emplaced the Mohawk till and formed an extensive drumlin field on older drift. A variety of deglacial events included lake development, glacial readvances, large-scale Great Lakes through-drainage, and subdued river flow. This history becomes complex to the east because pulses of the Oneida lobe alternating with lake outbursts in the western Mohawk basin influenced discharges into Lakes Albany and Vermont in the Hudson Lowland (LaFleur, 1975; Hanson, 1977).
A series of active ice-margin positions, recognized in the Schoharie Valley, are associated with the development of glacial Lake Schoharie (LaFleur, 1969). See Figure 2. In the Hudson Lowland, well-defined, progressively younger ice margins defended northward-expanding Lake Albany which maintained an elevation of about 330 feet at the latitude of Troy. However, tracing of ice-border positions westward through the Mohawk Lowland has proven difficult. Because the broad interfluve of the Helderberg upland did not receive ice-contact deposits in abundance, it is even difficult to secure correlations over short distances between Hudson and Schoharie valley ice margins. Rather than try to achieve a regional synthesis by using ice-front positions, our purpose here is to suggest relationships between high and low Mohawk discharges and lake stages, based on channel and terrace development and lacustrine stratigraphy.

STOP 1. Lake Albany 330-foot beach.
West of Bloominggrove Rd., one mile north of Defreestville, Troy South.
Reworked kame terrace gravels, berm, beach pond rhythmites.

STOP 2. Cohoes Falls.
Gorge of the Mohawk River is cut in folded Ordovician shale. Nickpoint marks post-Iroquois falls recession, about 2000 feet, from former point of upper gorge intersection with Fort Ann waters in the Hudson Valley. (Figure 11.)

STOP 3. Pit south of Lower New Town Rd.
In Lake Albany Halfmoon kame delta.
About 60 feet of section shows interbedded clinoform gravel and blue-gray flow till, fining upward to sand and siltclay varves. Typical of south-facing ice-edge lacustrine deposits from which the ice recedes northward. See Figure 5.

STOP 4. Coveville 240-foot sand terrace
Coveville 240-foot sand terrace, inset in Albany clay, and fed by discharge through Round Lake channel into Lake Coveville at Mechanicville. See Figure 9.

STOP 5. Willow Glen kame delta; D.A.Collins pit.
About 100 feet of section shows black shale overlain by cemented gravel and sand and blue-gray boulder till, in turn covered by clinoform, locally deformed pebble gravel, sand, and Albany clay. Is the cemented gravel pre-Mohawk, or does the entire section show only a readvance into Lake Albany, followed by ice recession?

STOP 6. Coons Crossing.
Round Lake terraced channel with modern underfit Anthony Kill.

STOP 7. Bemis Heights clay pit.
About 55 feet of section exposes ice-contact Albany gravel and clay overlain by Quaker Springs clay and Coveville sand.

STOP 8. Reynolds pit.
Late Coveville 200-foot terrace is underlain by 5-15 feet of fluvial gravel with abundant Taconic lithologies derived from Hoosick basin. Flow sense is to the south. Beneath the Coveville gravel, 15 feet of Albany clay overlies 15 feet or more of ice-contact gravel and sand containing mainly Hudson valley lithologies.

STOP 9. Gullies eroded in distal end of Quaker Springs Hoosick delta
Gullies eroded in distal end of Quaker Springs Hoosick delta, later beheaded by Hoosic River dissection of delta.

STOP 10. Several Holocene terraces near modern stream
STOP 10. Several Holocene terraces near modern stream inside eroded Hoosic delta; road climbs eastward over older terraces related to drainage of Lakes Quaker Springs, Coveville and Fort Ann.

B7: STRATIGRAPHY AND DEPOSITIONAL HISTORY OF THE ONONDAGA LIMESTONE IN EASTERN NEW YORK
Richard H. Lindemann
R.P.I. and Skidmore College
The Onondaga Limestone is prominently exposed in hundreds of outcrops over a 550+ km. belt extending from Buffalo to the Helderberg and south to Port Jervis. The formation is a coarse- to fine-grained limestone, which ranges in thickness from 21.5 m. in the central New York type sections, to 49+ m. in the eastern and western parts of the state. The Onondaga Formation was deposited during Eifielian time (Middle Devonian) (Rickard, 1975), prior to and during the initial clastic influxes from the Acadian Orogeny. The unit represents the last extensive carbonate and reef-building phase in the region.
In modern times the stratigraphy, petrology, and bioherms of the formation have been extensively studied. Most investigations have neglected the formation's non-biohermal paleoecology, as well as its eastern sections. Whole formation studies have concentrated in western and central New York, and have extended typical characteristics to eastern areas. The purpose of this trip is to examine the lithologic and faunal characteristics of the Onondaga Foraation in an area extending form the Helderbergs to Catskill, and to consider the paleoenviroumental conditions under which the unit developed.
No Stop Descriptions

