NYSGA 2000
FIELD TRIP GUIDE
72nd Annual Meeting of the New York State Geological Association
Conference Chair: Donald L.Woodrow ·
Field Guide Compiler: Brooks McKinney
September 29 - October 1, 2000
HOBART AND WILLIAM SMITH COLLEGES
GENEVA, NEW YORK
This guidebook is published by the New York State Geological Association. Additional copies may be obtained from the Executive Secretary of the NYSGA:
Dr. William Kelly, Executive Secretary of NYSGA
Room 3140, Cultural Education Center
New York State Geological Survey
Albany, NY 12330

A1: SURVEY OF THE GEOLOGY OF THE NORTHWESTERN ADIRONDACK MOUNTAINS AND BLACK RIVER VALLEY
S.E.ORRELL
HOBART AND WILLIAM SMITH COLLEGES
DEPARTMENT OF GEOSCIENCES
ROBERT S. DARLING
DEPARTMENT OF GEOLOGY
SUNY AT CORTLAND
INTRODUCTION
The geological history of New York State may be conveniently divided into four major phases, each represented by rocks or sediments or geomorphic features. These major phases include:
•Proterozoic orogenesis (represented primarily by exposed mid-crustal metamorphic and igneous rocks of the Adirondack region)
• Paleozoic events (represented by exposed and deformed sedimentary rocks throughout the state)
• Early Mesozoic crustal extension (represented by basaltic dikes and sills, and by sedimentary rocks in southeastern NY)
• Pleistocene glaciation and subsequent events (represented by sediments and geomorphic features throughout the state). Exposures in the northwestern Adirondacks and the Black River Valley permit the examination of relics of most of these events, although Mesozoic events are represented poorly at best. The current trip is designed as a north-south transect from the Northwest Lowlands, across the Carthage-Colton Mylonite Zone into the Adirondack Highlands at their western margin, up onto the Tug Hill Plateau, and along the Black River Valley (Figures 1 and 2). The Black River Valley, which separates the Tug Hill Plateau from the Adirondack Highlands, provides a wonderful opportunity to examine rocks, sediments, and structural features with ages ranging over a billion years.

A1: SURVEY OF THE GEOLOGY OF THE NORTHWESTERN ADIRONDACK MOUNTAINS AND BLACK RIVER VALLEY

STOP 1. ROCK ISLAND ROADCUT
Roadcuts on either side of Rock Island Road, immediately south of bridge over Oswegatchie River.
This large roadcut is one of the best places to observe the contact between Proterozoic marbles of the Adirondack lowlands and the Cambrian Potsdam sandstone. The marbles were highly deformed, intruded by basalt dikes (also exposed here), and deeply eroded. The Potsdam sandstone here was apparently deposited into sinkholes formed on the pitted marble surface. A clear and detailed description of this outcrop is provided in Van Diver (1976).

STOP 2. HAILESBORO ENTRY ROAD ROADCUT
Large white roadcut at intersection with Hailesboro entry road
This outcrop exposes white marble of the Northwest Lowlands, enclosing trains of dark amphibolite blocks. The rocks are complexly folded. According to Shoenberg (1974), the sequence of events that accounts for the features of this outcrop is:
foliation formation
folding
intrusion of basalt as dikes and sills
further folding and metamorphism, converting basalt to amphibolite, and folding and dismembering the dikes
Marble and basalt have considerably different mechanical properties, accounting for the difference in behavior during deformation; marble can flow at conditions that cause silicate materials to break. There is also abundant evidence for chemical interaction between the two rock types. The grain-size in the marble increases toward the dikes, and minerals such as tourmaline and feldspar, absent elsewhere, occur there.

STOP 3. Large dark roadcut on either side of Rte. 58 at intersection of Poplar Hill Rd.
The Popple Hill Gneiss is a widespread unit in the Northwest Lowlands. It is locally migmatitic formation extensively studied by Carl (1988). This exposure on Rte 58 is the best example of the migmatitic phase of the unit. Here the dominant rock type is a dark gray quartzo-feldspathic gneiss with biotite; subordinate rock types include concordant amphibolite layers, and leucosomes. As at Stop 2, the amphibolites as well as the leucosomes behaved differently from the surrounding gneiss and became folded and boudinaged in this case. Structural relationships demonstrate that the leucosomes formed in situ before or during major folding events.
Based on extensive chemical analysis, Carl (1988) proposed that the Popple Hill Gneiss originated as a dacitic volcanic rock.

Pass Gouverneur Talc mines.

STOP 4. Deformed anorthosite in Carthage-Colton Mylonite Zone
The rock here is a brown-weathering, pink, very coarse-grained gneiss with large bluish-gray relict phenocrysts of plagioclase. The pink mineral which resembles K-feldspar is also plagioclase, colored pink for the same reason that K-feldspar appears pink: its cleavages are decorated by small inclusions of earthy hematite. Foliation is defined by parallel alignment of wisps and stringers of dark minerals. Also parallel to this crude layering are large somewhat irregular oxide schlieren.

STOP 5. Mylonitic Gneisses of the Carthage-Colton Mylonite Zone
In these outcrops, mineral lineations are so well developed that lineation can easily be mistaken for trace of foliation. Lineation is defined by rods of quartz and K-feldspar, the latter occasionally forming rounded porphryoclasts. It is this moderately plunging, NNE-bearing lineation that is thought to represent the direction of tectonic transport, which slid lower-temperature rocks from the southeast and higher in the crust, down and to the northwest, and left them juxtaposed against deeper, higher-temperature rocks.

STOP 6. Coarse-grained massive granitic gneiss.
The pervasive foliation and lineation present in rocks exposed along Rte 812 for 5 miles to the north is simply not present here. The rocks here are much coarser grained, and clearly have not experienced mylonitization in the CCMZ. You have crossed the southeastern edge of the CCMZ and are looking at rocks of the Adirondack Highlands.

STOP 7. Granitic gneiss and amphibolite of the Adirondack Highlands.
Long low pink and gray roadcut on either side of Rte. 812
Rocks southeast and under the CCMZ are predominantly orthogneisses, and are at higher metamorphic grade than those northwest and above the CCMZ. The difference in grade is expressed primarily in the mineral chemistry and assemblages. Foliation here has fairly low dip and is defined primarily by the presence of amphibolite layers in coarse-grained pink granitic gneiss. While the rocks are not part of the CCMZ, they are still intensely deformed and contain lots of evidence for shearing, including: offset dikes, refolded folds, and augen feldspars, and local truncation of layering within the amphibolite against the granite.
There is fairly nice glacial polish with striae on the tops of outcrops on the east side of the road. Climb to top of outcrops on east side of road, and look to the east There is a good-sized sand and gravel quarry, in a glacial deposit.

Large quarry on east side of Rte. 812.
Unconformity with Precambrian rocks is at base of hill

If weather is clear, glance out to east, across Black River Valley.

Overlook of Utica Shale and Lorraine Group in Whetstone Gulf
Immediately beyond intersection, pull into grassy area and park. Cross Corrigan Hill to marked trailhead, and follow trail to brink of Whetstone Gulf
Overlook of Mid- to Late Ordovician Utica Shale and Lorraine Group in Whetstone Gulf From this point at the brink of Whetstone Gulf, you can see a stack of late-middle to late Ordovician rocks, with the Utica shale at the bottom grading up into finely bedded shales and siltstones of the Lorraine Group on the top. These rocks represent early sediments shed from the Taconic Orogen 150 km to the east. Also, note the fracture sets shown in the canyon walls.
Note the large Pleistocene glacial erratics perched on the rim.

STOP 9. Black River Valley Overlook
If the weather is clear, pull as far as possible off the road. Look out to east over the Black River Valley. You are standing on the Tug Hill escarpment. The valley below marks the boundary between Tug Hill and the western Adirondack Highlands. The Tug Hill escarpment consists of two distinct benches. The one on which you are standing is underlain by sandstones and siltstones of the upper Lorraine Group. The lower bench, marked by numerous dairy farms below you, is underlain by the Trenton and Black River Groups (limestones). Low in the valley and on the far (east) side, you may be able to distinguish a relatively level surface, created by the tops of deltas shed into glacial lake Port Leyden, during the Wisconsin deglaciation. Better views may be had further south, between Lyons Falls and Boonville. Beyond these and to the far horizon, metamorphic rocks of the Adirondack Highlands are exposed.

STOP 10. Fossils in Utica Shale.
By gently prying open bedding surfaces, many samples of fossils may be collected. Fragments of trilobites, and pyritized cephalopods are common, whereas graptolites are rare.

STOP 11. Unconformity between middle Ord and PreCambrian
Unconformity between middle Ordovician sedimentary rocks and pink quartz-feldspar gneisses of Adirondack Highlands.
If the creek is high, then this outcrop is not accessible. If the creek is low, drop down and walk upstream until you encounter nearly flat-lying sedimentary rock lying directly on top of pink quartz-feldspar gneiss in which the foliation dips steeply. Notice the pebbles of gneiss enclosed in the basal sedimentary rocks. These sedimentary rocks are part of the middle Ordovician Black River Group (rather than the upper Cambrian Potsdam sandstone as at Stop 1), which means that the difference in age between the rocks above and below the unconformity is roughly 600 million years. Notice the evidence for spheroidal weathering in the pink quartz-feldspar gneisses directly below the unconformity. The evidence decreases downstream (i.e. farther structurally below the unconformity). Consequently, we interpret this to be the result of middle Ordovician chemical weathering.

STOP 12. Dated locality of Lyon Mountain Gneiss at Ager's Falls.
The origin of the rock exposed at Ager's Falls Park is somewhat controversial. The country rock is a pink, medium-grained and equigranular granitic rock, which is host to abundant quartz-sillimanite "nodules", veins, and stringers. These elongate bodies have a set of preferred orientations that make the rock appear to have a tectonic foliation. It was mapped as metapelite by Florence and others (1995). However, the interpretation of Orrell and McLelland (1996), following arguments originally made by Vernon (1979) is that the rock formed as a granitic melt which created its own hydrothermal system as it crystallized, such that fluid flow was channelized. In areas of high flow, alkalis were leached away, leaving behind the relatively immobile silica and alumina, as quartz and sillimanite. Orrell and McLelland (1996) state that the origin of the quartz-sillimanite features of the rock are thus metasomatic rather than tectonic and the rock is therefore interpreted as undeformed and post-tectonic, and McLelland includes the rock with the Lyon Mountain granitic gneiss of the northern and eastern Adirondacks. Evidence in support of an igneous origin for this rock is provided by zircons, which are typically finely oscillatory zoned.
A sample from Ager's Falls has been dated, with a concordant single zircon grain giving an age of 1031 ±8 Ma (Orrell and McLelland, 1996).

STOP 13. Dated locality of undeformed pegmatite cross cutting Lyon Mountain Granite
Leave cars and head south across the northern bridge, and drop down into the Moose River bed on the western, downstream side. Staying fairly close to road, locate roughly one-half meter wide, steeply-dipping, undeformed white pegmatite dike, trending N35W. The dike is zoned, with quartz-albite rims and granitic, magnetite-rich interiors. Sillimanite is an accessory phase. Such undeformed pegmatites are generally rare in the Adirondacks. This particular example cross-cuts the Lyon Mountain Granite with abundant quartz-sillimanite nodules, as at Ager's Falls. This dike has been dated (Orrell and McLelland, 1996). Zircons give a well-defined upper intercept of 1034 ± 8 Ma. Monazites give a well-defined intercept age of 1027 ± 8 Ma. Because of the undeformed and hence post-tectonic character of the dike, this is considered to represent a minimum age for the end of Grenville orogenesis in the region.

STOP 14. Nelsonite ore body.
Note! There is both poison ivy and barbed wire in the woods. Proceed only with extreme caution!
Cross North Street, heading south and east, to outcrop visible from parking area. This gray rock is a pelitic gneiss with the assemblage quartz + plagioclase + garnet + sillimanite +biotite. Walk over the outcrop and down to the left. Proceed for about 40 meters downhill toward a few prospect pits and ultimately toward the water filled mineshaft at the base of the hill. The prospect pits are in weathered exposures of the nelsonite; fresh samples can be collected near the mineshaft. The nelsonite is described and interpreted by Darling and Florence (1995). It is a rare igneous rock commonly associated with rocks of the anorthosite-suite. Its mineralogy is dominated by fine-grained magnetite, fluorapatite, and ilmenite. Pyrite and pyrrhotite occur as well. Chlorite, pyrite and biotite are abundant near contacts with the country rock. Darling and Florence (1995) suggest the occurrence of this rock indicates anorthosite-suite rocks were once present in the western Adirondack Highlands.

A2: LAKE ONTARIO COASTAL GEOLOGY AND LAND MANAGEMENT - PROCESSES, PRODUCTS AND POLICY
Donald L. Woodrow
Hobart and William Smith Colleges
Charles E. McClennen
Colgate University
Sandra Bonanno
The Nature Conservancy
This field trip carries us to some of the most dramatic freshwater scenery to be found in New York State. From the broad sand beaches of the eastern shore to the bedrock shelves, gravel beaches and till bluffs of the southeastern shore, geomorphology, sedimentary processes and human activity are manifest. Balancing the needs of citizens with those of the natural world so that the region can be both enjoyed and nurtured is an ongoing issue. We will look at examples of various shoreline geomorphologies, explain as best we can the processes shaping them and consider some of the policy questions involved.
Along the eastern shore of Lake Ontario, sand is arrayed offshore and on broad beaches backed by dunes. The extensive beaches are separated by a few, low till bluffs. Beach/dune barriers protect extensive wetlands and bays. Obvious human impacts are limited to only a few areas of the shore. Determined efforts by governmental agencies, citizen groups, and individuals have had a marked positive effect on preservation, conservation, and low-impact recreational utilization.
The southeastern shore is marked by bedrock shelves, gravel beaches and high till bluffs. Wetlands and bays are less extensive than in the east. Evidence of human activities is ubiquitous: industrial sites, harbors, houses, farms and orchards, state and local parks. Efforts at conservation by government and various citizen groups are less in evidence along the southeastern shore which is not surprising given its greater extent and history of exploitation. Southeastern shore residents most often express concern about lake level and its effects on property, shore-related activities, and boating activities.
Glacial and post-glacial sediment in this region rest on Ordovician strata which is locally exposed along the shore.

