NYSGA 1994
FIELD TRIP GUIDEBOOK
NEW YORK STATE GEOLOGICAL ASSOCIATION
66th Annual Meeting
Edited by:
Carlton E. Brett, University of Rochester
and
James Scatterday, SUNY Geneseo
Technical Consultants:
Mary Nardi
York, New York
Richard D. Hamell
Monroe Community College
PREFACE
The Genesee Valley is a classic region for the study of sedimentary geology. The Genesee gorges at Rochester and Letchworth were explored geologically by many of the great early American geologists, particularly James Hall. Herman Leroy Fairchild, an early professor of Geology at the University of Rochester, and a founder of the Geological Society of America, made a career of studying the Genesee Valley glacial history.
The Genesee Valley area features an excellent cross-section of mid Paleozoic sedimentary rocks, ranging in age from the Late Ordovician to the Late Devonian. Upper Ordovician Queenston redbeds and overlying Lower to Middle Silurian mixed carbonates, shales, and sandstones, including the well known Clinton hematite, are exposed in the heart of Rochester itself. To the south are exposures of Late Silurian evaporites, shales and eurypterid-bearing dolostones, succeeded by fossiliferous beds of the Middle Devonian Onondaga Limestone. Still younger black and dark gray, exceptionally fossiliferous shales of the Middle Devonian Hamilton Group are exposed in tributaries of the Genesee River south of the Thruway. Outstanding exposures of Upper Devonian shales and siltstones of the "Portage" facies crop out in the spectacular cliffs of the Genesee River gorge at Letchworth Park, "the Grand Canyon of the East". Many of the outcrops in the Genesee area and the immediate vicinity are extraordinarily fossiliferous, and the strata themselves have been subject to substantial reinterpretation in the light of event and sequence stratigraphy, taphofacies, and models of foreland basin dynamics.
The Genesee region is an outstanding area for the study of surficial and glacial geology. The Genesee Valley was occupied by an extraordinary sequence of proglacial and moraine dammed lakes. Classic examples of eskers, kames, kettles and drumlins can be viewed in areas such as Mendon Ponds Park and also in the Pinnacle Hills moraine within the city of Rochester itself. Within the past decade, Pleistocene sand and marl deposits in the Genesee Valley region have yielded two exquisite mastodon skeletons, as well as other vertebrate and invertebrate fossils. The basic outlines of the complex Pleistocene geologic history of the Genesee Valley were established by Fairchild. However, renewed interest in surficial deposits, together with radiocarbon dating, has yielded a modified picture in the past several decades.
The Rochester area is also an ideal region for the study of urban geology and environmental hazards and problems. These include the highly publicized problem of roof collapse of the Akzo salt mine, landslides and slumps within Pleistocene sediments around the Irondequoit Bay region, problems of river erosion and flood control, including spectacular examples of migrating meander loops in the modern Genesee River, and the development of hazardous waste dumps in several places in the region.
This guidebook provides updated synthesis of several of these aspects of regional geology in the Genesee area. Bedrock geology of the Upper Ordovician to Upper Devonian is covered in a series of papers. Three other articles provide new syntheses and insights into aspects of surficial geology and environmental geology. Inevitably, there are gaps. There is no paper on the Salina Group, for example, which is unfortunate given recent interest in salt mining! Also, no tectonic or petrologic studies are included. However, on the whole, I believe that the guidebook presents a reasonable cross-section of Genesee Valley geology.
On a personal note, I cannot help but reflect that the first New York State Geological Association meeting that I attended as a student was held over twenty years ago in 1973, the last time NYSGA met in the Rochester area. (In fact, it was actually hosted by SUNY at Brockport.) It was on that occasion, while I was camped at Hamlin Beach State Park with some other students, that my friend, Gerry Kloc, came running back from the Saturday evening banquet full of excitement about a unique individual, named Gordon Baird, who knew about the geology of Erie County and other parts of New York State. I said "No way; nobody else really works on this stuff!" Nonetheless, the next day, accompanied by my fiancee (now wife), Betty Lou Hilton, I went to Old Dewey Hall at the University of Rochester to meet with this "Wunderkind". Sure enough, Gordon did know about Penn Dixie quarry, the North Evans conodont bed, and a great deal more that I thought that I had discovered. We had been working on the same stratigraphic sections for over five years without crossing paths. I was, of course, greatly impressed by Gordon's extensive collections of weird and wonderful geological specimens. More than that, I was struck by his incredible store of knowledge, wit and enthusiasm. Here, was a kindred spirit. Under other circumstances, Gordon and I could have become bitter rivals, like Cope and Marsh. That was not to be, however, for we both preferred cooperation to competition. From that September day onward, we became coconspirators in the "plundering of northeastern geology". By the time of the 46th Annual NYSGA, we had worked together enough to collaborate for the very first time in leading a field trip. Ironically, the trip dealt with the Windom Shale, a topic we again address in this guidebook, with considerable updating, some 20 years later. In the meantime, we have jointly studied over 1,000 streams and other outcrops in New York, have made many exciting discoveries, and have had countless conversations on the geology of the northeast during thousands of miles of travel on New York's Thruway and back roads. It has been an exciting ride, and a considerable part of it is logged in NYSGA guides.
I also note that the last time NYSGA officially met at the University of Rochester, in 1956, the guidebook, a thoroughly valuable contribution that was copied numerous times, was in more or less the form of handouts for student geological field trips. Since then, and even since 1974, the guidebooks have grown larger (yes, we have contributed to that), and of increasing quality. The NYSGA Guidebooks over the years, have become an invaluable trove of explicit information about New York's geology, coupled with road logs that enable students and professionals to assess for themselves the ideas presented in articles. These guidebooks present a great deal of information that is unavailable in any other source. I personally feel that the guidebooks have several very significant roles. The first, clearly, is that they are a vehicle for dissemination of often new, sometimes preliminary information. Certainly they continue to have a very critical teaching function. How many of us have at one time or another copied the road logs, figures or texts of NYSGA articles to supplement our class field trips? The articles in a guidebook, such as this one, present information, and more importantly, ideas, about geology, some correct, some perhaps incomplete or incorrect, but available for students in all categories of New York geology. In my view, the articles should present material in a variety of ways. Certain articles are geared for the more general audience, others are available for advanced students and for professionals specializing in particular areas. Another function which has not always been emphasized, but one which we have taken liberal advantage of, is that the guidebooks provide a vehicle for publication of fairly detailed information about regional geology. Where else can such information be published or found by the student interested in local details? Certainly, most of the professional journals, such as Geological Society of America, Journal of Sedimentary Research and others tend to publish articles that are broad, and of general interest, but typically, through editorial dictate, are "cleansed" of detailed outcrop-based information. In that regard, I feel that the NYSGA Guidebooks have a very important role to play as archives for such information.
I would like to express my sincere appreciation to numerous individuals who helped in the organization of this meeting and in the writing, editing and compiling of the present guidebook.
First of all, I owe a debt of gratitude to the authors of the several articles and leaders of the trips. They all came through and worked diligently to produce meaningful and interesting articles. Final preparation of manuscripts and compilation of the guidebook were aided greatly by the secretarial expertise of Susan Todd and Heidi Kimble of the University of Rochester. Mary Nardi, David Lehmann and James Scatterday helped greatly in the editorial process. Numerous reviewers, acknowledged in the individual papers, aided in the improvement of the final product. Dr. William Kelly of the New York State Geological Survey and presently head of the NYSGA, provided strong support and encouragement in the preparations for this meeting. Don Parry and Keith Kurz of the University's Conference Office also helped greatly in organization aspects of the registration and meeting logistics. Finally, several past and present students of the Department of Earth and Environmental Sciences helped in numerous ways to prepare for the meeting. I particularly wish to recognize the efforts of Wendy Taylor, Robyn Hannigan, Chuck Ver Straeten and Gerald Kloc. Richard Hamell of Monroe Community College helped me with design of the cover; we chose a pale purple in recognition of Rochester's lilac traditions. My colleagues in the Department of Earth and Environmental Sciences, especially Curt Teichert and Robert Sutton, have always been supportive and encouraging to me in my various projects, including this one. Gordon Baird has helped me over the past two decades in ways too numerous to mention. Finally, I should acknowledge the patience and support of my family, particularly Dr. Betty Lou Hilton Brett, for without that, none of this would be possible. She cannot say she was not forewarned! You may note that she was with me on that famous first meeting with Gordon Baird; and we were engaged within the same week as that fateful meeting of the NYSGA in the Rochester area in 1973.
The Empire Soils Corporation of Huntington Enterprises, Inc. of Rochester generously provided $200.00 in support of the meeting.
Carlton E. Brett, President
New York State Geological
Association - 1994

A1:THE HYDROGEOLOGY OF LANDFILL SITES IN WESTERN NEW YORK
William M. Goodman
The Sear-Brown Group
85 Metro Park
Rochester, New York 14623
RONALD B. COLE
Allegheny College
Department of Geology
Meadville, Pennsylvania 16335
DAVID F. LEHMANN
Huntingdon Engineering & Environmental, Inc.
535 Summit Point Drive
Henrietta, New York 14467
INTRODUCTION
Because existing state environmental regulations require extensive hydrogeologic reports for landfills, waste disposal sites provide a wealth of penetrative data that may be synthesized for characterization of regional surficial and bedrock geologic units. Access to penetrative data may be accomplished by filing a Freedom of Information request with the New York State Department of Environmental Conservation (NYSDEC).
Landfill siting and operation are governed by 6 NYCRR Part 360 regulations. This regulatory document contains a de facto table of contents for a comprehensive hydrogeologic investigation of landfill sites. Furthermore, the regulations require a literature search and analysis of broader, regional data in order to provide a context for definition of site-specific, hydrostratigraphic units. When properly completed, resultant hydrogeologic reports contain a plethora of penetrative and water quality data, as well as hydrogeologic interpretations, that academic researchers would find difficult to fund through grant-lending agencies. Consequently, in the course of local geologic or water resource investigations, hydrogeologic reports for landfill sites should not be ignored. When reconciled with data published by the U.S.G.S., U.S.D.A. Soil Conservation Service, NY State Geological Survey, and the academic community (e.g. in NYSGA guidebooks!), these hydrogeologic reports add considerable volumes of quantitative information to any geologic research database.
The purpose of this field trip is to provide an overview of the hydrogeologic aspects of the Part 360 regulations and to illustrate the diversity of hydrogeologic data collected for landfill sites. Furthermore, this article is intended to demonstrate how Part 360 data may be synthesized for characterization of geologic units in western New York. The field trip will also provide an opportunity for landfill operators to demonstrate how modern, secure facilities are planned, designed, operated and closed to minimize negative environmental impacts.
PART 360 LANDFILL SITING PROCESS
Landfill siting is a controversial and expensive proposition in New York State. The process had been particularly controversial for the private sector under previous versions of Part 360. One particular problem would commonly arise when a potential landfill site was selected, based upon economic and/or geographic characteristics, before performance of a formal Part 360 site selection study. Site selection studies, both under previous and current versions of Part 360, involve comparison of potential sites on the basis of hydrogeologic, engineering and socioeconomic properties. Ideally, the site selection process provides a means to determine the "best" site out of many potential landfill locations. Prior to the October 9, 1993 revision to the Part 360 regulations, when a preferred site would be chosen before other candidate sites were identified, expensive siting studies would subsequently have to be "retrofitted" to produce the desired conclusion that the preferred site is the most appropriate location among other "straw-man" candidate sites for the facility.
The New York State Department of Environmental Conservation apparently recognized the quandary in which project sponsors found themselves when the preferred, suitable site was identified prior to completion of the formal site selection study. Furthermore, the NYSDEC also apparently recognized that, because siting studies require analysis of non-hydrogeologic variables (e.g. transportation, population, utilities, etc.), less hydrogeologically suitable sites could potentially be promoted over sites with more desirable subsurface characteristics for reasons other than susceptibility to groundwater and surface water contamination. Apparently for these reasons, the NYSDEC recently revised the Part 360 siting process for project sponsors who identify sites that exceed minimum hydrogeologic and engineering criteria for landfill construction. Under certain specifically stated hydrogeologic conditions, an expensive site selection study may not be required to defend the obvious merits of a highly suitable site. The revised regulations ease the financial burden and the logistical difficulty in objective compliance with landfill siting requirements when specified hydrogeological conditions are met. By establishing standards which must be met in order to waive the requirement for a site selection study, the NYSDEC can still guarantee that landfills can be constructed and operated in a manner which minimizes the potential for negative impacts to humans, wildlife or the environment.

A1:THE HYDROGEOLOGY OF LANDFILL SITES IN WESTERN NEW YORK

STOP 1. BRIGHTON TOWN LANDFILL Facility: Brighton Solid Waste Management Facility
Location: Town of Brighton, Monroe County (Rochester East 7.5" Quadrangle)
Hydrogeologic Setting: Glaciolacustrine deposits and glacial till over bedded sedimentary rock.
Site Description: The site is located on the northeast-facing side of the Irondequoit Creek valley. The site includes 75 acres; only 24 acres are considered suitable for waste disposal purposes. Topographic relief across the active portion of the site is approximately 150 feet; the average topographic slope is approximately 5 percent. The site is bounded on the west by Thomas Creek, a small tributary of Irondequoit Creek, and on the north and east by Irondequoit Creek. Irondequoit Creek drains into a major bay (Irondequoit Bay) of Lake Ontario.
The following items, listed in the Part 360 Permit Application for this facility, reflect current site conditions:
• There is no evidence of leachate derived from this facility.
• Natural vegetation is present on previous disposal areas.
• Vegetation is established on all slopes of disposal areas.
• There is no evidence of significant erosion occurring on site.
• The disposal area is adequately covered and graded to maintain safe and efficient storm water runoff.
Surficial Geology: Overburden consists of probable lodgement till overlain by interbedded flow tills and stratified silt-to sand-rich glaciolacustrine facies. The overburden ranges in thickness from 22 to approximately 100 feet. The overburden is thinnest at the topographically highest (southwestern) portion of the site and thickens towards Irondequoit Creek, to the northeast. The strike of the surficial deposits generally follows the topographic contours of the valley.
The interbedded, stratified glaciolacustrine facies and water-lain till deposits include evenly laminated silt (offshore lacustrine deposits), evenly-and cross-laminated coarse silt and very fine sand (nearshore lacustrine deposits), and gravelly, clay-rich silts (tills). Based on detailed boring logs, split-spoon samples (Huntingdon-Empire Soils Investigations, Inc., 1994), and outcrop sections, the glacial and proglacial strata include, in descending order:
Unit 1: | Evenly laminated silt (10 to 25 feet thick)
Unit 2: | Very fine, silty sand (5 to 15 feet thick)
Unit 3: | Gravelly, clay-rich silt (5 feet thick)
Unit 4: | Evenly laminated silt (> 5 feet)
Unit 5: | Undifferentiated deposits (No boreholes with detailed logs or available split spoon samples penetrated Unit #4. However, tills are present over bedrock throughout the lower Irondequoit Creek valley.)
This succession mostly records accumulation in a proglacial lake basin. The glaciolacustrine succession disconformably overlies lodgement till that accumulated during the earlier glacial advance. A minor glacial advance is recorded by Unit 3, a waterlain diamicton or subaqueous flow till. The stratigraphic record of this advance is asymmetrical: offshore silts are overlain by flow till, and the flow till, in turn, is overlain by nearshore sands. Unit 3 may correlate with the Somerset Till described by Calkin and Muller (1992) 'from sections along the Lake Ontario shoreline. In general, lacustrine silts and sands are extremely well sorted with D10 values on the order of 0.05 mm or less for the very fine sands. N-values for these deposits generally range from 15 to refusal, with the lower N values correlating to shallowest subsurface sandy deposits.
Bedrock-Geology: Based on reported depth to bedrock, strata assigned to the Lower Silurian Medina and Clinton groups probably subcrop beneath glacial sediments. These strata consist of sandstone, shale, and limestone. In ascending order, the following formations are likely subcrop beneath the site: Grimsby Sandstone, Cambria Shale, Kodak Sandstone, Maplewood Shale, Reynales Limestone, and Sodus Shale.
Groundwater Flow: Groundwater flow is topographically controlled. Groundwater equipotentials are generally parallel to topographic contours; groundwater flows to the northeast.
1994 A1 W.M.Goodman, R.B.Cole, D.F.Lehmann #msn_Aqua -77.53418955435217,43.16206173306232,0 STOP 2. HIGH ACRES LANDFILL Site Location: Town of Perinton, Monroe County, New York Fairport and Macedon 7.5 Minute Quadrangles
Site Description: The east side of the site contains a north-south trending drumlin. The existing operational facility is constructed on the drumlin. The west side of the site is relatively flat-lying, interdrumlin terrain. The western area is presently under construction as a lateral expansion area to the landfill.
Surficial Geology: The drumlin on the west side consists of two separate till horizons: a lower, gray, bouldery lodgment till and an upper, brown weathering "altered till". The upper till contains fewer cobble and boulder size clasts than the basal, unaltered till (Dan Coon, personal communication). Given the difference in grain-size composition and density, the upper till may actually represent a separate genetic unit. One hypothesis is that the basal till correlates with the Furnaceville Till, whereas the upper till is correlative to the Somerset Till.
In the interdrumlin areas of the west side of the site, the surficial stratigraphy is more variable. The basal till that directly overlies bedrock is also divisible into a lower, unaltered zone and an upper weathered zone. The presence of this horizon may suggest a period of subaerial exposure prior to deposition of the overlying recessional sequence. Such an interpretation, however, is difficult to reconcile with the regional glacial history. An alternative hypothesis is that the "weathered till" may represent the diamictic facies of the younger Somerset Till equivalent and that the mixed water-lain and till deposits ("glacial till/outwash" deposits of Eckenfelder, 1992) may correspond to the upper water-lain till facies of the Somerset Till as defined by Calkin and Muller (1992).
Bedrock Stratigraphy: The bedrock strata that subcrop beneath glacial tills on the site are assigned to the upper part of the Silurian Vernon Shale. Eckenfelder (1992) reports that the drill core sections consist primarily of red and green shale with varying amounts of gypsum. Gamma ray logs were used to correlate borehole sections. Through correlation of gamma ray logs, Eckenfelder (1992) was able to document the regional southward dip of bedrock strata.
Groundwater Flow Conditions: Shallow groundwater flow tills and glacial outwash is topographically controlled. On the east side of the site, groundwater in the brown till horizon flows radially off the drumlin. In flat-lying areas, groundwater flow generally proceeds to the south. The low permeability of the glacial tills results in vertically oriented groundwater flow vectors. Flow lines are deflected to a more horizontal orientation in lenses of glacial outwash.
The bedrock fracture zone provides a preferred groundwater flow path. Upward gradients are common between the fractured bedrock zone and the underlying competent bedrock zone.

STOP 2. HIGH ACRES LANDFILL
Site Location: Town of Perinton, Monroe County, New York Fairport and Macedon 7.5 Minute Quadrangles
Site Description: The east side of the site contains a north-south trending drumlin. The existing operational facility is constructed on the drumlin. The west side of the site is relatively flat-lying, interdrumlin terrain. The western area is presently under construction as a lateral expansion area to the landfill.
Surficial Geology: The drumlin on the west side consists of two separate till horizons: a lower, gray, bouldery lodgment till and an upper, brown weathering "altered till". The upper till contains fewer cobble and boulder size clasts than the basal, unaltered till (Dan Coon, personal communication). Given the difference in grain-size composition and density, the upper till may actually represent a separate genetic unit. One hypothesis is that the basal till correlates with the Furnaceville Till, whereas the upper till is correlative to the Somerset Till.
In the interdrumlin areas of the west side of the site, the surficial stratigraphy is more variable. The basal till that directly overlies bedrock is also divisible into a lower, unaltered zone and an upper weathered zone. The presence of this horizon may suggest a period of subaerial exposure prior to deposition of the overlying recessional sequence. Such an interpretation, however, is difficult to reconcile with the regional glacial history. An alternative hypothesis is that the "weathered till" may represent the diamictic facies of the younger Somerset Till equivalent and that the mixed water-lain and till deposits ("glacial till/outwash" deposits of Eckenfelder, 1992) may correspond to the upper water-lain till facies of the Somerset Till as defined by Calkin and Muller (1992).
Bedrock Stratigraphy: The bedrock strata that subcrop beneath glacial tills on the site are assigned to the upper part of the Silurian Vernon Shale. Eckenfelder (1992) reports that the drill core sections consist primarily of red and green shale with varying amounts of gypsum. Gamma ray logs were used to correlate borehole sections. Through correlation of gamma ray logs, Eckenfelder (1992) was able to document the regional southward dip of bedrock strata.
Groundwater Flow Conditions: Shallow groundwater flow tills and glacial outwash is topographically controlled. On the east side of the site, groundwater in the brown till horizon flows radially off the drumlin. In flat-lying areas, groundwater flow generally proceeds to the south. The low permeability of the glacial tills results in vertically oriented groundwater flow vectors. Flow lines are deflected to a more horizontal orientation in lenses of glacial outwash.
The bedrock fracture zone provides a preferred groundwater flow path. Upward gradients are common between the fractured bedrock zone and the underlying competent bedrock zone.

STOP 3. PROPOSED HYLANDS ASH MONOFILL
Facility: Hylands Ash Monofill
Location: Town of Angelica, Allegany County (Angelica 7.5" Quadrangle)
Hydrogeologic Setting: Glacial Till Over Bedded Sedimentary Rock.
Site Description: The site contains a broad, south facing, hanging valley that forms a natural amphitheater. A small intermittent stream is supplied by a bedrock spring along the east side of the site and by overland flow toward the valley center in the southern portion of the hanging valley. Surface water drainage flows into Angelica Creek which, in turn, discharges to the Genesee River.
Surficial Geology: Glacial overburden consists of lodgement till overlain by ablation till. The overburden ranges in thickness between approximately 5 and 11 5 feet. The till is thinnest on hill crests and thickens rapidly toward the center of the hanging valley. An oxidation front marked by the vertical change from gray, unaltered till to brown, weathered deposits cross-cuts and partially obscures the lodgement till/ablation till contact. The lodgement till is over consolidated; assuming no net erosional lost of glacial sediments near the valley floor, the brown, oxidized lodgement till is estimated to have been compacted beneath a minimum of 500 ft. of ice and probably considerably more (Michael Mann, personal communication). The ablation till is generally less dense than the lodgement till and contains thin, discontinuous, water-sorted lenses.
High subglacial pore pressures are suggested by the fracturing of bedrock and injection of till seams to depths approaching 200 ft. below ground surface. The upper 20-30 ft. of rock is typically so intensely fractured that the contact between glacial till and bedrock may be completely gradational. In ascending order, the gradational interval consists of 1) in-situ rock mass with till seams; 2) approximately even proportions of in-situ rock mass and till with gravel-sized angular rock fragments; 3) boulder-size, rotated or detached blocks of bedrock in a gravelly clay till matrix (deformation till); and 4) channery lodgement till.
Bedrock Geology: Strata are assigned to the Upper Devonian (Fammenian) Canadaway and Conneault Groups and consist of a series of interbedded, fossiliferous sandstones, siltstones and clay shales (see Fig. 6A). In ascending order the following formations subcrop on site: Machias Shale, Cuba Sandstone and Wellsville Shale. The site is situated on the northwest limb of a northeast trending anticline. Strata dip to northwest at approximately 1 degree.
Groundwater Flow: A perched water table exists in the ablation till profile in the valley center. The perched groundwater table is recharged by interflow and overland flow directed toward the valley center from the east, west and north. Along the axis of the valley, groundwater flows southward toward the intermittent stream.
Groundwater flow in bedrock is divided into two flow systems. A high elevation flow system contains a recharge area in open pastures upgradient (east) of the site. The discharge zone occurs at the spring line that marks the base of the Cuba Sandstone subcrop belt along the east side of the site. A second, deeper bedrock flow system occurs in the Machias Shale beneath the landfill footprint. Strong downward gradients are characteristic of the upper portion deeper bedrock system. The horizontal flow vector is directed primarily to the west/southwest. Westward flow on the east side of the till-filled valley is impeded by the gray till aquiclude. Consequently, artesian pressure builds in the deeper bedrock system in the southeast corner of the site. Hydraulic gradients in bedrock beneath the west side of the site are steeply downward. Flow diverges on either side of the topographic divide in the shallow rock profile beneath the western site boundary. Deeper flow in rock trends toward the west/southwest.

A2: SUBSURFACE GEOLOGY OF THE LOWER GENESEE RIVER VALLEY REGION: A PROGRESS REPORT ON THE EVIDENCE FOR MIDDLE
WISCONSIN SEDIMENTS AND IMPLICATIONS FOR ICE SHEET EROSION MODELS
RICHARD A. YOUNG
Department of Geological Sciences
SUNY College at Geneseo
Geneseo, NY 14454
LES SIRKIN
Department of Earth Sciences
Adelphi University
Garden City, NY 11530
INTRODUCTION
Deep bore holes and gravel pit exposures in the Genesee Valley region north of Avon (Figure 1 ,9) have provided a number of organic-rich sedimentary horizons that have been dated at the University of Arizona AMS facility in the range between 26,000 and >48,800 years BP. A majority of the finite age determinations lie within the interval from 30,000± to 43,700± years BP, implying a Middle Wisconsin age for the deposits sampled. Most of the materials dated were collected from buried glacial outwash, lacustrine sequences, or overridden peat incorporated in younger till. The stratigraphic relationships suggest that the dated materials are most likely correlative with the Plum Point and/or Port Talbot Interstadials best known from localities in Ontario, Canada.
The most likely timing of the main ice advance into the Genesee Valley, based on the average of the best constrained ages, is circa 35,000± years BP. This coincides with the recent revision of the H-4 Heinrich event (iceberg discharges) in the north Atlantic and the Dansgaard-Oeschger cycles seen in the Greenland ice· cores (Bond and others, 1992, 1993; Taylor and others, 1993).
Whether or not Middle Wisconsin ice crossed the south shore of Lake Ontario and advanced very far into western and central New York has been a controversial subject (Berger and Eyles, 1994; Dreimanis, 1992; Hicock and Dreimanis, 1992). The implied extension of the southern margin of Middle Wisconsin ice sheets into the Genesee Valley and the northern Finger Lakes region has obvious implications for global climatic reconstructions and for additional fine tuning of eustatic sea level curves for the interval represented.
The most diverse and best sampled sections are located in two adjacent sand, gravel, and clay pits in northern Livingston County on the west side of the Genesee River where Middle Wisconsin strata are covered.by only 20 to 40ft (6 - 12 m) of Late Wisconsin glacial drift. Preservation of these Middle Wisconsin sections in an area of low relief within the broad Genesee Valley raises theoretical questions concerning how the older unconsolidated sediments survived being overridden by the younger, Late Wisconsin ice advance, which extended about 125 km (76 mi) further south into Pennsylvania. The near surface outcrop location also raises the question of under what circumstances ice sheets scour deep, well-defined bedrock troughs as opposed to advancing across unconsolidated sediments with little apparent erosive impact.
The existence of such a complex Wisconsin section also raises the issue of what similar stratigraphic sequences may be present throughout upstate New York that might not have been recognized due to an absence of preserved or obvious organic horizons. The Middle Wisconsin sediments in the sections studied in the Genesee Valley are very similar in appearance to overlying drift units, and except for the fortuitously preserved organic horizons, the stratigraphy and field relations do not appear very dissimilar from numerous other glacial drift exposures across the region. It is possible that the glacial drift stratigraphy of the region preserves a more complex record of Middle (or older) Wisconsin events than has been assumed, especially within bedrock troughs such as the Genesee Valley and adjacent Finger Lakes.