B7: STRATIGRAPHY AND DEPOSITIONAL HISTORY OF THE ONONDAGA LIMESTONE IN EASTERN NEW YORK

STOP 1. See Figure 5

STOP 2. See Figure 5

STOP 3. See Figure 5

STOP 4. See figure 5

B11: FIELD GUIDE TO THE CHATHAM AND GREYLOCK SLICES OF THE TACONIC ALLOCHTHON IN WESTERN MASSACHUSETTS AND THEIR RELATIONSHIP TO THE HOOSAC-ROWE SEQUENCE
Nicholas M. Ratcliffe
U.S. Geological Surve::
Reston, Virginia 32092
Introduction
Since 1977, the U.S. Geological Survey has been engaged in a program to compile data for a new bedrock geologic map of Massachusetts. Don Potter and I have been mapping in northwestern Massachusetts in an attempt to fill in unmapped or poorly understood areas. Detailed mapping of the Pittsfield West, Hancock, Berlin, Williamstown, and parts of the North Adams and Cheshire quadrangles have been completed. This trip will deal principally with new data regarding the age, distribution, and structural characteristics of major boundaries at the soles of the Taconic allochthons (Fig. 1) exposed along the New York State line, and on Mount Greylock. An attempt will be made to relate these features to rocks exposed in the eugeoclinal Hoosac-Rowe belt east of the Berkshire massif. Time constraints for movement of these materials across the autochthon and the modes of emplacement will be discussed.

B11: FIELD GUIDE TO THE CHATHAM AND GREYLOCK SLICES OF THE TACONIC ALLOCHTHON IN WESTERN MASSACHUSETTS AND THEIR RELATIONSHIP TO THE HOOSAC-ROWE SEQUENCE

STOP 1. Contact between Taconic allochthon and autochthon.
Contact between rocks of Chatham Slice of Taconic allochthon and autochthon. Canaan 7-1/2 quadrangle.
Walk down the slopes to the east to the railroad tracks.
Caution! This railroad is operating and trains may come from either direction. There is enough room in the center island or along the rock walls, should a train arrive.
The geologic relationships at this stop are shown in Figures 7 and 8. The exposures in the tunnel are on the east flank of a doubly plunging anticline that produces a semi-window exposing unit g of the Stockbridge Formation. The allochthonous rocks of the Chatham slice consist of purple and green slate, green silty slate, massive beds of Rensselaer Graywacke, and basaltic volcanic rocks believed to be flows and tuffs.
The outcrops in the railroad cut expose the contact between the Chatham slice and the autochthon. A folded thrust contact (T1, Fig. 9) between overlying green phyllite of the Nassau Formation can be seen. Note the truncation of beds in the limestone by the contact. In addition, a fault sliver of green phyllite underlies an inverted sequence of Stockbridge and Walloomsac in a small anticline nearer the portal (thrust T2, Fig. 9).
Fault T1 traces out of the cut and forms the western limit of the altochthon. Fault T2 is not exposed again in recognizable form.
The relationship here suggests that the autochthon and allochthon were tectonically mixed during emplacement. In this model, rocks of the autochthon were overturned during thrusting and overridden by younger thrusts as illustrated below in Model 1 of Figure 9.
An alternative model involves recumbent folding of the thrust contact as shown in Model 2.

STOP 2. Basaltic volcanicrocks of the Chatham slice
Park at edge of large field before house. Walk east-northeast across field to slopes.
Basaltic volcanicrocks of the Chatham slice are well exposed on the slopes above the Boys Farm. This zone associated with graywacke has been traced continuously from the State Line quadrangle north to the Jiminy Peak area for a distance of 19 km. Similar occurrences are on the Knob across the valley to the west. This eastern belt of volcanic rocks is better laminated than those on the knob and at Fog Hill in the State Line quadrangle. The associated graywackes contain fragments of coarse-grained granite containing oligoclase and perthitic K feldspar.
The association of coarse, continentally derived clastic rocks with basaltic volcanics and probable fluviatile red beds suggests rift facies rocks similar to Triassic and Jurassic rocks of the Atlantic passive continental margin. These rocks are restricted Chatham and Rensselaer Plateau slices.

Outcrops of unit c of the Stockbridge.

STOP 3.Large roadcut of purple and green-phyllite.
Excellent roadcuts expose purple and green laminated phyllites of the next higher Taconic slice, the Perry Peak slice that is correlated with the Everett slice on Figure 1. Strong secondary slip cleavage and microfaults, accentuated by pods of bull quartz are common. The contact between the Chatham slice and the higher Perry Peak slice is a late thrust probably of Acadian age. From this contact zone eastward to the carbonate belt, a complex system of late thrust faults have been mapped in which slivers of carbonate, Walloomsac, and Taconic rocks are found. To the north, this thrust zone roots in the Precambrian (Proterozoic) rocks of Clarksburg Mountain.
Volcanic rocks and thick graywacke are not recognized in the higher Taconic slices. Is the absence of these rocks of stratigraphic significance, or are the volcanic rocks absent because of faulting? This is a serious problem that has not been resolved. Certainly the Greylock and Hoosac Mounta in rocks are different stratigraphically than either the Chatham or Perry Peak rocks, as will be discussed at Stop 4.
From the roadcut, walk southwestward down to the old road and then follow the new wood road up the hill westward past green phyllite of the Perry Peak slice.
At 1550 ft elevation on bench a sliver of dolostone may be seen. The fault sliver occupies a position between the Perry Peak slice and Walloomsac of the autochthon below in a late fault.
This anticlinal belt of Walloomsac, however, underlies the Chatham slice rocks seen to the south at Stop 2.
From the carbonate rocks, walk northeastward down the slopes toward the brook, where inclusions of greenish-gray Taconic rocks may be found imbedded in the Walloomsac matrix.
This chaotic zone of wildflysch-like material evidently underlies the Chatham slice. Similar rocks are exposed to the south beneath the Chatham slice (Ratcliffe, Bird, and Bahrami, 1975, p. 82).
When the observations at Stop 1 and 3 are compared, the relations suggest that the Chatham slice was emplaced by a mechanism that involved recumbent folding, slivering of the autochthon, plucking of carbonate blocks signifying deformation of consolidated rocks. On the other hand, more ductile behavior with turbulent mixing of materials from autochthon and allochthon is necessary to account for the wildflysch-like breccias seen. A gravity induced spreading model to allow for creep in the autochthon may be the best explanation of these relationships. However, there is little evidence in favor of soft rock gravity sliding.