A2: LAKE ONTARIO COASTAL GEOLOGY AND LAND MANAGEMENT - PROCESSES, PRODUCTS AND POLICY

STOP 1. Chaumont Barrens
(We will not visit this locality but it will be discussed at the Friday evening briefing.)
Chaumont Barrens Preserve is a global ecological rarity: 1630 windswept acres of an intact alvar landscape. "Alvar" comes from the term coined by Swedish geologists to describe expanses of level, exposed limestone bedrock found on islands off the southeastern coast of Sweden. Northwestern Jefferson County features a chain of similar outcrops of level, exposed limestone, which supports a characteristic mosaic of rare ecological communities. Jefferson County is the southeastern limit of the alvar mosaic, which occurs in fewer than 100 scattered locations in New York, northern Michigan, Ontario and along an escarpment of Cambro-Ordovician limestone and dolomite at the edge of the Canadian Shield. Chaumont Barrens is the best preserved occurrence in New York.
The Chaumont Limestone and other units of the Ordovician Black River Group are the rocks on which the Chaumont Alvar is based (Isachsen and Fisher, 1970). They are light gray, fine-grained and rich in cephalopods, corals, stromatoporoids, gastropods, brachiopods, trilobites and burrows. Cephalopods, in particular, are commonly seen in outcrops on the preserve. Rectilinear joints, some of which are enlarged by solution, break the rock surfaces. Strata dip to the southwest at less than one degree.
There is some controversy about the origin and fate of the very thin, discontinuous soil cover. During glacial retreat, some 10,000 years ago, pro-glacial Lake Iroquois covered the area of the present-day barrens to depths of at least tens of feet. Wave-driven currents probably winnowed away sediments overlying the bedrock. This alone may be enough to account for the thin, discontinuous soils. Another idea holds that, during glacial retreat, ice dams formed to the northeast of this area. With further melting, the ice dams burst, loosing enormous volumes of water which exploded across the bedrock clearing any sediments which may have been deposited there whether on the surface or in solution-widened joints. Finally, some of the soil materials may have been washed into joints over time as they were widened by solution.
Whatever the cause, soils throughout northern Jefferson County are thin and alkaline. At Chaumont Barrens and other alvar sites, soils are often just a few inches thick. The areas with thinnest soils and few fissures flood deeply during heavy rains and spring runoff: then bake dry throughout the summer and early fall. Water movement is thought to be predominantly sheet flow across the landscape, mostly NE to SW, across a very subtle 1% slope. Artesian features are known in the area, however, so upwelling may be a partial source of flood waters. The hydrology of this region is not well understood but it is clear that the annual cycle of flooding and drought greatly limit the variety of life that can survive here.
The alvar mosaic at Chaumont includes three rare natural communities: limestone woodland, calcareous pavement barrens, and the rarest of all, alvar grassland. Limestone woodlands occur on shallow soils over limestone. The canopy may be entirely deciduous, entirely coniferous, or a mixture of the two. Ground cover can include a delightful array of wildflowers under deciduous stands, which tend to have a rather open canopy. The conifer stands are dense and dark, with only scattered spongy moss colonies beneath.
At Chaumont the calcareous pavement barrens community is made up of variable-sized patches of barren rock; platy gravel colonized by mosses, lichens, and a few small wildflowers; deep fissures sculpted into the joints, and patches of shallow soil inhabited by shrubs, a few trees, and open grassy areas. The arrangement of patches feels very random on the ground, but an aerial view reveals a striking NE/SW arrangement of alternating woody and open areas parallel with the regional joints. The pattern occurs because shrubs and trees frequently sink roots into the fissures where moisture and protection allow them to survive.
Alvar grasslands are the rarest part of the community mosaic, both in number and size of occurrences. In the U.S., there are only a handful of occurrences and those are found in northwestern Jefferson County, and northern Michigan. Extremes of flooding and drought alternate in the alvar grasslands every year. The resulting vegetation looks like a prairie, and contains prairie species rarely found in the northeastern United States. Prairie plants may have migrated here during a mid- to late-Holocene warmer/drier interval some 5000 years ago. Then, as the climate became more moist, prairie plants were replaced almost completely throughout the Northeast by plants attuned to more moist conditions.

STOP 2. Black Pond - El Dorado Beach
A newly built road, parking area, and boardwalk allow easy access to a set of contrasting ecosystems that have been subjected to minimal human impact over the last century or two. The outlet from Black Pond to Lake Ontario is a geomorphic boundary for Lake Ontario coastal classification. Sandy beaches extend to the south and bedrock coast to the north. Black Pond with surrounding sedge, scrub and forested wetlands is protected from wave attack by the dune-capped barrier beach and offshore shoals. The size and age of the trees on the dune tops and eastern faces demonstrate the stability and relict nature of the highest dune crests. Along the lake or western dune faces, grasses and scrub (sand cherry) growth prevail. Recent snow fence installation, dune-grass planting and walking path demarcation including a walkover to the beach face and conservation signage have encouraged a recovery of local vegetation and dune sand accumulation.
Beach sand at this locality contains rock fragments, quartz, magnetite and garnet (among other grains) and masses of shells and shell debris of Zebra- and Quagga-mussels. Beach berms, runnels and other ephemeral features of sandy shores are seen here as a result of changing lake level and storm waves. Reworking of previously accumulated sediment prevails since there is no source of sand other than limited long-shore drift, minor erosion of till and exchanges with the subdued nearshore sandbars.
Offshore, to the south of this location, side-scan sonar records and sub-bottom profiles collected in conjunction with surface sediment samples and vibracoring reveal a one to several meter thick sheet of very well sorted sand. On it are scattered meter-scale, circular and elongated patches of what appear to be mussel colonies (Figure 1). Side scan sonar records disclose exposed bedrock just offshore from this locality (Figure 2). The bedrock looks to be festooned with mussels and is marked by fracture patterns like those seen on land in Henderson and adjacent townships to the north and east and at the Chaumont Barrens. The boundary seen on shore between the unconsolidated sediment surface cover to the south and exposed bedrock to the north continues offshore to depths of roughly 30m (100 feet).

STOP 3. Southwick Beach State Park.
The sweeping extent of this low relief beach offers one of the best known vistas in eastern Lake Ontario. Sands on the beach, in the dunes and on the gently sloping foreshore are fine- to very fine grained. A history of intensive recreational use, sand mining and exploitation by private groups and government management agencies has significantly modified this section of formerly dune-capped barrier beach. The adjacent marsh was once a fen. Evidence for the prior existence of a fen comes in two forms. First, this is the type locality for a very rare moth, Hemileuca sp. (bog buckmoth), known from only 10 localities, world-wide and all of them fens. Hemileuca has not been seen in this wetland since the 1960's. Second, the site is now marsh but it has a "false bottom"- underlain as it is by a deeper peat mat. It is reasonable to assume that the fen was flooded and that the present marsh developed over it. The marsh is now valued as habitat for a variety of uncommon breeding waterbirds and migrating waterfowl.
Waves during the summer months are either southerly or face-on to the beach while in winter, they are more northerly. Sand-bars formed under each of those regimes serve as sand reservoirs with some transport onshore and off with little net movement. Sand is extracted from the system as dunes accrete and migrate and as barrier bars are breached and new inlets form with their baymouth bars. Dune accretion is likely greatest during times of low lake level and least when it is high.
Cooperative restoration efforts by The Nature Conservancy and New York State over the last three years have seen the installation of two dune walkovers and snow fencing to protect the transplanted and very rare Ammophila champlainensis (Champlain beachgrass). This grass is found only here, a few sandy beaches on Lake Champlain and at a few sites along the St. Lawrence River in Quebec.
Sand dune accumulation has already begun along with natural propagation of the dune grass and self-sown wormwood. Proposals for restriction or exclusion of camping from the lakeshore along a former dune line met with intensive public resistance. Campers clearly enjoy parking their vehicles between the access road and beach where there used to be a well developed natural dune ridge. The prevailing westerly winds of summer as well as the sight and sound of breaking waves make this section of the park very attractive.

STOP 4. Sandy Island Beach
Dune Reconstruction and Planned Development.
At this location, an early 20th century inlet through the barrier into Sandy (North) Pond was abandoned and became the locus of a dune. In more recent decades, a blowout formed at the dune site carrying sand from the beach into Sandy Pond and thereby almost duplicating the earlier inlet. The barrier and its dunes extend about two miles to the north where another a modern-day inlet opens into Sandy Pond. Other inlets that have opened and closed along the barrier in this century are recorded in aerial photography starting with a series in 1938 and continuing through 1988.
Until this year, crumbling and abandoned facilities, debris of all kinds and a cobble beach made this a much-degraded site. We will view new developments on the lakefront where Oswego County has constructed day-use park facilities. Beginning with land acquisition, The Nature Conservancy has supported both this development and that of NYSDEC as it "restored" the dune flanking the park to the north. To restore the dune meant that first, 44,000 ft3 of sand were moved from landward edge of the advancing blowout back to the beach/dune line. Plantings on the restored surface are now well established and are protected by fencing. Another significant volume of sand was moved to the beach face from the rear of what is now the parking lot to cover what had become the cobble surface of the beach. Finally, a gated, fenced, and cobbled access roadway has been established from the new parking lot north along the dune/beach line to ensure vehicular access for those home owners north of the site along the barrier. The addition of upland sand to this beach provides the opportunity for an experiment in sand movement along this section of shore.
Offshore just south of this location, seismic and side-scan records indicate that the sand sheet is patchy on an eroded till and/or bedrock surface (Figure 3). Vibracores taken in the sand sheet nearby disclose a layer of 2-10 cm diameter gravel resting either on well-sorted sands very much like those presently found on the beaches or on organic-rich peaty clays and silts. This gravelly surface is apparent in the seismic records where it marks the top of seismic Unit #2 (Figure 4). We take this gravelly sand to be a beach deposit which indicates that post-glacial Lake Ontario water levels were as much as 25 meters (80 feet) below present. This lower stage may be the "Dune Stage" of Sutton, Lewis and Woodrow (1970), a lower lake level whose existence was postulated on a much more limited data set. Carbon 14 AMS dating analysis results for the peaty deposits below the gravel may be ready by the time of the NYSGA 2000 field trip and should help to date the lower lake stage.

STOP 5. Shoreline at the Energy Center, Nine Mile Point.
Driving around to the southeastern shore of Lake Ontario, instead of dune-capped, sandy, barrier-beaches and adjacent wetlands and bays we see bluff exposures of till over bedrock. This location provides an example. The "beach" here is made up of minimally rounded boulders and slabs. The beach is developed on bedrock. The overlying till is exposed where continued erosion prevents establishment of vegetation. The steep bluff face and lack of trees on it suggest that erosion events recur on a decadal frequency, a frequency less than that seen further to the west. The presence of glacial-scour marks on the exposed bedrock indicates resistance to erosion and suggests an explanation for lesser erosion rates of the till at this locality.
The bedrock seen here is the Late Ordovician Oswego Sandstone (Isachsen and Fisher, 1970). Bedding planes exhibit light greenish-gray, fine-grained sandstones marked by low-angle, trough cross-strata and parting lineations. Rip-up clasts are found at the base of sandstone beds and some units display sole marks. Fossils are not seen at this locality. At other locations nearby, the Oswego is arrayed in fine-upward sequences typical of fluvial and/or tidal channels. The Oswego is part of a thick Late Ordovician basin-fill sequence the base of which is the Black River Group carbonates of Stop 1. Between that location and this more than 500 m of clastics from black shale to this sandstone are covered by the glacial and younger sediments. Next above the Oswego and not exposed on the south shore of Lake Ontario until the Genesee River Gorge in Rochester, is the red and green Queenston Shale which marks the top of the basin-fill.
Just east of this location are three nuclear power plants, a concentration of such plants greater than that found at any other location in the country. Siting the plants on stable bedrock near an abundant supply of cooling water and distant from large population centers made the location environmentally and politically attractive. In a linked location-decision, an aluminum-can production plant, located just to the west of here, also uses Lake Ontario waters for cooling and draws on the power grid for electricity. Cooling ponds at the plant required modification of many acres of wooded coastal wetlands. The ponds provide an expanded habitat, yielding some impressively large carp and other species.
For several miles east of the power plants, the coast consists of bedrock cliffs with a shallow bedrock platform just offshore. The cliffs, although accessible by road, are dangerous to scale because of groundwater seepage, clay-rich soils and slimy overgrowths. Cliff-edge trees at these locations often have roots exposed and locked into cracks suggesting a very slow rate of erosional retreat.

STOP 6. McIntyres Bluff
Drumlins and adjacent barrier-beach fronted wetlands.
West of the city of Oswego in the township of Sterling, the bedrock is no longer exposed along the lakeshore. Here are a series of north-south trending drumlins and connecting barrier beaches in front of ponds and wetlands, a geomorphic pattern which persists for about 30 km to the west. The drumlins have been truncated by storm-wave undercutting, particularly during periods of high lake level, and further eroded by a combination of mass wasting, streamlet runoff and wind erosion. The nature of the spring thaw, snow cover and rain-event sequencing generates a lot of inter-annual variability in the amount and style of slumping and sliding as well as gully washout and alluvial fan development. Long-shore wave-driven transport, which moves predominantly toward the east, redistributes the eroded till of the drumlins and deposits a progressively more rounded sand and gravel barrier. The fines are redeposited in the deeper waters of the lake or in the lows of inter-drumlin ponds and wetlands. The bluffs of drumlins show a variety of heights and morphologies, which are measured to be more and less steep, with and without gully development, and multiple kinds of alluvial fans and scarps at the toe of the bluffs along the beach.
The model (Pinet et al, 1998; Pinet and McClennen, 1997) that goes a long way to explain many of the observed patterns (Pinet et al, 1992), has a focus on the causal changes in bluff morphology as the erosion processes cut through the drumlin hills. Groundwater-flow and run off keep the bluff faces wetter in the initial stages of bluff retreat. After the crest portion of the drumlin has been removed the bluff faces are generally drier due to the landward direction of runoff and water table gradients, and exposure to wind. The local bluff height and retreat rates control to some extent the volume of drumlin till deposited on the beach. In combination these factors seem to explain the early, youthful, mature and old age stages of bluff retreat morphologies. They are modulated by inter-annual weather and lake level variations. The last stop of the field trip at Chimney Bluffs State Park will show a more fully developed example of the coastal retreat patterns and interpretations introduced at Mclntyres Bluff.