A2: ROAD LOG FOR LOWER GENESEE RIVER VALLEY MIDDLE WISCONSIN SITES AND GLACIAL GEOMORPHOLOGY IRONDEQUOIT BAY OUTLET TO CANASERAGA VALLEY
Objective: The purposes of this trip are: 1) to visit the two sites in the Genesee Valley that have recently produced the evidence for a Middle Wisconsin glacial advance (-35,000 BP) to near the latitude of Avon, N.Y., and 2) to provide an overview of the glacial geomorphology created by Late Wisconsin ice withdrawal from the lower basin. The events that shaped the surficial geomorphology of the modern valley are clearly related to the major preglacial lake stages, lake outlets, and prominent moraines found from the Valley Heads Moraine near Dansville to the Pinnacle Hills Moraine in Rochester. The geologic setting of the valley can best be appreciated by referring to the review articles by Muller and Calkin (1993), and Muller and others (1988). The existence of shallow, Middle Wisconsin tills, outwash gravels, and lacustrine sequences close to the elevation of the modern flood plain within the broad, open valley pose obvious questions about mechanisms of Late Wisconsin ice erosion and the possibility that similar sections might be preserved elsewhere in central New York.

STOP 1. SITE OF BAYMOUTH SAND BAR BUILT DURING RISE FROM EARLY LAKE ONTARIO
This location provides one of the few good overviews of the relief and topography of Irondequoit Bay, the baymouth bar, and their relationships to Lake Ontario. An orientation stop will be made here to view cross sections and large out-of-print and unpublished maps of geology and engineering projects used to interpret sections cored through the sand bar to depths of 380ft (116m). The geologic relations in the accompanying text Figures (2-8) will serve to focus the discussion. The Rt. 104 bridge can be seen spanning the bay 1.5 miles to the south. Eighteen deep exploration boring logs provide a detailed cross section view at the bridge (Kappel and Young, 1989) to compare with the subsurface stratigraphy cored by water test wells and bridge foundation borings at the sand bar.
The long bluffs to the southeast (nearly parallel to the bar), which dominate the anomalous northeast trend of the adjacent Bay shore appear to represent the north edge of an unnamed moraine potentially correlative with the Carleton Moraine to the west. An ice-contact feature in this position would reasonably account for the unusual and abrupt change in the shoreline trend near the mouth of the Bay. Gravel pits formerly present on the south edge of this northeast-trending ridge exposed coarse gravel and sand sequences with a southerly dip (now under Stony Pt. development), presumably the outer margin of a kame moraine complex. Older topographic maps (1935) show the top of the bluffs to have been a low ridge bordered by a large irregular depression at its western limit.
A moraine of this age would have been closely associated with the withdrawal of ice near the time of Lake Iroquois, whose shoreline (elev. 435± ft) lies about a mile south of the moraine at the location of Ridge Road (Rt. 104).

STOP 2. KAME MORAINE FAN AND LACUSTRINE SEQUENCE ON SOUTH EDGE OF BURIED PINNACLE HILLS MORAINE
Walk down slope to Irondequoit Creek, proceed upstream to Bridge and cross to exposure of Kame moraine fan with lacustrine sequence at top.
The Pinnacle Hills Moraine (most prominent pre-Lake-Iroquois moraine) extends from the University of Rochester to near this location where it is largely buried within the older Irondogenesee Valley, covered by lacustrine sediments from contemporaneous and younger glacial Lakes Dana(?), Dawson, and Iroquois (Fairchild, 1928; Muller and others, 1988). The till portion of the moraine seems to divide the groundwater regimes of the upper and lower Irondequoit Basin. The subsurface extent of the moraine was studied in a series of borings in an attempt to define its effect as a groundwater barrier and is described in Kappel and Young (1989). Groundwater upstream of the moraine appears to be locally more saline (trapped road salt) than groundwater north of Browncroft Blvd. This stop will utilize the cross section Plates from Kappel and Young (1989) and Figures from Young (1988) to examine what is currently known of the moraine and the size of the buried valley.

Pinnacle Hills moraine can be seen clearly on right 2 miles to north (radio towers).

STOP 3. VIEW AREA OF MIDDLE WISCONSIN SECTION SHOWN IN FIGURES 9, 10,11 OF ACCOMPANYING ARTICLE.
The geology of this stop is the focus of the second half of the accompanying article. It is the only complex Middle Wisconsin exposure in New York with the range of different depositional units, organic horizons, and multiple ice advances recorded both in this pit and the DeWitt gravel pit immediately to the south. The site has changed markedly over the past 4 years due to rapid extraction since the peat horizon in the lower till was discovered by R.A. Young in November 1990. The major units and dated horizons have largely been removed, but most of the section from the "bone horizon" (Figure 10) upward is still visible (June 1994) and the only good wood specimen found to date was collected from the lower till during a summer 1994 visit (submitted to Arizona AMS Lab). The local deposits have been used to supply "clay" to the new Monroe County (Rochester) Mill Seat Landfill in Riga, thus accounting for the rapid excavation of the lower rhythmite section, largely below the present pit water table. The success of this visit will depend entirely on how much excavation or construction occurs during the 1994 summer season and how much remains of the section shown in Figure 10 between this writing (June 1994) and October of 1994.
The DeWitt pit immediately adjoining this site on the south will be included in the stop, either by hiking across both pits (water conditions permitting) or rejoining the bus for a short ride. Participants are cautioned to stay clear of all vertical bluffs where very large (and dangerous) segments of the clay and gravel units slump unexpectedly.
If conditions are favorable time spent at this stop may be extended and the remainder of the trip shortened to allow interested participants to adequately explore this important, but rapidly disappearing site.

Cross Conesus Lake outlet.

Fowlerville Rd. Delta on right built into glacial Lake Scottsville.

Moraine (hill) on left is site of mastodon find in 1989-90.

STOP 4. INFORMAL STOP ALONG ROUTE 39 OVERLOOKING VALLEY
A broad moraine complex arcs westward into valley (road follows crest for ~3 miles) marking late Wisconsin ice readvance. The moraine is undated but is thought to be approximately correlative with Alden, Buffalo, and Niagara Falls moraines (Muller and others, 1988). The moraine is difficult to see from any given point but fills the Genesee Valley between Geneseo and Avon (1:24 000 topo.), eliminating the broad flood plain characteristic of the Genesee Valley to the north and south of this reach.

Roots Tavern Rd. on right marks end of obvious moraine ridges on topographic map.

STOP 5. VIEW OF ALDEN MORAINE NEAR ICE POSITION THAT CREATED LAKE HALL (-1000 ft elev.)
Genesee Valley south of this latitude was filled by Lake Hall as the ice retreated from the Alden moraine. The drainage outlet was to the west through the prominent Pearl Creek outlet where a large delta was built into the Wyoming Valley. The next leg of the trip will descend into the Pearl Creek outlet channel and climb out to the south, descending to the shoreline of glacial Lake Warren near elevation 845 ft.

STOP 6. STOP AT LAKE WARREN BEACH WITH VIEW EAST INTO GENESEE VALLEY
Glacial Lake Warren was the last large glacial lake embayment extending southward into the Genesee Valley from an ice front position near the NY State Thruway between 13,000 to 12,600 BP (Muller and Calkin, 1993). The shoreline presently indicates a relative postglacial uplift to the north of approximately two feet per mile between Geneseo and Victor, New York. Lake Warren shoreline features can clearly be seen along both sides of the Genesee Valley on aerial photographs southward to the latitude of Letchworth Park, whereas no other glacial Lake shorelines are still as obvious or continuous.

A3: GEOLOGY OF THE ERIE CANAL, ROCHESTER GORGE, AND EASTERN MONROE COUNTY, NEW YORK STATE: IN THE FOOTSTEPS OF AMOS EATON AND JAMES HALL
THOMAS X. GRASSO
Geosciences Department
Monroe Community College
Rochester, New York 14623
RICHARD M. LIEBE
Department of Earth Sciences
SUNY Brockport
Brockport, New York 14420
INTRODUCTION
The Phelps and Gorham Purchase, from the Seneca Nation in 1788, opened the lands west of Seneca Lake for settlement. Westward migration began as a trickle, but with the coming of the Erie Canal to the Genesee Country in 1822-23, a flood of immigration occurred that transformed western New York from dense forest to farmland, villages, and cities. For example, Rochester's first permanent settler did not arrive until 1812 while real growth blossomed in the 1820's. From the colonial period to the opening of the canal the west began at Schenectady.
The growth of geologic thought followed a similar pattern. A few random notices and sketches were made early on, primarily by army officers serving during the colonial wars and the Revolution. The Erie Canal changed all that. The surveys for the proposed project required organized, detailed, observations of the terrain and its underlying geology. Enter now DeWitt Clinton whose 1810 chronicle of a journey across the state, along with other writings, records numerous observations and interpretations of the geology from Albany to Buffalo. However, it wasn't until the seminal work of Amos Eaton (Father ofNew York Geology) in 1824 (A Geological and Agricultural Survey of the District Adjoining the Erie Canal in the State of New York) that a comprehensive and amplified attempt was made to unravel the superposition of western New York's strata. The foundation he laid ultimately led to the founding of the State Geological Survey in 1836. The following year James Hall came to the Genesee Country and examined its fossiliferous strata. Hall's work from 1837 to 1843 finally unraveled the stratigraphic column of western New York as we know it today, save for some modern refinements. This paper attempts to show the evolution of geological investigations in Eastern Monroe County and Rochester as revealed in the writings and quotations of Amos Eaton and James Hall. The Erie Canal, its history and geology, and the geology of the Rochester Gorge are equally main themes as they provided the framework for the development of geologic thought.
In 1826 Amos Eaton led an expedition by canal boat across New York State. The surviving journals of two of the participants, George W. Clinton and Asa Fitch, provide unique insights into the state of geological knowledge, the nature of the landscape, and human development in the region at that time. These are quoted throughout the text but more liberally so in the roadlog. The writings of James Hall and to a lesser extent Sir Charles Lyell, are included to illustrate the degree of scientific advancement in the score or so years following Eaton's labors.
The paper is divided into five major subdivisions including the roadlog. The life, geological thoughts, and contributions of Amos Eaton is followed by a section on James Hall which contains a brief description of the rise of the New York State Geological Survey. The middle portion is devoted to the history and geology of the Erie Canal and its impact on New York State. With all of the historical perspectives in place the paper proceeds to the site specific, fourth, section-a discussion of Rochester and the Rochester Gorge. Finally the roadlog and boat trip is devoted principally to retracing the route of Amos Eaton's 1826 tour to the Rochester Gorge. The journal entries of the participants illuminate what travel was like at that time as well as highlighting Eaton's personality and ideas. Here Eaton's geology is contrasted with that of James Hall along with today's interpretation of the stratigraphic sequence and glacial topography. Hall's ideas are revealed in his 1837 field notebooks housed in the New York State Library in Albany and of course his monumental 1843 Survey of the Fourth Geological District.

A3: GEOLOGY OF THE ERIE CANAL, ROCHESTER GORGE, AND EASTERN MONROE COUNTY, NEW YORK STATE: IN THE FOOTSTEPS OF AMOS EATON AND JAMES HALL

Pinnacle Hill with TV transmitters on top on left at intersection of Clinton Ave.

I-590 is on alignment of Old Erie Canal.

Cross Erie Canal

Route East to Macedon offers many fine vistas of drumlins and other glacial features.

Cross alignment of Old Erie Canal. Old Lock 61.

Lock 30 (Macedon Lock) on the Barge Canal.
Lock 30 has a lift of 17 ft. (5 m) West and was completed in 1916.
Board canal boat SAM PATCH for Lock 32 (Pittsford Lock) west of Pittsford. (There is no Lock 31 ).

Head ofLock 30.
The Erie Canal here partly restored the flow of the ancient Great Lakes (and pro glacial) waters through the Fairport meltwater channels. From here to Fairport the canal route follows the main meltwater channel.

Old Erie Canal channel veers left (S)
Old Erie Canal channel veers left (S) of the present canal through the hamlet of Wayneport. Start of widewaters created by Barge Canal construction which allowed water of present canal to back up against old canal bed.

Old canal loop enters present alignment - west end of widewaters.

Lynden Road Bridge
This site was known as Knappville -a sleepy community in old canal days.

Fairport (Main Street) lift bridge (1914-1915)
One of sixteen between here and Lockport and the first one west of the Hudson River on the Erie Canal. Daniel and Hemy Deland established the Deland soda and saleratus (baking soda) chemical works on north bank of the canal just east of this bridge in 1852. It burned in 1893. The Box Factory and Village Cafe occupy the site.

NY31 bridge over canal.
This site was known as Fullamtown in Amos Eaton's time as Elisha Fullam, in 1822, built a tavern and warehouse here along with other buildings. Travelers proceeding west to Rochester often transferred to stagecoach at Fullamtown as the overland route was 8.5 miles (13.7 km) shorter.

Start of the Oxbow on left (E)
A large loop ofClinton's Ditch that was cutoff when the enlarged Erie was constructed through here circa 1855.

Site of Bushnell's Basin canal break in November 1974.
Canal washed out due to collapse of a sewer tunnel being bored beneath the canal. Navigation was not restored until late 1975 ... nearly a year later.

East (SE) end of the Great Embankment.
The Erie Canal vaults Irondequoit Valley nearly 60 feet (18 m) above the valley's floor. A culvert nearly 500 feet (152 m) long conveys Irondequoit Creek beneath the embankment. The passage high above the surrounding terrain was sharply curved at its western end (NW) as it followed the serpentine crest of the Cartersville Esker. Dryer (1890, p. 203) described it as a "kame which extends from Cartersville on the west to and beyond Bushnell's Basin on the east. The north end is a sharp ridge of very coarse gravel, fifty feet in hight [sic], one mile long and in shape like a rude fish-hook ..... Irondequoit river ..... has cut the kame completely in two. In the southern portion the gravel is overlain by fifty feet of fine sand which spreads out toward the southeast ..... The Erie Canal avails itself of this kame to cross the valley and by a fifty foot embankment restores what probably once existed as a natural feature." Upham (1893, p. 190-191) described the feature as part of an esker and kame belt " .... from a point about a mile east-southeast of Pittsford village to its termination about a mile southeast and south of the village of Bushnell's Basin ..... " Fairchild (1896, p. 135-136) described it fully beginning with ......"nearly opposite Cartersville and north of Bushnell's Basin is a conspicuous esker ..... " Giles (1918, p. 208-211) named the Cartersville Esker and included a contour map of its northwest portion near Pittsford.
The "rude fish-hook" part of the embankment was deemed too sharp for tugs and barges during Barge construction. Therefore, a new great embankment was built cutting off the esker loop and straightening the canal's alignment. The old loop is still marked by a line of trees north of the present canal.
The new embankment was begun in 1908 and completed in the spring of 1912. The original part of the older embankment over Irondequoit Creek was also modified at this time. In October, 1912, the Great Embankment over Irondequoit Creek collapsed down to the level of the creek in the worst canal breach of its history in this district. Water leaking through the new concrete floor eventually weakened the Irondequoit Creek culvert until it collapsed. Within a few weeks the breach was dammed at each end and a temporary wooden flume erected on piles 60 feet (18 m) high to convey canal boats across the break until the embankment and culvert could be rebuilt. This was accomplished in 1918. The south (SW) wall of the current trough bows outward where the flume used to be as the engineers poured the new wall around the flume. They removed it in the winter of 1917-1918 to pour the new concrete floor. Small tunnels (galleries) were built into the new structure to channel off any leaks and to permit visual inspection. This part of the embankments has held ever since.

West (NW) end of Great Embankment.
When Eaton's party crossed the embankment in 1826 blowing sand prevented them from having a good view of the Great Embankment

Mitchell Road bridge.
The Clinton's Ditch Pittsford Lock (Lock 73) was located just southeast of this bridge. The LAFAYETTE locked up through here on Saturday May 13, 1826.

NY31 bridge -Enter Pittsford
Between this bridge and the Main Street bridge is the Schoen Place district. In the later part of the 19th century and into the 20th century lumber yards, a malt house, and warehouses lined the south side of the canal while coal sheds, a flour mill, and fruit evaporators were located on the north side. A grain and bean processing mill and Pittsford Lumber Company still survive on the north side amid the rows of boutiques, shops, and restaurants.

Conrail bridge.
The south abutment of the bridge rests on the Barge Canal Bed of the Vernon Formation of Ciurca (1990). It is the youngest of four eurypterid bearing horizons in the lower 100 feet (30 m) of the Vernon Formation. When the canal is drained in the winter the exposure reveals several feet of black shale grading upward into greenish shale. The fauna consists of Eurypterus pittsfordensis and rare Mixopterus remains.
The other horizons, in order of superposition are the Harris Hill Bed, Monroe Ave Bed and the Pittsford Bed. Ciurca equates the "Gananda Bed" of Hamell (1978) with the Barge Canal Bed although the two are 10 miles (16 km) apart.

NY31-Monroe Avenue bridge.
The state maintenance shops near the west end of the bridge were built around 1928. Clinton's Ditch ran on the south side of the canal from here to Lock 32.

The Old Erie Canal veers north
The Old Erie Canal veers north towards Monroe Avenue and downtown Rochester. The present channel from here to Greece was opened in 1918.

Cross alignment of Clinton's Ditch in its northward course to downtown Rochester.

Clover Street (NY65) bridge and Lock 32.
Lock 32 (1917) is the third Pittsford Lock. The first, Lock 73 (1822), was located near the Mitchell Road Bridge; the second, 0.9 mile (1.5 km) north of here is the Enlarged Erie Lock 62 (STOP 1). Lock 32 has a lift of 25 feet (7.5 m).

Cross alignment of Old Erie Canal.
In World War II landing craft were built on the south side of French Road in the old canal.

STOP 1. Enlarged Erie Pittsford Lock 62 and Pittsford Shale.
Lock 62 had a lift of 9.2 feet (2.8 m), going west, and was completed as a single chamber, enlarged lock (110 feet by 18 feet; 33.5 m by 5.5 m) by Jesse Petersen in 1855 for $26,260.77. It was doubled by James Wiltsey in 1873 for $34,269.19. At the upper end of this second chamber a drop gate was installed instead of the typical vertically hinged miter gates. This new type of lock gate was horizontally hinged and operated like a draw bridge so that when it was open it rested upstream on the floor of the canal. It was the invention of George Heath and was called Heath's Tumble Gate. They were installed on many Enlarged Erie Locks. The lock was lengthened in 1887-1888 to permit the passage of double headers (two boats lashed together) by B.T. Smith for $25,021.26. The final improvement came in 1890 when a water powered turbine, propelled by the overflow water, was installed at the base of the vertical shaft at the head of the lock. The turbine was in turn connected to geared shafts that operated rope cables wound around capstans and winches which then pulled boats in and out of the locks. These appliances were installed by Nicholas and William Wewple for $1,100. Lock 62 was abandoned at the end of the 1920 season.
Walk along the drive a few hundred feet north of Lock 62 at the base of the canal embankment behind Wegmans.
Pittsford Shale -Several feet of black shale and thin dolostones are exposed here. Ciurca (1990) has redefined the Pittsford Shale restricting it to only the eurypterid-bearing black shale and associated dolostones and renaming it the Pittsford Bed. The Pittsford Bed bears enormous numbers of the eurypterid Hughmilleria socialis along with Eurypterus pittsfordensis, Pterygotus monroensis, and several other non eurypterid species.

I-590 is built on the alignment of the Old Erie Canal.

Old Erie Canal Lock 65 (Reservoir Lock) on right.
It had a lift of 8.8 feet (2. 7 m) going west. This was one of the five locks (Locks 62 through 66) east of Rochester that locked westbound boats up to the aqueduct level. Lock 66 was just west of Monroe Ave. and was the last lock west toward Lockport. Locks 32 and 33 on the Barge Canal accomplish the same task today. Clinton's Ditch took a large loop to the south here hugging the base of Cobbs Hill. Enlarged Erie construction cut off the loop thereby creating large "widewaters" between the new towpath and old canal bed. Lock 65 was at the east end of this "reservoir". Lake Riley in Cobbs Hill Park is all that remains today.

STOP 2. Genesee River, Aqueduct, Court Street Dam.
Just downstream from the Court Street bridge was the head of the 14 foot (4.3 m) cascade that was the original Upper Falls of the Genesee River at Rochester. They were blasted to make way for the first Erie Canal Aqueduct.
Farther downstream is the Broad Street bridge resting on the Enlarged Erie Canal Aqueduct made of Onondaga Limestone and built from 1836 to 1842 by Josiah Bissell for $445,347. When it was completed it had an interior width of 43 feet (13 m), a length of 800 feet (244 m), and was the third longest of the 32 aqueducts on the entire line of the canal. This structure replaced the Clinton's Ditch aqueduct that was just to the north. The original aqueduct was completed in 1823, had an interior width of only 17 feet (5 m), and was constructed of Grimsby Sandstone. This is worth noting because all other Old Erie Canal aqueducts had wooden trunks supported by stone piers, with arches only on the towpath side for its support. The engineers opted for the stone design due to the severe floods on the Genesee River before the Mount Morris Dam was completed in 1953 (Figure 12). The deck that supports Broad St. was built in 1924 and rebuilt as it stands today in 1974.
Upstream from the Court Street bridge is the Court Street Dam, called a sector dam because each gate is a pie shaped section of a circle. Gates are hinged at the base of the downstream side of the structure and float in a chamber notched into the bed of the river. The level of the water in this submerged chamber can be raised or lowered thereby controlling the gates and the pool above. The dam was completed in 1917, as part of the Barge Canal construction for the canal's Genesee crossing south of here at Genesee Valley Park. RG&E generates hydroelectric power at the west end of these structures.

Cross Broad Street.
The 1826 travelers put in at Child's Basin, located where the bank is today at the northeast corner of Broad and Exchange Streets.
Eaton's party arrived at Rochester on Sunday, May 14th. George Clinton walked back on the canal about one mile to examine some "lime rock" [Lockport] along the banks, finding fluorspar in it. Clinton wrote:
"In the afternoon visited the falls and procured specimens of the saliferous rock [Queenston, Grimsby], grayband [Kodak], ferriferous slate, [Maplewood], iron rock [Seneca Park], ferriferous sandrock [Reynales] ... At this place . . . the geodiferous limerock [Lockport] and the calciferous slate [Rochester] meet, the latter becomes geodiferous."

STOP 3 Penfield Formation, Lockport Group in the Genesee River
Stop at drive leading down to the back of the Convention Center and RG&E Water Street Substation just north of Broad Street. Follow the path, through the gate between the aqueduct and the south end of the RG&E brick building.
At the river level several feet of crinoid rich, coarse grained, sandy dolostone of the Penfield Formation may be examined. Ripple marks on the tops of some beds. The Penfield grades into the crinoidal Gasport Limestone and Goat Island Dolostone of the Niagara Region. These ledges are all that remain of the original Upper Falls.
The RG&E building rests on the original 1827 foundation of Hervey Ely's flour mill. Across the river in the park was the original site of Indian Allen's 1789 mill. Upstream, through the arches of the aqueduct, the Court Street dam can be viewed.

STOP 4. Lower Falls
Eaton's entourage arrived at the west side of the Lower Falls on Monday May 15, 1826. Asa Fitch recorded that they stopped at the Upper Falls on route but could only see a small portion of them from the west side. Arriving at the Lower Falls at 10:00 AM they stayed until 2:00PM. On the west bank Amos Eaton, upon his arrival, gave a lecture on the strata " ..... could see the rocks clearly. They are 1st Saliferous rock [Queenston, Grimsby], 2nd Grayband [Kodak], 3rd Ferriferous slate [Maplewood], 4th Ferriferous Sandstone [Reynales]. .... " "Swam across Genesee River twice about 1/2 mile above falls 1.25 mile wide ..... " George Clinton noted (p. 289): "Is not Mr. Eaton's ferriferous sandstone rather poorly characterized. Some of the layers resembled shell limestone, contain petrifactions, and effervescing strongly with acids; others exactly resembled in external appearance the calciferous sandrock [Little Falls Dolostone, Tribes Hill Formation] obtained at Nose Hill [the Noses east of Canajoharie] and contained the same imbedded minerals, viz. homstone, chalcedony, semiopal and agate. Is he right in considering shell-limestone, vermicular limestone and gypsum as mere beds in calciferous slate?"
The Genesee River, diverted from its preglacial outlet through nearby Irondequoit Bay, has carved a post-glacial gorge approximately two hundred feet (62 m) deep during the past twelve thousand years. The strata revealed in the Rochester Gorge at this section are Upper Ordovician to Middle Silurian, overlain by Pleistocene till. James Hall, along with A.W. Grabau, named and described several of the formations in the gorge including the Rochester Shale, the first formally designated stratigraphic unit in North America (Brett, 1983).
The oldest unit in the gorge is the Upper Ordovician Queenston Formation, a series of brick-red, thin bedded shales and siltstones with several sandstone layers near the top (Figure 21). Although only the upper 50 to 60 feet (15-18 m) are exposed here, the Queenston Formation is more than 1,000 feet (300m) thick and underlies much of the Lake Ontario Basin. The Queenston Formation represents extensive nearshore deltaic deposits, which covered much of the northern portion of the Appalachian Basin during Upper Ordovician time. This paleoenvironmental determination is based on well preserved sedimentary features including cross-stratification, ripple marks of both current and oscillation types, desiccation features including mud cracks, mud-chip pebble conglomerates, and sole marks (Liebe and Grasso, 1988). Following deposition of the Queenston, an interval of emergence prevailed, and a major erosion surface called the Cherokee Unconformity (Figure 17), widely traceable in eastern North America, was formed.
The overlying Grimsby Formation (also known as the "Red Medina") is a series of red-green mottled sandstones and silty shales. In his 1837 field notebook Hall originally described this unit (and the Queenston) as "sandstone, variegated, red and green, with fucoids." The base of the formation is marked by a massive 10 foot (3m) coarse grained sandstone interpreted by Martini (1972) as a "low energy beach and/or bar(?)" deposit. This unit is overlain by a "Highly burrowed sequence of high tidal flat-flood plain or lagoonal environment which is cut through at times by shallow distributary channels and/or tidal channels" (Martini, 1972). Intraformational conglomerates and mud cracks are common. Fossils are rare in the formation, but specimens of the inarticulate brachiopod Lingula have been found elsewhere, and some of the massive sandstones near the middle of the unit contain excellent casts of the trace fossils Arthrophycus alleghaniensis and Daedalus archimedes (Hall's fucoids). The conspicuous bioturbated (burrowed) zone, 12 feet (4 m) below the Kodak Sandstone apparently correlates with the Thorold Sandstone of the Niagara Gorge (Brett et al., 1990). The origin of the prominent color mottling is not clearly understood; however, the green splotches are generally thought to represent the irregular alteration of ferric iron to the ferrous state by either downward percolating ground water or the presence of disseminated organic material (Liebe and Grasso, 1988).
The Grimsby Formation grades into the Kodak Sandstone, a 6 foot (2m) thick, massive, fine grained, bioturbated gray sandstone. Hall, in his initial work in the Rochester Gorge, followed Eaton and described this unit as the "grayband", a coarse, gray sandstone which was harder than the underlying sandstones and less destructible. At one time the Kodak Sandstone was thought to be correlative with the Thorold Sandstone in the Niagara Gorge. Work by Brett et al. (1990) recognized that these units are two distinct sandstones separated by 10 feet (2-3m) of red and green shale, informally known as the Cambria Member of the Grimsby Formation. This coincides with the work of Chadwick (1935) and Fisher (1966) who used the name Kodak for the prominent formation that forms the caprock of the Lower Falls.
The basal unit of Sequence II is the Maplewood Shale, a smooth, platy, in-part calcareous shale that unconformably overlies the Kodak Sandstone. This unit was described by Hall in his field book (1837) as a "ferriferous slate, soft and green, contains a few shells, and near its limit below, a very thin stratum, sometimes two, composed almost wholly of shells" In addition to these thin limestone layers, phosphatic pebbles are common, especially in the basal portion. The Maplewood is approximately 21 feet (7 m) thick here but becomes much thinner to the west where it is correlative with the Neagha Formation in the Niagara Gorge. Both formations are thought to represent either quiet, offshore marine or lagoonal deposits as part of the initial flooding of the transgressing Sequence II sea into the Rochester area.
The youngest unit exposed along the access road to the Power Station is the Reynales Formation, although Hall (1843) first designated this unit the "Pentamerus Limestone" for the numerous pentamerid brachiopods present. The Reynales Formation consists mainly of21 feet (7 m) of gray, crystalline limestone or dolomitic limestone with numerous shale partings and is divided into three members. The lower member, the Brewer Dock Limestone 3 feet (1 m), is separated from the upper Wallington Limestone Member by the well known Seneca Park Hematite (1 foot; 0.3 m). The Seneca Park was previously known as the Furnaceville, but recent mapping by Brett et al. ( 1990) revealed that the iron ore in the Genesee Gorge is actually at a higher stratigraphic horizon than the type Furnaceville in Wayne County and, therefore, cannot be the same unit. The Seneca Park Member was originally deposited as a fossiliferous limestone. The hematite has since replaced most of the calcium carbonate; however, samples will still effervesce when acid is applied, indicating much of the original carbonate material remains. The mechanism and time of replacement are much debated, but consensus seems to favor a penecontemporaneous alteration of the original fossiliferous limestone by iron-rich solutions from streams descending the iron-rich Taconic landmass located in eastern New York State at that time.
The Wallington Member (17 feet; 5 m) is a coarse grained, fossiliferous limestone, with beds of the smooth shelled brachiopod Pentamerus, as well as corals and bryozoans. The combination of dense strata packed with fossils and the replacement of some of the fossils and beds with chert make this unit particularly resistant, well suited to form the cap rock of the Middle Falls. The Reynales Formation then represents a shallow, clear water, offshore marine deposit of Sequence II.
Visible along the walls of the Rochester Gorge, but not easily accessible at this locality, is the upper member of Sequence II, the Sodus Shale, as well as the Williamson Shale and Irondequoit Fm. (Sequence VI) and the Rochester Shale (Sequence V). The latter unit, as well as the overlying Decew and Lockport Dolostone (Sequence VI) will be seen at STOP 5.