Side road leads to fossil locality
Side road leads to fossil locality in the basal part of the Walloomsac.

Rounds Rock.
Excellent cliffs west of road of green albitic Greylock Schist (optional stop).

STOP 4. Jones Nose.
Walk up the Meadow along the Appalachian Trail across limey albitic schist and schistose marble of the Walloomsac Formation here exposed by breaching of a refolded antiform that has a northdipping axial surface. This carbonate-rich unit is found at or near the base of the Walloomsac Formation regionally and on Mount Greylock, thus suggesting that older rocks are coming to the surface here. To the north, farther up the slope, a complementary, nearly recumbent syncline and anticline pair are exposed, also with north-dipping refolded axial surfaces. Section C-C' of Mount Greylock, Figure 3.

Greylock Schist / Walloomsac contact of autochthon
The bench the road follows is located on the contact between Greylock Schist and Walloomsac of the autochthon.

STOP 5. Stony Ledge.
Magnificant view to north and east into the Hopper. The ridge to the north is underlain by Greylock Schist, the valley by Walloomsac. To the east, the peak of Greylock and the steep west slope can be seen. Recent mapping suggests that there is double section of Greylock Schist exposed on Greylock with the axial surface of a large recumbent fold separating the mountain into lower limb and upper limb structures.
The Bellowspipe Limestone shown by Prindle and Knopf (1932) does not exist as a throughgoing unit but is sporadically developed.
Excellent late crenulation cleavage can be seen in the ledges of green phyllite. These folds are postmetamorphic and correlate with the Green Mountain uplift folds or folds of F5 regional structures.

Core of the recumbent synform.
Climb road past dark albitic and green albitic schist of the lower limb into fine lustrous phyllites forming the core of the recumbent synform.

STOP 6. Excellent view all around, weather permitting.
Discussion of the regional geologic relationships.
At crest of Greylock, we are standing on chloritoid-rich phyllite in the axial part of a large westward topping syncline. Darker albitic phyllite, quartzite and graywacke form a rather continuous marker horizon that separates the more chloritoid-rich rocks from green and gray-white albite spotted granulites. Locally, this transition zone contains lenses of salmon pink dolostone in boudins, magnetite-rich schist, and gneissic pebble conglomerate. Albitic schists crowded with albite in massive exposures can be seen on the crest of Ragged Mountain to the north, on Cole Mountain to the south, Rounds Rock, Jones Nose, and on Mount Prospect to the west.
The structural interpretation of Mount Greylock shown in Figure 3 calls for a thrust sheet that has been recumbently folded. Plunges are to the north and south into the sections. In addition to recumbent folds that involve the thrust contact, internal structures are shown which are also recumbent but which are truncated by the thrust contacts. This suggests that rocks of the Greylock slice were folded prior to emplacement on the Stockbridge-Walloomsac sequence.
Relationship of the Greylock to the Hoosac Schist
The ridge seen to the east is the Hoosac Hountain underlain by Precambrian (Proterozoic) gneiss to the south and Hoosac Schist to the north. The carbonate valley narrows to the north in the North Adams gap where the Hoosac Mountain approaches the Green Mountains. A longitudinal sketch section is shown in Figure 11. It identifies two major thrusts on Hoosac Mountain: a lower thrust places Precambrian (Proterozoic) gneiss with its unconformable cover (Hoosac Schist and interfingering Dalton Formation) over carbonate rocks of the autochthon. This fault is essentially the fault mapped as "Hoosic thrust" by Herz (1961). A higher thrust places Hoosac with a more easterly facies above the western Hoosac belt. This fault is termed the Hoosac summit thrust. The eastern Hoosac sequence contains green albitic schist, dark albitic and garnet-bearing schist and light green chloritoid schist. This sequence resembles closely Greylock Schist units, although a greater development of albite-rich rocks is found on Hoosac Mountain than on Mount Greylock. Stratigraphic units defining recumbent metamorphic fold structures within the eastern Hoosac are truncated by the Hoosac summit thrust.
East of the Hoosac belt is the Rowe Schist, a pale-green, fine-grained chloritoid phyllite with interbedded dark carbonaceous phyllite and amphibolite all of presumed Cambrian through Ordovician age. Stanley has recently suggested (1978) that a major thrust fault (Whitcomb summit thrust) separates the Rowe from the Hoosac on the basis of recognized truncation of units in the footwall and hanging wall (see Fig. 5). The Rowe also contains abundant pods of ultramafic rock. This unit may mark the locus of crustal convergence in the Cambrian and Ordovician (Stanley, 1978).
On the basis on the stratigraphic similarities between the eastern Hoosac sequence and the Greylock section, and the lack of similarity of Greylock with western Hoosac, the root zone of the Greylock slice lies either in the eastern Hoosac belt or between belt and the Rowe.
The root zone of the Greylock slice lies east of exposed Precambrian (Proterozoic) of the Berkshire massif at this latitude. Because the Greylock slice shows the closest affinity to cover rocks of the massif, it seems clear that the lower slices of the allochthon were derived from more easterly sites.