STOP 7. Chimney Bluffs State Park (under development).
At this location, we see an unusual landscape cut into a flat-topped drumlin. The landscape, like that at McIntyre's Bluff, is made up of spires, pinnacles and razor-edge ridges, some ending at lake-edge in sheer cliffs and all separated by steep-sided valleys. The drumlin is flat-topped (as are all of the other drumlins near the lake shore in this region) as the result of beveling by wave erosion in proglacial Lake Iroquois. Its crest stands about 50 m above the lake.
This landscape is the product of groundwater seepage (sapping), erosion by flowing water and wind, and solifluction. The solifluction effects are dramatic. In the spring, frozen cliff surfaces thaw over large areas in a matter of hours. Masses of till are loosed into the valleys as dense mudflows. The flows easily raft along boulder-sized clasts delivering them as part of a muddy slurry to the beach where the flows dewater and deposit their sediment load in fans. Valley surfaces are denuded as much as several cm in a day with the southwest, more fully exposed, faces experiencing the highest rates of loss. Once on the beach, waves erode the fans in several weeks or months. The biggest boulders are left at the fan head and form boulder-trains on the floor of the lake as the cliffs retreat. Cobbles and coarse sand are moved along the beach to the east and finer sediments are carried into the open lake. Ridge-ends are undercut by waves during lake high-stands and cliff-collapse is common at that time, adding to the rate of retreat. At the west end of Chimney Bluffs, faulting in the till has led to differentially rapid erosion along fault surfaces and the development of ephemeral caverns and clefts.
The west end of the Chimney Bluff drumlin is especially instructive. There, varved clays, apparently derived from the top of the drumlin as it was eroded by Lake Iroquois waves, are exposed in a 3-6 m cliff. The varves lap on to the till of the drumlin, thin up-section, are coarser toward the drumlin and show soft-sediment deformation caused by masses of gravelly sediment sliding down side of the drumlin.
New York State is slowly developing the park and, unlike developments at most lakeshore locations, is working to make a virtue of rapid erosion. However, the issue is joined because the edge of the low bluff just north of the lot in which we parked has retreated approximately 10 m in 35 years. Permanent structures at this location will have a finite lifetime independent of the life of the materials used to build them.

A3: STRATIGRAPHY, SEDIMENTOLOGY, AND GEOCHEMISTRY OF SENECA LAKE, NEW YORK
JOHN D. HALFMAN
Department of Geoscience
Hobart and William Smith Colleges
Geneva, NY 14456
INTRODUCTION
This field trip investigates the stratigraphy, sedimentology and geochemistry of Seneca Lake. The field trip is aboard the H-WS Explorer, and focuses on representative sediments that have accumulated in the northern part of the lake since deglaciation, which are typical of the other Finger Lakes. The trip also highlights ongoing efforts to collect and interpret high-resolution (2-12 kHz) seismic reflection profiles that image down to the glacial drift, and our recent understanding of the chloride and calcium concentrations/budgets in Seneca Lake in comparison to the other Finger Lakes.
The Finger Lakes of central New York State consist of 11 elongated, north-south trending basins just south of Lake Ontario (Fig. 1). The basins are glacially scoured into the northern edge of the Appalachian Plateau (Coates, 1968, 1974). At Seneca Lake, the bedrock is primarily Devonian shales (Hamilton Group in the northern end of the lake), and lesser amounts of sandstones and carbonates that gently dip to the south-southwest. Silurian carbonates, shales and most importantly evaporites (mostly halite) are found below the Devonian section.
Seneca Lake is the largest (by volume) and deepest of the Finger Lakes (Fig. 1, Table 1 ). Only Cayuga Lake immediately to the east of Seneca is longer (61 km) and almost as deep (132 m). The other basins are smaller, ranging in length from 5 to 32 km and maximum water depth from 9 to 84 m. The present day lake is fed by over 30 streams and major creeks and drains to the north-northeast through the Seneca River (New York State Cayuga-Seneca Barge Canal).

A3: STRATIGRAPHY, SEDIMENTOLOGY, AND GEOCHEMISTRY OF SENECA LAKE, NEW YORK

STATION 1. SHALLOW-WATER SANDY SILTS
NORTHERN END OF SENECA LAKE
The lake floor is covered by sandy silts, with the coarsest sediments in the northwest margin of the lake. Shell and plant debris and the occasional ice-raft pebble make up the other minor components. We believe that these sediments must be derived from the reworking of and erosion of glacial drift. Sub-bottom images suggests that the sand forms a thin wedge of sediment above the pink clays and/or glacial drift. In many places the seismic images are attenuated by gas (biogenic methane?).
Suitable substrate (coarse materials) is covered by zebra mussels. Zebra mussels are an exotic species that has been introduced in the lake during the past decade. They are prolific filter feeders, filtering, on average, a few liters of water each day, extracting the plankton from the water column. One possible measure of their impact is historical Secchi disc data. Secchi discs are used to measure water clarity. To a first approximation, deeper Secchi disc depths correspond to less turbid water (e.g., smaller plankton concentrations). Historical Secchi disc data have shown increasing Secchi depths over the past decade from a few meters to over 5 meters deep during the productive early summer months. This change is consistent with a decrease in chlorophyll concentrations. The exact reasons for the increase in water clarity (and decrease in chlorophyll) are not completely understood but the Secchi disc data suggests two hypotheses: that the burgeoning population of zebra mussels has become large enough to significantly reduce the standing crop of plankton, and/or an increase in the quality of sewage treatment by lake-shore residents has reduced the anthropogenic nutrient loading to the lake.

STATION 2. PROGLACIAL RHYTHMITES
MID-LAKE OFFSHORE OF BELLHURST CASTLE
To the south of station 1, pink clays may be found below a thin veneer of postglacial material. The pink clays are well stratified, very cohesive and exhibit light red to pink colors. Single pebble to granule sized grains and ostracode shells are found widely scattered in the sequence. Well defined, parallel to subparallel reflectors characterize these clays in the sub-bottom profiles. The reflectors commonly outcrop onto the lake floor in shallow water. We interpret these clays as preglacial rhythmites, typical of many preglacial lakes. It is unclear whether the couplets are annual events (varves). In the northern part of the lake, the pink clays are folded. The subbottom profiles suggest that the pink clays collapsed into ice-block holes in the underlying drift and/or the ice front experienced small re-advances.

STATION 3. POSTGLACIAL MUDS & LAKE GEOCHEMISTRY
OFFSHORE OF CLARKS POINT
Moving south across exposures of glacial drift, the lake floor descends to a flatter floor typical of the deeper parts of the lake. At this location the uppermost sediments are very fine grained, black to gray, stratified and rich in organics. These sediments blanket the older materials with thicknesses up to 8 meters in the sub-bottom profiles. The sequence thins rapidly in water depths shallower than 60 meters and on the steep slopes on either side of the basin. They contain no shell material, a few coarse grains of silt and sulfide minerals. These muds are interpreted as the postglacial sediments deposited since deglaciation. The source is the suspension of fine material carried into the lake by streams and/or erosion of older, shallow-water bottom sediments by surface and internal waves.
We will also deploy the CTD and analyze the surface water for its chloride and calcium concentrations at this site to discuss the unique source of the "extra" chloride to Seneca Lake and the recent depletion of calcium from the lake by zebra mussels.

A4: ANATOMY OF A COMPOSITE SEQUENCE BOUNDARY - THE SILURIAN-DEVONIAN CONTACT IN WESTERN NEW YORK STATE
CARLTON E. BRETT
Dept. of Geology
University of Cincinnati
Cincinnati, OH
45221-0013: carlton.brett@uc.edu
CHARLES VER STRAETEN
Center for Stratigraphy and Paleontology
New York State Museum
The State Education Dept., Albany, NY 12230
cverstra@mail.nysed.gov
GORDON C. BAIRD
Dept. of Geosciences
SUNY Fredonia
Fredonia, NY 14036
Baird@fredonia.edu
INTRODUCTION
Unconformities form the basis for sequence stratigraphy (Vail et al., 1977, 1991; Wilgus et al., 1988; Van Wagoner et al., 1988; Emery and Meyers, 1996). Widespread disconformities have long been recognized and Sloss (1963) used such major gaps - which typically expand cratonward- to delineate six major intervals, now termed supersequences, in the Phanerozoic record of North America. The boundary between the middle Ordovician - Lower Devonian - Mississippian Kaskaskia sequence was drawn at a major, if cryptic, disconformity that was later named the "Wallbridge Unconformity" (Sloss, 1963; Dennison and Head, 1975). The temporal significance of unconformities stems from a key assumption- fundamental to relating sequence stratigraphy and chronostratigraphy - all strata below an unconformity are everywhere older than all strata above the surface.
In addition to their importance in sequence stratigraphy, unconformities may have other far-reaching implications. Topographic features of the surfaces may provide insight into processes active during the hiatus in which the surfaces formed. Presence of early jointing may signify tectonic regimes. Sinkholes and collapse breccias may point to karstification, and paleosols may provide some hints as to climatic regimes. Three-dimensional study of unconformities - the production of paleogeologic maps along these key surfaces may yield very important insights, as to paleotopography and aid in defining the positions of relative highs (domes, arches) and lows (local basins).
Correlation of unconformities involves outcrop to outcrop tracing and/or independent data on biostratigraphy, event beds, etc. Such correlations may point to significant widespread lowering of relative sea level. Ultimately, intercontinental correlations may aid in identification of eustatic lowstands. Conversely, the localization of unconformities in otherwise continuous successions may lead to recognition of local tectonic effects (e.g., Ver Straeten and Brett, 2000). Commonly, two or more disconformities may merge laterally to form a much larger unconformity. This to may point to localized diastrophic or far field tectonic effects (Ettensohn, 1991).
Finally, as erosion surfaces are later onlapped by shallow seas they become transformed temporarily into rocky shorelines and rockground seafloors that may exhibit distinctive morphologies and faunas that typify the intertidal to shallow subtidal zone. Such rocky shorelines have received considerable attention of late (see Kobluk et al., 1977; Johnson; 1988, 1992; Johnson and Baarli, 1999).
In this paper we document details of widespread sub- Middle Devonian (Onondaga Formation) unconformities in western to west-central New York (map, Figure 1). We recognize up to three disconformity surfaces (sequence boundaries) in western to central New York that locally merge to form one. The true Wallbridge Unconformity may erosionally truncate three older, post-Bertie sequences. These results point to widespread erosion in the Late Silurian- Early Devonian west of Cayuga Lake. This surface was subsequently transgressed in the middle Early Devonian (Pragian) and draped with basal quartz sands of the Kaskaskia transgression (Oriskany Formation). A subsequent period of erosion removed much of the Oriskany and probably all of the overlying Esopus Formation during mid-Emsian time. This erosion surface was transgressed by late Emsian (Schoharie-Bois Blanc) shallow seas, which reworked sand and clasts of older units. Finally, another period of erosion, immediately preceding the deposition of latest Emsian-early Eifelian Onondaga Limestone removed much of the Bois Blanc and further modified the exhumed erosion surface.
Finally, we describe what appears to be a rocky shoreline with small sea stacks, submarine cavities, and fissures in Silurian dolostones, which are draped and filled with Devonian bioclastic sediment.

A4: ANATOMY OF A COMPOSITE SEQUENCE BOUNDARY - THE SILURIAN-DEVONIAN CONTACT IN WESTERN NEW YORK STATE

Manlius and Onondaga Fms
Low cuts of Manlius on left (south) side of highway, Manlius and Onondaga Fms. on right (north) side of highway. Reworked concretions of phosphate-cemented sands of the "Springvale Sandstone" of Schoharie age occur in the base of the Edgecliff Member.

STOP 1. ABANDONED QUARRY ("SCHOOLEY QUARRY"),
This abandoned quarry pit and a larger one to the east expose Lower to Middle Devonian strata of the Manlius, "Springvale Sandstone," and Onondaga (Edgecliff, Nedrow, and Moorehouse members) formations. The regional complexity of multiple unconformities is reflected at the small scale here by the local thickening and thinning, including pinchout, of the "Springvale" Sandstone along the quarry walls.
The lower walls of the quarry feature buff to gray, fine-grained limestones to dolostones, with local stromatoporoid buildups, assigned to the Manlius Formation. Two members appear present in the quarry; upper buff-weathering, mud-cracked dolomites to limestones of the Elmwood Member, and lower, gray weathering limestones with local stromatoporoid buildups of the Olney Member. Ciurca (1978), however, shows Olney at the contact in the area of Auburn. The upper contact of the Manlius Formation appears sharp.
A photograph (Figure 11) shows the succession through the units in the northwest corner of the "Schooley" quarry, along a ramp road. The top surface of the Manlius appears irregular and knobby. The overlying approximately 0.7 m consists of dark, argillaceous, phosphate-rich and locally glauconitic sandstone, with phosphatic concretions. A gray- to buff- to blue-colored resistant ledge of sandstone caps the "Springvale." Medium- to large-sized sandy phosphatic concretions occur at two horizons within; similar and smaller concretions in the upper part of the bed appear fragmented and reworked, possibly indicative of a time of erosion and unconformity between "Springvale and basal Onondaga strata.
The overlying 3.7 m-thick Edgecliff Member (Onondaga Fm.) is characterized by a lower non-cherty interval (0.3 m-thick) with common corals; the corals are mostly restricted to the lower 0.8 m of the member. Three cherty intervals (Clarence facies) occur up through the Edgecliff in the "Schooley" quarry. Examination around the walls of the quarry indicates local pinching and swelling of the "Springvale" sandstones.
In at least one area on the south wall, the Springvale is absent for a distance; sandy phosphatic concretions from the unit are seen reworked into the base of the Edgecliff Member.