Lower and Middle Falls on left.

STOP 5. High Falls (Upper Falls), Browns Race
Although visually attractive to visitors, the High Falls could rarely be seen as industrial development along Matthew and Francis Brown's mill race blocked the view. It was sometimes said that Rochester had developed the river, for commercial purposes, to such a degree that the best view of the river and its falls could only be had from the back door of a factory or mill.
The upper part of the Lewiston Member is exposed in the lowest part of the gorge's east wall below the Upper Falls while the Burleigh Hill Member of the Rochester Shale forms the conspicuous bulge in the middle portion (Figure 24). The overlying 25 feet (8 m) of the Gates Member makes up the upper portion of the gorge walls downstream from the Upper Falls while its uppermost beds form the brink.
The Decew Formation is exposed upstream from the lip of the falls, in the uppermost 6 to 10 feet (2 to 3 m) of the east side of the gorge just downstream from the falls and on the west side at the base of the stone wall, where the enterolithic structure is clearly discernible, (north wall of the Kidd Iron Works) east of the water wheel. Another exposure is at the top of Falls Street just north of its intersection with Brown Street.
Walk along Brown's Race Street to view Brown's Race at Commercial Street. From here walk east on Commercial Street and opposite the High Falls Parking lot climb the embankment to the railroad. Walking east cross the river on the north side of the railroad bridge above the lip of the falls. Excellent vistas of the gorge and the historic district are obtained from this bridge. Continue walking east and then north along the railroad spur for Genesee Brewery to the Platt Street (Pont de Rennes) bridge (see Figure 32 for a 1910 view taken from this bridge) crossing back to the west side and returning to the starting point.

A4: STRATIGRAPHY AND FACIES RELATIONSHIPS OF THE EIFELIAN ONONDAGA LIMESTONE (MIDDLE DEVONIAN) IN WESTERN AND WEST CENTRAL NY
STRATIGRAPHY AND FACIES RELATIONSHIPS OF THE EIFELIAN ONONDAGA LIMESTONE (MIDDLE DEVONIAN) IN WESTERN AND WEST CENTRAL NY
CARLTON E. BRETT and CHARLES A. VER STRAETEN
Department of Earth and Environmental Sciences
University of Rochester
Rochester, New York 14627
The Middle Devonian Onondaga Formation of New York generally represents broad, carbonate platform facies that were deposited in the northern part of the Appalachian Basin during early to middle Eifelian time. Finer-grained, more basinal facies in central New York shallow laterally to the east and west into more biologically productive platform settings toward the Buffalo and Albany areas. Numerous biostromal to biohermal buildups, which include pinnacle reefs in the subsurface of southern New York, are rooted in the shallowest-water basal Onondaga facies.
Carbonates of the Onondaga Formation are characterized by calcarenitic to cherty to argillaceous limestones and minor shales deposited in a shallow epicontinental sea. The formation comprises a generally deepening-upwards succession, but apparently represents two major (third order) transgressive-regressive cycles. It is generally subdivided into four members across New York State (Edgecliff, Nedrow, Moorehouse, and Seneca, from the base upwards; Oliver, 1954; Rickard, 1975). A fifth member (Clarence) has been recognized only in western New York (Ozol, 1964; Oliver, 1966b); we herein designate the Clarence as a local facies of the Edgecliff Member.
The basal contact of the Onondaga Limestone is conformable in parts of eastern New York, but westward becomes unconformable and overlies increasingly older Devonian to Silurian strata. Throughout western and central New York State Eifelian-age strata are underlain by a major sub-Onondaga unconformity, commonly referred to as the Wallbridge Unconformity. The Wallbridge was recognized long ago by Sloss (1963), as one of the major sequence-bounding erosion surfaces in the Phanerozoic of North America. He used it to define the boundary between his Tippecanoe and Kaskaskia Megasequences. In actuality, the sub-Onondaga unconformity in Western New York State is a composite of two to three distinct erosion surfaces which are locally merged (Oliver, 1966c; see below). The nature of the upper contact has long been debated; it appears to represent a westward-younging, sediment-starved, submarine unconformity below overlying black shales at the base of the Middle Devonian Hamilton Group.
Underlying the Onondaga Formation in some parts of west-central to western New York are quartz arenites and minor carbonates of the upper Lower Devonian Tristates Group. These rocks, which include strata equivalent to the Oriskany Sandstone and/or the Carlisle Center and Schoharie Formations of eastern New York, occur sporadically across the region. In the Buffalo region a westwardly-thickening wedge of cherty limestone (Bois Blanc Formation) appears and thickens into southern Ontario.
Limestones of the Onondaga Formation (Figure 1) represent relatively tabular, clean, dominantly biogenically-derived sediments deposited in the northern part of the Appalachian Basin during a period of relative tectonic quiescence. Underlying and overlying clastics (Lower Devonian Tristates Group and Middle Devonian Hamilton Group, respectively) represent terrigenous sediments shed from a rising mountain belt in New England during two separate active "tectophases" of the Devonian Acadian Orogeny (Ettensohn, 1985). The concentration of altered volcanogenic strata (Tioga Bentonites/Ash Beds of Dennison and Textoris, 1970, 1978, 1987) in the upper part of the Onondaga Limestone heralds the progradation of clastic sediments into the Appalachian foreland basin.
Interestingly, the area of maximum erosion and, presumably greatest uplift, during pre-Onondaga Emsian time experienced an inversion of topography in the early Eifelian. The main basin axis during deposition of the Onondaga Formation was a northeast-southwest oriented trough of active subsidence that intersects the New York outcrop belt approximately at the location of the central Finger Lakes (e.g., Seneca Stone quarry between Seneca and Cayuga Lakes =Stop 6 of this trip), but which migrated eastward through the Eifelian.
In this paper we will examine the following: 1) a new detailed stratigraphy for the Middle Devonian Onondaga Formation and associated underlying strata in western to west-central New York; 2) the occurrence of the Tioga Bentonites cluster in the Onondaga Formation; 3) apparent lateral shifts in more basinal facies through Onondaga time; 4) a sequence stratigraphic interpretation of the Onondaga and underlying strata of the upper Lower Devonian Tristates Group; and 5) a new regional synthesis of the Onondaga Formation and equivalent strata in the northern and central parts of the Appalachian Basin (New York and Pennsylvania).
THE LOWER PART OF THE MIDDLE DEVONIAN MARCELLUS "SHALE," CENTRAL TO WESTERN NEW YORK STATE: STRATIGRAPHY AND DEPOSITIONAL HISTORY
CHARLES A. VER STRAETEN
DAVID H. GRIFFING
Department of Geological Sciences
State University of New York at Binghamton
Binghamton, New York 13902
CARLTON E. BRETT
A major succession of Middle Devonian siliciclastic rocks (Hamilton Group), which ranges from 90 m to approximately 1,000 m in thickness, overlies carbonates of the Onondaga Limestone all across New York. The lowest part of these clastics is composed of black shale-dominated strata with minor limestones, and eastwardly coarsening, more sand-dominated, progradational strata, presently referred to as the Marcellus Formation. The Marcellus Formation is the lowest of four formations in the traditional subdivision of the Hamilton Group in New York State (Cooper, 1930, 1933, 1934).
Part of this fieldtrip will concentrate on lower Marcellus strata, which across New York consist of black shales, some thin limestones, and in eastern outcrops, calcareous shale to sandstone facies. These strata range in thickness from zero to less than one meter southwest of Rochester to over 180 m in southeastern New York near Kingston (Figure 1). Recent detailed work across the state indicates that the lower part of the Marcellus Formation comprises a fifth major cycle within the Hamilton Group, which is best developed in eastern New York (Brett and Baird, in press). In addition, the fauna of this interval is distinctly different from that of underlying and overlying rocks. With this in mind, we would like to present an informal preview of a new revision of the lowest part of the Hamilton Group that recognizes the significance of these strata. The revised stratigraphic nomenclature will be formally proposed elsewhere. In this revised scheme, the "Marcellus Formation" will be raised to subgroup status and subdivided into three formations: 1) the Union Springs Formation (=lower part of the "Marcellus subgroup"); 2) the Oatka Creek Formation (=upper Marcellus subgroup basinal black shale-dominated facies of western to central New York); and 3) the laterally equivalent Mount Marion Formation (=upper Marcellus subgroup basinal black shale to shoreface sandstone facies of eastern New York). Uppermost Marcellus strata in eastern New York are represented by non-marine, fluvial-dominated sandstones of the Ashokan Formation (Rickard, 1975, 1989).
The transition from the relatively shallow marine carbonates of the Onondaga Formation to clastics of the Marcellus subgroup marks a substantial reorganization of the Devonian Appalachian foreland basin. Major changes in sedimentation, basin geometry, faunas, and paleoecology are associated with overdeepening of the foreland basin due to thrust load induced subsidence (Ettensohn, 1985a) and eustatic sea level rise (Johnson et al., 1985) during a second active tectophase of the Acadian Orogeny (Ettensohn, 1985a).
Apparent extinction of some of the endemic Onondaga faunas and immigration of two successive biotas into the Eastern Americas Realm from Arctic Canada and Europe, respectively, are recorded in rocks of the Marcellus subgroup (Koch, 1988). The first migration is marked by a unique brachiopod and coral fauna found in the newly redefined Union Springs Formation in eastern New York. The first appearance of the classic Hamilton Group fauna occurs in the lower part of the overlying coeval Oatka Creek and Mount Marion Formations across New York. In addition, an important world-wide "extinction-radiation-extinction" bioevent involving pelagic goniatite and dacryoconariid faunas, the Kacak-otomari Event, occurs through this same time interval (Chlupac and Kukal, 1986; Walliser, 1986; Truyols-Massoni et al., 1990).
Analysis of laterally persistent discontinuities and macrofossil "hash" beds within skeletal limestones of the Marcellus subgroup (specifically those in the Bakoven, Hurley (new), and Cherry Valley Members) indicates condensation by short-term events which reworked long-term, time-averaged accumulations. Although the limestones of the Cherry Valley Member comprise distinctly different facies and represent relatively deeper-water deposition, they share a similar origin with younger Hamilton Group limestone members (Griffing, 1994).

A4: STRATIGRAPHY AND FACIES RELATIONSHIPS OF THE EIFELIAN ONONDAGA LIMESTONE (MIDDLE DEVONIAN) IN WESTERN AND WEST CENTRAL NY

Cuts and quarry
Cuts in upper part of highly fossiliferous Penfield Dolostone (Middle Silurian Lockport Group}; Gates quarry in Penfield and Eramosa (Oak Orchard) Formations to left.

Cuts on right and in median in lower sandy dolostone of Penfield Formation.

Outcrops on both sides of highway in upper Penfield and basal Eramosa Formations.

Begin ascent of Onondaga Escarpment.

Camillus Shale (Upper Silurian Salina Group)
Camillus Shale (Upper Silurian Salina Group) cuts on Rte. 19 and adjacent road to right.

Buttermilk Falls
Walk down track to left (east) to Buttermilk Falls of Oatka Creek, a spectacular falls capped by Clarence facies of the Edgecliff Member of the Middle Devonian Onondaga Limestone.
2012: Railroad is gone, but the falls are still here.

Route to the LeRoy Bioherm Quarry
Randall Road, route to the LeRoy Bioherm Quarry, site of one of Sunday's trips (see Wolosz, this volume).

Mill Street on left
Route to Oatka Creek exposure of Onondaga-Marcellus contact.

Bacon Street on left
Route to Oatka Creek exposure of Oatka Creek Formation (type section) and contact with overlying Stafford Limestone of Skaneateles Formation.

Bethany-LeRoy Road on left
Road to classic Middle Devonian Hamilton Group localities.

Cross Black Creek

Berms of quarry visible on left.

STOP 1. GENESEE-LEROY STONE COMPANY QUARRY, STAFFORD.
This relatively large quarry provides an excellent overview of the middle and upper parts of the Onondaga Limestone (Clarence facies of the Edgecliff Member, Nedrow, Moorehouse and Seneca Members; see Figure 5 of Brett and Ver Straeten, this volume). This stop serves as a reference section for western facies of the Onondaga Formation.
The quarry operates in five main lifts. The lowest two are commonly below water level but the second is exposed during drier seasons. Walls of the sump pit below the second lift exhibit heavily cherty Clarence facies of the Edgecliff Member. The overlying platform displays numerous large, spheroidal, chert-replaced heads of Favosites which are overlain by a thin shaly parting. This contact is thought to represent the base of the Nedrow Member at Stafford. It is overlain by an approximately four m-thick interval with distinctly cyclic alternations of dark gray chert-rich micritic limestone and pale pinkish-gray crinoidal limestone with light gray chert and abundant rugose corals.
The next platform is floored by one of the most distinctive marker beds in the western outcrops of the Onondaga; a greenish-gray argillaceous limestone with skeletal hash of crinoids, bryozoans, and brachiopods in addition to abundant and diverse tabulate and rugose corals. Because of its shaly nature, well-preserved fossils are easily obtained from this bed. It is interpreted as a condensed, time-rich fossil bed within the Nedrow Member.
The base of the third lift (5 m high) consists of 1.6 m of dark gray, very cherty, micritic limestone that weathers shaly toward its top and is capped by a 5 cm-thick shale bed. This shale and overlying less cherty, coral-rich, light weathering limestone are also readily correlatable in the Stafford-LeRoy area. The interval is interpreted here as the upper portion of the Nedrow Member. The upper part of the cherty limestone and the 5 cm thick shale are thought to correlate with the lower, thick black shale bed of the upper Nedrow of central New York (Stops 5 & 6). The overlying light-weathering, slightly cherty limestone and succeeding thin shale appear to represent the white limestone and Schizophoria shale bed of the uppermost Nedrow Member as defined herein.
The third lift is capped by another persistent crinoidal hash and coral-rich shaly bed that forms a major platform in the quarry. An old road in the northwest corner of the quarry provides access up to some of the higher beds of the Moorehouse Member. Much of the lower parts of the wall consists of sparsely fossiliferous cherty micritic limestone with dark brownish gray chert. A particularly distinctive bed occurs approximately 1 m below the fourth platform of the quarry. This is a biostrome of thicket-type (fasciculate) rugose corals (Synaptophyllum and/or Eridophyllum). The light-colored corals contrast with surrounding large, dark gray, ellipsoid chert nodules. Slightly higher on the fourth platform, a variety of solitary and colonial rugosans and large favositids are exposed in the quarry floor. This coral-rich interval and immediately overlying crinoidal pack-and grainstones appear to represent the first of two major cycles in the Moorehouse. Slightly above the fourth platform is a distinctly non-cherty, slightly argillaceous and medium gray lime mudstone unit approximately 1.6 m-thick. This unit displays abundant spreiten of Zoophycos (which appear on weathered joint surfaces as gently curved laminae) and thin hash beds of brachiopods. This non-cherty interval weathers with shaly fissility and correlates to a middle Moorehouse shaly, "false Nedrow" interval that occurs widely throughout the Appalachian Basin (see Brett and Ver Straeten, above). It is sharply overlain by coarse-weathering, slightly cherty (pale gray chert) crinoidal pack-and grainstones of the upper Moorehouse, including strata that feature abundant large Paraspirifer brachiopods. This upper 3 m-thick interval comprises the Paraspirifer acuminatus zone recognized by previous workers. It represents the second major shoaling cycle of the Moorehouse. This crinoidal-rich facies yields excellent specimens of the crinoids Arachnocrinus and Schultzicrinus. Two prominent, clay-rich partings in the upper part of the Moorehouse (above the Nedrow-like shaly unit) represent the First and Second Cheektowaga Bentonites (Conkin and Conkin, 1979, 1984; Conkin, 1987; 2.7 and 0.5 m below the base of the Seneca Member, respectively).
Highest beds in the Stafford Quarry are in the Seneca Member of the Onondaga Formation. A distinctive, thick (ca. 20 cm-thick) clay bed that is traceable around the quarry represents the Tioga B or Onondaga Indian Nation Ash Bed that marks the base of the Seneca. The member is comprised of crinoidal wacke-to packstones with a relatively minor number of horizons of large, brownish-weathering chert nodules. The upper beds are exceptionally rich in brachiopods which tend to weather pale-cream to pinkish in color; Leptaena, Megastrophia, Atrypa, and Megakozlowskiella are all abundant here. No upper contact of the Seneca Member has been observed here. However, dredge piles of black shale south of the quarry suggest that the contact with the overlying Marcellus subgroup lies a short distance above the upper platform of the quarry at Stafford.

Cross over Oatka Creek
Falls over Stafford Limestone immediately north
of bridge.

Perry Road on left
Route to 5 or 6 large quarries in the Onondaga
Limestone along Perry Road and adjacent Gulf Road.

Village of Limerock
Site of famous stone fences where paleontologists since James Hall have collected crinoids and other fauna of the Onondaga Formation.

Eastward access to Onondaga quarries along Gulf Road to
north.

Quarry Road on Right
Old quarries in Onondaga down the road.

Descend onto floodplain of the Genesee River.

Junction with Wadsworth Avenue
South to classic Middle Devonian Hamilton Group outcrops.

View of three drumlins to the left (north).

Cross Works Road
Small outcrop of Onondaga Limestone on right along Works Road.

Diagonal joints beautifully exposed in lower Moorehouse to left.

STOP 2a. lower part of Honeoye Falls quarry.
This relatively large and active quarry in the southeastern corner of Monroe County exposes an essentially complete section of the Onondaga Limestone and lower strata of the Marcellus Shale subgroup, including the Cherry Valley Member (see Figure 5 of Brett and Ver Straeten, this volume). Strata in this quarry are slightly deformed (Alleghanian?), and rocks display a gentle dip roughly to the south at a steeper angle than the regional 0.5° dip. Two prominent sets of nearly vertical joints occur in the quarry; the middle portion of the Onondaga also shows a distinctive pattern of diagonal jointing oriented at approximately 080-31 S and 080-50 S. The Honeoye Falls quarry is the only site in the western portion of the state that displays the entire Onondaga Formation (although the Edgecliff Member is only poorly exposed). The Onondaga Limestone at Honeoye Falls is typical of western exposures. The quarry is particularly notable for the unusually coarse facies of the Cherry Valley Member (Oatka Creek Formation) and for the distinctive channeling beneath it that in places chops out nearly the entire Union Springs Formation.
Mining operations work from six main lifts in the Honeoye Falls quarry. The lowest rocks exposed occur in a small, approximately 6.5 m deep sump pit in the northeast portion of the quarry. These rocks are rarely well exposed, commonly covered by water or by a muddy coating. The Upper Silurian (Akron Formation) - Middle Devonian (Onondaga Formation) unconformity is reportedly present in the lower part of the pit (General Crushed Stone Corp. records) although, based on regional trends, we would estimate the contact to lie some meters below. The sides of the small pit are composed of the cherty Clarence facies of the Edgecliff Member. The walls of the overlying larger pit expose a complete section of the Nedrow Member. The base of the Nedrow essentially forms the floor of the large pit in the northeast area of the quarry. Overlying micritic limestones interbedded with more fossiliferous crinoidal wacke-and packstones are characterized by alternating light gray and dark cherts. The middle part of the member features two distinctive subunits; lower, relatively coarse crinoidal pack-to grainstones with scattered corals, somewhat similar to the Jamesville Quarry facies of the Edgecliff Member, and a distinctive interval of greenish-gray argillaceous limestones and green shales 2.8-3.4 m below the Nedrow-Moorehouse Member contact. The green shales are rich in coral and crinoid material, and are correlative with similar strata at the Stafford quarry (Stop 1). The top of the green argillaceous interval occurs at the top of the second wall and forms the base of the third main platform within the quarry, similar to the Stafford quarry. Ellipsoidal and elongate nodular to bedded cherts, which may feature dolomitic rinds, occur scattered throughout generally light gray micrites of the upper Nedrow. A prominent hackly dark chert bed 1.6 m above the green argillaceous interval is probably associated with a prominent, dark to black shale in the upper Nedrow noted widely throughout parts of New York and Pennsylvania.
The Moorehouse Member, as defined herein, begins 2.8 m above the base of the third lift and is relatively thick at this locality (ca. 17 m) Limestones in the lower portion of the member (ca. 5.5 m-thick) appear increasingly fine-grained up to the level of the fourth lift. Nodular chert bands and several layers of bedded, hackly-breaking chert are common. Thin shaly to clay-rich interbeds are also found. Faunal diversity is rather low through the lower part of the Moorehouse.
The middle to upper parts of the Moorehouse at the Honeoye Falls quarry show a general coarsening-up trend. The upper part of the member is generally inaccessible in the high walls of the south face of the quarry, below the Onondaga Indian Nation bentonite (OIN;= Tioga B of Way et al., 1986). Comparison with nearby sections (e.g., Stafford quarry, STOP 1) indicate a rapid coarsening up above a thick, notably more argillaceous unit that occurs above the middle of the Moorehouse (this argillaceous unit is widely recognized across the Appalachian Basin throughout New York and Pennsylvania into at least northern West Virginia; see discussion in Brett and Ver Straeten, above). Where accessible the upper beds of the member are highly fossiliferous and yield well preserved brachiopods and some crinoid crowns (particularly Arachnocrinus) on weathered surfaces. These strata represent the coarsest facies of the upper part of the Onondaga Formation.

STOP 2b. Upper part of Honeoye Falls quarry.
The Tioga B (Onondaga Indian Nations bentonite) forms a prominent break within the quarry at the base of the overlying Seneca Member. The Seneca is characterized by 6.6 m of dominantly tabular wacke-to packstones with minor pale gray cherts. Thin clay-rich partings, most notably at 1.75, 3.05, 3.95, 4.7, and 5.4 m above the base of the Seneca, represent altered volcanic ashes (K-bentonites). The upper bed of the Seneca Member, which consists of relatively coarse crinoidal and brachiopod rich limestone is capped by a sharp lithologic break with the overlying Union Springs Formation.
A thin, mm-scale black shale at the Onondaga-Union Springs contact overlies a relatively minor but widespread submarine unconformity across New York. Overlying strata comprise basal deposits of the Middle Devonian, siliciclastic-dominated Hamilton Group. Recent quarry operations in 1993-1994 have exposed a fascinating cross-section of lower strata of the Marcellus Shale subgroup (see Figure 7 and text of Ver Straeten et al., this volume). The rock exposed comprise the Bakoven and Hurley Members of the newly redefined Union Springs Formation and the Cherry Valley and overlying black shale facies of the also newly redefined Oatka Creek Formation. The Honeoye Falls quarry represents the westernmost known exposure of the Cherry Valley Member and underlying Union Springs strata in New York State (NOTE: terminology used for Marcellus strata above the Onondaga Formation in this field trip guide follows the as yet informal stratigraphic revision presented in Ver Straeten et al., above).
A 15 cm-thick coarse, biotite-rich tuff of the Tioga F bentonite bed immediately overlies the thin skim of black shale at the Seneca-Bakoven Member contact. Overlying thin styliolinid limestones and black, platy, laminated shales of the Bakoven represent deposition under relatively deep, oxygen-starved conditions. A prominent phosphatic fish bone bed that yields abundant conodonts and fish remains, including onychodid teeth and dermal armor of arthrodires (discussed above) occurs within the package of thin limestones above the Tioga F. The Bakoven Member varies in thickness from 7 cm to at least 1.7 m along the outcrop as a result of extensive channeling along the discontinuity surface at the base of the overlying Cherry Valley Limestone.
A relatively thin, light-weathering, richly fossiliferous limestone found toward the eastern part of the Union Springs-Oatka Creek exposures represents the widespread Chestnut Street submember of the new Hurley Member (Union Springs Formation). Pygidia and cephala of the proetid trilobite Dechenella haldemanni are the most diagnostic fossils from this unit. Also present are small to medium-sized brachiopods, auloporid corals, sponge spicules and calyces of the diminutive crinoid Haplocrinites. The upper and lower contacts of this bed are sharply defined.
Along most of the exposure the Chestnut Street submember appears to have been removed; along with varying amounts of the underlying Bakoven Member by an extensive, channeled erosion surface that underlies limestones of the Cherry Valley Member. The Cherry Valley is extremely variable in thickness in this quarry, ranging from just over 40 centimeters upwards to over three meters along 300 meters of outcrop exposed in fall 1993-spring 1994. It is represented a very atypical facies for the unit, which consists dominantly of crinoidal pack-to grainstones with lesser amounts of fenestrate bryozoan and styliolinid material. As previously stated, the basal surface of this unit is extremely irregular and the Cherry Valley appears to fill low spots cut into the underlying Union Springs Formation. In contrast to most other localities, cephalopods are generally not particularly common at this location, although poorly preserved conchs of Agoniatites as well as some orthoconic nautiloids (e.g., Striacoceras) have been obtained. The upper surface of the Cherry Valley Member is also quite sharp and distinct; it commonly appears as a pyrite-coated corrosion surface. It displays an abrupt contact with overlying black shales assignable to the Berne Member.
To date, the highest beds observed in the quarry consist of barren, black, laminated shales with minor styliolinid hash beds. This interval at nearby localities (e.g., bed of Oatka Creek at LeRoy) features a richly fossiliferous bed of brachiopods and small corals that represents the first occurrence of the classic Hamilton Group fauna informally termed the LeRoy bed (=gray bed of Baird and Brett, 1986; see Ver Straeten et al., above); the LeRoy bed has not as yet been found at the Honeoye Falls quarry and likely occurs in strata above the erosional contact of the Oatka Creek Formation with overlying glacial till deposits.
As previously noted, the basal contact of the Cherry Valley Member shows significant paleorelief across the quarry exposure, including distinctive channel-like structures. The cause of the channeling is unknown; in all other localities the Cherry Valley displays a nearly planar, although sharp, basal contact. We presume that the erosional scour was developed as a result of submarine channeling by gradient currents during a relative low stand in sea level. Similar erosional furrowing associated with maximum regression and subsequent earliest transgression has been observed at other localities in younger Middle to Upper Devonian strata (for example, see Brett and Baird, 1990).