Small crops of green chloritoid phyllite
Small crops of green chloritoid phyllite, with strong late fault fabric. Crops continue intermittently for 0.7 mile. Dark Walloomsac biotite grade phyllite is seen near north end of crops.

Large crop of Walloomsac.

Crop of Walloomsac (Owl)
Crop of Walloomsac (Owl) and isoclinal F1 folds.

Optional Stop: Cataclastically deformed phyllite
Stop at large crops of black Walloomsac 1.1 miles west. Cataclastically deformed phyllite can be seen faulted against green phyllite of the Nassau Formation. Characteristic plication of foliation, slickensides, and bull quartz pods mark a series of late faults in the Buxton Hill fault zone. This zone projects east of the late fault zone seen at Stop 3.

Crops of Stockbridge (OCsg) and Walloomsac (Ow)
Brodie Mountain ski area.

Large outcrops of sheared Walloomsac
Large outcrops of sheared Walloomsac in a late thrust zone.

STOP 7. Large road cuts in Stockbridge (OCsg).
Excellent recumbent folds can be seen, crossfolded by folds in N. 20° W. 22° NE dipping axial planes. The origin of the cross folds is not known but may be an expression of compression of a faulted sliver within the Buxton Hill fault zone.

Large crop of Stockbridge (OCsg) on east.
Large crop of Stockbridge (OCsg) on east. Thin zone 1 m thick of Walloomsac in a slickensided fault sliver is traceable for 75 m in this outcrop. This is an excellent example of character of the fault slivering within this late fault zone. 419 58.0 Large crops of fault slivered and cataclastic Walloomsac opposite the Mill on the Floss.
The valley to the north at South Williamstown to the east are highly fault intercalated zones of green albitic and nonalbitic phyllite of the Greylock slice. To the west and north are green phyllites of Brody Mountain and Deer Hill. Exact placement of the boundary of the Greylock slice has not been possible. Allochthonous rocks on the northern end of Brody Mountain, however, are separated from the autochthon by a complexly intermixed zone of Walloomsac and green phyllite similar to the zone of mixed rocks seen below the Chatham slice at Stop 3, according to work by Don Potter. Because the Greylock slice does not have similar emplacement breccias and because the Greylock stratigraphy contains a greater abundance of albitic rocks than the Brody Mountain slice, the two slices are believed to be discretely different allochthons.

Large crops of fault slivered and cataclastic Walloomsac
The valley to the north at South Williamstown to the east are highly fault intercalated zones of green albitic and nonalbitic phyllite of the Greylock slice. To the west and north are green phyllites of Brody Mountain and Deer Hill. Exact placement of the boundary of the Greylock slice has not been possible. Allochthonous rocks on the northern end of Brody Mountain, however, are separated from the autochthon by a complexly intermixed zone of Walloomsac and green phyllite similar to the zone of mixed rocks seen below the Chatham slice at Stop 3, according to work by Don Potter. Because the Greylock slice does not have similar emplacement breccias and because the Greylock stratigraphy contains a greater abundance of albitic rocks than the Brody Mountain slice, the two slices are believed to be discretely different allochthons.

Excellent view of Mount Greylock, the Hopper, Geen Mountains
At crest of hill, excellent view of Mount Greylock and the Hopper, and the Green Mountains to the north. The broad carbonate valley extending from Williamstown east to North Adams consists of complexly folded rocks that appear to be detached from the Green Mountains by a major thrust fault that roots in the Hoosac Gap area. This fault slice, the Stone Hill slice, is named for exposure of the faulted rocks on Stone Hill south of Williamstown.

Stone Hill section
At dirt road, continue to north if permission to drive in is available. If not, we will walk in.
The Stone Hill section can be traced north to Buxton Hill where slivers of Stamford Granite Gneiss, Dalton and Cheshire thrust across units b and c of the Stockbridge in a complex thrust zone (see Stop 9).
The Stone Hill slice is believed to be a thin flap of autochthon originally rooted in the Adams or North Adams area that was thrust westward out of the North Adams gap area during an early deformation stage.
East-west trending hinge lines for early folds dominate the structure within the slice eastward to Mount Greylock where a late fault, the Clarksburg thrust, truncates structures in the slice.