Montezuma National Wildlife Refuge
Cross into Seneca County and pass through Montezuma National Wildlife Refuge, at head of Cayuga Lake

STOP 2. SENECA STONE QUARRY.
The classic Seneca Stone quarry exposes a succession of Lower to Middle Devonian strata from the upper part of the Manlius Limestone to the top of the Cherry Valley Member of the Oatka Creek Formation (Marcellus subgroup of Brett and Ver Straeten, 1994 ). Two prominent, north-directed thrust faults occur in the upper part of the Onondaga Formation within the quarry. One of the faults has been long known, and is visible in the east and west walls toward the south end of the quarry. An additional, recently exposed fault occurs in the northwest wall. The section at Seneca Stone is otherwise relatively undisturbed.
Fine-grained, micritic limestones of the Lower Devonian Manlius Formation (Olney Mbr.) of the Lochkovian 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 (Pragian Tristates Group). The intervening break between the Olney, which is mid-Lochkovian, and the Oriskany, interpreted to be late Pragian represents on the order of four to six million years (based on Rickard, 1975 and new geochronologic dating by Tucker et al., 1998). This break represents the true Wallbridge Unconformity at the base of the Sloss's (1963) Kaskaskia Supersequence. Clasts of the older Manlius Limestone occur in the base of the Oriskany, sometimes overgrown by tabulate coral colonies. Small (cm-scale) undercut ledges of the Manlius may also be found at the unconformity, with the intervening space filled by quartz arenite (Figure 12a).
The Oriskany Formation is characterized by white quartz arenites that occur locally as pods or lenses across central New York. The spottiness of these occurrences is shown well within the base of the Seneca Stone quarry. Approximately 0.6 m of quartz sandstone is found near the central sump pit of the quarry; however, the whole unit pinches out a short distance to the south (visible in the quarry walls). The classic "big brachiopod community" of the Oriskany Formation is well shown in the sandstones at Seneca Stone quarry (Figure 12b), with numerous large, robust brachiopods (including Costispirifer arenosus, Rensselaeria, and Hipparionyx), platyceratid gastropods, and favositid and rare rugose corals (Oliver and Hecht, 1994).
The Emsian-age, phosphate- and locally glauconite-rich sandstone strata noted at Auburn during the previous stop are absent at Seneca Stone quarry. They do appear, however, to be represented, as phosphatic-cemented sandstone clasts in a lag of reworked conglomeratic sands in the base of the Onondaga Formation (Figure 12c; sourced from the Springvale Mbr., as seen in situ at Stop 1). Based on the recent Devonian time scale revision of Tucker et al. (1998), the gap between basal Onondaga strata (uppermost Emsian) and the Oriskany Formation (upper Pragian) represents approximately 15 million years.

Elderlee Sand and Gravel operation
Elderlee Sand and Gravel operation on right and 0.6 miles ahead.

STOP 3: OAKS CORNERS QUARRY
The walls of the Oaks Corners quarry displays strata of the upper Silurian Akron Formation and the Lower to Middle Devonian Edgecliff, Nedrow, and part of the Moorehouse Members of the Onondaga Formation. The unconformity between Silurian and Devonian strata is well exposed in the quarry walls (Figure 13), and commonly exhibits an irregular topography of small mounds and adjacent lows that are filled with basal Onondaga limestones or locally-occurring patches of quartz sandstone.
On the south wall at Oaks Corners, basal Onondaga strata of the Edgecliff Member generally rest directly on beds of the Upper Silurian Akron Formation, a massive, dark brownish buff-weathering saccharoidal dolostone. Thin, locally-occurring quartz arenite lenses occur in the quarry, as well as quartz-sandstone filled karstic cavities that extend down as far as the quarry floor (D. Woodrow, pers. commun.). The age of the sandstones (Oriskany, Bois Blanc, or reworked at the base of the Onondaga) is presently unresolved. In the absence of the sandstones, weathered pyritic crusts leave distinct rusty stains along the Akron-Onondaga contact. The unconformity is approximately six meters lower in the Silurian section four miles to the northwest (Rte. 88-Phelps cuts, Stop 4), where the unconformity surface is cut down to the level of the older Scajaquada Shale. At the Oaks Corners quarry, large channel-like depressions, up to several meters across and with a relief of up to one meter, occur along the unconformity.
Basal, chert-free beds of the Jamesville Quarry facies of the Edgecliff Member (Brett and Ver Straeten, 1994) occur within hollows on the combined Wallbridge, sub-Bois Blanc-Schoharie(?), and sub-Onondaga unconformities. These lowest Edgecliff strata comprise fine- to medium-grained crinoidal grainstone, typically pinkish-weathering, which range from 40 to 120 centimeters in thickness as a result of the irregular topography over the unconformity. Immediately overlying chert-rich strata (Clarence facies) consist of cherty, crinoidal pack- to wackestones. The remainder of the approximately 8.5 m-thick Edgecliff Member at the Oaks Corners quarry is dominated by the Clarence cherty facies, and consists predominantly of pale gray-weathering, micritic limestone with 20 to 30% dark gray chert.

Outcrops on both side of road
Outcrops on both side of road of Edgecliff Mbr., Bois Blanc Fm., "Springvale Sandstone," Oriskany Fm., and Upper Silurian Scajaquada and Fiddlers Green Fms. Park along side of road.

STOP 4: ROADCUTS ALONG NEW YORK RTE. 88, NORTH OF PHELPS.
Roadcuts along NY Route 88, immediately south of the New York State Thruway, display Upper Silurian strata of the Bertie Group (Pridolian, Scajaquada Formation) and Lower Devonian rocks interpreted here to represent the Emsian Bois Blanc Formation, a lateral equivalent of the Schoharie Formation of eastern New York.
Medium to slightly reddish-gray shales and argillaceous dolostones of the Scajaquada Formation characterize the lower part of the succession here and to the east along the Thruway. Small salt crystal casts may be found in the formation.
The Wallbridge Unconformity lies at the top of the Scajaquada Formation. The new Devonian time scale of Tucker et al. (1998) indicates that the unconformity between the Bois Blanc and the Scajaquada represents on the order of 16 million years.
The contact of the Scajaquada Formation with overlying Devonian strata is sharp. However, a record of unconformity-related processes is visible in the upper part of the Silurian strata. Thin fissure fillings of Oriskany quartz sand are seen to extend 30 to 40 centimeters downward below the upper surface of the Scajaquada Shale. The upper 10-20 cm also show an indistinct mottled texture (Figure 14a), and the upper surface of the dolostone features common Trypanites hardground borings, infilled with quartz sands. The contact is overlain by a conglomeratic sandstone bed with pebbles to cobbles of dolostone, sandstone or phosphate (Figure 14b ). Some of the clasts even show an interior core of dolostone that may be up to 2-3 cm thick, surrounded by 2-3 additional centimeters of lithified sandstone that may also feature a thin exterior rind of phosphate.
Recent study of the Devonian strata at the Phelps cut indicates a distinct two-part lithologic subdivision: a lower, only slightly calcareous sand-rich unit (1.6 m-thick) and an upper carbonate interval above (4.2 m-thick). The character of the much of the outcrop, including lithology and fauna, appears strikingly different from the Edgecliff Member of the Onondaga Formation across the region. We interpret the outcrop to represent the easternmost known outlier of the Emsian-age Bois Blanc Formation in New York State. This is supported by Oliver's (1963) report of low exposures of cherty, micritic Bois Blanc limestones along the New York State Thruway near Phelps, 1.7 miles west of the Rte. 88 cut. Pending a revision of Emsian strata across the region, we assign the lower sand-rich unit to the "Springvale Member" of the Bois Blanc Formation, and the lower 2.9 m of the upper carbonates to an unnamed, upper member of the Bois Blanc.
The lower part of the Bois Blanc Formation ("Springvale Member") here is relatively sand-rich. Three subdivisions can be recognized, consisting of a lower coarse sandstone unit with a basal conglomerate-rich bed, overlain by finer-grained, knobby-bedded/nodular strata, with thin shaly drapes between layers (Figure 14c). Local lenses of "salt and pepper" quartz and phosphate sandstones occur at the contact of the lower and middle units. The upper unit is coarser-grained again, although still knobby-bedded. Irregular nodules of apparent phosphatic and/or cherty composition occur in both the middle and upper subunits of the sand-rich interval. Phosphate appears to be especially common in the middle, finer-grained unit, although it also commonly occurs as reworked concretions in the basal lag bed.
The upper sand-rich subunit features common fossils, including medium- to large-sized brachiopods, uncommon small rugose corals (one larger rugosan seen), cephalopods, and a conularid. Little to no crinoidal material is visible. Of interest is the appearance of large brachiopods, including a spiriferid, in the sand-rich facies of the Springvale. Similar large brachiopod assemblages are seen in the apparent Bois Blanc-Schoharie-age sandstone facies across central New York (e.g., Jamesville and vicinity).
Limestones comprise the succeeding 4.2 m of the section at Phelps. Much of the interval is characterized by relatively fine-grained, knobby-bedded, cherty limestones (Figure 14d), with coarser-grained beds noted near the base and especially about a meter below the top. The lower to middle beds generally appear poorly- to nonfossiliferous, again excepting the basal bed and another approximately 1.2 m above the base of the carbonate section. Of note, the topmost bed on the east side of the road at Phelps is a relatively coarse limestone bed with scattered rugose corals. The presence of the corals, and the relative coarseness of the bed is similar to the lower part of the Edgecliff Member of the overlying Onondaga Formation across New York, and across the Appalachian Basin. On the west side of the road, it is overlain by two additional limestone beds. The upper of these features small, light gray chert nodules, analogous to the lowest occurrence of chert in the Edgecliff Member. We interpret the coral bed to represent the base of the Edgecliff Member. The horizon of the Bois Blanc-Edgecliff contact is not exposed well in the cuts; following the regional trends, we could project it to be unconformable.
Four miles to the southeast, at the previous stop (Oaks Corners quarry), basal strata of the Edgecliff Member directly overlie the Cobleskill-Akron Formation of the Upper Silurian. This is in sharp contrast to the cuts here at Route 88. Regional study shows an additional six meters of erosional truncation of Silurian strata here relative to Oaks Corners. This local topographic low appears to have provided accommodation space for deposition of the Bois Blanc, in addition to providing a shield against erosional truncation of Bois Blanc preserved in the low. 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. The geographic extent of the area of the low is not known, but Oliver's (1963) report of additional local exposure of the Bois Blanc indicates a feature of some extent. We project that the relatively deeper water, cherty non-fossiliferous carbonates and the finer-grained sand-rich unit of the Bois Blanc, along with the additional strata were deposited in a locally incised valley that developed during one or more of the sea level lowstands associated with the Wallbridge and sub-Bois Blanc unconformities.

Outcrop of Nedrow Mbr. of Onondaga Fm
Outcrop of Nedrow Mbr. of Onondaga Fm. in bed and bank of Flint Creek, to left (south) of NY Rte. 96 (opposite ice cream shop).

Base of the Onondaga escarpment.
Exposures of Upper Silurian strata on left (east) bank of road toward top of escarpment.

Top of Onondaga Escarpment.

Dolomite Products Corporation quarry entrance on right
Dolomite Products Corporation quarry entrance on right; old quarry scoop shovel seen on left.

A5: PROGLACIAL LAKES, SOUTHERN CAYUGA AND SENECA VALLEYS
PETER L.K. KNUEPFER
Dept. of Geological Sciences and Environmental Studies
Binghamton University
Binghamton, NY 13902-6000
email: knuepfr@binghamton.edu
STEPHEN M. HENSLER Dept. of Geological Sciences and Environmental Studies
The modern Finger Lakes troughs of central New York developed by a combination of glacial scouring and the action of high-pressure sub-glacial meltwater (Mullins and Eyles, 1996). Seismic stratigraphic relationships suggest that the stratigraphic and morphologic record left behind by this event-including the Valley Heads Moraines (VHM) as well as much of the infill of the Finger Lakes troughs themselves--must have occurred between (and including) VHM time, around 14.9-14.4 ka 14C yr. B.P. (Muller and Calkin, 1993). Late-stage trough-fill sediments were deposited until 13.6 ka 14C yr. B.P. (Wellner et al., 1996), by which time ice had retreated north of the modern Finger Lakes and the lakes probably had dropped to near their current elevations. This sedimentologic development in the troughs themselves was produced by pro-glacial lakes that dropped in height above the modern lakes as ice retreated north through the troughs. Early in this late-glacial history, local high-level lakes were impounded in many tributary valleys as ice retreated from the uplands but persisted in the main north-south troughs. Our goals on this field trip (Figure 1) are to examine some of the evidence of high-level and pro-glacial lakes in the southern parts of the Cayuga and Seneca troughs, as these areas illustrate many of the relationships that are characteristic of the other Finger Lakes as well.

A5: PROGLACIAL LAKES, SOUTHERN CAYUGA AND SENECA VALLEYS

STOP 1. OVERVIEW OF CAYUGA TROUGH DRAINAGE OUTLETS
The highway continues south to Ovid from here. We are stopped on a bench at an elevation of approximately 820 feet (250 m), with a quarry into bedrock to our east (Figure 2). Ahead, Ovid sits on a surface on the nose of the Tully Escarpment cuesta (von Engeln, 1961) that has an elevation of 980-1000 feet (300-305 m), also seen on Figure 2. This level was likely scoured as the ice retreated northward, opening a drainage-way for spillover from Lake Ithaca into the Seneca Lake trough, forming Lake Newberry (Figure 3a). We interpret the lower level, marked at several nearby locations by rock quarries, as the bench/shoreline formed at the Lake Hall level (Figure 3b ).

Descend from the Lake Ithaca to Lake Newberry and then Lake Hall levels.
As we drive southeast we descend from the Lake Ithaca to Lake Newberry and then Lake Hall levels.

STOP2A. TAUGHANNOCK FALLS OVERLOOK
The parking areas on both sides of the road are located on a delta surface hanging high above the modern Cayuga Lake. The elevation of the highest delta above the parking lot-at 820 feet or 250 m was likely graded to the Lake Hall level. The view area affords an excellent perspective of the main Taughannock Falls, situated approximately 1.4 km (0.8 mile) upstream of the mouth of the gorge. Here the creek drops some 65 m through late Devonian Genesee Group sediments. The top of the falls is formed in resistant siltstone of the Sherburne member (Grasso et al., 1986); the notch at the lip of the falls has remained little changed since a rockfall in the late 1880s or early 1890s. One question to consider is how much the waterfall has retreated upstream and how much gorge incision has occurred in post-glacial time. The record of progressively lower deltas, coupled with the evidence of the rapid lowering of the proto-Cayuga Lake (Knuepfer and Lowenstein, 1998), all point to rapid incision during and immediately after ice retreat, while the Cayuga Trough was occupied by Lakes Ithaca, Newberry, Hall, Dana, etc.

STOP2B. GRAVEL QUARRY
Cross Taughannock Park Rd. from the Falls Overlook parking area and walk onto the unpaved road on the left side of the small parking lot northwest of the road. Walk about 100 m into a reactivated gravel pit. This pit is cut into the front edge of the most prominent high hanging delta of Taughannock Creek (the Lake Hall level). Recent working of the northeast wall of the quarry has resulted in a clear exposure of the delta-front foreset beds (Figure 4). Sediments include well stratified sands and gravels with some clayey and silty interbeds.