Cross Canandaigua Outlet Creek

Manchester quarry in Onondaga Limestone is 1.6 mi. south along Rte. 7.

STOP 3 (Optional). FLINT CREEK. WEST OF PHELPS.
The bed and banks of Flint Creek just west of Phelps provide an excellent exposure of the lower and middle parts of the Nedrow Member in its typical west-central New York facies. The banks expose medium gray, soft, bioturbated mudstones alternating with thin (up to 30 centimeters thick) tabular, somewhat argillaceous, fossiliferous wackestones. Bedding here appears rhythmic and some bundling of limestone beds is evident toward the top of the exposure. The shales near the stream level are extremely rich in well-preserved brachiopods, particularly robust specimens of Pseudoatrypa, Leptaena, and Pentagonia. Scattered crinoid debris and small rugose corals are also present.
The rhythmic bedding within the Nedrow Member may represent minor climatic oscillations. Neither the carbonate nor the mudstones appear to represent major event deposits. The limestone and mudstone bands both consist of multiple beds, some of which may represent thin event deposits, but with bedding largely obscured by bioturbation. Contacts of the interbedded limestones and shales appear to be relatively gradational and generally burrowed by Chondrites traces. Hence the alternations are thought to represent variations in the input of siliciclastic mud. The sharp contrast between of varying siliciclastic content has probably been diagenetically enhanced by early cementation of the more carbonate-rich intervals (discussed in Brett and Ver Straeten, above).

STOP 4. (OPTIONAL) ROADCUT ON NEW YORK ROUTE 88. PHELPS.
Rock cuts on both sides of this north-south road display a Silurian-Devonian carbonate section. Because of the relatively strong component of southward dip, a relatively long section is exposed here. The lower part of the outcrops just south of the New York State Thruway-bridge are in the upper part of the Upper Silurian Bertie Group that display an unconformable contact with the overlying Devonian strata. The unconformity overlies the Scajaquada Formation of the Bertie Group. Medium to slightly reddish gray shales and shaly dolostones display distinct small casts of salt crystal cubes, but few, if any fossils are obtainable from these beds.
The erosional Silurian-Devonian contact at the Wallbridge Unconformity is marked by thin stringers of quartz arenite, apparently of the Lower Devonian Oriskany Sandstone. Thin fissure fillings or neptunian dykes also of Oriskany quartz sand extend 30 to 40 centimeters downward below the upper surface of the Scajaquada Shale. The contact is overlain by a conglomeratic bed containing phosphatic or cherty clasts within a sandy limestone matrix. This bed is only a few centimeters thick, and is overlain conformably by brownish gray-weathering, very cherty micritic limestone (wackestone). Dark bluish-gray chert nodules up to fist size (10 to 20 cm in diameter) occur within these limestone beds. The rock is sparsely fossiliferous, but contains fragments of brachiopods, corals, and echinoderm debris. This unit is clearly not typical of the lower Edgecliff Member of the Onondaga Limestone; it is tentatively assigned to the upper Lower Devonian Bois Blanc Formation. Oliver (1963) reports minor exposures of apparently similar cherty, micritic limestone along the New York State Thruway in the vicinity of Phelps. The contact of the Bois Blanc and the underlying lenses of the Oriskany Sandstone represents a second, post-Wallbridge and pre-Bois Blanc unconformity.
The highest beds exposed in this roadcut consist of pale, pinkish gray-weathering crinoidal grainstone. These strata appear to be in sharp contact on the underlying Bois Blanc and are assignable to the basal Edgecliff Member of the Onondaga Limestone; this contact represent a third sub-Onondaga unconformity. In addition to the abundant crinoid skeletal material, the lower Edgecliff strata contain scattered solitary rugose and tabulate corals. The basal Onondaga contact contrasts markedly with the basal Devonian contact observed in the Oaks Corners (Stop 5} approximately 5 km to the southeast (discussed below).

Outcrops of Upper Silurian Bertie Group.

STOP 5. OAKS CORNERS QUARRY. SOUTH WALL.
The old south wall of the active Oaks Corners quarry displays an excellent section ranging from the basal contact of the Onondaga Formation up through the lower two-thirds of the Moorehouse Member (see Figure 5 of Brett and Ver Straeten, this volume). The quarry can be approached by walking through a narrow strip of field just north of Cross Road at about 0.2 miles west of the junction of Ontario Co. Rte. 6 (Pre-Emption Road). Beds exposed at the level of the field and road are in the upper part of the Edgecliff Member (Clarence cherty facies) near its contact with the Nedrow Member. These flats are some 12-15 m above the base of the quarry. By walking to the left (west) and carefully proceeding down an abandoned quarry road from the upper platform it is possible to examine the lower part of the Onondaga down to the contact of the Edgecliff Member with the underlying Upper Silurian strata.
At the Oaks Corners quarry, in contrast to the Route 88 roadcuts (Stop 3), the Onondaga Limestone generally rests directly on beds of the Upper Silurian Akron Formation, a massive, dark brownish buff-weathering saccharoidal dolostone. J.W. Scatterday (personal commun.) reports a thin, locally-occurring sandstone in part of the quarry similar to that seen at Stop 4; it is presently unknown whether these strata are related to Oriskany or Tristates Group sandstones ("Springvale"). Where the sandstones are absent, the Akron-Onondaga contact is typically marked by rust staining, as a result of weathering of pyritic crusts that occur along the erosional surface. The unconformity is approximately four to five meters higher in the Silurian section than at the Rte. 88 exposures (Stop 3), where the unconformity surface is cut down to the level of the older Scajaquada Shale. In the Oaks Corners quarry, the unconformity displays relief of up to one meter. Large channel-like depressions, up to several meters across, occur along this boundary. Again, in contrast to the Route 88 cuts, where possibly four to five meters of Bois Blanc Formation occur above the unconformity, the Bois Blanc is missing at this location and the basal beds of the Edgecliff Member occur within hollows on the combined Wallbridge, sub-Bois Blanc (?), and sub-Onondaga unconformities.
The lowest unit of the Edgecliff Member is a fine-to medium-grained crinoidal grainstone, typically pinkish-weathering, which ranges from 40 to 120 centimeters in thickness as a result of the irregular topography at its base. The transition to chert-rich strata (Clarence facies) is abrupt but gradational and consists of cherty, crinoidal pack-to wackestones. The remainder of the Edgecliff Member is dominated by the Clarence cherty facies, and consists predominantly of pale gray-weathering micritic limestone with 20 to 30% dark gray chert. Skeletal wacke-and packstones, which feature large crinoid columns and tabulate and rugose corals, occur approximately three and six meters above the base. These form two light pinkish gray-weathering bands in the wall of the quarry and thus constitute important markers as well as represent the apparent tops of minor shallowing-up cycles. A 46 cm-thick, medium dark gray, sparsely fossiliferous and very calcareous shale occurs high in the Edgecliff Member. This interval closely resembles the higher Nedrow Member, but it is separated from the latter unit by 1.2 meters of micritic cherty limestone typical of Clarence facies. The Edgecliff is approximately 8.5 m-thick at the Oaks Corners quarry.
A sharp limestone-shale contact at the top of the Edgecliff marks the base of the Nedrow Member. Lowest shales of the Nedrow contain a relatively abundant fauna of Pseudoatrypa, Leptaena, small rugose corals, and other fossils. The Nedrow Member itself is approximately 5.3 m-thick at this location and consists of medium to dark gray, very calcareous shale or mudstone that alternate with argillaceous lime mudstones or wackestones. Some of the rhythmic bedding and bundling of limestones observed along Flint Creek in the corresponding interval (STOP 2) is also apparent here, although somewhat more subtle in this outcrop. The upper portion of the Nedrow Member contains a distinctive dark gray to black shale interval with small black chert nodules. This black shale marker bed has proved to be very widespread across the Appalachian Basin and is recognized at present across parts of New York to southern Pennsylvania (see above). A 40 cm-thick, light-weathering limestone bed with minor pyrite separates this bed from an overlying brownish-gray shale interval that contains a thin nodular limestone bed rich in the brachiopod Schizophoria sp. This bed forms the floor of the second highest lift near the abandoned quarry access road along the south wall of the quarry, where the brachiopod fauna and spectacularly weathered Chondrites burrows can be observed.
The Moorehouse Member in the Oaks Corners quarry consists dominantly of medium-to thick-bedded micritic limestones (slightly argillaceous fossiliferous wackestones). Several intervals of medium to dark gray chert occur within this section. Particularly heavy cherty beds occur approximately four to five meters above the base of the Moorehouse. Thin intervals of medium to dark gray, very calcareous shale that closely resemble the Nedrow Member (particularly the Schizophoria bed) occur approximately 2.2 and 3.0 m above the base of the Moorehouse. A relatively thick calcareous shale (80 cm thick) that features well-preserved specimens of Pacificocoelia as well as Schizophoria occurs 5.4 m above the base of the Moorehouse and is well displayed in a cut along the side of a second, more westerly abandoned roadway that leads into the quarry along the south side. A cherty micritic limestone bed approximately 1.5 m below the Pacificocoelia shale contains abundant coiled nautiloid cephalopods (Gyroceras) which are well displayed on a glacially polished surface just east of the second access road.
Highest beds of the Moorehouse are quite fossiliferous, and are particularly rich in brachiopods. Argillaceous beds about one meter below the top of the quarry contain a fauna dominated by atrypids and other brachiopods such as Megakozlowskiella, Leptaena, Schizophoria, and others. Trilobite material is rather common in the upper shaly beds and includes specimens of Phacops and Odontocephalus. Echinoderm material is relatively sparse, although rare specimens of an undescribed stalked rhenopyrgid edrioasteroid have been obtained from the shaly beds. Overall, the Moorehouse appears to have at least four to five minor shallowing-up cycles, each of which commences with calcareous shales and culminates in more massive, cherty, micritic limestones that may contain corals such as Acinophyllum. The upper part of the Moorehouse Member and the entire Seneca Member are absent at this location due to post-Devonian erosion.
The lower part of the Onondaga Formation at Oaks Corners is similar to more western sections in that the Edgecliff Member is dominated by Clarence cherty facies. Only a relatively small proportion (approximately 10% of the member) consists of the more classic chert-poor crinoidal packstones characteristic of the Jamesville Quarry facies (see body of paper) of the Edgecliff. The remainder of the member is relatively cherty, although not as chert-rich as the Clarence in Erie and Genesee counties. The Edgecliff here (ca. 8.5 m-thick) contrasts markedly with that seen at the Seneca Stone quarry (STOP 5; 21 km southeast) where the member is quite thin (< 3 m-thick) and consists mainly of the crinoidal wackestone facies with only a single band of cherty micritic limestone (see stop description below). The Nedrow Member at Oaks Corners is considerably shalier and less fossiliferous than the equivalent beds seen at the Honeoye Falls quarry (STOP 1; 50 km west) where the member is composed of micritic limestones with light gray to dark chert and greenish-gray argillaceous limestones rich in a diverse assemblage of rugose and tabulate corals, gastropods, brachiopods and other fossils. At the Oaks Corners quarry the Nedrow is only sparsely fossiliferous and carries a fauna dominated by a few species of brachiopods. Moreover, the upper portion of the member contains the distinctive black marker bed, which in the Stafford and Honeoye Falls quarries (STOPS 1 & 2) appears to be represented by fossiliferous greenish shales. The Nedrow interval at Oaks Corners is, on the other hand, quite similar to that seen at Seneca Stone quarry (STOP 5).
The Moorehouse Member at Oaks Corners displays features suggestive of an intermediate setting between those seen in the Honeoye Falls and Seneca Stone quarries (STOPS 1 & 5). It is thicker, more chert-rich, and more fossiliferous than the equivalent interval at Seneca Stone quarry. However, it contains considerably less crinoid material and is dominated by brachiopod-rich wackestone lithologies as opposed to the crinoidal wacke-and packstones of the Moorehouse at the Honeoye Falls quarry. It carries a fauna rich in brachiopods assignable to the Megakozlowskiella, Atrypa, and Pacificocoelia communities recognized by Feldman (1980).
Overall, the Onondaga appears to be uniformly of more fine-grained, more argillaceous, and probably deeper water facies than those seen in the corresponding intervals at and to the west of the Honeoye Falls quarry (STOP 1). However, the relationship of facies to those of the Seneca Stone quarry is not so clear cut. The lower Edgecliff Member appears to be distinctly finer-grained, more cherty, and less fossiliferous than the equivalent strata at Seneca Stone quarry. We suggest that only the upper beds of the Edgecliff at Oaks Corners quarry are continuous into the Seneca Stone quarry, where the lower units have pinched out over the irregular topography below the combined Wallbridge and sub-Onondaga unconformities. Those upper Edgecliff beds show distinct facies changes between Oaks Corners and the Seneca Stone quarry 21 km to the southeast. In particular, the chert-rich intervals appear to grade southeastward into crinoidal wacke-and packstones, whereas the dark gray Nedrow-like shale interval approximately 7.3 m above the base of the Edgecliff appears to grade into a single chert-rich micritic bed at the Seneca Stone quarry. Hence, it would appear that the Edgecliff Member is uniformly of deeper water character at Oaks Corners than at Seneca Stone quarry, which suggests a more basinal setting to the west at that time. The Nedrow Member appears very similar at both localities. The Moorehouse Member, in total contrast, appears to represent distinctly shallower water facies at the Oaks Corners quarry than it does at the Seneca Stone quarry, a complete reversal of the trend seen in the Edgecliff Member. This suggests that the basin axis or center of subsidence shifted through time from a more westerly position (probably west of Oaks Corners) eastward to the vicinity of the Seneca Stone quarry during deposition of the Onondaga Limestone.

Large gravel pit on left.

Bridge over Seneca River

STOP 6. SENECA STONE QUARRY.
The Seneca Stone quarry is another relatively large quarry that exposes a complete section from the upper part of the Lower Devonian Manlius Limestone to the top of the Middle Devonian Cherry Valley Member of the Oatka Creek Formation (Marcellus subgroup; see section in Brett and Ver Straeten, this volume, Figure 5). Strata within the quarry generally appear undeformed, with the exception of a prominent north-directed thrust fault that cuts up through the upper part of the Onondaga Formation (visible in the southeast and southwest parts of the quarry).
Limestones of the Lower Devonian Manlius Formation (Helderberg Group} are found in a small sump pit in the bottom of the quarry, overlain unconformably by quartz arenites of the Lower Devonian Oriskany Formation (lower part of the Tristates Group). These two units are separated by the true Wallbridge Unconformity that marks the base of the Kaskaskia Megasequence. Clasts of the older Manlius Limestone are visible in the base of the Oriskany, where they may be overgrown by tabulate coral colonies. The white quartz arenites of the Oriskany Sandstone also feature numerous large, robust brachiopods (including Costispirifer arenosus, Rensselaeria, and Hipparionyx), platyceratid gastropods, and rare rugose corals.
Twenty-five km northeast of the Seneca Stone quarry, at Auburn, sand-dominated strata of the upper part of the Tristates Group (Carlisle Center and Schoharie Formations) are present, similar to strata reported for the Syracuse area (see Brett and Ver Straeten, above). At Seneca Stone quarry, however, these rocks are absent except as reworked phosphatic cobbles in a basal sandstone bed of the Edgecliff Member (Onondaga Formation). Reworked, phosphatized clasts of the Manlius and Oriskany Formations are also found in the basal Edgecliff sandstone bed. A thin interval of coral-rich limestone is succeeded by two cyclic packages of Edgecliff strata that appear to be equivalent to the two upper Edgecliff cycles seen at Oaks Corners (STOP 5). Well developed fine-grained, cherty Clarence facies are only developed within the lower part of the second cycle at Seneca Stone; the Edgecliff member in general here appears coarser than equivalent strata at Oaks Corners (STOP 5).
A sharp change into overlying calcareous dark shale-dominated strata marks the base of the Nedrow Member. The Nedrow and lower to middle parts of the overlying Moorehouse Member are best exposed in the east wall of the quarry below the third platform. The lower part of the Nedrow consists of alternating dark shales and argillaceous wackestones. Several distinctive crevices within the middle to upper Nedrow here may represent altered volcanic ash beds. The distinctive "black bed" in the upper Nedrow, which at Seneca Stone quarry consists of black shale with several bands of black chert nodules, is highly visible in the eastern wall. The bed, as observed at the previous locality (STOP 5), is overlain by a light weathering limestone and the dark "Schizophoria bed" at the top of the Nedrow. Overlying strata assigned to the lower part of the Moorehouse Member consist of alternating calcisiltite limestone beds (<1 m-thick) interbedded with thin (ca. 5-15 cm thick) calcareous shales. This interval is relatively similar to facies that characterize the Onondaga-equivalent Selinsgrove Limestone of central Pennsylvania. Two paired crevices approximately 0.9 and 1.0 m above the Schizophoria bed represent apparent K-bentonite beds that are widely traceable across the central part of the Appalachian Basin (see Brett and Ver Straeten, above). Quartz pebbles and granules have been noted in a 14 cm-thick calcareous shale bed 2.5 m above the base of the Moorehouse. A 45 cm-thick argillaceous unit 6 m up in the Moorehouse, just below a platform on the east wall, correlates with the prominent "false Nedrow" shale seen at Stafford (STOP 1) and other localities across much of the Appalachian Basin (see Brett and Ver Straeten, above).
More resistant, coarsening-up strata of the upper Moorehouse Member Form the wall of the lift above the Nedrow-like shale unit up to the thick Tioga B-OIN Bentonite bed at the base of the overlying Seneca Member. Two conspicuous crevices, which feature biotite-rich claystones, represent the First and Second Cheektowaga Bentonites of Conkin and Conkin, (1979, 1984; Conkin, 1987). A 10 cm-thick, dark chert bed forms the cap of the 9.8 m thick Moorehouse Member at Seneca Stone, immediately below the Tioga B-OIN bentonite bed.
The Seneca Member represents a general fining-up trend from the relatively coarse upper part of the Moorehouse Member. The Tioga B-OIN bentonite marks the base of the member. Five and possibly seven additional bentonites occur within the Seneca Member and the base of the overlying Union Springs Formation at Seneca Stone. Two fining-to coarsening-up cycles within the Seneca represent relatively smaller scale cycles superimposed on the general deepening-up trend (see Brett and Ver Straeten, above). Lithology of the member ranges from poorly fossiliferous wackestones to low diversity brachiopod-rich packstones (e.g., "Pink Hallinetes (formerly Chonetes) Zone," 3.2-4.0 m above the base). Nodular cherts and impure dolomitic cherts occur scattered throughout the member. The Seneca Member, as defined herein, totals 7.15 m in thickness. The upper contact of the Seneca Member at Seneca Stone quarry as defined herein is marked by a distinctive bedding plane with large horizontal burrows, scattered fish debris, and some pinkish weathering, apparently hematitic, limestone "clasts." The bed is immediately overlain by eight cm of black shale and a thin (3 cm-thick) k-bentonite bed. Overlying dark, fine-grained, styliolinid limestone beds are assigned herein to the Bakoven Member of the Union Springs Formation. The prominent, rusty-weathering Tioga F bentonite (ca. 12 cm-thick) occurs 65 cm above the base of the Bakoven at Seneca Stone. The lower 1.3 m of the Bakoven is dominated by the previously mentioned thin styliolinid limestone beds. Black shales become more prevalent above, but occur interbedded with numerous thin (ca. 2-20 cm-thick) micritic limestone beds. The top of the Union Springs Formation at Seneca Stone quarry is represented by the richly fossiliferous Chestnut Street submember of the Hurley Member. The Chestnut Street beds, with their characteristic lighter-weathering color and fauna (e.g., proetid trilobites and the microcrinoid Haplocrinites clio), form a thin ledge of limestone approximately 10 cm in thickness that is firmly welded to the base of the overlying Cherry Valley Member (Oatka Creek Formation).
The Cherry Valley Member at Seneca Stone is more typical of its occurrence along much of its outcrop west of the Albany area. Three subdivisions, a lower massive, middle nodular, and upper massive limestones comprise an approximately 50 cm-thick section of organic-rich, pyritic, bedded to nodular wacke-to packstones. The classic goniatite and nautiloid cephalopod fauna of the Cherry Valley, which includes Agoniatites vanuxemi and Striacoceras typum, is well displayed on the excellently exposed upper bedding plane seen above the south wall of the quarry. Truncated cephalopod shells, fish bone material, and scattered pebbles, along with the development of a firm-to incipient hard-ground and pyritic crusts on the upper surface of the Cherry Valley Member, indicate a period of submarine sediment starvation prior to deposition of overlying shales. Overlying strata are not at present exposed, but Baird and Brett (1986) report dark shales that include a distinctive bed (LeRoy bed=gray bed of Baird and Brett, 1986; see Ver Straeten et al., above) in which the classic fauna of the Middle Devonian Hamilton Group makes its first appearance in the Appalachian Basin.

A5: FRASNIAN (UPPER DEVONIAN) STRATA OF THE GENESEE RIVER VALLEY, WESTERN NY
WILLIAM T. KIRCHGASSER
Department of Geology
SUNY-Potsdam
Potsdam, New York 13676
D. JEFFREY OVER
Department of Geological Sciences
SUNY-Geneseo
Geneseo, New York 14454
DONALD L. WOODROW
Department of Geoscience
Hobart and William Smith Colleges
Geneva, New York 14456
History of Investigation
The Frasnian section in the Genesee Valley is located in the western part of the central Devonian outcrop belt of New York State that stretches from the Catskill Mountains to Lake Erie. The Genesee Valley was close to the center of the Fourth Geologic District of the first state survey, the district between Cayuga Lake and Lake Erie, covered by James Hall. Hall's final report, the monumental Part IV of the Geology of New York (Hall, 1843), is the starting point for Devonian studies in the region (Figure 1). The rocks of the classical Genesee, Portage and Chemung divisions consist of a succession of marine siliciclastics beginning with dark basinal shales (Genesee) that contain a pelagic molluscan fauna, which are overlain by lighter colored shales and siltstones that contain a pelagic and benthic fauna (Portage and Naples to the east) that were deposited in basin-and-slope environments. These strata are overlain by siltstones and sandstones bearing a benthic brachiopod fauna (Chemung) that were deposited on the slope and outer shelf. Most of the fossils in these units were described in monographs by Hall (1879) and Clarke (1899, 1904). The excellent exposures in the Genesee Valley made this section a center for geological studies of the distal rocks of the Catskill Delta, which record stages in the filling of the Appalachian Foreland Basin. Beginning with Hall's (1843) observation of the lateral changes in lithology within each division ("constant increase of arenaceous matter" to the east and "increase in mud or shale" to the west) the Genesee Valley section came to play a central role in the application of the facies concept to the Appalachian Devonian.

A5: FRASNIAN (UPPER DEVONIAN) STRATA OF THE GENESEE RIVER VALLEY, WESTERN NY

Retsof mine collapse
The highway was closed in March 1994 due to road and bridge damage west of the Genesee River near Cuylerville that resulted from roof collapse of the Retsof salt mine and subsequent subsidence and formation of sink holes. The salt beds are approximately 300 m (1,000 ft) below the valley floor in the Upper Silurian Vernon Formation.

STOP 1A. Fall Brook
(Property is posted, access by permission only.)
Erosional base of Genesee Group, pyritic lag, dark colored petroliferous shales, interbedded carbonates, Givetian-Frasnian boundary, and major deepening of the basin represented by planktic-fauna carbonates. Leicester Pyrite, Geneseo Shale, Penn Yan Shale, Genundewa Limestone.
Strata of the Moscow Formation (Hamilton Group) are exposed in the stream bed and banks below the falls. Fossiliferous bluish-gray shales of the Kashong Member are overlain by bioturbated fossiliferous medium gray calcareous shales and carbonate beds of the Windom Member (Figure 10). The steep banks prevent close investigation of Genesee strata. Stratigraphic relationships and fallen debris can be examined in the gorge, in place collections can be made from a side creek or STOPS 1B (Dewey Hill) and 1C (above falls) where strata are more accessible. Caution: large blocks have been known to fall from overhangs and strike eminent geologists.
The Genesee Group consists of the Leicester Pyrite, Geneseo Shale, Penn Yan Shale, Genundewa Limestone (resistant bed forming falls), and West River Shale. The base of the Genesee Group is marked by the Leicester Pyrite, a 0-20 cm thick sharp based accumulation composed almost entirely of pyrite nodules, pyritized burrows, and pyrite replaced fossils that represents a condensed lag accumulation above a major disconformity. The bed contains a mixed conodont and cephalopod fauna of Hamilton, Tully, and Genesee nature (Figure 5). The unconformity is the result of submarine erosion, corresponding to the Taghanic Onlap (Baird and Brett, 1986a). Look for pyritized cephalopods (Tornoceras uniangulare), crinoids, bivalves, burrow fills and rare brachiopods and trilobites in fallen blocks of the Leicester, which is distinctive due to the orange-brown weathered surface.
The Geneseo Shale gradationally overlies or is locally interbedded with the Leicester Pyrite. Here at Fall Brook the Geneseo is 8.2 m thick (base of lower black shale to top of upper black shale), characterized by a lower 1.7 m thick and an upper 1.4 m thick dense black petroliferous shale units separated by 5 m of medium-dark gray shale and thin carbonate mudstone beds. [In deWitt and Colton (1978) only the lower black shale is considered to be the Geneseo.] The Geneseo black shale thickens eastward, absent at Lake Erie (possibly represented as a parting between the North Evans Limestone and Genundewa Limestone) to about 30 m thick in the Finger Lakes (Figure 2).
The continuous limestone band in about the middle of the gray Geneseo shale interval is the Genesee Limestone (GL), with Pharciceras and a disparalis Zone conodont fauna that includes Polygnathus linguliformis gamma and Po. dubius. The Fir Tree Limestone, represented here by a thin carbonate mudstone bed 1.2 m above the Genesee Limestone, is a distinctive horizon in the Finger Lakes region that contains a pyrite-bone bed lag developed on the corroded surface of a carbonate bed (Baird et al., 1989).
The Penn Yan Shale lies above the upper thick black shale of the Geneseo and is characterized by medium-dark shale and interbedded thin carbonate mudstones, styliolinid packstone/grainstones, and thin black shale beds. The Lodi Limestone, a nodular carbonate 1.1 m above the base of the Penn Yan, marks the local first occurrence of Ponticeras perlatum and Skeletognathus norrisi, indicative of the norrisi Zone, the latest zone of the Givetian. Ancyrodella rotundiloba early form, which defines the base of the Frasnian and MN Zone 1 of Klapper (1989), and the Givetian-Frasnian boundary, occurs just above the Lodi Limestone east of the Genesee Valley (Figure 3, 5). Based on graphic correlation with the Frasnian Composite Standard of Klapper et al. (1993), however, the Givetian-Frasnian boundary would lie in the Geneseo-Penn Yan transition (Figure 6). The Lodi Limestone can be collected from the side creek, and will also be seen at Dewey Hill (Stop 1B).
The Genundewa Limestone caps the water fall of Fall Brook. The Genundewa is a 0.3 to 0.5 m thick, wood-bearing, cephalopod styliolinid packstone-grainstone that consists of several amalgamated beds separated by discontinuous shale laminae. The grainstone consists almost entirely of the small conical shells of Styliolina fissurella, an enigmatic organism that may be a protist (Yochelson and Lindemann, 1986). The lower surface is irregular, indicating scouring of the sea floor prior to or during deposition. Reworking and erosion are indicated by current alignment of the styliolinids and corrosion/wear features. The Genundewa is interpreted as the result of deepening of the basin; consequent flooding of the terrigenous sediment source and near shore sediment trapping resulted in accumulation of planktic organisms, without dilution by siliciclastics. Several styliolinid laminae and thicker packstone-grainstones occur in the upper Penn Yan indicating cyclic deepening and consequent sediment starvation. The base of the Genundewa is recognized by a regionally persistent, thin (10 cm) black shale bed that underlies the prominent carbonate band. The Genundewa will be viewed in place at STOP 1C; however, samples can be easily collected from large slabs in the stream bed.