STOP 8. Stone Hill slice.
One of the most complete stratigraphic sections of the Dalton Formation through unit C of the Stockbridge Formation is exposed in the area of Stone Hil l . Thin Cheshire Quartzite 10-0 m thick is interlayered with underlying black quartzose phyllite of the Dalton Formation. Dolostone of unit a of the Stockbridge overlies the Cheshire. Lithostratigraphic units of the Stockbridge here match closely rock section of the Vermont Valley sequence to the north.
The most anomalous features of the Stone Hill section are t he very thin Cheshire and the dissimilarity of this section to the Dalton-Cheshire section exposed on the Green Mountains to the north. Dark quartzose schists with a very thin quartzite is also a characteristic of the more easterly belt of Dalton and Cheshire mapped along the base of Hoosac Mountain and in the North Adams gap area.
Excellent recumbent folds can be seen in the cliffs above the road. The contact between the Cheshire and dolostone of unit a of the Stockbridge can be seen at the base of the quartzite cliffs to the north.

Crops to right are Chesire Quartzite.

STOP 9. Buxton Hill
Outlier of Stamford Granite Gneiss and blastomylonite and the sole of the Stone Hill slice.
The ridges to the south consist of blastomylonitic gneiss and Dalton with excellent recumbent fold thrust style. Syntectonic biotite from the blastomylonite yielded a K- Ar age of 387 ± 14 m.y. (394 ± 14 m.y. age calculated using new decay constant.) The biotite age is interpreted as a cooling age and a minimum for emplacement.
Crops around the north and east end of the hill are dolostone of the autochthon.

STOP 10. Hoosic thrust.
Herz (1961) drew the Hoosic thrust at the base of the exposures which he assigned to the Hoosac Formation. Reexamination indicates that these dark albitic, graphitic schists quartzites and limy schist should be assigned to the Walloomsac. Faulting is indicated by the shallow dipping spaced crenulation cleavage.
These exposures are on the north-plunging lower limb of a large recumbent syncline cored by Walloomsac that is refolded by north-trending late folds.
If time allows, we will drive into the quarry at natural bridge where an excellent recumbent anticline in unit e of the Stockbridge can be seen. This structure is on the lower limb of the major synclinal structure.
Those wishing to examine the excellent solution features in Mr. Elder's natural bridge, may do so for a slight fee. Those wishing to disband at this point, feel free to do so. Hard core elements may continue on to Hoosac Mountain!
2015: Mr. Elder's widow sold the tourist attraction to the state after he died in 1984, and it is now a state park.

Small crops of Dalton Formation
At the base of Hoosac Mountain are small crops of Dalton Formation interfingering with dark albitic schists of the western autochthonous Hoosac.

Green muscovitic chloritoid and garnet bearing schist of the eastern Hoosa
At the hairpin turn, green muscovitic chloritoid and garnet bearing schist of the eastern Hoosac may be seen. Excellent recumbent folds outlined by thin vitreous quartzite. This section is separated from the autochthonous Hoosac by the Hoosac summit thrust.

STOP 11. Top of Hoosac Mountain by observation tower
Excellent view back at Greylock, Taconic Range beyond, Green Mountains, and the North Adams Gap. Summary discussion of the relationships of the Hoosac-Greylock-Taconic belts and paleogeographic reconstructions.

B12: PRECAMBRIAN STRUCTURE AND STRATIGRAPHY OF THE SOUTHEASTERN ADIRONDACK UPLANDS
Brian Buddington Turner
Department of Chemistry
George Mason University
Fairfax, Virginia
ABSTRACT
The area of interest for this paper is the northern portion of the Bolton Landing quadrangle and adjacent parts of the North Creek and Paradox Lake quadrangles. Although there appear to have been at least five episodes of folding in the region, the southeastern Adirondacks appear to have undergone only four of the events (F1, F3, F4 and F5). F1 folds are large nappes. F3 folds range from isoclinal to tightly appressed similar folds in the study area. F4folds are moderately appressed similar folds, and F5 folds are relatively open similar folds. A large body of charnockite associated with F3 folding has the geometry of a nappe but was emplaced as a magma in advanced stages of crystallization. A structural dome of leucocratic granite was produced anatectically and solidified after F5 folding. Similar dome-like bodies of granite which do not show evidence of anatexis have fabric elements suggesting they were subjected to all four episodes of folding. The stratigraphic column of metasedimentary "formations" interspersed with "formations" of layered granite and quartzofeldspathic gneiss proposed by Walton (Walton and deWaard, 1963) is reinterpreted as recumbent synformal bodies of metasedimentary rocks separated by antiformal granitic nappes whose amplitudes are measured in tens of kilometers.

B12: PRECAMBRIAN STRUCTURE AND STRATIGRAPHY OF THE SOUTHEASTERN ADIRONDACK UPLANDS

STOP 1A. Alaskitic granites with some paragneiss
Outcrops on right (west) side of road are largely alaskitic granites with some strongly contorted layers of paragneiss. Although the outcrop is just outside the leader's field area, it was mapped at his suggestion by McConnell in 1964 and is deemed to be "basement". A two-meter exposure of an isoclinally refolded isoclinal fold is one of the main features of this stop. The first-formed fold has axial plane foliation and is believed to be an F1 fold. The second-formed fold deforms foliation and is believed to be an F3 fold. The other important feature of this exposure is the strong suggestion that the granite is an anatecti c product of the paragneisses.