Note the small delta surfaces across which we drive.
The youngest delta, of course, is the active delta complex on which much of the developed area ofTaughannock Falls State Park is located. This is one of the largest deltas on Cayuga Lake. If we use the analog from Canandaigua Lake and the evidence that Mullins and co-workers have provided, we can assert that this delta probably began to form in latest glacial time, after base level for Taughannock Creek had dropped to approximately its modern position. Again, we can consider how much of the incision of bedrock occurred during this drop in lake levels, and how much is post-glacial.

STOP 3. COUNTY GRAVEL PIT AT THOMPSON PROPERTY
Cayuga County has been removing sand and gravel from the lower part of the long exposure. This work has been continuing for some years, and the local property owner indicates that the bluff used to extend nearly out to Salmon Creek Road. The current excavation exposes several meters of sand and gravel (possibly outwash) overlain by varved clays, in turn overlain by a diamict (Figure 5a). The geomorphic surface above these exposures is at an elevation of only 700-720 feet (210-215 m), which could correspond to the Lake Warren level (von Engeln, 1961). The varved clays likely were deposited by one of the earlier, deeper lakes (Hall or Newberry). The overlying diamict is problematic.

STOP 4. GENOA SAND AND GRAVEL PIT
A larger operation just north of the Thompson pit has been recovering sand and gravel from locally deformed outwash(?) deposits below the 700-foot (210-m) level. No foresets are exposed; all sediment is flat- or nearly flat-lying, indicating these probably are not deltaic deposits. Here thrust faulting has offset well bedded sands and gravels exposed in some of the active walls in the pit (Figure 5b). What we see during the field trip depends on the recent activity of the operators. We interpret these deposits as ice-proximal outwash, possibly overridden by a local re-advance, and the deformation likely occurred while the sediments were frozen (given the intact nature of most of the deformed beds).

STOP 5. (LUNCH) BUTTERMILK FALLS AND BUTTERMILK GLEN
Not only is the main waterfall here at the mouth of the gorge, which contrasts sharply with the situation at Taughannock Creek, but delta surfaces are not as well preserved here - perhaps because the drainage basin is smaller, but also because Buttermilk Creek probably did not re-excavate its pre-last glacial gorge. Instead, the morphology here is consistent with a pre-late-glacial "proto-Buttermilk Creek" gorge located about 300 m to the north and occupied by a small, unnamed modern creek. This situation - abandonment of the pre-glacial gorge-was suggested by Matson (1904).

STOP 6. H&H AUTO SALES GRAVEL PIT
This gravel pit exposes interbedded sands and gravels. When the main quarry north of (behind) the auto shop was operated by the Town of Enfield some years ago, it exposed foreset beds below a 1200-1230 foot (365-375 m) poorly preserved surface. These beds were overlain by a poorly consolidated, thin (less than 2 m exposed) till. Currently only part of the foreset beds are exposed, once again being worked for sand and gravel, although most of the active workings expose flat-lying sediments. We interpret the deltaic sediments as marking the input of local creeks into a high-level lake, which we informally name Lake Enfield. As noted previously, this lake drained southwest through the Fish Kill outlet (Figure 7b), through which we will drive next. We interpret the overlying till as indicating that a nearby ice margin overrode the sediments during a brief re-advance.

Robert Treman State Park
Turn into the upper entrance to Robert Treman State Park. Although we won't go into the park, it preserves a spectacular example of joint-controlled erosion and re-excavation of a pre-glacial valley (a more detailed description is provided by Knuepfer and Lowenstein, 1998). We'll now drive into and through the outlet of the highest upland lake of Enfield Creek, though Fish Kill.

Marsh is head of Fish Kill and the outlet of Lake Enfield.
Note the marsh to the east, which is the head of Fish Kill and the outlet of Lake Enfield.

Gravel pits in this area and immediately to the south
Gravel pits in this area and immediately to the south expose thick sections of sands and gravels. Most exposures show foreset-type dips, suggesting deposition into another upland lake (which we call Lake Newfield). The controlling outlet for this lake was at Pony Hollow to the southwest, at a modern elevation of about 1230 feet. However, small upland lakes persisted until ice completely retreated from the main Cayuga Trough to the east, as indicated by the thick foreset sequence at the next stop.

STOP 7. TABER GRAVEL PIT
This pit exposes a thick section ( 70 ft or 21 m) of bedded sands and gravels. It is part of a lobe along West Branch Cayuga Inlet between 950 and 1050 feet (290-320 m) that we interpret these as a deltaic complex. This is most properly interpreted as a kame delta into Lake West Danby; the outlet extends to the southeast along a kame surface between the West Branch of Cayuga Inlet Creek (here) and Van Buskirk Gulf at the northwestern end of the Valley Heads Moraines sequence at West Danby (pictured and described by von Engeln, 1961).

Brief stop at Pony Hollow
Brief stop at Pony Hollow to view outlet of Lake Enfield-Lake Newfield complex.

Outlet for Lake Watkins and Lake Newberry
This area formed the outlet for Lake Watkins and Lake Newberry, as the Seneca Lake trough, later connected to the Cayuga Lake trough, maintained a stable lake level throughout retreat of the ice sheet from the Valley Heads Moraine position here to the north end of modern Seneca Lake and until an outlet to the west at Batavia was opened (Fairchild, 1899; von Engeln, 1961).

Shequaga Falls, aka Montour Falls
Shequaga Falls, aka Montour Falls, is 0.3 mile (almost 0.6 km) west. An excellent view of the falls and the broad deltaic surface of Lake Watkins at Odessa are available from the bridge at the top of the falls. If time permits, we will detour to this viewpoint. Otherwise, continue north on Hwy. 14 into Watkins Glen.

Lower entrance to Watkins Glen State Park.
This is certainly the most famous and most visited of all the Finger Lakes glens (gorges). Watkins Glen Creek descends some 450 feet through a narrow gorge marked by cascades and falls and accessible along a spectacular gorge-bottom trail.

STOP 8. LAKESIDE PARK, WATKINS GLEN
Here at the south end of Seneca Lake we are afforded a spectacular view not only of the Cargill salt facility immediately to the west, but of the Seneca Lake trough. The lower slopes of the trough at its southern end are precipitous, and most tributary streams enter via waterfalls at or near the mouth of their incised glens. Tributaries are marked by hanging deltas, just as is the case in the southern Cayuga Lake trough. Here, however, the top delta tends to be very broad with thick sediments, the result of the relatively long-duration (at least compared to the other Finger Lakes) stable Lake Watkins pro-glacial impoundment. Particularly prominent examples are preserved at Hector Falls Creek, visible to the east (Figure 6), and at the upper parking area for Watkins Glen State Park.

Bridge over Keuka Lake Outlet and junction Hwy. 54.
Although the barbed shape of Keuka Lake, the next Finger Lake to the west, suggests an original southward drainage system, modern post-glacial drainage is to the northeast through this channel connecting Keuka Lake with Seneca Lake. We drop to Keuka Lake Outlet across a series of delta-like terraces, many with gravel pits. Although we have not studied this area, we suspect that the terraces record incision that mostly occurred during late-glacial lake-level drops below the Lake Hall level, as is most likely true for the other tributaries to Seneca Lake. Detailed study of these deposits could well yield a much more precise chronology for the early post-glacial lake evolution.

Belhurst Castle on right; entrance to Village of Geneva.

A6: GEOLOGY AND THE DEVELOPMENT OF UPSTATE NEW YORK'S DISTINCTIVE COBBLESTONE ARCHITECTURE
D. BROOKS McKINNEY
Department of Geoscience
Hobart and William Smith Colleges
Geneva, NY 14532
Email: dbmck@hws.edu
Cobblestone buildings are the most distinctive structures in upstate New York's regional architecture. Most of these handsome and durable buildings are farm houses built between 1825 and 1860, the prosperous years following the completion of the Erie Canal. Most of them are found in the glaciated lowlands bordering Lake Ontario in a belt that extends from Syracuse to Buffalo. Upstate cobblestone construction is characterized by 1-2 foot-thick, rubble-filled walls that are more than 50% by volume lime mortar, which are faced with a veneer of fist-sized cobbles laid in horizontal courses. Individual cobbles are "framed" with hand-profiled mortar joints. The horizontal mortar joints separating the horizontal courses of stones are typically continuous across an entire wall and therefore more visually prominent than the vertical joints between adjacent cobbles within a course (Figure 1). Cobblestone construction techniques were used to build at least four of the architectural styles popular during the later half of the 19th century: Federal, Greek Revival, Gothic, and Italianate. Although U.S. examples of cobblestone buildings can be found from New England to Colorado, roughly 90% are located in upstate New York with the greatest concentrations are in Ontario and Wayne counties.
The development of cobblestone architecture and its prevalence in Ontario and Wayne counties is remarkable example of the interplay between the area's 19th-century human history and the bedrock and surficial geology of the area. The Erie Canal and the economic development it fostered was the impetus for constructing most of these buildings, but the lay of the land and the types of materials which were (and were not!) available to builders did much to determine how those buildings were constructed.
This paper and the accompanying field trip is designed primarily as an introduction to cobblestone architecture for geologists. Somewhat paradoxically, then, it focuses more on architecture and history, which most geologists will know less about, and less on geology, which most geologists will already know or easily learn. The first part of the paper is a cobblestone "primer" describing the technique and the types of materials it employs and the architectural styles to which it was adapted. The second part examines the cultural and geologic reasons for the development of cobblestone architecture in upstate New York.

A6: GEOLOGY AND THE DEVELOPMENT OF UPSTATE NEW YORK'S DISTINCTIVE COBBLESTONE ARCHITECTURE

STOP 1: COBBLESTONE TOOLS AND TECHNIQUES, HWS CAMPUS
A demonstration of basic cobblestone techniques. Some cobbles, mortar, stone and basic masonry tools will be available and participants will have a chance to test their skills as cobblestone masons.

The Cobblestone Restaurant on the SW corner
The Cobblestone Restaurant on the SW corner of this intersection was originally a single story cobblestone house built in 1838/39. The building contract for this house is preserved in the Ontario County Archives. The house was built by Clark Morrison, Amos Siglee, and Samuel 0. Coddington for a price of$1550 excluding materials, which were supplied by the owner, Joseph H. Tuttle. The stucco second story was added in 1915.

STOP 2. BARNES HOUSE
BARNES HOUSE, FIELDSTONE GREEK REVIVAL HOME, 1835 TO 1838.
This house is an excellent example of a Greek Revival cobblestone (Figure 5). It was built over a period of three years, beginning with the north wing in 1835 and completed in 1838. Key features identifying this as a Greek Revival are the portico with Ionic columns, the wide cornice moldings which simulate the entablature of a Greek temple, the recessed doorway, and the massive lentil over the doorway. Features to examine and discuss: lithologies of the cobblestones, cut-stone components and their tool marks, character of mortar joints, variations in technique from the front to the back of the house, assignment to one of the cobblestone periods (early, middle, late).

STOP 3. RIPPEY HOUSE,
STOP 3. RIPPEY HOUSE, LAKE-WASHED ITALIANATE HOME, 1854
This is home is made of lake-washed cobbles and was built in the Italianate style very late in the era of cobblestone construction. The features which identify it as Italianate are the shallow roof angles, the deep eaves, the decorative brackets supporting the eaves, and the paired windows with rounded arches. The Italianate style called for "compressed" vertical elements, tall and relatively thin windows, for example. After 1850, improvements in glass-making technology allowed these windows to have a few large panes of glass, in contrast to the small panes used in earlier styles. The other common Italianate style, though though rarely made of cobblestones, is the "cube and cupola," a two story box like house with a shallow-angled roof that rises in four panels to a central cupola. Features to examine and discuss: lithology, size and sorting of the cobblestones, nature of the mortar joints, quality of mortar work around the windows, comparisons with Barnes house, assignment to one of the cobblestone periods (early, middle, or late).

Baron House, a Greek Revival cobblestone
Baron House, a Greek Revival cobblestone house built in 1848, on the right (north) side of the road.

STOP 4. OLIVER WARNER HOUSE
OLIVER WARNER HOUSE, FEDERAL STYLE FIELDSTONE HOUSE, 1840
This house was clearly built in stages; the front, west wing was built in 1840 in the Federal style. Features which mark this as a Federal style house the semi-circular stone-trimmed fanlight, the door treatment, the shallow cornices, and the relatively thin, elegant moldings. Unlike the Greek Revival style, the Federal style uses thin vertical elements and shallow openings which accentuate the building's flat surfaces. Features to see and discuss: types and variety of cobbles, extraordinary cut-stone work, variations in construction techniques in different wings of the building, comparisons with other buildings we have seen. Can you hypothesize on the chronology of the wings?

STOP 5. PLAINSVILLE SCHOOL, 1853, AND SECOND BAPTIST SOCIETY CHURCH, 1835.
COMPARISON OF EARLY AND LATE COBBLESTONE PERIODS
These two structures, now private residences but once public buildings, are on opposite sides of Plainsville Rd. in the village of Gypsum, also called Plainsville. They are excellent examples of the differences between early and late cobblestone construction. In examining the buildings, make sure to note the contrasts in quoins, lintels, sills and other structural components, sizes and lithologies of the cobblestones, mortar, and the tooling of the joints. The owner of the church building says that the building was built by the congregation with the help of a mason and relates the following story, the truth of which is difficult to assess: The mason showed the amateur builders how to lay cobblestones in the parts of the wall framing the front door, where the joints are relatively straight and horizontal. As the distance from the door increases and the amateurs took over, the joints bob and weave like drunken sailors. Features to examine and discuss: the contrasts in materials, techniques and architectural styles between these two buildings.
Gypsum is so named for gypsum deposits in the Salina formation that were discovered along the Canandaigua Outlet just south of town in 1812. The town was originally called Plainsville, but when it got its own post office the name had to be changed because there was already a Plainsville, N.Y. (Parmalee, 1986).

Outcrop of Onondaga Limestone on the right (south) side of road

Onondaga Limestone flanks the road.
Pass under NYS Thruway, outcrops of the lower portions of the Devonian Onondaga Limestone flank the road.

Cross Flint Creek
The village of Phelps is unusual in that it has both excellent cobblestones and 19th century buildings made with cut stone blocks. This reflects the fact that Phelps is located on the falls of Flint Creek as the creek cuts across the resistant Onondaga Limestone and exposes this good building stone.

Phelps Town Hall
The town hall, a beautiful limestone block building that combines elements of both Greek Revival and Federal styles, was built in 1849 from limestone quarried just west of town (Parmalee, 1986).