STOP 1B. Dewey Hill: Penn Yan Shale including Lodi Limestone Member, SB bed, and Linden Horizon.
Pull off and park before guard rail on right. Exposures are in ditch and cuts on both sides of the road; the section described is on the south side.
Here we will be able to closely examine beds below the Genundewa Limestone in the side walls of Fall Brook at Stop 1A. The Penn Yan Shale is comprised of dark to medium gray shale with interbedded carbonate and black shale. The Lodi Limestone, exposed in the road ditch, is the lowest key bed. The Lodi consists of thin (5 cm) discontinuous beds and nodules that are traceable to the Finger Lakes region and represents the latest Givetian (Middle Devonian) in New York State; Ponticeras is the predominant goniatite, but it is rare this far west. The Givetian-Frasnian (Middle-Upper Devonian boundary) is taken as the base of the shales overlying the Lodi, recognized by the first occurrence of Ancyrodella rotundiloba early form, which is used to define the base of MN Zone 1 (lowest Frasnian). Gastropods and rhynconellid brachiopods may be found in the nodular Lodi at this locality.
The SB bed is a 20 cm thick distinctive black shale interval that is characterized by a conodont and lingulid lag horizon in the lower few centimeters. The horizon interval represents a phase of benthic anoxia-dysoxia with preservation of organic material, as well as a hiatus/erosion surface and concentration of phosphatic bioclasts. Conodonts of MN Zone 1 can be recovered from the shale.
In contrast to the larger scale sequence marked by the disconformity at the base of the Genesee Group, smaller scale sequences in the Geneseo, Penn Yan, Genundewa, and West River formations (basin facies) seem symmetrical, preserving sediments that represent both the deepening and shallowing without development of a pronounced hiatus. The SB phosphate lag is an example of a cryptic disconformity within a minor cycle that marks a deepening maxima phase in the basin.
Nodular and continuous carbonate beds in the middle-upper Penn Yan contain cephalopods (genera include Koenenites, Acanthoclymenia, and Tornoceras) and conodonts. The key styliolinid bed is the Linden Horizon (LH) that contains Koenenites styliophilus. In this horizon the goniatite shells are often filled with crystalline pink and white barite. This level marks the base of MN Zone 2 in New York (Ancyrodella rotundiloba late form).

STOP 1C. Fall Brook above falls: Genundewa Limestone and West River Shale.
Extreme Caution: the edge of the Genundewa is unmarked and the drop to the base of the falls is over 100 feet.
The Genundewa Limestone consists of approximately 35 cm of several amalgamated beds of styliolinid grainstones separated by discontinuous shale partings that can be traced from Lake Erie to Keuka Lake. The base of the Genundewa is marked by a persistent black shale bed that separates it from carbonate beds in the upper Penn Yan. Note here the irregular contacts in the Genundewa and proximal strata and apparent rippled surfaces. The styliolinids are aligned, indicating current orientation, however, the nature of the current(s) responsible is enigmatic: contourites, waves on pycnocline boundaries, storm waves, ocean gyres, or density currents are possible mechanisms.
The upper and lower Genundewa contain distinctive faunas. The lower beds are characterized by Ancyrodella rotundiloba late form, indicative of MN Zone 2. The upper Genundewa contains the first appearance of Manticoceras and conodonts of MN Zone 3, including Ad. rugosa, Ad. alata, and Ad. sp. B (Kralik, in press; Figures 3, 6).
The lower West River Shale is exposed in the creek bed and banks above the falls. The West River Shale consists of dark to medium gray shales and thin carbonate beds, lithologically similar to the Penn Yan Shale, that indicate shallowing and a return to fine clastic sedimentation following Genundewa deposition. A thin (3 cm) styliolinid carbonate bed approximately 2 m above the base of the shale contains numerous conodonts of MN Zone 3 [USGS SilurianDevonian cat. No. 8122SD (Huddle, 1981 )]. The upper West River Shale is exposed at the base of the Mt. Morris Dam at STOP 2.

STOP 2. Mt. Morris Dam
(access by permission from US Corps of Army Engineers)
Gorge overlook: dark gray shale of upper West River Shale at base above and below dam (river level); black shale of Middlesex Shale and green/gray shale of Cashaqua Shale, Sonyea Group; and gray/black shale of Rhinestreet Shale, lower West Falls Group to the top of the exposure (Figure 11). An apparent correlative of the Belpre Ash Bed may be visible.
Exposures are along the dam access road and "Burma Road" that descends gorge wall upstream from dam.
The Letchworth Gorge of the Genesee River is a Pleistocene hanging valley cut into shales, siltstones, and sandstones of the Genesee, Sonyea, and West Falls groups. Three main waterfalls in the upper gorge are formed on resistant sandstones of the upper West Falls Group. The section exposed at the dam includes gray shale of upper West River Shale at the base above and below the dam (river level); black Middlesex Shale and green/gray Cashaqua Shale, Sonyea Group; and gray/black Rhinestreet Shale, lower West Falls Group up to the top of exposure. The two black shales represent major transgressions.
The lower Rhinestreet Shale and upper Cashaqua Shale are exposed in the access road to the top of the dam. The Cashaqua consists of green-gray shale and mudstone that are darker at the base, lighter colored and highly bioturbated in the middle, and darker gray at the top. This lithologic change indicates a shallowing cycle, superimposed on which there are numerous shorter-duration cycles indicated by darker shale bands and concretionary horizons. The medium gray shale of the upper Cashaqua exposed at the dam contains numerous bivalves and coalified plant fragments. The prominent concretionary band in the upper Cashaqua is the Shurtleff Septarian Horizon. These concretions contain a diverse conodont fauna of MN Zone 6 (Palmatolepis punctata, Ancyrodella nodosa), as well as mollusks replaced or filled with pink or white barite, including the goniatites Manticoceras sinuosum and Prochorites alveolatus (Figure 7; House and Kirchgasser, 1993).
The base of the Rhinestreet Shale and the West Falls Group is marked by a sharp transition from medium-to-dark gray shale below to thick black shale. The Rhinestreet is the thickest and most widely distributed black shale bed in the Upper Devonian of New York and represents a major transgression and deepening (Figures 2, 8). Plant remains, rare cephalopods, conodonts, and other fossils can be recovered from bedding planes.
If time and weather permits the entire Cashaqua can be accessed on the "Burma Road" which enters the gorge upstream of the dam. If pool level is low the upper West River and Middlesex may also be exposed, however, out-croppings are likely to be partially covered by mud and debris. The base of the Cashaqua denotes the start of MN Zone 5 (Palmatolepis punctata) and Probeloceras lutheri Zone. A diverse molluscan fauna can be recovered from the greenish shales, including Probeloceras lutheri and numerous bivalves; among the most common are Buchiola, Ontaria, and Pterochaenia (see Clark, 1904).

STOP 3. I-390 Mile 32: slope-basin muds and turbidites of Gardeau Shale, West Falls Group.
Pull off shoulder and park at Mile Marker 32, exposures are in road cut on both sides of highway; measured section is on the west side of the southbound lane.
In the gorge section, the Gardeau Shale overlies the Rhinestreet and extends upstream to the Middle Falls, consisting of approximately 100 m of interbedded green-gray shale, black shale, and silts that represent an influx of fine and coarse clastic material into the basin. The exposure here of the Gardeau Shale consists of interbedded medium gray and dark shales that may represent small scale cycles that are overlain by interbedded silty shales and thin silt-sandstones that may also represent small scale cycles (Figure 12). The shales have yielded a low diversity and sparse fauna of nowakiids. Inarticulate brachiopods and trace fossils occur in the coarser (silt-sandstone) beds. The brachiopods and trace fossils in the silt-sandstone beds indicate development of dysoxic-oxygenated benthic waters and a suitable substrate for benthos. The silt-sandstones are graded, consisting of a scoured base, massive lower sand, and ripple to hummocky cross-laminated upper surfaces that are sharply overlain by gray shale. Scour features on the bases of silt-sandstone beds are oriented east-west. Many of the scours are laterally asymmetric, possibly the result of helical flow of the scouring current. The silt-sandstones are interpreted as turbidites, however, the upper surfaces have been reworked by subsequent currents.

STOP 4. I-390 Between Mile Markers 15 and 14
Shelf sands of upper West Falls Group, Nunda or Wiscoy sandstone; ichnofossils, channel sand and shell-rich basal channel fill.
High exposures on both sides of road between mile markers 15 and 14, pull well off shoulder at southern end of the exposures near the crest of the hill and park.
These sandstone exposures are questionably of the Nunda Sandstone which represents the upper West Falls Group and coarse-grained lateral equivalent of the Angola Shale in the Genesee River Valley. The sandstones are composed of tabular to lenticular thin to medium beds. Brown weathering sands are muddier, often low angle cross-laminated, and may contain rip-up clasts of brown mudstone and plant fragments. Medium blue-gray sands are ripple surfaced and cross-laminated, locally bioclastic (bivalves, brachiopods, and crinoids), and moderately to completely bioturbated. Identifiable trace fossils include Skolithos, Diplocraterion, Scalarituba?, and small Chondrites?, as well as poorly preserved lined and unlined horizontal to subhorizontal burrows. These sands are similar to the bluestones that were a common quarry stone near Portageville at the head of the Genesee gorge in the 1800's and early 1900's. Also notable in the section are resistant spherical weathering zones, suggestive of concretions developed in the sandstone.
In the southern most outcrop of the south bound lane is a channel cut filled with light gray weathering sandstone. The base of the channel consists of a 40 m long, 0.4 - 0.7 m thick dark-brown weathering fossiliferous sandstone to sandy carbonate. The stratum contains numerous brachiopods of a deep shelf environment (Cyrtospirifer, Douvillina, Nervostrophia, Spinatrypa), as well as cephalopods, crinoids, fish remains, and a diverse polygnathid conodont fauna. The fauna is characteristic of MN Zone 12.
The current reworked and bioturbated sands, brachiopod fauna, Skolithos-Curziana ichnofacies, and polygnathid conodont fauna are indicative of a moderate energy shelf environment. These sands correlate to finer grained green-gray and dark gray shale of the Angola to the west (Figure 2). The Pipe Creek Shale, a thin transgressive black shale unit, separates the Nunda from the overlying Wiscoy Sandstone, the lateral equivalent of the Hanover Shale (highest Frasnian). The Pipe Creek is not well developed in this region and has not been locally identified. More nearshore channel and deltaic sandstones are found to the south in Famennian strata. These shallow water shelf and near shore sandstones record the late stages of progradation of the Catskill Delta across New York State and the filling of the Appalachian Foreland Basin.

B1: LAND INSTABILITY IN THE GENESEE RIVER VALLEY-LIVINGSTON COUNTY
Lawrence Lundgren and Weiyang James Wang
University of Rochester
Rochester, New York
Land instability in the Genesee River Valley in Livingston County takes three forms: River-bank failure during meander migration, landsliding, and subsidence over abandoned salt mine workings. River-bank failure is a completely natural process possibly influenced by controlled discharge from the U.S. Army Corps of Engineers Mount Morris Dam in Letchworth State Park. Landsliding is a natural process along the Genesee River. Subsidence over abandoned salt-mine workings is a process induced by mine collapse. Only the subsidence stop (1) and the meander migration stop (2) will actually be visited on this trip.

B1: LAND INSTABILITY IN THE GENESEE RIVER VALLEY-LIVINGSTON COUNTY

STOP 1. Wang sites SE-01-88 and SE-02-88
Note that these sites are only accessible with permission of the land owner. They may or may not be accessible at the time of the NYSGA field trip. If they are not, then they will be viewed from the parking area at the New York State Historic marker site.
Discussion topics: ( 1) The inception of slope instability on previously stable forested slopes. (2) The initial removal of the soil-zone slab. (3) Interaction among different types of slope failure.
These sites are the key to our interpretation of slope instability and evolution. Landslides have been evolving dramatically in the 6 years since observations were begun by Wang.
The pre-landslide character of the slopes at this site is evident from the still vegetated slopes around and above the active landslides on the east side of the bay. Oak, maple, poplar, and other large trees are rooted in the meter-thick soil blanket developed on slopes as steep as 40°. Up to 1951, the entire slope at this site was stable and completely covered by bushes and trees, many of them 50 years old or older. The slope first became unstable sometime between 1953 and 1960.
In 1988, when Wang made his first observations, multiple landslides were already evident (Figure 3). Figure 3 illustrates what we infer to be the initial stages in the destabilization processes affecting Irondequoit Bay slopes. The meter-high scarp surrounding the landslide complex reveals a meter-thick soil zone. Initial slope failure entailed the downslope movement of slabs the base of which is approximately the base of the soil zone. This slab carried with it all of the trees rooted in the soil zone. Even large oak trees have been transported down slope while initially remaining in upright position. Slab A began to move down slope in April 1990 to the position shown in April 1993.
This initial movement of the soil-zone slab effectively removes the protective cover from the slope, but it does not change the value of the slope angle. This process of block sliding takes place on differing scales as may be seen from the way in which the main scarp of this initial and largest landslides is itself cut by the scarps of several smaller landslides. Some of these smaller landslides are similar in character to, but younger than the largest scarp. In other words, some of these smaller landslides have the same character as the largest slide.
In addition to these slab-like landslides, the lower part of the slope displays slumps, landslides created by failure along a spoon-shaped slip surface. These slumps typically form in material from which all vegetative cover has been removed. The most recent of these have all formed in the summer and fall of 1993. These slumps apparently are triggered by undercutting at the shoreline, especially if the slope above has been denuded of vegetation. The formation of these slumps creates regions where the slope is very steep, commonly vertical. These vertical faces are inherently unstable, and failure occurs here through topple and fall as illustrated at stop 2. It appears that once this stage has been set in motion, a threshold has been crossed so that slope steepening becomes the rule.

STOP 2. Wang site SE-09-88
Access from Bayview YMCA Parking lot. From Bayview YMCA walk down road to burned-out building and through it to the ORV trail marked by orange paint blazes. Continue to Stop 2 at the shoreline. (Alternative access from Smith Road at Empire Boulevard. Smith Road terminates at the east shore of Irondequoit Bay adjacent to a quonset hut owned by the Rochester Canoe Club.)
Discussion topics: ( 1) Lake Iroquois sediments. (2) Present-day processes, especially topple and slump observable in real time. (3) Inception of bluff development in the 1960s.
This site displays 3 bluffs (very steep unvegetated slopes), each of which is vertical in its upper part. The highest bluff rises 26 m (85ft) above water level. The vertical upper face of these bluffs is created in a cohesive clay unit. Earth slump and earth flow of the non-cohesive materials that underlie this clay unit set the stage for the opening of vertical joints in the clay unit. Blocks of the clay unit as large as 2 m on a side then fall from this free face, sometimes remaining intact and sometimes breaking into numerous small blocks.
Below the vertical face are fans of material that has fallen from above and then accumulated at the base. Some vegetation has taken root in this material. During the summer and fall of 1993 and the late spring of 1994, these aprons were being eroded by wave action, and this erosion and undercutting of the base was triggering earth slumps 2.5 to 3.6 m (8 to 12 ft) high at the base of the bluffs. Earth flow is also common in the fans. Most of the steps in the process can be observed in real time whenever waves and boat wakes break along the base of this bluff.
These 3 bluffs first appear in the 1961 aerial photographs; they cannot be recognized in older photographs. They are interpreted as the end product of landslide processes that first operated on steep but vegetated slopes. Remnants of these slopes are still present. Complete removal of the original soil blanket and the vegetation rooted in that blanket set the stage for the operation of slump processes. Undercutting by wave action during periods of high lake level (as in 1973 and 1993) removed the protective aprons, cut a shelf under the vertical bluff, and set the stage for earth topple noted above.

STOP 3. Wang site NE-05-88
Walk north along trail to water tower and then down the west-facing slope west of the water tank at the Webster Water pumping facility.
Discussion topics: (1) Use of multiple scarps in establishing landslide history (oldest and highest scarp dates from 1930 or earlier). (2) Role of high water level and wave activity in setting the stage for slump activity. (3) Probability of future landslide activity. (4) Nature of Lake Iroquois sediments.
This slope displays at least 6 different landslide scarps ranging in age from 1930 (or older) to 1994. The oldest scarp (top at 33 m -110 ft) above water level outlines a landslide area (probable earth block slide) visible on the 1930 aerial photograph. The entire slope within this oldest scarp displays none of the large trees that are uniformly present in the area outside of the scarp line. There were few large trees on this slope even in 1930. The upper part of this oldest landslide is covered by grass, bushes, and by a few trees less than 15 cm (6 in) in diameter.
All of the other scarps lying within the slope area bounded by the oldest scarp are displayed at lower elevations ranging from 8 m to 33 m (27 ft to 108 ft) above water level. Each scarp bounds a separate landslide, some of which are earth slumps. The youngest of these landslides, re-activated in 1993 when lake level was at a 20-year high, illustrates the conversion of a steeply sloping landslide site to an earth slump and vertical bluff.
The earth slump displayed in the lowermost 15 m (50 ft) of this slope began to form prior to 1978. It exposes an excellent sample of the type of section generally seen north of the Route 104 bridge. A clay layer at the base of the slope is overlain. by at least 6 m (20 ft) of sand and silt displaying the climbing ripples characteristic of all northern sections. The upper edge of the scarp of this slump was at 15 m (50 ft) above lake level in May 1994. The upper 2 m of section display clay and silt layers with prominent pillow structures.
The inferred history of this site is as follows: (1-pre 1930) Undercutting at the base; large-scale earth-block sliding of blocks made up of the soil horizons. There were few trees left on this slope after this event. (2) Removal of tree cover, followed by episodes of high lake level led to the inception of the processes active in 1993-1994. (3) Undercutting of the base of the slope by wave action during periods of high water level. Major periods of high water level occurred in 1952, 1973, and 1993. (4) Failure by earth slumping, flow, and topple. These three types of landslide activity occur in conjunction with one another as illustrated by relationships expected to be visible in October 1994.

STOP 4. Genesee River at Dutch Corners Road.
Discussion topics: (1) Rates of migration of Christiano meander (this stop) and Route 20A meander (compare figures 7 and 8), (2) Meander migration process at times of high discharge, (3) Possible role of controlled discharge controlled by the Mount Morris dam.

STOP 5. Route 20A at Boyd Parker Park.
This bridge was destroyed by subsidence 12 March 1994. It is not known at this time (June 1994) if this site will be accessible.
Discussion topics: (1) The sequence of subsidence events (see figure 8), (2) The relation between subsidence and the mine workings, (3) Hydrologic questions, (4) Future prospects for subsidence and hydrologic impacts.

B2: ORDOVICIAN AND SILURIAN STRATA IN THE GENESEE VALLEY AREA SEQUENCES, CYCLES AND FACIES
CARLTON E. BRETT
Department of Earth and Environmental Sciences
University of Rochester
WILLIAM M. GOODMAN
The Sear-Brown Group
85 Metro Park
STEVEN T. LODUCA
Department of Geography & Geology
Eastern Michigan University
Ypsilanti, Michigan 48197
DAVID F. LEHMANN
Huntingdon Engineering and Environmental
535 Summit Point Drive
Henrietta, New York 14467
Upper Ordovician and Silurian strata in New York State are well-known from their spectacular exposures in the Niagara and Genesee River Gorges. Because of the excellent exposures in western New York, the descriptive stratigraphy of these units is well-refined, and the interval has recently been used as a test case for models of eustatic and tectonic stratigraphic dynamics. Important modern works concerning the litho-and biostratigraphy of these strata include Gillette (1947), Fisher (1953, 1960, 1966), Kilgour (1963), Rexroad and Rickard (1965), Zenger (1965, 1971), Rickard (1969, 1975), Martini (1971), Brett (1983), Duke (1991) and Loduca and Brett (1991 ). Allostratigraphic analyses have been performed by Duke and Fawcett (1987), Brett et al. (1990a, b; 1991) and Goodman and Brett (1994).
The Upper Ordovician and Silurian strata of the Genesee Valley and surrounding areas were deposited near the northern reaches of a dynamic and rapidly evolving Appalachian foreland basin. The striking patterns of unconformity and lateral basin axis shift are striking given that the Late Ordovician and Silurian Periods are generally considered to be times of tectonic quiescence between the Taconic (late Middle Ordovician) and Acadian (Middle to Late Devonian) Orogenies. Foreland basin flexure produced asymmetric marginal unconformities, but the differential subsidence did not obscure relative sea-level trends in litho-and biofacies that correlate with patterns in other basins. Thus, the stratigraphic interval exposed in the Genesee Gorge is an excellent field laboratory for the interaction between tectonic foreland basin flexure and eustatic sea-level changes.
During the Late Ordovician and Silurian, the northern Appalachian Basin was situated within a subtropical climatic belt, probably at about 20 to 25 degrees south latitude (Van der Voo, 1988, Witzke, 1990). Climates apparently oscillated from relatively arid during the Late Ordovician to humid during the Early Silurian and back to very arid during the Late Silurian. During the Late Ordovician and Early Silurian, the bulk of the basin fill in western New York represents marginal marine to nonmarine settings. Siliciclastic sediment that infilled the basin appears to have been shed from rejuvenated Taconic source areas primarily located to the east and southeast. Open marine facies that are time-correlative to the Queenston Shale and Medina Group are situated northwest of the Niagara region.
A low forebulge, Algonquin was intermittently uplifted along to northwestern rim of the basin (Figure 1).
Subtidal ramp carbonates are preserved in the lower Clinton Group between Niagara and Wayne Counties, New York. The onset of clean carbonate deposition stratigraphically above a low angle, regional unconformity at the top of the Medina Group suggests structural uplifting of the Algonquin Arch during lower Clinton time. Unfortunately, a late Llandoverian unconformity that divides the Clinton Group into two units removed a significant portion of the lower Clinton stratigraphic record in western New York. Consequently, paleogeographic reconstructions can only be indirectly inferred from biofacies and textural trends in the truncated carbonates and siliciclastic facies belts situated farther east.
During the Late Silurian (Wenlockian and Ludlovian Epochs), upper Clinton and Lockport carbonates accumulated on the western basin ramp. Except for the Wenlockian eustatic sea-level highstand during which the fossiliferous Rochester Shale accumulated over significant portions of the basin, persistent siliciclastic sedimentation was restricted to the eastern ramp and basin center. Shales and mudstones commonly occupy the central, offshore facies belt. The eastern strandline facies belt is dominated by sandstone and conglomerate.
Late in the Silurian (Pridolian Epoch), circulation within the basin became restricted in response to increased aridity and fringing reefs of the Guelph Formation (Rickard, 1969). Increased siliciclastic sedimentation associated with the formation of the Bloomsburg-Vernon deltaic complex may signal rejuvenation of the eastern basin flank and cannibalization of Upper Ordovician and Lower Silurian strata during the Salinic Disturbance. Following accumulation of deltaic red beds across western New York, a thick sequence of peritidal carbonates, mudstones and evaporites (Salina Group) accumulated in western New York and surrounding areas. Resumption of more normal shallow marine conditions is recorded in the Cobleskill biohermal dolostone which is the youngest pre-Helderberg Silurian unit preserved west of Cayuga County.
In this paper, details of upper Ordovician and Silurian stratigraphy are provided in a regional context so that a framework may be established for the Rochester area facies. Where interpretations of allostratigraphy have been developed, depositional sequences and smaller, component cycles are discussed. This presentation proceeds in ascending stratigraphic order.

B2: ORDOVICIAN AND SILURIAN STRATA IN THE GENESEE VALLEY AREA SEQUENCES, CYCLES AND FACIES

Ascending Pinnacle Hills moraine
Ascending Pinnacle Hills moraine to crest at Highland Avenue; Mt. Hope Cemetery on left is built on eggs-in-a-basket kame sand and gravels; this classic cemetery displays beautiful small-scale kettles and kames. Modern Genesee Gorge was initiated when Lake Scottsville waters poured over low spot in the Pinnacle Hills moraine just west of the cemetery at University site.

Descending Pinnacle Hills moraine

Rochester's oldest building
Site of Rochester's oldest building (1 Mt. Hope), on left made of local Medina sandstone

Access to the Middle Falls of the Genesee.
Brewer Street to left at St. Matthews Church with red tiled roof; this small road provides access to the Middle Falls of the Genesee.