STOP 1B. Older Paragneiss
At the T-intersection with the Beaver Pond Road, an outcrop of Older Paragneiss (informal stratigraphic name) is located on the south side of the road. The outcrop contains a heterogeneous group of gneisses, quartzites and amphibolites. Of particular interest are the rotated (penetrative) clots of sillimanite and minor folds whose axes plunge about 20° in an azimuthal direction of 60°-65°, which is the local axis of F3 folding. This unit is believed to lie unconformably below the base of the supracrustal metasedimentary rocks, and in the opposite stratigraphic direction grades into granitic gneisses. A whole-rock, Rb-Sr age of 1210± 45 m.y. has been obtained from this outcrop.

STOP 2. - Brant Lake Gneiss
Brant Lake Gneiss (informal name) is exposed on the south side of the road. This rock is found throughout a structural dome to the south of the exposure. This granitic gneiss has a very uniform modal composition of approximately 35% quartz, 25% microcline, 30% sodic plagioclase, 3% mesoperthite, 5-7% biotite and 1% opaques. The granitic rocks of this dome yield a whole-rock, Rb-Sr age of 1119±39 m.y. It has been proposed that this granitic gneiss is an anatectic product of the Older Paragneiss (Bickford and Turner, 1971). This is a very brief stop.

OPTIONAL STOP
Older paragneiss in the road cut on the north side of Rt. 8 consists of quartzofeldspathic gneisses with accessory biotite and garnet. Most, if not all, minor isoclinal folds in this exposure show axial planar foliation. This paragneiss mantles the structural dome whose granitic core rock was observed at Stop #2, and may be traced almost continuously around the dome (see Plate 2 of accompanying description)

STOP 3. Simple set of folds.
In the road cut on the east side of the road is perhaps the simplest set of folds in the Swede Mountain structural complex. A large isoclinal synform is outlined by the contrast between quartzite and sillimanitic schists. Sillimanite needles just above the quartzite closure plunge about 5° in an azimuthal direction of 80°. Closer to the road, a minor fold crenulation plunges 20° in an azimuthal direction of 80°. The synform is thought to be an F3 fold. The isoclinal synform is clearly refolded. A stereographic beta diagram of attitudes of compositional layers shows an intersection which plunges 22° in an azimuthal direction of 116°, which comports with the axis of F4 folding. About 15 meters uphill along the road cut, a pair of refolded isoclinal folds about 3 meters long may be observed. Measurements of hinges and crenulations in these produce the same pair of data as for the large refolded synform.

STOP 4.- Pull into turn-out area on the right and park.
Walk back across Rt. 8 and continue east for about 50 meters. On the south side of the highway is a low road cut about 70 meters long. An isoclinal fold, whose limbs may be traced 55 meters to its closure, is exposed. Crenulations in the hinge plunge about 10° in the azimuthal direction of 103°. At least one minor isoclinal fold within the larger isocline displays axial plane foliation. This is probably an F1 fold. In the eastern part of the road cut, the limbs of the isocline have been refolded by an F4 fold. A beta diagram of the refold shows an axis plunging 30° in the azimuthal direction of 117° .
Returning to the western end of the road cut, and at about right angles to the cut, the outcrop portion of the exposure contains evidence of three episodes of folding (see Figures 1,2 and 3 of accompanying description). A complex F1 isocline has been isoclinally refolded into an F-? synform, and several smaller F4 folds have been superimposed on the refolded mass. Axial plane foliation in the F1 fold has been rotated by F?, and a weak F4 foliation with strong quartz rodding penetrates the outcrop. A beta diagram of compositional layers in the nose of the synform shows an intersection plunging about 5° in an azimuthal direction of 110°. This does not correspond with an F3 axis, and may represent an F2 refold. A beta diagram of the limbs of the refold shows an intersection plunging 15-20° in an azimuthal direction of about 120°, which corresponds with F4 fold axes. Although the beta maxima are only 10° apart in azimuth, the difference is believed to be real because measured hinge axes correspond with the 110° beta direction and measured quartz rods with the 120° beta direction.

STOP 5. Pull into turn-out area on left.
At this point the group may wish to split into two parties. Assuming that time permits, the leader will take a group of physically able participants on a 4-kilometer hike (total distance) to examine evidence of large nappe structure in Swede Mountain. Those persons not wishing to take the hike are invited to examine the 1.0 kilometer of nearly continuous exposure of Swede Mountain beside Rt. 8, which includes the structures seen at Stop #3.

STOP 6. (optional)
You are in the northeast quadrant of the North Creek 15' quadrangle, mapped by Geraghty (1973). The outcrops on the east side of the road are predominantly quartzofeldspathic schists and gneisses with abundant biotite, sillimanite and garnet (kinzigite) and quartzite. The author believes the kinzigite is an iron-rich facies of the basal khondalite seen in Swede Mountain. Some minor folds display axial plane foliation and may be F1 folds. Numerous axial traces of minor folds strike 60°-70° in azimuth, a biotite-sillimanite crenulation shows plunge of about 42° in an azimuthal direction of 59°, a beta diagram of one fold shows an intersection at plunge 26° in an azimuthal direction of 53°, and one minor fold hinge plunges 15° in an azimuthal direction of 70°. The foregoing reflect F3 folding. Several F4 cross folds are present and measured lineations and hinges have a range of plunges of 45° to 55° in azimuthal directions of 115° to 120°. At least one F5 fold is apparent in the outcrop, and its axial trace is about 10° in azimuthal direction.