Two cobblestones, an early and a late one
Two cobblestones, an early and a late one, face each other across Main St. Note the off-color Portland cement mortar that was used to repair the structure on the left (north) side of the street.

A small Greek Revival house built with cut stone.

STOP 6. HAWKS HOUSE
LAKE-WASHED GOTHIC REVIVAL HOME, 1848
This house is a great example of the Gothic Revival style. Features that identify this as a Gothic Revival style include the pointed arches of the windows, the steeply pitched roof, the cross gables, and the wall-dormer windows of the second story. Features to examine and discuss include: comparisons with other structures, use of arches instead of than lintels to support window openings, an contrast between the front and rear of the home. Careful examination of the east-facing gable reveals that this house was added on to with a latter cobblestone addition.

STOP 7. GRAVEL QUARRY IN GLACIAL OUTWASH DEPOSITS
A brief "arm waving" stop to see some of the glacial outwash deposits being quarried here and to review local glacial geology. Just visible to the west of this site is the Onondaga Limestone escarpment and a large quarry (the Oaks Corners quarry). Just to the north, across the Canandaigua Outlet, is the morainal topography of the Waterloo recessional moraine. Discussion of the materials needed for cobblestone masonry and their abundance in the region.

Cross bridge over Canandaigua Outlet.
Once one crosses the Outlet, the drive from this point northward is through some of the best developed drumlin fields in the area. The underlying tills are filled with cobbles!

Climb on to the Waterloo recessional moraine
Climb hill on the north side of the Outlet's floodplain and into the morainal topography of the Waterloo recessional moraine

NYS Thruway underpass.
Morainal topography quickly gives way to drumlin fields from this point northward.

STOP 8. VANDEVORT HOUSE
LAKE-WASHED, GREEK REVIVAL HOME, 1847
We will make this stop only if time allows. This house is remarkable for the way in which the mason who built it used various shapes and sizes of stones to simulate moldings, particularly on the front of the house. It would be interesting to know what the mason and the Vandervort's thought about these "moldings." Is this a high-refinement of the technique? or has the technique been pushed to the beyond the limit of the materials being used? Discussion: What were these people thinking?

Good view of drumlin on the left (west) side of road

Federal fieldstone cobblestone house, right (east) side of road

STOP 9 SALINA FORMATION
Green, tan, and maroon shales of the Silurian Salina formation are exposed in a low road cut at this site. Casts of hopper-shaped salt crystals can be found in some of the weathered shales. The Salina formation is significant to this field trip because of the topographic control it exerts over the regional landscape, creating the east-west lowland that made it possible to construct the Erie Canal. Discussion: Topography and the feasibility of the Erie Canal.

STOP 10. OLD LOCK 56 OF THE ERIE CANAL
The significance of this stop is two fold. First, it provides a fine setting in which to review the importance of the Erie Canal to the economic prosperity it helped to produce, and of which cobblestone farm houses are one manifestation. Second, it is a good place to review the "Erie Canal theory," the idea that cobblestones were built by unemployed masons who had been imported to build the canal. The disparities between the type of construction used on this lock and cobblestone construction should be quite clear.

A7: GLACIAL FEATURES OF THE WESTERN FINGER LAKES LANDSCAPE
BRUCE GILMAN
Department of Environmental Conservation/Outdoor Recreation,
Finger Lakes Community College
4355 Lakeshore Drive
Canandaigua, New York 14424
During the Pleistocene Epoch, repeated episodes of continental glaciation affected the Great Lakes region of eastern North America. The most recent ice advance, known as the Wisconsin Stage (65,000-12,000 years B.P.) is largely responsible for the appearance of our modern western Finger Lakes landscape, although there is little doubt that it followed the pattern left by earlier glaciations. During Wisconsin time, ice filled the Lake Ontario basin, split into sublobes and flowed southward across western New York. Distribution and movement of these sublobes has been deduced from the orientation of striae and drumlins (Dreimanis and Goldthwait 1973 ). As the ice margin retreated across the Finger Lakes region, glacially scoured valleys were filled with trapped meltwater. Drainage to the north was blocked by the ice sheet, and to the east and west by higher ground. The first proglacial Finger Lakes, with their southern drainage, had come into existence. Fairchild (1909) wrote about these glacial lakes. Their names are not as familiar as the modern Finger Lakes: Lake Hall near Dansville in the Genesee Valley, Lake Naples in the southern Canandaigua Valley, and Lake Italy in the Italy Valley to name a few. These lakes were short-lived, for as soon as the ice margin retreated farther north, lower spillways were uncovered. In the Canandaigua Valley, Lake Naples was replaced by Lake Middlesex as soon as an eastern drainage outlet was free of glacial ice. Today the signs of the historic presence of these lakes can be found in hillside shorelines (strandlines because these beaches are located some distance from the modern lake beaches) and gravelly delta deposits at the mouths of abandoned spillways. Perhaps, too, the fertile lacustrine sediments of a valley floor where no lake stands today will serve as a reminder of our recent glacial past.
The glacial geology of the western Finger Lakes region will be discussed at several stops on this field trip. The road log provides background figures and brief explanations for each stop. Two types of illustrations are presented for each stop: a photocopy reproduction of the relevant portion of a U.S.G.S. topographic quadrangle sheet and a digital elevation model (DEM) of the entire quadrangle sheet. For the former, the contour interval is 20 feet and north is at the top when the map is oriented to read. Map scale varies as each photocopy was enlarged in order to accentuate the glacial features. For the latter, DEM files were selected from Cornell University's geographic information resources library (search on the worldwide web for cugir). Relevant files were decompressed and extracted. For each DEM, the image file has been projected through Arc View's © Spatial Analyst Extension accepting the hillshade default settings.

>A7: GLACIAL FEATURES OF THE WESTERN FINGER LAKES LANDSCAPE

STOP 1. JUNIUS PONDS AS VIEWED ALONG ROUTE 318
This disintegration landscape of stagnant ice features contains kettles and kettle hole lakes within a large and rather unique kame moraine complex. Chunks of glacial ice, varying in size, were buried here. When melting occurred, depressions were formed. Several basins are spring fed today - the Junius Ponds complex. The complex consists of eight inter-connected basins separated by wetlands or sediment sills. The basins range in total depth from 8 to 17 meters, with the deepest basin exhibiting meromictic water circulation conditions. Original work on the limnology of the basins was published in 1931 by Burkholder. Since then, several unpublished graduate studies have been conducted (Principle 1981, Pend! 1982, Besse 1984 and Schloss 1985).
The surrounding kame moraine is composed of stratified (washed) sand and gravel that was deposited on, against, or immediately in front of the glacial margin. It is unusual and distinctive from other kame moraine complexes in New York State. Exposures in highway cuts and adjacent gravel pits indicate that portions of the moraine were affected by a major ice re-advance. Sediment structure was distorted and the surface was remolded by the ice sheet overriding previously formed features. In addition to this site's unique glacial history, the natural communities here support several New York State rare species. Wetlands are particularly diverse, with some developing acidic bog-like conditions while others exhibit marly fen-like conditions apparently associated with calcareous seepage.

STOP 2. CHIMNEY BLUFFS ALONG THE SOUTHERN SHORE OF LAKE ONTARIO.
Over 10,000 drumlins lay in the plain between Lake Ontario and the Finger Lakes ... the largest field of drumlins in the world!
The processes that form drumlins is complicated and involves a certain amount of rational guess work. Most drumlins are built up with concentric layers of gravel bound together by an excess of clay. It is widely agreed that drumlins are built by accretion, a subglacial plastering and lodgement of till as the ice sheet moved forward. A fairly flat landscape and thin ice are required. At this site, it is thought that a reduced lobe of ice occupying the future basin of Lake Ontario radiated out over the adjacent land. The basal debris in this ice was pulverized shale from the lake basin - hence the high content of clay. The thin ice margin was not exerting as great a pressure on the landscape as before. With a thrust from behind (a slight readvance), the ice tended to slip, or slide over the ground without digging in. Where it passed over a slight obstruction, the clay at the bottom adhered and was added to, layer by layer. The obstacle may have been a heap of glacial till or a small protrusion of bedrock. Later, when the Lake Ontario basin rebounded from the loss of ice mass, water levels began to rise. The bluffs were formed as the rising waters eroded the toe of the slope in the surf zone. Today, the "badlands" topography is maintained by several processes. Ongoing wave action loosens till fabric at the beach. Wind and rain combine to sculpture exposed bluff faces. Water that percolates downward near the rim of the drumlin contributes to slumping wherever it re-emerges along the bluff face. Freezing and thawing cycles may exacerbate these processes. It has been estimated that the bluffs erode up to five feet per year. Differences in composition and compression account for the more resistant strata features at the lakeshore.

STOP 3. Hopper Hills in hamlet of Ionia
KAME MORAINE, LOCALLY KNOWN AS THE HOPPER HILLS, VIEWED FROM STRONG ROAD NEAR THE HAMLET OF IONIA.
These kames were heaped upon the landscape during Lake Warren time (a predecessor to Lake Erie that extended across western New York) and their striking contrast to the flatter land surrounding them suggests an exceptionally debris laden ice front at this particular site. In adjacent sand and gravel pits, the internal structure of the kames can be seen. They are stratified and show evidence of land-water contact (ripple marks) throughout their layers but especially towards their base.

STOP 4. THE JUMPOFF AT ONTARIO COUNTY PARK ON GANNETT HILL.
The main road to the Ontario County Park ascends up the west flank of the glacially carved Canandaigua trough (broad U-shaped valley). Along the road, a small stream has carved a ravine that exposes a thin glacial ground moraine underlain by Upper Devonian shales and sandstones. Looking southward from the top of the hill one can see the Appalachian Plateau with its near alignment of summits believed to have resulted from water erosion of the preglacial peneplain. The ice sheet then selectively eroded the pre-existing north-south streams into the wide troughs that separate these flat hilltops.
The Jumpoff overlook in the park is at an elevation of 2100 feet above sea level and almost 700 feet above the valley floor! Looking northwest (right) into Berby Hollow the graceful curved cross-section of a glacially carved trough can be seen. On clear days, the city of Rochester located on the Lake Ontario plain is visible in the distance. Below the Jumpoff and to the south (left) is a hummocky valley floor composed of a recessional moraine plug containing lower Silurian sandstones whose nearest source is in bedrock outcrops near Rochester. Glacial transport can be the only explanation. Other transported rocks and boulders, known as glacial erratics, are common in the woodlands of Ontario County Park.
Small glacial lakes once situated in Berby Hollow and the Bristol Valley had to drain eastward into the Canandaigua trough, breaching the drainage divide near Boswell Corners. Recall, the margin of the ice still blocked any northward escape of meltwater. At the bottom of the hill along the main entrance road to the park is a small hamlet known as Bristol Springs. Just beyond it is a gravelly delta, deposited where these small lakes drained into Glacial Lake Naples occupying the Canandaigua valley thousands of years ago. The delta deposit is stratified, clearly indicating sorting by glacial meltwater. Cross-bedding of the layers suggests that water altered its drainage pattern across the delta many times. The particle sizes and texture of the deltaic material is coarse; the finer silts and clays are absent. They were probably carried by the raging meltwater currents out into Lake Naples, eventually to become varve deposits along the bottom of the Canandaigua trough. Drifting icebergs along the lake surface added dropstones to the accumulating bottom sediment.

STOP 5. THE WEST HILL HANGING VALLEY
VIEWED FROM GANNETT HILL ROAD NEAR THE INTERSECTION WITH SEMAN ROAD.
Glacial striations produced as the ice advanced over native bedrock in the western Finger Lakes landscape have a compass orientation within a few degrees of south. The ice sheet selectively eroded pre-existing north-south valleys because they aligned with the basal ice flow direction. In this regard, the Canandaigua Valley, originally V-shaped and occupied by the "Canandaigua River", was extensively scoured along its bottom and its sidewalls transforming it to a typical U-shaped glacial trough. Preglacial, east-west tributaries were not as deeply scoured during the Pleistocene. After ice sheet retreat, these tributaries were left elevated above their preglacial outlets (the now deeply eroded north-south valleys). Spectacular, scenic gorges trace the course of these hanging valley streams as they cascade down into the over deepened glacial troughs (a gorge will be visited at stop 9). ~

STOP6. CANANDAIGUA LAKE OVERLOOK
CANANDAIGUA LAKE OVERLOOK AND BARBED TROUGH JUNCTION WITH THE MIDDLESEX VALLEY AS VIEWED FROM COUNTY ROAD 12.
To the north (left) is the large, water-filled Canandaigua trough with its glacially scoured and steepened walls. Initially, erosion may have been enhanced simply due to faster ice flow but it soon was assisted by increasing thickness of ice as the valley was deepened. Joining the Canandaigua trough from the east is the Middlesex trough (today occupied by the meandering West River). This trough is also the product of glacial scour. The barbed trough junction at the confluence of the two valleys closely resembles the shape of modern Keuka Lake and supports the idea of a south flowing pattern for the western Finger Lake valleys during preglacial times (Fairchild 1909). Just south of Naples, a similar barbed trough junction is present where the Italy Valley joins the Canandaigua Valley. Some geologists theorize that the drainage then turned westward into the north flowing "Dansville River", an ancient predecessor of the Genesee River. Others suggest the drainage continued southward eventually joining the Susquehanna basin. Conklin Gorge may be seen along the far wall of the Middlesex trough. The gorge is postglacial and has built a considerable alluvial fan (locally known as Parish Flats) on the valley floor.

STOP 7. THE VALLEY HEADS MORAINE
THE VALLEY HEADS MORAINE AS VIEWED ALONG ROUTE 21 SOUTH OF THE VILLAGE OF NAPLES.
Just south of the village of Naples, Route 21 ascends from the valley floor of the Canandaigua trough. The landscape becomes hummocky, composed of small rolling hills and valleys, called a knob and basin morphology by glaciologists. This is a recessional moraine, a massive glacial deposit that accumulated from drainage off the Appalachian Plateau. It was banked up against the stagnant ice front reaching a thickness of over 600 feet! It is a somewhat stratified deposit, affected by the presence of trapped meltwater along the ice sheet margin. As the ice downwasted, kames and kettles were formed on the surface of the moraine. The Valley Heads recessional moraine is estimated to be between 13,500 and 15,000 years old. Today, the Valley Heads moraine marks the major drainage divide between the St. Lawrence Seaway and the Susquehanna River. It effectively dams the southern end of the Finger Lake valleys, trapping water in eleven of the glacial troughs, and forcing their modern drainage northward.