STOP 1A-GENESEE RIVER GORGE AT LOWER FALLS ON RG&E ACCESS ROAD
The best section of the Upper Ordovician and Lower Silurian rock in the Genesee Gorge is exposed along the access road to the Rochester Gas and Electric Company (RG & E) Power Plant #5 on the east side of the Genesee Gorge (Liebe and Grasso, 1988). The road is open to pedestrians as a fisherman's access, and starts at a gate just south of Seth Green Drive, opposite the intersection of St. Paul Street and Norton Street. Stratigraphically lowest outcrops on the roadcut are beneath and just south of the newly reconstructed Driving Park (Avenue E) Bridge; roadcuts extend for about 0.7 km northeast of the bridge along the access road.
The easily accessible portion of the succession ranges from the Queenston Shale upward to Reynales carbonates. These units will be described successively in the following sections.
Queenston Shale
The lowest unit exposed in the Rochester area is brick red mudstone and fine-grained sandstone of the Late Ordovician (Ashgillian) Queenston Shale. The Queenston Shale is believed to be separated by an unconformity from the overlying Silurian beds, although the magnitude of this unconformity is difficult to determine because of the unfossiliferous nature of rocks above and below it.
Only the upper 15 to 20 meters of Queenston Shale is exposed in the Genesee Gorge below the Lower Falls. The formation is estimated to be over 300 m (1 000 ft) thick in the Rochester area. Sandstones are typically lenticular and exhibit small-scale trough cross stratification, asymmetrical ripples and desiccation cracks (Duke, 1987). The Queenston Shale exposed in New York State generally lacks body fossils but contains varied horizontal and vertical burrows. One fine-grained sandstone displaying Skolithos occurs immediately below the contact with the overlying Medina Group. Paleoflow directions determined from crossbedding indicate a dominant north-northwest current orientation.
Broadly, the Queenston reflects post-orogenic molasse derived from the Taconic source terrain which existed some 300 km to the southeast of Rochester during late Ordovician time. The Queenston culminates a shallowing-upward (pro-gradational) sequence and records over-filling of the Appalachian basin with siliciclastic debris. The formation is often regarded as a tectonic fan delta, the so-called Queenston Deltaic Complex.
Medina Group
The Medina Group exposed in the Genesee River Gorge is composed of 17 m (50 ft) of red-and white-mottled sandstone with a few beds of red mudstone and siltstone. The sequence has recently been revised and divided into five units: the Devil's Hole, Grimsby, and Thorold sandstones, Cambria Shale, and Kodak Sandstone.
The lowest three meters of reddish coarse sandstone represent a distinct interval thought to be correlative with the Devil's Hole phosphatic sandstones in western New York and Ontario (Duke 1987; pers. comm. 1988). This lowest Medina interval weathers as a massive ledge of planar laminated to trough cross-stratified, subarkosic, medium-space to coarse-grained sandstone and can be informally divided into two portions. The lowest bed displays a sharp to slightly undulating contact on the uppermost fine-grained sandstone beds of the Queenston Formation. There is some evidence for erosion on this surface which represents a widespread Ordovician-Silurian disconformity of considerable magnitude (Cherokee discontinuity of Dennison and Head, 1975). The presence of iron and phosphatic ooids and crinoids, together with coarse quartz granules suggest that this basal unit in part represents a transgressive lag deposit (Duke, 1987). These sediments have probably been reworked in a shallow marine bar-tidal channel complex. Higher parts of the Medina, assigned to the Grimsby Sandstone,include three small scale bed-thickening and coarsening-upward successions. The predominant lithologies are red and white mottled, cross-laminated to planar bedded sandstone and maroon shale. The tops of the cycles are sharply overlain by channel-filling sandstone bodies that display lateral accretion surfaces. The erosive bases of these channels have removed much of the underlying coarsening upward strata in underlying cycles. Upper portions of the sandstone bodies are strongly bioturbated.
A highly distinctive interval of massive pink and white mottled sandstone overlies the Grimsby with a sharp, erosive contact. The basal massive ledge, about 4m below the white Kodak Sandstone displays spectacular Arthrophycus and Daedalus trace fossils, which probably represent mining traces (fodinichinia) of large worm-like organisms. The latter consists of complexly swirled spreiten structures that protrude downward for up to 70 cm. This interval, formerly referred to as Daedalus bed, has recently been correlated with the Thorold Sandstone of western New York and Ontario (Brett et al, 1990a,b; Duke, 1991 ); in contrast, most previous workers (Gillette, 1947; Fisher, 1953, 1960) correlated the Thorold with the higher Kodak Sandstone of Rochester.
The presence of larger-scale, coarsening-upward sequences capped by fining-upward channel sandstones suggests aggradational tidal flat and channel settings of the upper Grimsby and Thorold sediments. The absence of body fossils in the sandstone may indicate the presence of brackish water in which the trace makers of Daedalus and Arthrophycus apparently flourished; recent discoveries suggest that these two traces represent different behavioral patterns of a single species of infaunal animal.
The maroon siltstones and shales of the Cambria Shale, which conformably overlie the "Daedalus bed", were apparently deposited in restricted subtidal settings. Ostracodes are present in drill cores as far east as Webster, New York and a trilobite resting trace, Rusophycus, has been noted in Cambria strata of the Rochester area.
The Kodak Sandstone forms a distinctive 1.5 m light gray band of heavily bioturbated friable arenite. This unit displays a sharp but probably conformable contact with the underlying Cambria coarsening upward cycle. Iron in the Kodak has been reduced or leached altered due to percolation of reducing waters from the overlying Maplewood muds. Hence, the Kodak is (pale) greenish grey color, as is any unit which directly underlies the Maplewood (Duke and Fawcett, 1987; Duke, 1991 ). This diagenetic "bleaching" has resulted in a light zone at the top of the Medina at all localities in western New York, despite the presence of various units beneath a regionally angular unconformity; as a result the Kodak was previously miss-correlated with the Thorold in the west. The Kodak Sandstone, which forms the cap rock of the Lower Falls on the Genesee River, is poorly dated because of an absence of zonally significant fossils, but it is generally regarded as of early Llandoverian age (Maxwell and Over, 1994).
Clinton Group
The Clinton Group at the Genesee River Gorge consists of a heterogeneous assemblage of shale and carbonates and one thin hematitic bed, totaling about 55 m (170 ft) in thickness. These rocks span middle Llandoverian to early Wenlockian age. The Clinton contains a major unconformity, recently described in detail by Un and Brett (1988) and thus can be informally subdivided into upper and lower Clinton strata, following the earlier use age of Gillette (1947).
The Maplewood Shale, lowest of the Clinton units, consists of 6 m (18 ft) of soft greenish-grey clay shales. Despite its prominence in the Genesee Gorge, the unit pinches out at Webster only 10 km northeast of Rochester. Macrofossils are very rare in the Maplewood Shale, although recently S.J. Ciurca (pers. comm.) has obtained lingulid brachiopods, nautiloids, eurypterid fragments, and complete specimens of a new species of crinoid from it. The Maplewood is noted for its diverse and well preserved microflora acritarchs and chitinozoans (Fisher, 1960; Miller and Eames, 1982). The Maplewood muds were probably deposited in shallow, but stagnant, low energy nearshore settings (lagoonal).
Maplewood shales are bounded by phosphatic pebble beds at the base and top. A zone, up to 10 cm thick, at the base of the unit carries large clasts of phosphatized sandy carbonate and black fossil steinkerns of fluoroapatite (Boger and Sutphin, 1984; Paxson, 1985). This zone, the Densmore Creek phosphate bed, records a significant disconformity that can be traced westward into Niagara County, where it erosionally truncates the underlying Kodak Sandstone. This establishes the basal sequence boundary of Sequence II. To the east of Rochester this pebble bed is more hematitic and grades in the Webster bed of the Furnaceville Formation (LoDuca and Brett, 1994). The unit apparently records an interval of sediment starvation and erosion associated with the initial Clinton sea level rise. The upper contact of the Maplewood is also marked by a phosphatic bed at the base of the overlying Brewer Dock Member of the Reynales Formation.
The Reynales Formation is a carbonate-rich interval well exposed along the upper end of the RG&E access road; the age of this formation is debatable, but it probably ranges around Middle Llandoverian and contains the boundary between the D. kentuckyensis and staurognathoides conodont zones (Maxwell and Over, 1994). The formation is subdivided into three members (Paxson, 1985). A basal 0.6 m (20 in) thick Brewer Dock Member consists of nodular silty limestones with abundant phosphate pellets and interbedded green shales. This unit is rich in fossil bryozoans, brachiopods, and crinoid ossicles. The Brewer Dock is overlain by a distinctive, 30 cm-thick hematite band which, incorrectly, has been called Furnaceville. The hematite bed, referred to as the Seneca Park Hematite by LoDuca and Brett (1994), overlies a prominent zone of ball-and-pillow deformation. It is dull-red fossil ore, comprising hematite-replaced Helopora and other bryozoans, crinoid columnals, and rare ooids. The hematite bed displays cross-stratification with a north-westward paleo direction and a rippled top.
The upper Reynales (or Wallington Member) is a 5-6 m (16-18 ft) thick interval of thin to medium bedded, medium grey dolomitic limestone with greenish grey silty shale interbeds and partings particularly near the base. Most of the carbonate is laminated pelletal grainstone. Several beds in the lower portion of the unit contain bluish-grey chert nodules. Fossils, include Eocoelia brachiopods and complete specimens of the unusual crinoid Stipatocrinus (Eckert and Brett, 1987). Several beds, most notably a one meter thick ledge-former near the top of the formation, contain large specimens of the brachiopod Pentamerus oblongus, indicative of shallow, agitated shoal settings.

STOP 1B. LOWER FALLS, GENESEE RIVER
This overlook provides a panorama of the Lower Falls of the Rochester Gorge. The Lower Falls, with a drop of 30 m (97 ft), is capped by resistant sandstones of the Upper Grimsby and Kodak Formations.
The stratigraphic units examined previously (Stop 1 A; Queenston Shale to Reynales Limestone) are clearly visible near the base of the gorge beneath and immediately south of the Driving Park Bridge. Higher units of the Clinton Group can also be viewed from this vantage point although their limited accessibility precludes close examination during this trip.
The Reynales carbonates are observable immediately opposite this point near the base of the large water surge tank of the Rochester Gas and Electric Company. They are overlain by an interval of shales which actually constitute two distinct units. The lower 4.4 m (13 ft) of greenish to purple Lower Sodus Shale is unconformably overlain by 2 m (6 ft) of black to greenish-grey, graptolite-bearing Williamson Shale. The contact of these formations is cryptic but actually represents a significant, regional, angular unconformity that bevels successively older units in a westward direction (Lin and Brett, 1988). This erosional surface, which may reflect the eastward migration of a forebulge, is onlapped by a widespread dark shale of the latest Llandoverian Williamson Formation. The Williamson Shale is followed by thin-bedded dolomitic carbonates and grey shales of the Rockway Formation. The overlying Irondequoit Formation is thicker-bedded and contains small bryozoan-algal bioherms up to about 2 m in height. These can be seen to deform strata in the cliff near the deck level of the Driving Park Bridge. They were initiated on a single horizon of crinoidal packstone near the base of the Irondequoit Limestone. In turn, the Irondequoit Limestone is overlain here by about 3 m of brownish-grey, fossiliferous Rochester Shale, which is bevelled and overlain by glacial deposits.

STOP 1C. HIGH (UPPER) FALLS PARK, GENESEE RIVER
This park provides a view of the 25m (80 ft) High Falls, formerly a major source of water power for industry. Rochester developed as a grain milling center in the mid 1800's largely as a result of its location on the Erie Canal and the presence of this source of power (seeGrasso and Leibe article in this guidebook). Nearly vertical cliffs in the Genesee River Gorge below the High Falls display almost complete section of the Rochester Shale. This may be the oldest type locality in North America, the Rochester Shale having been named by James Hall in 1839. The Rochester Shale, here about 30 m (98 ft) thick, contains grey, calcareous shale with numerous thin calcisiltites (Brett, 1983a). The Rochester Shale is moderately to sparsely fossiliferous with an abundance of brachiopods and the trilobite Dalmanites. However, it is largely inaccessible at the type section. The Rochester appears to record a slight shallowing of relative sea level, with an increase in the number and thickness of dolomitic carbonate interbeds toward the top as it passes up into the predominantly carbonate DeCew and Lockport Formations. The upper unit of the Rochester Shale, comprising approximately a third of the diff at this section, is the Gates Member. The Gates, DeCew, and Lockport units will be examined in greater detail at Penfield quarry (Stop 3). Rochester and DeCew strata represent shallow subtidal, muddy marine deposits, as indicated by the abundance of fossils and lack of tidal features.

Broad St; bridge on old aqueduct

Penfield and Eramosa fms.
Former "Can of Worms" area, minor low cuts in upper Penfield and Eramosa formations of Lockport Group formerly biostromes were exposed near top of Penfield.

There are low cuts in DeCew dolostone along exit.

STOP 2. PALMER'S GLEN (TRYON PARK)
Walk into the field into the right of the highway and then straight, paralleling the highway, down a bank, to ramp road of sewage treatment plant leading down to the level of small creek.
This unnamed creek, informally referred to as Palmer's Glen, also serves as an overflow stream for the storm sewer system. The water in the creek is contaminated to some degree and should be dealt with cautiously.
Lowest exposures along the banks of this creek are at the lower part of the Sodus Formation. This interval is slightly above the upper beds viewed at the Genesee gorge along Seth Green Drive. The shales here range from greenish gray to light purplish gray in color. The purple colored shales appear to cap small shallowing cycles within the Sodus. These cycles commence with thin shelly and, in some cases, phosphatic beds and pass upward into greenish gray shales and these latter gray upward to purplish hued shales. Both green and purple shales contain a shallow marine fauna of the classic Eocoelia biofacies of (Boucot, 1975) Bedding plane assemblages are dominated by Eocoelia cf. E. hemispherica. These are mixed with small bivalves (pteriniids), rare Leptaena, small tabulate corals, Tentaculites, and abundant ostracods of the Zygobolba decora zone. At this locality thicker coquina beds of sandy limestone rich in Eocoelia also occur near the top of the Sodus.
The Sodus is capped by a major erosion surface, probably the largest unconformity within the Silurian. However, the unconformity is relatively cryptic at this locality, and is overlain by hard black shale of the Williamson Formation. The contact here is marked by a thin yellowish clay, which could be a bentonite. The basal Second Creek bed of the Williamson Shale is a thin phosphatic, skeletal rich sandstone generally less than one centimeter in thickness. Higher beds consist of an alternation of decimeter-scale hard dark gray shale and soft greenish gray shale beds. The black shales contain laminae of fine quartz sand, some of which possess small scale asymmetrical ripples on their tops. The black sandy shales also display well preserved graptolites of the Monograptus clintonensus-Retiolites venosus assemblage. These graptolites, together with abundant conodonts obtained from basal lags within the Williamson Shale, indicate a latest Llandovery (or late Telychian) age for these shales. The Williamson here is approximately four meters in thickness. It is overlain at a minor disconformity by the dolomitic limestones and greenish gray shales of the Rockway Formation. A thin bed at the base of the Rockway contains quartz granules and small pebbles as well as black phosphatic nodules, but these are highly scattered and the bed is difficult to observe. In turn, the Rockway is approximately 2.8 m-thick and is overlain by 3.2 m. of dolomitic crinoidal wacke-to packstones of the Irondequoit Formation. These rocks occur high in the bank at this section, and can be best viewed by walking downstream approximately 100ft to the fork of Browncroft Creek, and walking upstream (south) into the Browncroft fork. Here the Rockway, Irondequoit and basal Rochester Shale can be viewed at a small waterfall section.

Small stream on right exposes upper portion of Rochester Shale

Ascending hill out of Irondequoit Valley
This is the old River Valley of the preglacial Genesee River, now occupied by underfit Irondequoit Creek.

STOP 3. DOLOMITE PRODUCTS QUARRY, PENFIELD
This large, active dolomite quarry, about 30 m (100 ft) deep, exposes a nearly complete section of the Lockport Group and its contact with the underlying Clinton Group (Grasso and Friedman, 1989; Zenger, 1965). Crushed stone quarried at this location is used primarily for road-paving material. The quarry is famous among amateur mineral collectors as a source for euhedral crystals of saddle dolomite, calcite, sphalerite, galena, pyrite, celestite, selenite, and especially, clear bluish fluorite which occur in 20 to 50 cm. diameter vugs within the dolostone at several horizons. The source and timing of the mineralization is enigmatic but it occurred at temperatures of approximately 150°C. Mineralization occurred selectively within cavities produced during dolomitization, many of which represent former coral and stromatoporoid heads. Dolomitization in the Lockport Group is evidently of replacement type and has resulted in strong recrystallization and obliteration of much of the primary carbonate fabric. Dolomitization may have been produced by seepage refluxion of brines during deposition of the overlying Salina Group or may be of deep burial origin.
The Penfield Quarry was studied in detail by Zenger (1965), who designated this exposure as the type section of his Penfield Member, here comprising 19.2 m (63 ft) of sandy dolostone and dolomitic sandstone. Zenger also identified the upper 5.2 m (17 ft) of the section here as basal "Oak Orchard Member," which is now referred to as the Eramosa Formation. Recent deepening of the quarry and detailed regional correlation permit a reevaluation of this stratigraphy (Brett, et al., in prep.). The Gates Member of the upper Rochester Shale is the lowest unit exposed in the quarry. It can be observed in a sump pit near the western edge of the quarry. The Gates contains dark grey, sparsely fossiliferous, bioturbated, silty, dolomitic mudstone and argillaceous dolostone. Planar and irregular (hummocky?) cross-stratification common in silty layers; many bedding planes contain the dendritic feeding trace Chondrites and oscillation/interference ripple marks aligned roughly NE-SW. Lingulid and rhynchonellid brachiopods and crinoid ossicles are present, a spectacular occurrence of over 1000 complete crinoids (Dimerocrinites) was discovered in this portion of the quarry.
The Gates Member is overlain at a sharp contact by about 3 m (15') of thick-bedded to massive DeCew Dolostone. The lowest meter is a blocky bed of sandy, pale gray, buff-weathering dolostone with soft sediment deformation and hummocky cross-stratification that is prominently displayed in the main lower floor of the quarry. The hummocks are ellipsoidal, average approximately 1 m in length along their long axes, and are spaced about 0.5-1.0 m apart.
The basal DeCew was probably the lowest unit exposed when Zenger measured the quarry. Subsequent cutting of the sump pit revealed that the quarry floor was very close to the base of the DeCew, (whereas Zenger had apparently considered it the top of that formation). This bed is overlain by about 5 m (15 ft) of dolomitic sandstone and arenaceous dolostone with two prominent partings which display rusty staining due to ground water seepage. The DeCew is sparsely fossiliferous except for scattered stringers of crinoid columnals and occasional orbicerloid brachiopods, but sandy beds contain vertical Skolithos-like burrows. The Gates-DeCew interval is interpreted as mixed siliciclastic and allodapic carbonate sands and silts which were rapidly deposited basin-ward of shallow, winnowed platforms developed north (?) of this area. Gates-DeCew sediments accumulated in shallow subtidal areas below fair-weather wave base but subjected to frequent storm wave disturbance. Most of the higher quarry wall is composed of brownish grey to medium grey, medium-to thick-bedded, sandy dolostone which displays planar and bidirectional cross-stratification. Layers and lenses of crinoidal grainstone occur in the lower 5 m which terminate at the top of the lower level of the quarry. The meter-thick bed just below the second bench of the quarry (approximately 12.5 m) is highly crinoidal and contains intraclasts as well as rare rugosan and favositid corals. It is overlain by a 9 m (28.5 ft) interval of medium and even-bedded, sandy dolostone, with thin shaley partings, that appears to correlate with the Goat Island and Eramosa formations of the Lockport Group.
The entire 15 m interval, corresponding to the members of the Gasport, Goat Island, and Eramosa formations, is enriched in quartz sand in the Rochester area, and the name Penfield Formation is perhaps useful in emphasizing this facies distinction. However, it should be noted that members, and even certain marker beds, in the Gasport interval can be traced across the facies change. Crowley (1973, unpubl.) emphasized the locally sandy nature of the Penfield and interpreted the unit as representing a shallow water sandy shoal or "Penfield island"; but the persistence of sedimentary cycles and elements of the typical Gasport marine fauna into the Penfield area indicates an environment similar to that of the typical Gasport facies. Crinoidal grainstones of the Gasport and sandy crinoidal dolostones of the lower Penfield represent similar environments, i.e., a shallow wave-winnowed and perhaps tidally-influenced (bimodal cross stratification) shelf with local shoals or bars, close to fair weather wave base. The increased sand content of this facies in the Penfield area appears to indicate a local source of siliciclastics north of this region. Upper units are thinner-bedded and more argillaceous than the Gasport equivalents and record a transition to somewhat lower energy, probably deeper water environments similar to those in which the Gates-DeCew interval sediments accumulated.
The highest beds exposed in the Penfield Quarry consist of massive, highly fossiliferous and vuggy dolostones that were assigned to the lower 5.5 m (17 ft) portion of the "Oak Orchard Member" by Zenger (1965); recent study demonstrates that the term Oak Orchard is invalid, and we assign these beds to the Eramosa Formation Prominent, 0.5 m thick, light grey-weathering, dolostone beds occur about 2 and 3 m below the top of the quarry. Dark biostromal beds on either side of these horizons are rich in poorly preserved, and typically mineralized tabulate corals (Favosites, Cladopora), and small domal stromatoporoids. These beds contain numerous large vugs which are lined with nodular anhydrite, scalenohedral calcite, pink saddle dolomite, celestite, sphalerite, rare fluorite and sulfides; these vugs are the principal source of the Penfield minerals. Although the vuggy beds are inaccessible in the vertical quarry walls, they can be examined readily in large fallen blocks piled on the higher bench in the quarry.
The upper Lockport strata at Penfield (>5 m) are distinctly less sandy than the lower beds and more highly fossiliferous. The Eramose interval records a general decrease in the input of siliciclastic sediments and the development of coral-stromatoporoid biostomes and associated carbonate sediments in shallow, but relatively quiet water environments.

Westernmost known exposure of Wolcott Limestone
A small outcrop in ditch is the westernmost known exposure of Wolcott Limestone; the unit is truncated between this locality and Rochester.

STOP 4. (optional) OLD FRUITLAND ORE PITS PARK
Park in lot near building and walk to the right (north) past end of pond and then left (west) along the north side of the pond onto dump piles of rock dug from the pond.
The ponds in this park represent old pits dug in the Furnaceville hematite or iron ore bed for the production of red paint oxide (Gillette, 1947). Although in-place rock is no longer accessible within the flooded pits, dump piles provide an overview of the lithology of the Reynales Formation. Most slabs consist of dolomitic limestone with minor bluish gray chert nodules. Molds of pentamerid brachiopods are common on certain slabs. Pentalobate columns of the newly described inadunata crinoid Haptocrinus are relatively abundant. While most of the hematitic band was removed for the paint ore production, occasional blocks and slabs show the highly fossiliferous, oolitic hematite.

Furnace Road (named for old blast furnaces for iron production from Furnaceville iron ore).

Williamson Shale type section
Cross Salmon Creek, type section of the mid Silurian Williamson Shale is slightly upstream (south) of road.

Small exposure of yellowish weathering Rockway Shale is in ditch.

Very minor low outcrops of Rochester Shale in ditch to south.

View of large wave modified drumlin on right (south).

Rochester Shale below road.

Glenmark Shale with distinctive fauna
Note ditch to north (left) near Wallington town line; yellowish clay is weathered Glenmark Shale (formerly considered as upper part of Rochester Shale). This small exposure has yielded very abundant brachiopods, especially Nucleospira pisiformis, and small Enterolasma (rugose corals) Stegerhynchus neglectum. The Glenmark horizon with its distinctive fauna can be correlated from this small outcrop southward into the central Appalachians of Pennsylvania, Maryland, and West Virginia.

STOP 5A. SECOND CREEK AT ALTON
Park opposite southern fence line segarating planted field to south from sheep pasture on left (west) side of Shaker Road. This is the former Shaker Tract, or Alasa farms: white barns to the north now house the Lake Plains Wildlife Rehabilitation Center
Follow along edge of fence back to woods bordering east side of Second Creek: enter woods and turn right following near tog of bank for about 0.1 mile to where an old logging road descends to creek level: go downstream {north) for one major bend and walk across floodplain and creek to bank on west side.
This creek bank exposes a small but excellent section of the Clinton strata. Lowest beds exposed are in the Wolcott Furnace Formation, which consists of alternating greenish gray fossiliferous shales and limestones, containing an undescribed stricklandiid brachiopod, together with chaetetid sclerosponges, crinoid ossicles and small Enterolasma rugose corals. These beds also display thin fossiliferous hematitic limestone bands. At the top of this interval is a thin, but distinct bed containing granular black phosphatic material. About 20 cm of overlying greenish gray shale may represent the westernmost occurrence of the Sauquoit Shale, an interval which exceeds 30 m (100 ft) in thickness in east central New York, south of Utica. Here the interval has very nearly been truncated by an erosional surface. This unconformity is marked by a sharp surface and a very distinctive lag conglomeratic bed (the Second Creek phosphatic bed), best developed at this locality. This bed is approximately 1 to 2 cm in thickness, but in places, it contains clasts of dolomitic limestone, evidently derived from nearby exposures of the Wolcott or other lower Clinton carbonates. The clasts rarely exceed a cm in thickness, but may be up to 10 cm across. In places, these clasts are edgewise and may jut upward into the overlying Williamson Shale a few centimeters. The erosional clasts are packed in a matrix of dark gray, very pyrite-and phosphate-rich crinoidal grainstone. Pebbles of black phosphate and quartz up to 1 centimeter in diameter are present within the matrix. The lower surface of the bed is typically sharp and slightly irregular. Its upper contact is sharply overlain by black or very dark gray Williamson Shale and typically displays an abundance of the brachiopods Eoplectodonta and Atrypa. Current aligned specimens of the graptolite Monograptus clintonensus occur on the contact in some places. The unconformity here is the same one examined at Palmers Glen near Rochester (STOP 2). However, here the Williamson Second Creek phosphate bed unconformably overlies a remnant of the Sauquoit Formation, whereas at Rochester, the Williamson rests on the lower portion of the Sodus, some 10 m lower in the section. Hence, the unconformity is regionally angular and has truncated successively older Clinton strata to the west.
The overlying Williamson Shale includes alternating relatively hard, very dark gray to black graptolitic shale and soft greenish gray claystones. As at the Palmers Glen exposure (STOP 2), graptolites are generally confined to the dark gray layers and may occur on laminae of quartz sand or very coarse silt. Greenish gray layers are generally barren of fossils but may contain bedding plane assemblages of frilly Atrypa and Eoplectodonta. We will walk upstream along the bank of Second Creek to outcrops of the Rockway Dolostone and shale and the Irondequoit Limestone. The Rockway, well displayed in slabs recently ripped up during flooding from the creek floor, is fossiliferous, somewhat greenish gray silty mudstone, which weathers to a yellowish color. It contains an abundance of brachiopods, particularly Clorinda, (considered a classic deeper water, benthic assemblage 4 to 5 indicator), Leptaena, Atrypa, and others. The shales also contain scattered specimens of the small rugose coral Enterolasma and this locality has yielded specimens of the probable green alga Ischadites. Thin, muddy, micritic limestones interbedded with the shales contain scattered crinoid-bryozoan debris, including calyces of the tiny inadunata crinoid Pisocrinus. The contact with the overlying Irondequoit Limestone at this locality appears conformable, but relatively sharp. The Irondequoit consists of approximately 3 m of crinoid-and brachiopod-rich wacke-and packstone limestone. Small bioherms of bryozoans and possible algal bound micrite are also present at several levels in the creek bed and minor waterfalls here. The Irondequoit is interpreted as a relatively major sea level low stand or shallowing event that separates the maximally transgressive Williamson and Rockway deposits from the overlying deeper water Rochester Shale. The small patch reefs appear to have grown upward during times of relative deepening as the Irondequoit passed upward into mudstones of the Rochester Formation.
If time permits, we may walk further upstream to sample from the richly fossiliferous lower Rochester Shale which contains a diversity of brachiopods, small corals, and trilobites. Most of these fossils, however, are present as disarticulated and somewhat fragmented material.

STOP 5B. (optional) SECOND CREEK AT RED MILL ROAD
If time permits, we may look at the section along Second Creek at Red Mill Road. Immediately downstream from the road bridge are bank outcrops of green to purplish colored Upper Sodus Shale, containing a diverse Eocoelia brachiopod and ostracod rich Zygobolba decora fauna. These beds are sharply overlain by crinoid-and pentamerid-rich grainstones of the Wolcott Formation.

Good view of Sodus Bay to left (north).

STOP 6. UNNAMED TRIBUTARY OF SODUS CREEK
Unnamed tributary of sodus creek immediately east of Norris road and south of US route 104. Pull off to right and park on shoulder of NY 104: walk down into small gully immediately south of the highway at point where an exposed yellowish clay (Rochester Shale) is visible on bank above gully: you can then continue to the south into woods along the unnamed tributary of Sodus Creek.
This small creek provides a relatively complete outcrop of the upper portion of the Rochester Shale. The section begins with the weathered bank parallel to and south of Route 104. This bank yields good specimens of weathered brachiopods, particularly Eospirifer, Rhynchotreta, and Whitfieldella. Upstream, along the main creek, are good exposures of the middle and upper portions of the Rochester Shale. Thick calcisiltite beds occur near the mouth of the stream in some of the lowest exposures. Upstream, a series of low waterfalls or riffles expose highly fossiliferous, bryozoan rich layers corresponding to the upper marker beds of the Lewiston Member (Lewiston E or bryozoan beds in Niagara County, New York), alternating shales and thin biostromal limestones, rich in the small ramose bryozoan Chilotrypa. Associated with these layers are abundant articulated and specimens of the brachiopods Whitfieldella, Rhynchotreta, Eospirifer, Atrypa and rare well preserved specimens of the trilobites Calymene, Bumastus and others.
The change to more sparsely fossiliferous shales above this small falls marks the contact between the Lewiston and Burleigh Hill members. The upper beds, south to the bridge of York Settlement Road, are within the upper part of the Rochester Shale and consist of alternating mudstones, thin shell layers and calcisiltite beds. Some layers particularly near the top are rich in trilobites such as Dalmanites, and brachiopods such as Stegerhynchus, Coolina, Dalejona and occasional small rugose corals (Enterolasma). The change from bryozoan-rich biostromes to more sparsely fossiliferous shales marks a relatively major flooding surface within the Rochester Shale that can be identified throughout much of New York State and Pennsylvania. The upper shaly interval is more monotonous than the lower portion, reflecting highstand conditions. However, in the uppermost 2 to 3 m the shales become increasingly interbedded with dolomitic calcisiltites.
The section is capped by a low waterfalls immediately north of the bridge on York Settlement Road. This falls is capped by a distinctive 40 em-thick massive dolomitic limestone bed, referred to as the basal Glenmark bed. This bed, which contains small favositid and rugose corals, as well as the distinctive brachiopod Nucleospira, marks the approximate position of the DeCew Dolostone of western New York. This bed and the overlying shales, which are rich in distinctive brachiopods, particularly Nucleospira, and Whitfieldella {cf. W. marylandica) represent an important marker interval that is traceable from this area of New York State southward through much of central Pennsylvania Appalachians and into Maryland and West Virginia. This interval, previously unrecognized or treated as simply an upper portion of the Rochester Shale is herein recognized as a distinctive unit referred to as the Glen mark Formation. In nearby Sodus Creek, this 3 · m interval is overlain by thinly bedded micritic limestones and very dark grey, fissile shales, as well as thrombolitic and intraformational conglomeratic horizons marking the base of Sconondoa Formation, the lateral equivalent of the lower part of the Lockport Group of western New York. It represents a distinctive shallowing to nearly peritidal or shallow lagoonal conditions in the late Wenlock or early Ludlow time.