B13: LATE WISCONSINAN - RECENT GEOLOGY OF THE LOWER RONDOUT VALLEY, ULSTER COUNTY, SOUTHEASTERN NEW YORK
Russell H. Waines
Department of Geological Sciences
State University of New York College at New Paltz
Lower Rondout Creek extends eleven miles northeast from High Falls through Rosendale to the Hudson River at Kingston, New York. In this distance it drops from an elevation of about 120 feet at High Falls to sea level at Kingston. From High Falls to Rosendale the stream represents an easterly departure of the northeasterly-flowing Rondout Creek from its ancestral (preglacial) valley northwest of the Shawangunk Mountains. Maximum bedrock depths in the central Rondout Valley are considerably lower than the level of High Falls (Frimpter, 1970). A northeasterly retreating ice lobe in the central Rondout Valley with attendant preglacial impoundments and sedimentation at ever decreasing elevations controlled a final base level at about 400 feet.
At this point the ice lobe in the Wallkill Valley had begun to melt in such a way that the 400 foot level could not be maintained in the central Rondout Valley and base level was lowered to 250 feet or less. In the lower Wallkill (now lower Rondout) most sand deposits occur below 260 feet. The deflected Rondout now flowed into the northern (lower) portion of the ancestral Wallkill Valley bringing with it considerable sands and silts and some gravels as it cut headward in the central Rondout Valley cannibalizing preglacial sediments previously formed at higher elevations. The ultimate effect may have been the deposition of "wall-to-wall" sand in the lower Rondout Valley.
There is some question as to whether the interlaminated (varved) clays and silts of the lower Rondout Valley are contemporaneous in part with the sands which generally overlie them. The clay beds appear to have formed in front of ice, beside ice or under floating ice. The variation in elevation of the clay-sand contact, the absence of clay from some parts of the lower Rondout Valley and the general absence of interbedded clays, silts, and sands suggest the clays were formed before the sands and were even partly eroded before the sands were deposited. This would require considerable fluctuation of base level, largely controlled by the disposition of the ice lobe in the Hudson Valley, especially opposite Kingston.
In any event the sands seem to have been deposited under fluvial conditions with an ascending base level. The maximum elevation of 250 feet seems to have been controlled by spillage into the Hudson Valley through The Hell opposite Ulster Park (fig. 1). Soils maps suggest a dissected delta at the foot (east side) of The Hell.
After some evidence of a local glacier readvance over the sandplain at Maple Hill (Connally, 1968) and the development of possible small dunes at Tillson and Maple Hill the ice on the uplands on the north side of lower Rondout Creek appears to have stagnated. The ice lobe in the Hudson Valley seems to have withdrawn little by little, lowering base level in successive stages. In response to this, Rondout Creek seems to have begun headward erosion into sands and clays and eventually the production of paired and unpaired terraces at at least six different levels (Irving, 1972).

B13: LATE WISCONSINAN - RECENT GEOLOGY OF THE LOWER RONDOUT VALLEY, ULSTER COUNTY, SOUTHEASTERN NEW YORK

Bridge over Esopus Creek.

Esopus Creek and floodplain on right.

Divide between present day Esopus and Rondout
Divide between present day Esopus and Rondout drainage systems ca. 400 feet.

400 foot sandplain for next 0.4 miles
400 foot sandplain, somewhat dissected and possibly terraced for next 0.4 miles.

Road descends through cut in sandplain for 0.15 miles.

250 foot sandplain.

STOP 1. High Falls.
When blocked to the north while at a 400 foot base level Rondout Creek apparently found an outlet eastward into, under or around ice in the lower Wallkill drainage system. The river later established a base level at 250 ft. and subsequently has cut down to approximately 170 feet, the present level of bedrock (late Silurian Rondout Formation) at the top of the falls. The 250 foot sandplain can be seen to the north.

Village of High Falls
Delaware and Hudson Canal, Locks and Museum.

Approaching 210 foot sandplain terrace.

Rondout Creek on left.

STOP 2. Hurley Sand and Gravel Co., Inc. Sand and gravel pit.
This extensive pit has been developed in the 210 foot sandplain terrace. Remnants of the original 250 foot sandplain occur locally. Although stratigraphic exposures are poor, several large piles of coarse water-worn gravels remaining from sieving operations attest to the considerable gravel content of the sands. About 50 feet of gravels and sands fine downward to silts which in turn are underlain by clays. No where else in the lower Rondout Valley are gravels so abundant in the upper sands.

Till on hillside to left.

90 foot floodplain ahead.

Bridge over Rondout Creek.

Cross bridge over Rondout Creek. Village of
Rosendale.

Continue on sloping sandplain terrace ca. 100 foot level.

Descend to 50 foot floodplain and/or terrace.

STOP 3. Rondout Creek, Rosendale.
This floodplain and/or terrace was flooded in the summer and fall of 1955. Buildings on the north side of the river were flooded to the middle of their second stories. Part of the Army Corps of Engineers' stream channelization efforts in response to the 1955 floods can be observed.

Town of Rosendale Recreation Center on 70 foot terrace on right.
Ascend through sands to sandplain level.

250 foot sandplain for next 0.35 miles.
Village of Tillson.