STOP 8. THE GLACIAL LAKE NAPLES SPILLWAY
THE GLACIAL LAKE NAPLES SPILLWAY ALONG ROUTE 371 BETWEEN NORTH COHOCTON AND COHOCTON.
Traveling farther south, the hummocky surface of the Valley Heads moraine gives way to a flat plain of virtually stone-free soils. This is the bottom sediment of Glacial Lake Naples! A silty and productive farm soil, coring would undoubtedly reveal buried varves that tell the story of seasonal accumulations of silt and clay. Lake Naples is estimated to have been 13 miles long, 2 miles wide and over 800 feet deep! It had a surface elevation of 1340- 1350 feet above sea level. Glacial Lake Italy, at an elevation of 1370 feet above sea level, drained into Lake Naples forming the Tannery Glen delta.
Watch along the valley wall for evidence of this ancient lake's shoreline. Often small sand and gravel pits on local farms, or elevated deltas along tributary streams pinpoint the location. Traveling south and just before entering Cohocton, the lake bottom and valley floor suddenly narrow ... the entrance to the Lake Naples spillway. This outlet is about 1000 feet wide and must have been impressive when torrents of water drained through it. Today, a much smaller Cohocton River slowly meanders southward to join the Chemung River.
On the return to Naples, take a moment to appreciate the view from the top of the Valley Heads moraine. Notice the barbed trough junction (STOP 6) where the Canandaigua and Middlesex troughs join just north of the village. Remember, this Y-shaped junction supports the idea of a south flowing preglacial drainage system for the western Finger Lakes.

STOP 9. POST-GLACIAL GULLY EROSION
A TRIP INTO CLARK'S GULLY ON STATE OWNED LANDS OFF WEST AVENUE.
Steep, narrow V-shaped gullies are common wherever hanging tributaries retrace their course into over deepened glacial troughs. Each Finger Lake has excellent examples, including the popular Watkins Glen, Enfield Glen and Taughannock Falls. North of Naples along Route 245, Conklin Gorge may be seen along the east at the barbed trough junction. Despite being post-glacial, and therefore geologically young, it has built a considerable alluvial fan on the valley floor locally known as Parish Flats.
Just ahead on the west side of the Middlesex trough is a magnificent post-glacial gorge called Clark's Gully. All the land here is part of the state-owned High Tor Wildlife Management Area. Walk the lower section of the gully. Watch for exposed shale and limestone in the gorge walls. Notice glacial erratics in the stream and peculiar concretions known as "septarians".

STOP 10. GLACIAL LAKE MIDDLESEX SPILLWAY
GLACIAL LAKE MIDDLESEX SPILLWAY ALONG ROUTE 364 EAST OF MIDDLESEX.
Some 11,000 years ago, the Middlesex and Canandaigua troughs were jointly occupied by the same body of water. Then, ice sheet retreat uncovered a hilltop notch east of Middlesex that was 220 feet lower than the Cohocton spillway used by Lake Naples. Suddenly and catastrophically, the surface elevation of Lake Naples fell and a new lake came into existence ... Glacial Lake Middlesex! South Hill emerged as a large island in this 600 feet deep lake.
The conspicuous spillway is traversed by Route 364 between Middlesex and Potter. Notice the depth, width and unusually straight form of this spillway. The small stream now found in the hilltop notch could not have had the erosive power to produce a channel of these dimensions. We will stop briefly by a small waterfall eroded by this same stream and let you make the visual comparison. One can also notice the forest damage caused by a localized tornado (microburst?) in 1996. Continuing down the spillway, we arrive at the next glacial trough, the broad expanse of the Potter Swamp (now largely converted to muck farming). A large, gravelly delta deposit is located here where waters draining from Lake Middlesex entered this valley. Cross-bedding of the layers is very evident due to the coarse texture of this deposit.

B1: THE LATE DEVONIAN CLASTIC WEDGE IN CENTRAL NEW YORK AND NORTHERN PENNSYLVANIA
Donald L. Woodrow
Geneva, NY 14456
This field trip has been designed as a study trip in which the rock sections are discussed and problems for further study are suggested. We will be concerned with what we see in individual exposures, selected to illustrate facies and their origin. Temporal relationships, though well constrained in the lower part of the section (House and Kirchgasser, 1993), become less so toward the top. Details of temporal relationships in the Fammenian sections are problematic. As a result, concepts of sequence stratigraphy have yet to be applied over much of this section.
We will start with the Tully Limestone and move upsection through black shales, turbidites, fossiliferous sandstone and shales, interbedded red/green and gray strata, and end in coarse sandstones at or just above the Devonian/Carboniferous boundary. Broadly interpreted, the facies represent deeper water marine environments which give way upsection to shallower marine environments, the shore and lowland alluvial plain. Facies sequences seen upsection express Walther's Law within the time intervals that have been sufficiently well deciphered to permit such analyses. That is, deeper water facies are replaced toward shore by shallower water facies. Our predecessors working on these and related sections in Pennsylvania and New York established the patterns over the past century or so.
Insights about the Late Devonian sequences garnered over the past 30 years or so include: elucidation of the physical and chemical processes responsible for these rocks, placement of rock sequences in a plausible time framework and explanations of their regional relationships, facies development in relation to tectonics and paleoclimate, and interpretation of faunas and floras based present-day biology and ecology. Among the next steps will be development of quantitative models of deposition and stratigraphy, more complete outline of temporal relationships, better understanding of paleoclimates, fauna and flora and their relationships to facies development, and development of models of fluid/gas movements.

B1: THE LATE DEVONIAN CLASTIC WEDGE IN CENTRAL NEW YORK AND NORTHERN PENNSYLVANIA

STOP 1. Kashong Creek, Bellona, New York.
After parking on the west side of the road, we will come into the stream bed from the north, through the woods.
The section in the stream is
Geneseo Shale (above the falls)
Tully Limestone
Windom Shale (below the falls)
This location was the site of a mid-19th century grist mill with its mill-dam. A flood in the 1950's took out the dam and the lip of the falls has retreated somewhat since then. Some of the large blocks downstream of the plunge pool are remnants of the dam. The mill was reroofed about 25 years ago, otherwise the building is mostly a shell. When the mill was active, the low building just south of the bridge over the creek served as the mill office, town store, post office, and a lively dance hall.
The section is typical of those seen at falls on streams tributary to any of the Finger Lakes. The resistant unit, whether it be limestone as seen here or sandstone as seen further east, is surrounded upsection and down by less resistant shale or siltstone. Post-glacial erosion has proceeded at rates controlled by rock-unit resistance and the falls result.
The Tully at this location is gray, fine-grained biomicrite with crinoid fragments as a prominent component. The unit is about 2.5 m thick. Upper and lower subdivisions are recognized within it (Heckel, 1973). The Tully thickens to the east and south of Bellona but it does not extend much further west. West of the Genesee River, the comparable stratigraphic position is marked by the Leicester pyrite. Erosion surfaces bound the Tully top and bottom and mark its internal subdivision.
Below the Tully is the Windom Shale of the Moscow Formation (Brett and Baird, 1994). Gray and fossiliferous at the base, it grades upsection into poorly fossiliferous, black, fissile shale. A prominent erosion surface separates the Windom from the overlying Tully. Above the Tully is the Geneseo Shale, a poorly fossiliferous, black, fissile shale which on freshly broken surfaces, yields a strong petroliferous odor. The Tully/Geneseo is not exposed here but elsewhere is seen to be sharp or gradational over a few cm.
How are we explain the abrupt change from black shale to clean, fossiliferous carbonate followed by a return to black shale? Deposition in relatively deep water seems to be required for the Geneseo given its very fine grain size, laminations, dark color, petroliferous materials, and lack of benthonic or infauna. Its very great areal extent (New York to Alabama and west into the mid-continent as part of the Chattanooga Shale sequence) suggests deepening in response to eustatism (Johnson, Klapper and Sandberg, 1985). Acadian tectonism to the east provided the siliciclastics found in the Geneseo and probably contributed to the deepening.
The Tully at this location, on the other hand, represents a time of reduced siliciclastic influx and increased deposition of primarily biologic carbonates. Heckel (1973) explained the reduced clastic influx to the Tully deposits in New York by postulating a fault-bounded uplift further east. Alternatively, Brett and Ver Straeten suggested that the uplift might be a foreland bulge (reported in Heckel, 1997, p.80). Whatever the explanation for the lack of clastics in the Tully, a rapidly subsiding basin existed to east in New York. The easterly basin trapped enormous volumes of sandstone and shale represented, for example, in southeastern NY and northeastern Pennsylvania by the Sparrow Bush Sandstone (Woodrow and Fletcher, 1972). The basin filled rapidly and the boundary uplift was overwhelmed, spilling finer sediments to the west and flooding the Tully depositional surface and forming the Geneseo Shale as sea level rose.

STOP 2. Watkins Glen State Park.
THIS IS A HARDHAT LOCATION.
Vertical cliffs about 50 m high bound the stream draining from the narrow mouth of Watkins Glen. In the cliff are exposed medium gray, fine-grained sandstones and dark gray, silty shales of the Penn Yan (and West River?) Shales of the Genesee Group. With the Geneseo below, these rocks and the younger Devonian rocks above form a basin-fill about 2000 m thick in this region, of which all but a tiny percentage is siliciclastic
Exposures of the Group are available at many other locations around the south end of Seneca Lake. These rocks extend, at approximately the same elevation, from north of Watkins Glen south to Montour Falls village where they are exposed in a falls. The Fir Tree Point anticline crests about 4 km north of Watkins Glen and this fold disrupts the regional southerly dip of a degree or less and renders the sequence nearly horizontal for a north/south distance of at least 10 km.
Watkins Glen village has long been the site of salt production and tourism and, occasionally, disastrous flooding. Two companies are presently extracting salt by solution from the Salina Group about 700 m below ground. Tourists come to WGSP and its campground, the Glen auto-racing track on the hill above, the nearby wineries, and Seneca Lake. Few people, however, are aware of the flooding potential posed by the creek which flows through WGSP, Watkins Glen village and into the adjoining marsh. The stream flows out of the Glen on to the alluvial fan on which the village is built. This means that much of the village is subject to the sedimentary processes associated with fan development. An example: on a summer evening in July, 1938, 7- 8" of rain in a few hours time resulted in a mass of water, mud, boulders, tree trunks, pieces of railroad bridge and other flotsam plugging the Glen mouth and then bursting out on to the town. In the resulting flood, one person died, several houses were destroyed, and much of the village suffered damage. Major flooding events look to have about a high recurrence at intervals of about 30-50 yrs and are little thought about in the interim.
The sandstones and shales in this exposure are arrayed in cm-scale fining-upward sequences. Body fossils are extremely rare but there is scattered plant debris and some bioturbation. The sandstone beds are sharp-based with their basal surfaces marked by groove casts and rare, flutes. The sandstones are fine- to medium-grained at the base, some contain shale chips, and they fine upwards to siltstone and shale. Well defined small-scale and steep cross-strata, some arrayed as climbing ripples, are found at the base of individual beds with larger-scale, low angled cross strata at the top. Sandstones grade into shales at the top of each couplet.
The sequence looks to be a stack of turbidites made by dilute, relatively slow-moving and lightly erosive density currents. No complete turbidite sequences are found in these exposures. Most are based on Bouma subdivision "c" and a few are based on subdivision "b." (Bouma, 1962; Isley, 1981; Woodrow and Isley, 1984). As differentiated by color in the cliff face, it is apparent that there are 3-5 m thick, repetitive sequences, probably fifth-order sequences or cyclothems.
It should be noted that the sequences in and near WGSP are typical of those seen in this facies in the Late Devonian of New York and Pennsylvania which strongly suggests that the Late Devonian sea floor in this region was of low, steady gradient. Abrupt changes in gradient were the exception, not the rule. This interpretation is based on the absence of channeling, slump scars, slumped masses and thick "slope muds," all typical of modern-day continental slopes. That channels are rare in this sequence is demonstrated by their being only a single channel-fill in rocks of this facies known to this writer and that is exposed along I-390 south of Danville, NY (Kirchgasser, Over, and Woodrow, 1997). Further, sediment transport and deposition on a low-gradient ramp would explain the weakly erosive turbidity currents responsible for the turbidites seen here.

STOP 3. Cowanesque Dam Spillway.
THIS IS A HARD-HAT LOCATION. PERMISSION TO VISIT THIS AND THE TIOGA/HAMMOND DAMS MUST BE OBTAINED FROM THE US ARMY CORPS OF ENGINEERS AT 570-835-5281 OR 570-827-3143.
Pull off the road and walk downhill on the dirt access road. Exposures in spillway, cliffs below and above road.
Completed in 1980, the Cowanesque dam, like the Tioga/Hammond dams to the south, is mainly a flood-control structure. Construction of the three dams was impelled by devastating hurricane-related flooding in 1972. Exposures resulting from the construction of the three dams plus those along US 15, a rerouted railroad and local streams provide the most complete and extensive late Frasnian sections in this region. The exposures presently available will be added to by new exposures along US 15 in NY and PA as it is upgraded to interstate specifications. The Tioga gas-storage field underlies the hills between the Cowanesque and Tioga/Hammond dams and data from the wells drilled in it will provide further insights into the local stratigraphy. A well in the Tioga gas field provided samples which constitute the type section of the Middle Devonian Tioga Bentonite.
At Cowanesque, the stratigraphic position of the rocks is latest Frasnian (pre-Dunkirk Shale) equivalent to the Wiscoy Sandstone of New York. The Pennsylvania Geologic Survey places these rocks in the Lock Haven Formation. Without more detailed mapping and work on the fossils, more confident temporal placement of these beds is not possible.
At the spillway is a 60+ meter section made up of medium-grained sandstones and gray, silty mudstones and shales. A stratigraphic section will be provided on the trip. Thickness of individual sandstone beds varies from a few cm to a meter. Cross-strata occur at many scales in the sandstones and some are hummocky. Mudstones are heavily bioturbated. The finer grained rocks contain many fossils, mostly brachiopods. Bone fragments and plant debris are found scattered through the section.
These strata represent shallow-water marine environments. Waves effects are apparent in the sandstones and the diverse epifauna and infauna indicate shallow water as well. Red strata are about 100 m upsection and to the southeast, toward the ancient shoreline, red strata are developed in this interval within 50 km of this location.
In the cliff above PA 49 (and inaccessible to us) are several, 5-8 m thick bodies of medium gray, medium- to coarse-grained sandstone. They rest on strata like those seen in the spillway and are taken to be distributaries or distributary-mouth bars built on to a muddy sea floor.