Maplewood Shale was exposed in ditch between two lanes of Rt. 104.

Bay Road
A turn left here would lead to Glen Edith Road and outcrops along road leading down to restaurant by Irondequoit.

East side Irondequoit Bay
Note slumps of soft lake silt; views of bay and bay mouth bar from bridge.

Cross Densmore Creek
Good exposures of Medina and lower Clinton outcrop along the Creek west of the highway to Densmore Road.

B3: THE LEROY BIOHERM REVISITED: EVIDENCE OF A COMPLEX DEVELOPMENTAL HISTORY
THOMAS H. WOLOSZ
Center for Earth & Environmental Sciences
SUNY College at Plattsburgh
Plattsburgh, N.Y. 12901
DOUGLAS E. PAQUETTE
Safety and Environmental Protection Division
Brookhaven National Laboratory
Building 535A
The LeRoy Bioherm is among the best known rock exposures in New York State, having been designated a National Fossil Coral Reef by the U.S. National Parks Service and having been the subject (at least in part) of three past studies (Crowley and Poore, 1974; Coughlin, 1980; Lindemann, 1988). Despite this the uniqueness of the LeRoy bioherm has generally gone unnoticed. It is the only Edgecliff bioherm known to have a mound building community of the very delicate branching tabulate coral (Ciadopora) and the only known Edgecliff mound with a thickness greater than about 1.2 meters that was not built by phaceloid colonial rugosans (Wolosz, 1992a). Further, the LeRoy Bioherm is the only bioherm in this area with a well developed coral mound facies, while all other Edgecliff bioherms in western New York State are thicket/bank structures (as defined by Wolosz , 1992a). The ecological zonation of reef building species both within mounds and across reef tracts due to environmental gradients is a well known feature of both Recent and ancient reefs (Wilson, 1975; James, 1983). Hence, the unusual nature of the mound building community at the LeRoy Bioherm (as compared to the typical rugosan dominated Edgecliff mounds), and the size of this cladoporid dominated mound, suggests that environmental conditions in the area must have differed in some way from those prevalent at the other Edgecliff bioherm locations.

B3: THE LEROY BIOHERM REVISITED: EVIDENCE OF A COMPLEX DEVELOPMENTAL HISTORY

STOP 1.00 LEROY BIOHERM
Stop at curve, road leading into quarry is overgrown. Walk past east side of house on north side of road to dirt road. Follow dirt road into quarry.
NOTE: PLEASE ASK PERMISSION AT HOUSE BEFORE ENTERING PROPERTY.
The most direct entrance into the quarry is down the talus slope which covers much of the east wall bioherm. From the top of the quarry wall the central bioherm can clearly be seen in the center of the quarry pit. The core facies of the bioherm are massive, weathering to a dark gray and can be easily differentiated from the bedded flanking facies which are very light gray to almost white limestone (see text for description). The quarry walls consist of highly fossiliferous Edgecliff shallow marine facies.

B4: LATE SILURIAN SEDIMENTATION, SEDIMENTARY
STRUCTURES AND PALEOENVIRONMENTAL SETTINGS WITHIN AN
EURYPTERID-BEARING SEQUENCE [SALINA AND BERTIE GROUPS],
WESTERN NY AND SOUTHWESTERN ONTARIO, CANADA
RICHARD D. HAMELL
48 Saranac Street
SAMUEL J. CIURCA, JR.
Monroe Community College
Department Geoscience
1000 East Henrietta Road
One of the most fascinating aspects of Late Silurian sedimentation in the Appalachian Basin is the occurrence ofthick sequences of evaporites and associated sediments. In western New York and southwestern Ontario, Canada, these sequences comprise the Salina and Bertie Groups and have been, or are economically important sources of both halite and gypsum.
Our particular interest in this evaporite sequence stems from the peculiar occurrence of complex eurypterid assemblages distributed, cyclically, throughout the sequence. If there is any hope of understanding the true habitat of the eurypterids, it will come from a more detailed examination of all lithofacies and contained sedimentary structures. We continue in this paper, and associated field trip, to call attention to the great variety of rock types, sedimentary structures, unusual fossil assemblages, and their stratigraphic and geographic distribution.
In the following text, it will be noted that eurypterids are mentioned throughout. This is not only an attempt to illustrate the importance of the eurypterid faunas found throughout the region, but to show their intimate association with part of the sedimentological record reviewed. Furthermore, because eurypterids are structurally complex; because they molted frequently during their growth; and because they often became disarticulated, eurypterid parts were subjected to fragmentation, redistribution by sorting and orientation, and even comminution as bioclasts. We suggest that these processes are important sedimentological features worthy of observation and study. Likewise, "algal" stromatolites, those mound like to laminar structures so often encountered in some of the eurypterid beds, are seen herein not only as important biological structures that affected the local sedimentological regimes, but as contributors to the regional sediments as particles and pieces ripped from the biostromes and redistributed, along with eurypterid debris, into flat-pebble conglomeratic accumulations within, primarily, the waterlimes (e.g. Ellicott Creek Breccia) and the finely-crystalline dolostones (e.g. Victor Dolostone) of the Fiddlers Green Formation (Bertie Group).

B4: LATE SILURIAN SEDIMENTATION, SEDIMENTARY
STRUCTURES AND PALEOENVIRONMENTAL SETTINGS WITHIN AN
EURYPTERID-BEARING SEQUENCE [SALINA AND BERTIE GROUPS],
WESTERN NY AND SOUTHWESTERN ONTARIO, CANADA

STOP 1. OATKA CREEK AT GARBUTT
Excellent exposures of the Syracuse Fm. (Salina Gp.) occur along Oatka Creek both upstream and downstream of the Union Street Bridge over the creek. Over 50 feet of strata have been measured along the south side of the creek and the entire section appears to represent the Upper Syracuse Formation. Included are argillaceous, thin-bedded (flaggy) dolostones, massive limestones and dolostones (particularly along the banks ofthe creek), thin waterlime units and evaporites. The site was extensively mined for gypsum and the ruins of some of the buildings that were constructed are still visible on the north side of the creek just upstream from the bridge. Note the buildings were constructed with glacial erratics and slabs of Syracuse Formation. An account of the gypsum mining activity here, and in nearby areas, can be found in Newland (1929).
Very few fossils have been described from the Syracuse Fm. of the region. The eurypterid Waeringopterus was traced into western New York but has not been found along the Oatka Creek Valley (Ciurca, 1990, p. D10). Eurypterus has been found in a waterlime bed immediately upstream from the bridge. The exposures in the wall on the south side of Oatka Creek have yielded cephalopods and Medusaegraptus. An algal stromatolite horizon occurs near the top of the section.

STOP 2. VICTOR DOLOSTONE ERRATICS
Massive Victor Dolostone (middle member ofthe Fiddlers Green Fm.) can be observed in the waterfall at nearby Buttermilk Falls. The large erratics at the driveway exhibit the finely crystalline character typical of the Victor Dolostone. Bedding planes are often covered with the small brachiopod, Whitfieldella.

STOP 3. THE NEID ROAD QUARRY
This quarry exposes a fine section of the Late Silurian Bertie Group overlain by massive beds of the cherty Onondaga Group. The erosional Silurian-Devonian unconformity is well displayed here. The quarry floor is comprised of the upper waterlimes of the Fiddlers Green Fm. and includes an eurypterid fauna consisting of Eurypterus and Dolichopteris. The irregularity of portions of the floor is due to algal stromatolite mounds. Salt hoppers and associated relict halite structures are common at this level.
Brecciated waterlimes (Ellicott Creek Breccia) are present just above the quarry floor, particularly at the north wall of the quarry. Immediately overlying this is 5-8 feet of the Scajaquada Formation, an argillaceous, mostly thin-bedded dolostone containing several chert nodule horizons.
The Williamsville Formation, here a particularly drab gray to cream colored dolostone, is exposed along the north wall of the quarry. Fossils are exceedingly rare in this unit. Only phyllocarid telsal spines and a few articulate brachiopods have been found here.
The Akron-Cobleskill is nearly missing from the section. At nearby Buttermilk Falls, the Scajaquada, Williamsville and Akron Fms. are all missing, the Onondaga Limestone rests directly upon the Fiddlers Green Formation.

STOP 4. STEAM LOCOMOTIVE AND SHOVEL
Turn-of-the-century (1902) steam shovel used quarrying on right.

STOP 5. FORT HILL WATERLIME
Uppermost Camillus Fm. is well-displayed in the roadcuts along both sides of NY19. At the top is a thin waterlime unit, the Fort Hill Waterlime. The overlying Oatka Formation is concealed by overburden. The Fort Hill Waterlime is considered the base ofthe Bertie Group and bears an Eurypterus Fauna (Ciurca, 1973, p. D3). It is also accessible near the base of nearby Buttermilk Falls.

STOP 6. BUTTERMILK FALLS
Follow the abandoned railroad east to Oatka Creek. A trail to the base of Buttermilk Falls is located on the west side of the valley, north of the railroad bridge over the creek. Note: walls of the gorge are steep. The safest trail to the bottom enters the gorge about 1.25 mile north of the falls.
Buttermilk Falls is capped by resistant Onondaga cherty limestone. The underlying Bertie Group forms the reentrant at the unconformable contact with the Onondaga Group.
At creek level is uppermost Camillus Formation (Salina Group). The Bertie Group here starts with the Fort Hill Waterlime, a complete section of the Oatka Formation, and most of the Fiddlers Green Formation. The Scajaquada, Williamsville and Akron Formations are missing due to erosion prior to the deposition of the Middle Devonian Onondaga Limestone.

B5: FIELD STUDIES OF THE MIDDLE DEVONIAN LUDLOWVILLE-MOSCOW SEQUENCE IN THE GENESEE AND SENECA VALLEYS, NY
STEPHEN M. MAYER
Department of Geology
SUNY College at Fredonia
Fredonia, NY 14063
Numerous authors have studied and described in detail the unique depositional environments and the excellent fossil preservation found in the Middle Devonian Hamilton Group sediments of New York State (Grabau, 1899; Cooper, 1930; Grasso, 1973; Brett and others, 1986; Savarese and others, 1986). The advancement of high resolution stratigraphic mapping has permitted detailed correlations of facies divisions in the uppermost Ludlowville Formation across western and central New York (Mayer, 1989; Mayer and others, 1994). The focus of this field trip is to examine the spatial and temporal sedimentary relationships as well as the abundant and well preserved fossils in the Upper Ludlowville-Lower Moscow Formations of the Hamilton Group; in particular, the uppermost Wanakah Shale, Jaycox Shale and Tichenor Limestone Members in the Genesee and Seneca Valleys (Figure 1 ).
Note: Road log and stop descriptions accompanying this article follow paper by Brett and Baird (this volume).
DEPOSITIONAL SEQUENCES, CYCLES, AND FORELAND BASIN DYNAMICS IN THE LATE MIDDLE DEVONIAN (GIVETIAN) OF THE GENESEE VALLEY AND WESTERN FINGER LAKES REGION
CARLTON E. BRETT
Dept. of Earth & Environmental Sciences
GORDON C. BAIRD
Department of Geosciences
Fredonia, New York 14063
Late Middle Devonian (late Givetian) deposits in the Genesee Valley central Finger Lakes region are represented in ascending order by the Moscow Formation of the Hamilton Group, the Tully (Limestone) Formation, and the lower third of the Genesee Formation. This succession records a dramatic facies transition from fossiliferous subtidal shelf mudstones in the Moscow Formation through outer lagoonal-to-shelf carbonate deposits in the Tully Limestone, into black shales recording anoxic basinal conditions in the Genesee Formation. The Tully-Geneseo succession records a dramatic shift from carbonate platform conditions to a deep-water, anoxic foredeep setting due to inferred flexural loading of the craton by a pulse of orogenic thrusting (Ettensohn, 1985, 1987).
The Moscow-lower Genesee stratal succession yields abundant and diverse fossils ranging from robust, shallow water forms to delicate taxa that lived under conditions of near-anoxia. Moscow and Tully biotas are highly diverse and have been well known since the publication of James Hall's "fourth district" report in 1839. Well preserved fossils can be collected at all of the field stops.
Strata discussed herein were deposited as muds in a foreland basin setting linked to a key phase of the Acadian Orogeny, a collision event involving the "docking" of one or more microcontinents in what is now New England and the central Atlantic states (Faill et al., 1978; Woodrow 1985; Ettensohn, 1985, 1987). Orogenic uplift and overthrusting in the tectonic settings to the east and southeast of New York State led to flexural downbending of the craton in eastern North America (Quinlan and Beaumont, 1984; Beaumont et al., 1988). This loading produced a foreland basin characterized by greater regional subsidence and often greater water depths (Figure 1). Erosion of orogenic highlands in the east led to the formation of progradational complexes ("Great Catskill delta") which filled in the Devonian shelf seas associated with the foreland basin, thus producing the Devonian stratal record in New York State, Pennsylvania, Maryland, and Virginia. In actuality, several inferred collision and overthrusting events are believed to have produced tectophases of overthrust induced basin deepening and progradational basin-filling (Ettensohn, 1987; Ettensohn and Elam, 1985). A mainly quiescent phase at the end of Tectophase II is recorded by the upper Hamilton Group (Moscow Formation). However, the Tully-Genesee transition records a grand deepening and progradational pulse associated with the onset of Tectophase III.
The Devonian ("Catskill") clastic wedge provides a classic example of an ancient deltaic complex. Because orogenic events took place to the east, sediments supplied to the basin came from the eastern Acadian mountain belt. This is typically, though not always, reflected in the eastward-thickening of sediments within the Catskill clastic wedge. It is also reflected by west-to-east facies changes (limestone-to-terrigenous sediment, shale-to-siltstone, siltstone-to-sandstone, etc.) at almost all stratigraphic levels. These diachronous facies shifts are well displayed in the Devonian time-rock stratigraphic chart for the state (Rickard, 1975). The Catskill Delta is also a story of numerous isochronous events: evolutionary and immigration (epibole) events, volcanic eruptions, and sea level changes can be traced stratigraphically over long distances.
In this paper, we will focus on the record of sea level oscillations which have left a detailed record of sedimentary cycles during the Late Givetian Age (approximately 380-375 million years ago). Numerous thin limestones, marine erosion surfaces, and stratigraphically condensed intervals record sediment starvation events associated with transgression events; these are well displayed in strata discussed herein. Recent advances in our understanding of Catskill Delta depositional processes involve the use of principles of sequence stratigraphic mapping.
The purpose of the present paper and associated field trip is fourfold: first, we document a rich assortment of shelf-to basin facies which is characterized by a broad array of Devonian fossils; second, we illustrate advances in stratigraphy which have been developed with the past few years, particularly involving application of sequence stratigraphy concepts to Paleozoic foreland basin deposits; third, we illustrate patterns of differential subsidence and migration of the foreland basin centers; finally, we illustrate several excellent Late Givetian sections within two hours' drive of Rochester which yield abundant, diverse, and well preserved fossils for the Devonian enthusiast.
We have chosen to describe Moscow subdivisions in some detail in the present paper in order to provide the details upon which our interpretations are based and as a guide to the various fossil bearing levels to aid paleontologic studies. Because most horizons are laterally traceable for tens of kilometers we have followed the practice of assigning many bed names for those divisions. This is not intended to overwhelm the reader with detail but to facilitate unambiguous communication about the many levels. The more general reader may wish to bypass these sections and read the sections on sequence and cycle interpretation.

B5: FIELD STUDIES OF THE MIDDLE DEVONIAN LUDLOWVILLE-MOSCOW SEQUENCE IN THE GENESEE AND SENECA VALLEYS, NY

Cross Honeoye Creek in approximate pre-glacial valley of
Genesee River

Cross tributary of Conesus Creek

Middle Devonian Jaycox Shale
Minor hill slope exposures of Middle Devonian of Jaycox Shale; middle Devonian; excavation for I-390 in 1979 yielded a prolific fossil assemblage at this site.

Cross Conesus Creek (swampy stretch)

Middle Devonian Centerfield Limestone
Farm on right side borders Conesus Creek at Triphammer Falls, about 0.25 miles north of Triphammer Road; this is a classic locality for the Middle Devonian Centerfield Limestone.

OPTIONAL STOP A. WHEELER FALLS
For optional stop pull off on shoulder of Rt. 39. Walk back to path along fence to west banks ofJaycox Creek.
(See Description for Jaycox Creek)

STOP 1: JAYCOX RUN
White Devon Farm on left. Pull off on right shoulder near gateway into pasture, walk straight west from gate through pasture to clump of oak trees along Jaycox Creek, south branch for Stop 1 . Note: Visitors must obtain permission from the Wadsworth Estate, Geneseo to study this locality.
Locality
Exposures along the south (main) fork of Jaycox Creek, on the property of William P. Wadsworth (White Devon Farm), 0.4 km (0.25 mi) west of NY Rt. 39 about 0.8 km. (0.5 mi) north of Nations Road, Geneseo, Livingston County, N.Y. (Geneseo 7.5 ft Quadrangle, 1950).
References
Cooper (1930), Grasso ( 1 973), Baird (1979). The following description is from Brett and Baird ( 1981).
Descriptions of Units
Jaycox Creek exposes a nearly continuous section of the Ludlowville (Centerfield, Ledyard, Wanakah, and Jaycox members) and lower Moscow (Tichenor, Deep Run, Menteth, and basal Kashong members) formations (Figure 10). Exposures to be examined during the field trip are those in the upper portion of the Jaycox ravine associated with a series of three low waterfalls held up the thin limestone bands; a low upper falls is formed by the Menteth Limestone, a middle falls by the Tichenor Limestone, and the highest, lower falls by a calcareous band in the Jaycox Member.
The Jaycox through Menteth interval will be examined in detail. Faunal lists for these units are given by Grasso ( 1973). Units are described in ascending order as follows.
Ludlowville Formation
Wanakah Shale Member: The upper 4 m (13.2 ft) of the Wanakah Shale Member are visible below the lowest falls in Jaycox Creek. This constitutes an undifferentiated interval of medium gray fissile, friable shales with a low diversity fossil assemblage. Ambocoelia umbonata, Mucrospirifer, chonetids, and Athyris, the small rugose coral Stereolasma, trilobite remains (Phacops and Greenops), and various bivalves are common. No calcareous bands or concretions are present in this portion of the Wanakah Shale.
Jaycox Shale Member: Baird (1979) selected this creek exposure as the type section for his Jaycox Shale Member, the uppermost member of the redefined Ludlowville Formation. At this locality, the Jaycox consists of about 4 m (13.2 ft) of soft, bluish-gray shale with abundant thin fossil-rich horizons (biostromes) and calcareous bands (see article by Mayer, this volume).
The basal Hills Gulch bed of the Jaycox Member (Unit A) is a bioturbated, silty, argillaceous limestone band 30-35 cm (~1 ft.) thick, which grades upward from the calcareous uppermost Wanakah Shale (Figure 11). This blocky band which caps the lower falls of Jaycox Creek is notably rich in brachiopods (Mucrospirifer, chonetids, and Mediospirifer), bivalves (Actinopteria, Modiomorpha, Paleoneilo, and Cypricardella), and gastropods (Mourlonia and Palaeozygopleura). This bed has yielded exceptionally well preserved bivalves, including rare specimens in burrow positions. The bed contains numerous spreiten of Zoophycos. Westward this bed merges into a large coral-bearing unit resembling the overlying Tichenor limestone. Coral beds which occur at several levels within the Jaycox Member (Units 8-C) contain assemblages very similar to those of older Centerfield Limestone, including a diversity of corals such as Eridophyllum, Heliophyllum halli, and the colonial form Heliophyllum confluens which is essentially restricted to this member. Large favositids and Thamnoptychia are also common at several levels within the Jaycox Member. Fossil layers contain abundant fenestellid bryozoans and large runner-like columns of crinoids modified as hold fasts (stolons). Diagnostic brachiopods of the Jaycox include Parazyga hirsuta and Pentamerella pavillionensis. These brachiopods are restricted to coral rich facies and recur only in association with biostromes (Centerfield Limestone, Jaycox Shale, Tichenor Limestone, and Windom coral beds).
Moscow Formation
Tichenor Limestone: The Tichenor Limestone (Unit D) constitutes a 30 cm ledge-forming band of medium gray, buff-to rusty weathering biomicrite (pack-or grainstone). As elsewhere, the Tichenor is an encrinite with abundant rugose and tabulate corals. The basal surface of the Tichenor Limestone represents a minor disconformity (Baird, 1979). Undersurfaces of projecting ledges, which can be examined in detail at this locality, show an irregular, sharp contact with the underlying Jaycox Shale. Very large hypichnia, probably crawling furrows similar to Cruziana, occur abundantly on the undersurface of the Tichenor.
The upper contact of the Tichenor Limestone at Jaycox Run is gradational through 15 cm of calcareous shale into the overlying Deep Run Member.
Deep Run Shale Member:
Between the middle and upper falls, Jaycox Creek bed exposes 2.5 m (8.25 ft) of medium gray, calcareous mudstone of the Deep Run Member. These mudstones are distinctly harder (more calcareous) than most of the Jaycox Shale and break with irregular fractures due to the lack of fissility. Lower Deep Run shales (Unit E) contain a fauna similar to that of the Jaycox coral biostromes, including Heliophyllum, Eridophyllum, (but H. proliferum rather than H. confluens) and large favositid heads. Small mounds of fistuliporoid bryozoans project upward some 50 cm into the base of the Deep Run Member; these are exposed in the floor of Jaycox Creek. Associated with these mounds are abundant large stems and stoloniferous holdfasts of camerate crinoids; calyces of Dolatocrinus, Megistocrinus, and other crinoids occur rarely in the basal Deep Run. The Deep Run Member is particularly noted for the large size of its trilobites. Specimens of Phacops rana, Greenops boothi, and Dechenella sp. are abundant and are typically very large relative to those found in underlying and overlying shale units.
The upper beds of the Deep Run (Unit F) are sparsely fossiliferous bluish gray shale mudstones containing very abundant limonitized (pyritized) sinuous burrows. Occasionally, vague Zoophycos traces can be observed. These sparsely fossiliferous shales contain scattered stringers and lenses of large crinoid columnals and fenestellid bryozoans suggestive of storm lags. The Deep Run Member is gradational into the overlying Menteth Limestone Member.
Menteth Limestone Member: The Menteth Limestone (Unit G) which caps the uppermost falls in Jaycox ravine, consists of approximately 28-30 cm of light gray, buff-weathering irregularly bedded, strongly bioturbated calcisiltite (biomicrite). The lower contact of the Menteth is gradational, but the upper surface is sharply defined and hummocky suggesting a slight discontinuity or burrowed omission horizon. The Menteth contains a very abundant and often well preserved traces (Zoophycos) and scattered body fossils including spiriferid brachiopods, rare corals, and large trilobite fragments.
Kashong Shale Member: Only the lowest 30 - 50 cm of bluish gray, calcareous Kashong Shale (Unit H) crop out in Jaycox Run. These basal shales contain abundant fossils including the ramose tabulate coral Thamnoptychia, various bryozoans, brachiopods, camerate crinoids, and large trilobites.
Discussion
The basal Moscow Formation in the Genesee Valley represents a slightly different spectrum of environments. This sequence begins with the Tichenor Limestone which, as in most western N.Y. localities rests with marked disconformity on the Ludlowville Formation (Baird, 1979). Presumably, a portion of the upper Jaycox interval has been removed by submarine erosion prior to the deposition of the Tichenor. The Tichenor Limestone was probably deposited in a high energy, above wave base setting, as indicated by winnowing of fines, abrasion of fossil fragments, vague cross lamination, and overturned favositid coral heads. This unit is inferred to represent the shallowest water conditions in the entire sequence exposed at Jaycox Run. Gradation of the Tichenor into the overlying Deep Run calcareous mudstone indicates a return to lower energy, mud depositional conditions. The Deep Run thickens rapidly eastward into a lentil of calcareous mudstone which attains a maximum thickness of about 18 m (59.4 ft) near Canandaigua Lake and then thins again eastward toward Cayuga Lake where the Deep Run pinches out (Baird, 1979). This lenticular configuration suggests active subsidence of a localized basin following the Tichenor deposition. The Deep Run locally contains cross laminated calcisiltite and calcarenite lenses which were probably transported into the depositional basin from nearby shoal regions during severe storms. Hence, the unit was deposited below normal wave base, but within reach of storm waves.
Deep Run mudstones grade upward into the Menteth Limestone, a uniformly thin (30-40 cm) but very widespread carbonate unit. The Menteth is a thoroughly bioturbated calcisiltite and is inferred to represent the terminal phases of infilling of the Deep Run depositional basin. Processes of sediment winnowing, probably aided by biological activity, became dominant over deposition of clays, resulting in a thin, lag deposit of skeletal debris and carbonate silt. Locally, coral beds developed on the upper surface of the Menteth. Menteth Limestone, in turn, grades upward into Kashong mudstones which faunally and lithologically somewhat resemble portions of the Deep Run. The entire Deep Run-Kashong interval (equals Portland Point of earlier workers; Baird, 1979) is inferred to represent deposition during a generally regressive interval. The sequence is bracketed by units which yield evidence of deposition under shallow water conditions. Minor oscillations of environmental conditions may have been the result of regional subsidence or downwarp of a shallow basin or trough.