Drive N up the gentle slope of the 250' sandplain.

Entering region of low sand hills on 250 foot sandplain.

STOP 4. Tillson sand hills.
Low sand hills rise 10 to 15 feet above the 250 foot sandplain along the southern margin of the Rondout Valley in the vicinity of Tillson. Inspection of a trench in the flank of one sand hill revealed a structureless non-stratified fine sand to silt. The hills are here thought to represent small sand dunes formed on the 250 foot sandplain just in advance of an ice front in the uplands on the north side of the Rondout Valley.

Turn right over sand hill onto Carroll St.

Swing right leaving sand hill area.

Sand hills to left (west) behind houses.

STOP 5. - Sand pit in 250 foot sandplain.
Almost the entire uppermost 110 feet of section is exposed with varying degrees of perfection. This is a shovel-stop. Sands fine downward into silts which overlie interlaminated (varved) clays and silts at about the 150 foot elevation. Extensive slump structures have been observed in the silts about 20 to 30 feet above the silt-clay interface. Gravels in the sands are fine and very infrequent. Current bedding, current and climbing ripples have been noted in the sands where bedding is generally thin to laminar.

Descend cut in sands.

50 foot terrace and sometime floodplain.
Modern floodplain at 40 feet along south side of Rondout Creek.

Flood control dike on right.

STOP 6. Maple Hill sand pit in 250 foot sandplain.
Here in an 80 foot sequence sands grade downward into silts which overlie interlaminated (varved) clays and silts at an elevation of about 160 feet. Little can be seen presently of the structure in the sands and silts. This pit was investigated as a potential sanitary landfill site but a high water table and water-saturated silts above the clays preclude its use for that purpose. A few low sand hills occur in the wooded area northeast of the pit. Of some interest is the till-like material overlying the sandplain near the pit entrance and elsewhere. Sieve analysis has yielded a polymodal distribution of particle sizes. This material is one line of evidence for the Rosendale Readvance of Connally (1968). Several samples of split-spoon core obtained in test-borings in the pit will be displayed.

STOP 7. Bloomington sandplain 190 foot terrace.
Local borings, some over 100 feet to bedrock, have encountered an almost total sand-silt sequence with little or no clay. Exposures of the upper sands may be seen in cuts southeast of the fire house.

190 foot sandplain terrace.

Lock of Delaware and Hudson Canal on left.

Large glacial clasts from "boulder train"
Large glacial clasts from "boulder train" crossing Rondout Creek on left. "Fines" have been removed from glacial till by the downcutting creek leaving clasts too large to move.

Delaware and Hudson Canal on left.

Small bridge over Greenkill Creek.
Rondout Creek and modern floodplain to right. Slightly higher floodplain terrace on far side of Rondout Creek.

50 foot terrace to right across Rondout Creek.

STOP 8. Sand pit. Do-it-yourself stop.
This pit is developed in the side of a typical sand-silt sequence r1s1ng to a 170 foot sandplain terrace. Ultimately about 130 feet of sands and silts are exposed and none of the typical interlaminated clays and silts have been encountered, even as low as the 40 foot elevation.

On the left, the ancestral Wallkill River probably passed.
On the right the Delaware and Hudson Canal descended through locks to tidewater.

STOP 9. New Salem sand pits.
The sequence on the hillside from the top down is as follows: The top sands occur 170 feet above the road or at about 260 feet elevation. The sands fine downward to silts for some 90 feet and red clays start about 80 feet above the road or about 170 feet above sea level. The sequence is somewhat similar to those of Stops 5 and 6 and unlike those of Stops 7 and 8.

Ancestral Wallkill River may pass under Show Boat on right.

STOP 10. City of Kingston sand and gravel pit.
Foreset beds of deltaic sands and gravels rest against steep bedrock surfaces. Sands and silts in attitudes of slump appear to have been deposited over ice. High up on the hillside to the northwest glacial striations are well-developed. Some of the foreset gravels are cemented to the hillside by means of calcium carbonate.

Gravel pit on left.

STOP 11. Sand pit. View stop.
This pit is developed in the lower portion of a sand-silt sequence rising to a 210 foot sandplain terrace to the northwest. The exposed sediments represent the bottom 160 feet or so of a 190 foot plus sequence. To the northwest sediments have been deposited against steep bed rock surfaces. Slumped sediments in the southwest corner of the pit may have been deposited over ice.

STOP 12. Twaalfskill Valley.
This narrow valley incised into Upper Silurian and Lower Devonian strata may represent an ancient drainage system from the north, possibly the ancestral Esopus. The bedrock profile in the center of the Twaalfskill Valley is not entirely known. This valley appears to have allowed passage of glacial waters and sharing of base level between the Esopus and lower Rondout Valleys. Sands at the 250 foot level extend through part of Kingston up the east side of the Esopus Valley.

STOP 13. View stop, 250 foot sandplain remnant.
From the road the confluence of the Hudson River and Rondout Creek can be viewed. Glacier ice in the Hudson Valley at this point influenced drainage and effective base level in the lower Rondout Valley. A second location about 50 paces southwest of the end of the road affords a view southwest up the lower Rondout Valley as far as Maple Hill. With skill various terrace levels and remnants of the 250 foot sandplain can be distinguished.