To south is Wadsworth estate with ancient white oak trees

Genesee Fm Penn Yan
Beginning of Dewey Hill roadcut; Genesee Formation
(mainly Penn Yan dark gray shales)

STOP 2. FALL BROOK, GENESEO
Walk across highway and enter pasture along Fall Brook at gateway. Proceed on foot upstream to exposures.
Locality
0.37 mile east of U.S. 20A and 39 and below Fall Brook Falls, Geneseo, Livingston County, N.Y. (Geneseo 7.5 ft Quadrangle, 1950).
References
Cooper (1930), Baird ( 1 978), Baird and Brett (1983). The following description is from Brett and Baird (1981).
Description of Units: This stretch of Fall Brook exposes the upper portion of the Middle Devonian (Givetian) Moscow Formation (Windom and Kashong Shale Members) as well as the overlying Upper Devonian (Frasnian) Genesee Group (Figure 12).
Low cut banks along Fall Brook near U.S. 20A expose the upper 1.7 m (5.6 ft) of the Kashong Shale Member. This unit is comprised of sparsely fossiliferous, bluish gray mudstone with abundant pyritic tubular burrows. Body fossils include large ramose bryozoans, the brachiopods Lingula and Tropidoleptus, rare Dipleura trilobites, and phyllocarid fragments.
The disconformable contact with the overlying Windom Shale Member is exposed here and consists of a mudstone band approximately 10 cm-thick. This unit contains an admixture of reworked Kashong and Windom fossils and small phosphatic steinkerns and nodules (Little Beards phosphate bed). This heavily bioturbated sediment has been interpreted as a biogenically blurred unconformity or "stratomictic discontinuity" (Baird, 1978). The zone of phosphatic pebbles in the upper Kashong has been traced from Erie County, eastward to Owasco Valley, and is inferred to represent a widespread disconformity within the Moscow Formation (Baird, 1978). The informal "Unnamed Member" is absent here, having been cut out by erosion beneath the Little Beards bed.
Overlying the phosphatic pebble bed is typical basal Windom Shale: soft, medium gray shale with abundant specimens of Ambocoelia umbonata. A calcareous bed rich in trilobites occurs about 20 cm. above the Little Beards phosphatic nodule bed. Aside from the basal 30-50 cm, the lower 4.5 m (14.9 ft) of the Windom, are largely covered with slumped talus and are not accessible at Fall Brook. However, a complete Windom thickness of 15.63 m (51.6 ft) was measured at this locality.
The Windom section continues upstream at the base of a high cliff face on the northern side of Fall Brook. The lowest unit exposed here is soft shale rich in Ambocoelia brachiopods which may occur in small prod-like concentrations. The overlying Bay View bed consists of medium gray calcareous and very fossiliferous mudstone. Abundant fossils include Pseudoatrypa, Mucrospirifer consobrinus, Protodouvillina, the rugose corals, Stereolasma and Amplexiphyllum, crinoid columnals, and abundant Phacops trilobites. This unit is gradationally overlain by a band of medium gray calcareous shale and argillaceous limestone, approximately 40 cm-thick, which forms a falls in the creek bed. This is gradational above and below into less calcareous mudstone and contains abundant crinoid columnals in stringers, the small rugose coral Stereolasma, and fragmentary and complete specimens of the trilobites Phacops rana and Greenops boothi. Trace fossils in form of pyritic, sinuous burrows are very abundant in this zone. This bed is traceable into the "Smoke Creek bed" of Erie County, NY (Brett, 1974; Baird and Brett, 1983). The unit, in turn, is gradationally overlain by gray, calcareous and relatively fossiliferous mudstone with a fauna resembling that of Unit A which grades upward into darker, less fossiliferous shale.
A band of darker gray, relatively hard, fissile shale, forms a slight projection in the bank in some areas about 8 m (26.4 ft) above the base of the Windom. This interval (the Fisher Gully beds) contains abundant Emanuella praeumbona, large specimens of Ambocoelia umbonata, and occasional Leiorynchus and Spyroceras. It is overlain abruptly by a bed of crumbly medium gray mudstone packed with fossils including Cystilphylloides, Helioplyllum, and other large rugose and tabulate corals, atrypid brachiopods (Pseudoatrypa and Spinatrypa), Mediospirifer, and at least 55 other species of invertebrate fossils. Unit E, which occurs 8.57 m (28.3 ft) above the base of the Windom at Fall Brook, has been designated the Fall Brook coral bed closely resembles that of the slightly older Bayview coral bed and indicates a recurrence of nearly identical environmental conditions under which coral biostromes developed widely in western N.Y. The Fall Brook bed has been traced from Central Genesee county, eastward to Seneca Lake, a distance of approximately 90 km (56 mi). Large rugose corals are restricted to a 30-40 cm-thick band, however, other fossils including small rugose corals (Amplexiphyllum and Stereolasma), Pseudoatrypa, Mediospirifer, Douvillina, abundant crinoid columnals, and bryozoans persist upward for approximately 1.5 m (5 ft) into the overlying mudstone. This richly fossiliferous, but non-coral bed assemblage has been termed the Taunton beds by Baird and Brett (1983). The upper portion of the Taunton interval bears three zones of large, calcareous, nonseptarian concretions. Fossil bands run continuously through concretions, which indicates possible relationship between carbonate diagenesis and organic remains.
A thin (30 cm-band) of argillaceous limestone containing abundant small rugose corals (Stereolasma) and a few atrypid brachiopods Spezzano Gully bed occurs about 11 m (36.3 ft) above the base of the Windom Shale at Fall Brook. This unit grades upward into dark gray, slightly calcareous, petroliferous shale with abundant pyritic sinuous burrows and occasional nodules of pyrite and scattered fossils including Stereolasma and Pseudoatrypa.
The upper Windom Shale at Fall Brook consists of very dark gray fissile, pyritic shale (Gage Gully Bed). This shale is generally sparsely fossiliferous, but some layers contain abundant Allanella tullius, small Ambocoelia, Devonochonetes, and rare Leiorhynchus and E. praeumbona. A zone of pyritized fossils near the top of this interval has yielded nuculid bivalves, the trilobite Greenops boothi, the nautiloid Spyroceras, and rare large specimens of the goniatite Tornoceras cf. T. uniangulare. The highest beds of the Windom are black, platy shale with Allanella tullius. The contact between these beds and the overlying Geneseo Black Shale is often difficult to recognize in the Genesee Valley area because their lithologies are similar. However, the Geneseo is somewhat harder, weathers rusty and is more petroliferous than the upper Windom. The contact, here, as elsewhere in western New York, is sharp and unconformable.
Small lenses of Leicester Pyrite generally less than 10 cm-thick, occur at the Windom/Geneseo contact. The Leicester in this area contains abundant tubular pyrite, apparently reworked burrow fillings, as well as small brachiopods, nuculid bivalves, and rare nautiloids and goniatites from the erosionally truncated Windom (Brett and Baird, 1982).

STOP 2A. Scenic overlook of Fall Brook Gorge
Pull off at wide area along shoulder; walk up bank to right and proceed down dirt path to brink of Fall Brook Falls.
Dark shales on upper creek banks are West River Member of Genesee Formation falls is capped by Genundewa Limestone (20 in-thick). Caution: Stay back from edge, vertical drop of over 100 feet. (Possible lunch stop).

Cross Fall Brook

Upper end of Jaycox Creek tributary
Genundewa Limestone in exposed south of road.

Cross Conesus Creek
Outlet from Conesus Lake flows into the Genesee River.

Valley of Honeoye outlet creek.

View of Bristol Hills to south

Turn right for classic Windom localities
Rt. 64 to right leads south into Bristol Valley and classic Windom localities; near this location the "Unnamed member" is becoming truncated.

Type locality of the widespread Centerfield Limestone is on Schaeffer Creek north of Rt. 20

Cross Schaeffer Creek

Creek to left exposes Levanna black shale.

Cross Hopewell Ravine
Creek just below 20 exposes Jaycox and Tichenor members, small but excellent outcrop.

Cross Flint Creek

Large landfill site on right

Pre-Emption line
Pre-Emption line is an old western boundary line of Massachusetts territory.

Crossing Wilson Creek
Downstream is a large waterfall over Centerfield Limestone; top phosphatic bed is exposed near the Pre-Emption Road bridge.

Benton Run on left exposes nearly complete Ludlowville Formation.

STOP 3. KASHONG CREEK, LOWER FALLS
Locality
Exposures along the bed and banks of Kashong Creek just south of Kashong Road and 1.5-2.0 km (0.9-1.2 mile west of NY 14, township of Geneva, Seneca County, NY (Geneva South 7.5' Quadrangle, 1953).
References
Description of Units
This creek section is, arguably, one of the most complete upper Hamilton sequences exposed in the Finger Lakes Region; it is a classic reference section and the type locality for the Kashong Shale Member. Nearly the entirety of the Ludlowville and Moscow formations are exposed on Kashong Gully. We will examine the Moscow Formation in detail, commencing with the Tichenor Limestone which caps the highest waterfalls (10 m, 33 ft) in the glen; a somewhat lower (8 m, 26 ft) waterfall 400 m upstream from the latter, shield up the Menteth Limestone Member, and a third very low falls (approximately 2 m, 6.6 ft high) is formed by the resistant upper phosphatic shell bed at the top of the Kashong member and the overlying basal siltstone beds of the Canandaigua Member. A short distance upstream from this uppermost falls the section ends and the creek flows on glacial till.
The Hamilton beds in this area are gently deformed by Alleghenian (?) folding and faulting. The creek cuts most perpendicularly through a small anticline-syncline pair near the Kashong shale type section; the axis of the syncline is approximately at the low falls over the Kashong/Windom contact beds (discussed above); this contact is exposed again about 100 m upstream on the opposite (western limb) of the syncline, at the position of the old bridge across the creek. The bulk of Kashong section is exposed downstream from the small falls on the strongly west dipping eastern limb of the syncline. The crest occurs just downstream (east) of the high Menteth waterfalls. Below that falls the creek flows down the gentle east limb dip slope on the lower Deep Run beds for about 100 m (330 ft) before descending over the high Tichenor capped waterfalls. A relatively large down-to-the east normal fault with about 20 m (66 ft) displacement and minor splay faults occur near the mouth of Kashong Creek, but will not be examined on this trip.
The Tichenor through basal Windom sequence will be described and examined in detail; lower stratigraphic units at the base of the high Tichenor waterfalls are accessible by a steep (dangerous!) pathway down the south side of the gully or by walking upstream from the mouth of the Kashong Glen; however, we will simply observe these units from the top of the waterfalls. Stratigraphic units are described below in ascending order.
Ludlowville Formation
Upper Wanakah Shales: The lowest stratigraphic units observable in this part of the gorge are medium to dark gray shales on the upper Wanakah Member. These shales outcrop below a smaller waterfall 100 m (330 ft) downstream from the large Tichenor-capped falls; this latter falls is capped by silty, calcareous mudstones of the basal Jaycox Member (correlative with Unit A of the Jaycox run description; Stop 10, page 86). Upper Wanakah at the base of this falls consists of relatively fossiliferous, gray shale characterized by an abundance of small Pleurodictyum corals, brachiopods (such as Athyris, chonetids, and Ambocoelia), and Phacops trilobites. This sequence is capped by a fossil hash bed, identified by Baird (1981) as the Bloomer Creek bed. Overlying this layer in the face of the small waterfall are 2 m (6.6 ft) of dark gray to nearly black shales, bearing Leiorhynchus, small Tropidoleptus and small ambocoeliids.
Jaycox Member: The face of the high waterfalls and the creek-bed down stream to the cap of the next small falls expose a light bluish gray mudstone of the Jaycox Member. The lower half of this sequence consists of alternating calcareous mudstone and fossil rich limestone layers; these latter have a diverse fauna of abundant fenestrate and fistuliporid bryozoans, corals, especially Trachypora, brachiopods such as Tropidoleptus and Longispina, and abundant crinoidal debris. The upper Jaycox beds (upper half of falls face) consist of sparsely fossiliferous, hard, blocky, calcareous mudstone containing scattered very large specimens of the tabulate coral Pleurodictyum. The uppermost few centimeters of the Jaycox beds are visible at the top of the waterfalls.
Moscow Formation
Tichenor Limestone: This is a very widespread, thin (0.5-1 m, 1.7-3.3 ft) carbonate interval, traceable from Lake Erie, eastward at least to Chenango Valley; east of Cayuga Lake. (Baird, 1979; Griffing, 1994). The Tichenor is sometimes referred to as the basal bed of the "Portland Point" Member (Baird, 1979) At Kashong Glen this member, which crops out just upstream from the brink of the highest waterfalls, consists of thin bedded argillaceous, crinoidal packstone. The Tichenor is highly fossiliferous, characterized by large crinoid columnals and bryozoans with a few solitary, large rugose and tabulate corals.
In the Seneca Valley, the Tichenor does not form a compact, sharply based ledge, as it does at localities both east and west of this area. In fact, the basal disconformity which characterizes the Tichenor at all other locations here is either very cryptic or absent, and the lithology closely resemble that of more fossiliferous beds in the under-and overlying Jaycox and Deep Run members.
Deep Run Member: Overlying the Tichenor is about 10 m (33 ft) of hard, blocky, calcareous mudstone referred by Cooper (1930) to the Deep Run abundant, poorly preserved Zoophycos trace fossils. However, beds occurring about 1-2 cm above the Tichenor Limestone are highly fossiliferous, biostromal, argillaceous limestones resembling the Tichenor. The creek flows on dip slope of these units exposing relatively large bedding planes; these display small mounds of fistuliporoid bryozoans and crinoid columns (up to half meter in length); some of these columns form rhizomatous ("runner") holdfasts. Other common fossils include fenestrate and sulcoreteporid bryozoans, varied brachiopods, bivalves, large trilobites and well preserved (but difficult to extract) calyces of crinoids and blastoids. The large size of many fossils (especially trilobites) indicates favorable environments in terms of food supply, as might be expected in shallow muddy areas; however, the rarity and scattered to patchy distribution of fossils in most of the Deep Run Member suggests that colonization of the sea floor by benthos was sporadic and probably limited by soft, unstable substrate and/or high turbidity near the sea floor.
Note the considerably greater thickness of the Deep Run at Kashong Glen than at Jaycox Run (Stop 1). The Tichenor and Menteth limestones converge and eventually merge both east west of this area.
The Deep Run wedges out abruptly both east and west of the Finger Lakes. This unit which closely resembles the calcareous mudstone facies of the older Mottville, Centerfield, and Jaycox carbonate intervals apparently characterizes deposits of a shallow rapidly subsiding trough bordered by very shallow (within wave base), crinoidal sandy shoals.
The Deep Run facies is considered to represent a wedge of rapidly-deposited, fine-grained sediments which were winnowed from adjacent shallow tichenor-type shoal environments that bordered a central trough. Inter-fingering of Tichenor-like lithologies with the barren mudrock indicates close proximity of the two types of facies.
Menteth Limestone Member: This is compact, 30 cm-thick silty; siliceous, heavily bioturbated limestone which caps the moderately high waterfall west (upstream) of the Tichenor falls. This limestone is particularly characterized by an abundance of Zoophycos burrows, Mucrospirifer, Spinocyrtia, and large specimens of Phacops.
The undersurface of the Menteth in some areas appears gradational with the underlying Deep Run; elsewhere, as here, it is undulating and displays large scoured out burrow fillings indicating some erosion prior to its deposition.
This unit appears nearly identical throughout its outcrop despite thickening and thinning of synjacent shales (see Jaycox Run, Stop 1, descriptions). We have interpreted this unit as a winnowed, bioturbated calcisiltite reflecting reworking of Deep Run muds, following infilling of a subsided trough.
Kashong Shale Member: The Kashong Member abruptly overlies the Menteth. It consists of bluish gray mudstones which are somewhat softer, less calcareous and silty than the Deep Run Member, with horizons of small irregular ovoid to pipe-like carbonate concretions, silty limestones and highly fossiliferous calcareous mudstones. Fossils are moderately abundant in the bluish gray mudstones and include, particularly, brachiopods (Tropidoleptus, "Spirifer" marceyi, and Mucrospirifer), the tabulate coral Pleurodictyum, bryozoans, bivalves, large trilobites, including Dipleura, phyllocarids, and crinoid stems.
The Kashong at this location, displays repetitive, cyclic motifs, consisting of: (a) sparsely fossiliferous blue gray shale, (b) zones of grotesquely- shaped carbonate concretions, capped by, (c) thin beds of burrowed calcisiltite resembling the Menteth Limestone, and/or (d) complex condensed shell beds. There are two complete cycles and two thin incomplete cycles within the member. These are interpreted as minor regressive, shallowing upward hemicycles, the complex shelly phosphatic pebble beds record sediment starvation and/or winnowing associated with cycle reversals.
A widespread, complex shell bed occurs within the Kashong Shale about 2.6 m (8.6 ft) above the base. Informally named the "Rhipidomella-Centronella" bed (or R-C bed) this unit contains a great abundance and diversity of fossils including the nominal brachiopods and the large spiriferid Spinocyrtia (commonly highly corroded), Douvillina, varied bryozoans, bivalves, gastropods, trilobites, and crinoid debris. This bed, which locally approaches the appearance of the Tichenor Limestone (and was formerly considered to be the top of the Portland Point Member; Cooper, 1930; Baird, 1979) appears to represent a widespread interval of winnowing and shell concentration, perhaps associated with a minor shallowing cycle. It is overlain by bluish gray shale resembling the lower Kashong.
Unnamed Shale Member: Only the basal 2 m (6.6 ft) of this previously unrecognized member of the Hamilton Group are exposed at this section. The unit commences with the Barnes Gully phosphatic pebble bed, a slight discontinuity may exist. At eastern localities a tongue of typical Kashong mudstone with Tropidoleptus is present between the phosphatic bed and the Curtice Road bed. This bed resembles burrowed calcisiltites of the Menteth, and consists of Zoophycos-burrowed calcareous silt, with a fauna of Spinocyrtia, Mucrospirifer, chonetids, Pholidostrophia and other brachiopods.
Also, the basal "unnamed" unit locally displays a shell bed especially rich in strophomenid brachiopods and containing rare rugose corals. The silty bed shows a gradational top, passing upward into silty shales with a deeper water biofacies of small chonetids which then passes up into soft medium gray shales with very abundant Longispina. This reflects a deepening event, stronger than those of the lower Moscow, which resulted in a return of lower aerobic to dysaerobic, deeper water environments in western New York. This transgression apparently explains the recurrence of litho- and biofacies closely similar to those of the lower Hamilton formation. We presume that such facies coexisted with the shallower water facies of the Moscow interval, but that they were displaced southwestward into the basin axis and do not appear anywhere within the New York outcrop belt during deposition of the Jaycox to Kashong interval.
Discussion: The upper Hamilton Group in the vicinity of Kashong Glen displays several differences from outcrops of the equivalent interval to the west (Genesee Valley, see Stop 1). Several units (e.g., upper Ludlowville, Tichenor, and Deep Run shales) show subtle differences indicating deeper water in the Kashong Glen area than at sites either east or west of this region. For example, the Wanakah and Spafford-equivalent shales which are represented by fossiliferous, gray mudstones at Genesee Valley, and by comparable but siltier facies at Cayuga Lake, here are composed mainly of dark gray, fissile shale with a low-diversity, Leiorhynchus-dominated fauna; this seems to indicate deeper, more dysaerobic water in an area centered in the Seneca Valley than in the bordering areas. Similarly, the Tichenor-Deep run units are differentially thicker here than at Genesee Valley or the Cayuga region; they are also less carbonate rich; in the case of the Tichenor the limestone is a pack- or wackestone in the Seneca Lake region but a grainstone both to the east and west. It is less rich in large corals and crinoids and appears to be nearly conformable above and below whereas to the east and west it is bounded by an erosional unconformity at the base and, locally, on the top. Again, this seems to indicate an area of differentially deeper, quieter water near the Seneca Lake meridian.

STOP 4: KASHONG CREEK AT BELLONA
Exposures at waterfalls along Kashong Creek 0.1 km east (downstream) from Pre-emption Road and upstream to 0.2 km west of road, town Bellona, Yates County, N.Y. (Stanley 7.5' Quadrangle, 1952).
Reference
Heckel (1973)
Description
This outcrop provides an excellent section of the top of the Hamilton Group (Windom Shale), the unconformable overlying Tully Limestone, and the basal Genesee Group (Geneseo Shale). This classic section was critical in Heckel's (1973) subdivision of the Tully Formation into the lower and upper members separated by an unconformity.
Moscow Formation
Windom Shale: Lowest units exposed in this portion of Kashong Creek are fossil-rich medium bluish gray shales of the upper Windom Member ("Taunton Beds"); this 7 m (23 ft) interval contains many thin, lenticular brachiopod-, rugose coral-, bryozoan-bearing shell beds, mutually separated by sparsely fossiliferous mudstones. Thicker beds probably record relatively long spans of slow deposition during which shells accumulated and were reworked by occasional strong storm waves; overlying mudstones apparently represent rapid influxes of mud that terminated shell buildup.
The uppermost 2 m (6.6 ft) of the Windom display marked change to dark gray or nearly black shale with diminutive brachiopods. This records a relatively strong transgressive (deepening event) that occurred near the close of Hamilton deposition.
These beds display a sharp, erosional contact with the overlying Tully limestone. An interval of diastrophic upwarp and erosional truncation, perhaps associated with subaerial exposure prior to Tully deposition. Nonetheless, despite this evident break both the Windom and the lower Tully belong to the same conodont subzone (middle P. varcus subzone).
Tully Limestone: At the falls the light-gray, micritic Carpenter Falls bed (0.6 m-thick) of the Tully Lower Member, overhangs the Windom Shale; its basal surface displays large elongate burrows up to 8 cm. across, that were produced in over compacted Windom muds and subsequently infilled with Tully matrix. The Carpenter Falls bed contains the index brachiopod Hypothyridina, as well as atrypids, small rugosans, trilobites, and crinoid debris. At the upper surface of this bed Heckel observed a widespread mid-Tully erosion surface, and, at this locality (upstream from Pre-emption Road Bridge), he noted possible truncated stromatolites at this surface. Hard fossiliferous wackestones, of the Taughannock Falls bed (Tully Upper Member) overlies this intraformational disconformity. The Taughannock Falls bed is capped by a thin, shaley bed with very abundant large rugose corals (Heliophyllum and Cystiphyllolides) and Favosites termed the Bellona coral bed for this excellent exposure. Upstream (west) from Pre-emption Road, the large corals are clearly visible on a large bedding plane on the creek floor. The Bellona coral bed has proven to be a key mappable unit. The Bellona bed is abruptly overlain by a thin (0.6 to 1.0 m) remnant of the Moravia bed; the upper Moravia bed and Fillmore Glen bed are absent here.
The top of the Moravia bed is marked by an erosion surface that, in this area, shows a thin layer rich in crinoidal debris, conodonts, fish bones, pyrite and glauconite; a few thin stringers of this lithology recur in the overlying black Geneseo Shale. This lag debris is believed to be a lateral equivalent of the Leicester Pyrite which is know to overlie the erosional top of the Tully about 12 km (7 miles) northwest at Gorham. This bed has yielded conodonts diagnostic of the upper hermanni-cristatus subzone, whereas the underlying Moravia bed is of the middle varcus Zone age. Evidently, a considerable hiatus separates these units, during which time the upper Tully units were erosionally bevelled, prior to Geneseo deposition.
Geneseo Shale: The erosional upper surface of the Moravia bed, or, locally, the Bellona bed, is sharply overlain by platy, black Geneseo Shale, which is fossiliferous, except for the stringers of reworked crinoidal debris, mentioned above. This unit records major deepening of the Taghanic onlap. It is presently considered of the latest Middle Devonian (late Givetian) age.

Entrance to Oak corners Quarry on left.
This is an excellent Onondaga Limestone section (Ver Straeten et al. trip - this guidebook).

Cross Flint Creek; outcrops of upper Silurian dolostone

Bertie\Bois Blanc\Onondaga
A right turn here leads up to cuts below Thruway in Bertie\Bois Blanc\Onondaga

Outcrops of Onondaga Limestone in Flint Creek left side

Nedrow shale along Flint Creek
Driveway to left leads to outcrops of Nedrow shale along
Flint Creek; (see Ver Straeten, this volume).

Field exposure of Camillus Shale on left

Rising onto moraine; rest stop at top

B6: DEVONIAN FOSSIL LOCALITIES IN WESTERN NEW YORK

STOP 1. JAYCOX RUN
Turn right into driveway of "White Devon Farm" (watch for sign). Park along left side of driveway. Be careful to leave ample room for horse trailers and traffic.
Entrance to the Wadsworth property and Jaycox Run is through a farm gate immediately across the road. Walk across the field to Jaycox Run (NW corner). Last person through gate MUST secure and fasten!
Locality: Exposures along the south (main) fork of Jaycox Creek, on the property of William P. Wadsworth (White Devon Farm), 0.4 km (0.25 mi) west of N.Y. Route 39, about 0.8 km (0.5 mi) north of Nations Road, Geneseo, Livingston County, New York.
References: Cooper (1930), Grasso (1973), Baird (1979). The following description is from Brett and Baird (1981 a).
Description of Units: Jaycox Creek exposes a nearly continuous section of the Ludlowville (Centerfield, Ledyard, Wanakah, and Jaycox members) and lower Moscow (Tichenor, Deep Run, Menteth, and basal Kashong members) formations. Exposures to be examined during the field trip are those in the upper portion of the Jaycox ravine associated with a series of three low waterfalls held up by thin limestone bands. A low upper falls is formed by the Menteth Limestone, a middle falls by the Tichenor Limestone, and a highest, lower falls by a calcareous band in the Jaycox Member.
The Jaycox through Menteth interval will be examined in detail. Faunal lists for these units are given by Grasso (1973). For further detail of unit descriptions see Brett and Baird in Miller, M.A. (ed.), 1986.

STOP 2. FALL BROOK.
Turn around in driveway of the "Christiano Alfalfa Milling Co." (mustard colored sign on left) and park along guardrail facing uphill. Entrance to Fall Brook is at the uphill end of the guardrail.
Locality: Exposures along the bed and banks of Fall Brook 0.2-0.6 km (0.1-0.37 mi) east of U.S. Route 20A-N.Y. Route 39 and below. Fall Brook Falls, Geneseo, Livingston County, New York (Geneseo 7.5' Quadrangle, 1950).
References: Cooper (1930), Baird (1978), Baird and Brett (1983). The following description is from Baird and Brett (1981 b).
Description of Units: This stretch of Fall Brook exposes the upper portion of the Middle Devonian (Givetian) Moscow Formation (Windom and Kashong Shale members) as well as the overlying Upper Devonian (Frasnian) Genesee Group.

STOP 3. TAUNTON GULLY
Pull off road just past small white house on right; park along roadside next to small field adjacent to house, before guardrail.
Walk back along edge of field, cross railroad tracks immediately behind the house and continue to far left-hand comer of field. Access to Gully is on small path through woods.
Locality: Gully exposures approximately 0.1 miles west of Route 36,2.4 miles south of intersection of N. Y. Routes 36 and 63
References: Kirchgasser (1973; "Stop 6"), Patchen and Dugolinsky (1979; "Stop 35")
Description: About 25 feet of uppermost Windom Shale is exposed upstream from the railroad. There are a number of concretionary horizons occurring with layers of pyrite nodules. The shales below the first waterfall are blue-grey, shaly mudstones becoming darker and more compact further up in the section.
Faunal diversity is greater in the lower shales, consisting of bryozoan beds, stereolasmatid corals, trilobites, crinoids, and a rich brachiopod fauna. Above the first falls the fauna consist of most Phacops fragments and stereolasmatid coral horizons.
The Leicester Pyrite overlies the Windom. It is 4-6 inches thick and poorly exposed. Heavy collecting is discouraged to preserve the extent of the exposure.
The Geneseo and Penn Yan shales are exposed above the Leicester Pyrite (60-70 feet) and capped by one foot of Genundewa Limestone at the upper falls.

STOP 4. BROWN'S CREEK
Proceed 0.4 miles to large, grey, metal pole bam on left just after bend in road (split-rail fence; parking on left side of road on either side of fence). Take wooden stairwell down to house and creek exposure.
Locality: Stream excavation 0.1 mile north of York Road East, about 0.4 mi east of Town of York on property of Jim Nardi
References: None for Ledyard Shale at this locality as it is a relatively new exposure
Description of Units: Until recent excavations, the Ledyard Shale was only poorly exposed upstream from the classic Centerfield/Levanna locality. The horizon studied on this trip is an excavation (widening) of the creek bed approximately 15 feet above the Ledyard/Centerfield contact. Of special interest are concretionary horizons and a horizon containing large Phacops trilobites. These are generally dark grey shales with many Ambocoe/ia brachiopods.