Alternate STOP 4. Roadcut, PA rte 287, west of Tioga village.
THIS IS A HARDHAT LOCATION.
This is one in a group of a closely-spaced exposures found along the RR track below rte. 287, on both sides of rte. 287 and on both sides of the access road from rte. 287 to the Hammond Dam Overlook on the hillside above. About 75 m of section are available here. If the trip visits this location, sections on the north side of rte. 287 and the Overlook access road will be examined.
These are highly fossiliferous sandstones and shales. A bed of rugose corals is found at the base of the section. A meter-thick sandstone, granule-bearing sandstone about 15 m above the base of the section has in it well preserved bivalves and spiriferid brachiopods. Brachiopods and bivalves are common in the higher strata and are the predominant feature in some beds. Ball-and-pillow structures occur in reddish-gray sandstones toward the top of the section.
By projection, these strata look to underlie those seen in the Connecting Channel (and those at STOP 5) by about 100 meters. The relationship of these strata to those exposed at the Cowanesque Spillway is uncertain but if both sections are pre-Dunkirk then their stratigraphic positions may be comparable.
Three separate, but closely spaced exposures: along a railroad, on both sides of rte 287 and along road to the Hammond Dam Overlook, provide access to about 75 m of section. A stratigraphic section of the road exposures will be provided on the trip.
The section is made up of medium grained sandstones and gray silty shales with many fossils throughout. Notable strata include: a bed of rugose-corals near the base, two quartz granule-bearing sandstones about 15 m higher, profusely fossiliferous strata about 15 m above that and ball-and-pillow structures in dusky red, fine-grained sandstones near the top. Brachiopods, bivalves, and crinoids are the most common fossils.
Knowing the stratigraphic position of these strata is difficult. Projecting them across the valley to the Connecting Channel suggests that they are 100 m lower than the rocks seen there. That would make them Late Frasnian, a position in accord with finding rugose corals. Those corals are a well-known feature in Frasnian strata in New York.

STOP 4. Tioga/Hammond Dams connecting channel.
Sections are available here along the various access road and in the channel proper. Be very careful as we walk on the paved ledges beside the channel. These rocks appear to span the Frasnian/Fammenian boundary. Gray, marine rocks are at the base of the section and red beds are found at the top.

STOP 5. Road cuts on US 15 east of Tioga Dam.
THIS IS A HARDHAT LOCATION.
This section duplicates most of what is seen at Stop #4 except that the section is less well exposed over much of its extent and the din and danger of heavy traffic is constantly in evidence. However, the section is available for study at any time with no permission needed.
Much of the section is not well exposed along the highway. The red beds at the top of the section are more readily accessible here as is the sandstone/shale section at the base.

STOP 6. Roadcuts on US 15 at Blossburg, PA.
This section is new and has not been examined in detail. The lowermost strata are thought to be latest Devonian with the Devonian/Carboniferous boundary higher in the section. The coarse grain size of the sandstones, presence of non-persistent sandstone bodies as much as 10 m thick, rarity of gray strata, presence of channel-fill cross-strata and lack of body fossils and bioturbation all suggest that these rocks are non-marine.

B2: MASTODON ROAD LOG
MASTODON ROAD LOG
John Chiment, Cornell University

B2: MASTODON ROAD LOG

Lakeshore Park.
"The Geneva" lake tour boat on the right. To the left, the Finger lakes Railroad (a privately owned railroad with 100 miles of track).

Rose Hill Mansion.
Greek revival style mansion. Built in the early 1800s. Site of many early agricultural experimental plantings.

Marker for Clinton-Sullivan Campaign of the Revolutionary War
Historical Marker commemorating the Clinton-Sullivan Campaign of the Revolutionary War. In August 1779 four thousand soldiers of the Continental Army marched out ofPennsylvania against the Iroquois. The Drain Tile Museum, just behind the marker, commemorates the introduction of drain tiles to the western hemisphere.

Seneca Army Depot.
Decommissioned, former home of nuclear warhead missiles. Now the home of Kids Peace organization and N.Y. State Correctional Facility. Home to a herd of white deer.

Sampson State Park.
Former Navy and Air Force training area.

Old Seneca Army Airbase.
Reported to have the longest runway on the East Coast.

Kendai-i, site of an Iroquois village
Kendai-i, site of an Iroquois village destroyed by the Clinton-Sullivan Campaign. (marker)

Willard.
Originally a hospital during the Civil War (War of Northern Aggression). In 1864 it became the first N.Y. State Land Grant University. Later it was a psychiatric hospital and is now a prison for drug offenders (don't pick up hitchhikers).

Look at the cute County Buildings on the left.
The courthouse, Sheriff's office and library are known as "the three bears".

Drainage divide between Seneca and Cayuga Lakes.
Notice the flat horizon of the Devonian seabeds.

Interlaken.
Summer home of the Westinghouse family and Rod Serling. Site of the infamous sponge fossil find at Mike Potts' service station (see exhibit at PRI).

Across the lake is Milliken Power Plant.
Coal-fired plant supplied by a train from Pennsylvania.

Smith Woods.
Large trees in an old-growth forest.

See Taughannock creek on the right.

Former home of Ithaca College Professor Moog.
Father of the Moog Synthesizer, used by the Beatles on the Abbey Road album.

Kimberlite dikes intersect the creek bedrock.
These were discovered following the flood of 1935. Diamond mine opened in 1935-36. Sorry folks, no diamonds.

Creek's path is joint-controlled.

Taughannock Falls overlook on the right
Taughannock Falls overlook on the right (restrooms, water fountain). The bumper-stops are concretions from the Tully Limestone.

Taughannock Creek Delta.
Quick! Look right to see Lower Taughannock Falls, spilling over the Tully Limestone.

Gorge Road.
As you climb, be sure to notice the precipitous drop into the gorge on your right.

This area was settled by Quakers in the 1820s.

Well contamination
The houses on your left were temporarily abandoned because of well contamination.

Spikes BBQ.
Best BBQ in the area. Pick up a bumper sticker that says, "You Can't Beat Spike's Meat".

Bellwether Hard Cider
(you can stop for a sample ... )

ISA Babcock Chicken Hatcheries.
Currently owned by a French company, this small hatchery produces a large portion of the world's laying hens.

STOP 1. Paleontological Research Institution
This is the Paleontological Research Institution, a former International Order of Odd Fellows orphanage, where you will meet such odd fellows as Cornell's Big Red Mastodon (aka the Chemung Gilbert Mastodon), PRI' s Hyde Park Mastodon, and the skeleton of a Right Whale.

View of Cornell University on Ithaca's East Hill.

View of Ithaca College on Ithaca's South Hill.

Flood of '94 inundated parking lot
During the flood of '94 the Tops/Wegman's parking lot to your right was a fishing and water-skiing paradise for about a day and a half.

To the right it the proposed site of a "big box" store.

To the left is the entrance to Buttermilk Falls State Park

To the right is the site of a Tutelo Indian village.
The Tutelo were subject to the Iroquois, and were granted a sort of "reservation" here. The Clinton-Sullivan Campaign wiped out the village in 1779.

The entrance to R.H.Treman State Park.

Gables Inn
On the left, the building with the amazing color and architecture is the Gables Inn. It was originally called "Sunny Sides" and was the home of the founder of The Agway and P&C stores. It has survived several reincarnations as a restaurant.

Devonian shale exposed in road cuts.

On the right Arnot Forest, Cornell research facility.

On the right, Connecticut Hill, highest point in Tompkins County.
In the 1780s the subject of a land dispute between New York, Pennsylvania and Connecticut.

Lawn Ornaments
On the left- almost anything you can imagine in plaster or concrete for your lawn!

On the right is old-growth forest that has never been logged.

This is the old Hinman Turnpike.
Don't worry- they don't charge anymore.

This 3-WAY intersection is known as "The Corners".
It marks the boundary of the Watkins-Flint purchases of 1795. Continue south on C.R. 14.

On the right is Catherine Creek, a world famous trout stream.
It used to be the Chemung Canal, the only canal in this area to cross the Susquehanna/St. Lawrence drainage divide.

STOP 2. Demonstration Site
Turn left and park at the Demonstration Site for GPR, GPS, and Coring Demonstrations. This is an open grassy area on the left.

B3: FACIES AND FOSSILS OF THE LOWER HAMILTON GROUP (MIDDLE DEVONIAN) IN THE LIVINGSTON COUNTY-ONONDAGA COUNTY REGION.
GORDON C. BAIRD
Department of Geosciences
SUNY College at Fredonia
Fredonia, NY 14063
CARLTON E. BRETT Department of Geology
University of Cincinnati
Cincinnati, OH 45221
CHARLES VER STRAETEN
Center for Stratigraphy and Paleontology
New York State Museum
Albany, NY 12230
The stratigraphic interval between the top of the Late Eifelian Onondaga Limestone and the base of the Givetian Ludlowville Formation (Union Springs, Oat.ka Creek, Skaneateles formations) has traditionally received less attention from stratigraphers and paleontologists than overlying Hamilton Group formations. This is due partly to poor exposure of these units in the western New York region, but also to the general impression (largely correct) that this overall succession consists of sparsely fossiliferous and unfossiliferous dark gray to black shale facies. Discovery of widespread fossil-rich condensed limestone beds within the Union Springs and Oat.ka Creek formations and associated corrosional discontinuities in these same formations (Baird and Brett, 1986, 1991; Griffing and Ver Straeten, 1991; Ver Straeten et al., 1994) has served to enhance our understanding of foreland basin dynamics during a key pulse of the Acadian Orogeny. Study of fossil-rich levels in the Skaneateles Formation in central New York induced the present authors to trace known key beds westward across New York into the undivided shale succession of the Levanna Member (Baird et al., 1999).
The present paper continues from the theme of last year's NYSGA paper and field log (Baird et al., 1999) which reviewed lower Hamilton facies and key beds between Buffalo and the Genesee Valley. This paper and excursion examines the same divisions in the region from the Genesee Valley eastward to the Cazenovia meridian in central New York. Because the stratigraphy and issues surrounding units in the Union Springs and Oat.ka Creek formations have been covered extensively in the Baird et al. (1999) field trip and comprehensively in Griffing and Ver Straeten, (1991); Ver Straeten et al., (1994), these units are treated more synoptically in this paper. However, a brief review of key issues pertaining to these formations is provided below and in the stop description for the Seneca Stone Quarry (STOP 1). The present paper focuses on correlational connections within the Skaneateles Formation, most notably the relationships of key Levanna Member markers (top-Cole Hill discontinuity, Papermill Bed, Roanoke Bed, Pole Bridge Bed, Wadsworth Bed, Slate Rock beds), described in Baird et al. (1999), to recognized member-capping divisions in the central New York Skaneateles section.

B3: FACIES AND FOSSILS OF THE LOWER HAMILTON GROUP (MIDDLE DEVONIAN) IN THE LIVINGSTON COUNTY-ONONDAGA COUNTY REGION.

STOP 1. ONONDAGA LIMESTONE-BASAL OATKA CREEK FORMATION-SUCCESSION IN SENECA STONE QUARRY
Seneca Stone Quarry has been written up in many previous reports (see Ver Straeten et al., 1994) particularly with respect to the stratigraphy of the Oriskany sandstone and overlying Onondaga Limestone. On this trip we focus on the post-Onondaga succession exposed on the top-riser at the south end of the quarry.
The Seneca Member of the Onondaga Limestone, forming the highest wall below the riser, is bracketed by the Onondaga Indian Nation K-bentonite at its base and dark post-Onondaga shales at its top. Units belonging to the Union Springs Formation are represented by the Bakoven Member, represented here by black, bituminous shale and ribbon limestone facies and by the thin overlying Chestnut Street Limestone submember which is gray in color and rich in fossils. The Bakoven records lower dysoxic to near-anoxic highstand conditions and is marked by a maximum flooding surface at its base. A prominent bone bed rich in Onychodus teeth is present at the base as are several K-bentonites which are developed in the vicinity of the bone bed. Higher Bakoven strata yield Camarotoechia, styliolinids and the large bivalve Panenka. Bitumen ("dead oil") is conspicuous along fractures and bounding surfaces associated with the limestones. The Chestnut Street submember occurs amalgamated to the base of the overlying Cherry Valley Limestone and is partly overstepped by the unit at this locality. Key fossils in the unit include the proetid trilobite Dechenella and a very small inadunate crinoid Haplocrinites. The Chestnut Street submember displays an erosional disjunct contact with the underlying Bakoven Member.
The Oatka Creek Formation overlying the Union Springs Formation is represented in the quarry by the Cherry Valley Member, Berne Member and Halihan Hill Bed, all of which are highly condensed and/or erosionally truncated. The Cherry Valley is represented by 0.7 meters of friable brown limestone which is distinctly nodular and petroliferous. It is rich in styliolinids, auloporid corals and distinctive for large cephalopod conchs. Orthoconic cephalopods and the early goniatite Agoniatites vanuxemi occur in the uppermost bed of the unit; these were spectacularly exposed along the top-Cherry Valley discontinuity surface in this quarry for a number of years. The Cherry Valley is part of the transgressive systems tract succession above the Stony Hollow-Chestnut Street submember regression maximum; it is highly condensed, contains internal discontinuities and yields a largely pelagic fauna.
Post-Cherry Valley strata at this locality are represented by the 0.7 meter-thick black shale interval of the Berne Member and by the fossil-rich Halihan Hill Bed which is occasionally seen in the quarry scrapings. The Berne represents basinal early highstand deposits over a wide region and it overlies a regional corrosional discontinuity surface on the Cherry Valley in western New York. The somewhat enigmatic Halihan Hill Bed, by contrast, yields the greatest diversity of fossils observed in the lower Hamilton Group.

STOP 2. UPPER SKANEATELES-THROUGH-BASAL LUDLOWVILLE FORMATION SUCCESSION IN FAYETTE TOWN QUARRY
The Fayette Town Quarry exposes the uppermost part of the Skaneateles Formation and the overlying Centerfield Member of the basal Ludlowville Formation. Skaneateles Formation deposits comprise gray and dark gray shale of the Levanna Member which are exposed in the lower 7.5 meters of the quarry section. Two prominent shell beds rich in Ambocoelia, Devonochonetes, Mucrospirifer, nuculoid bivalves and orthoconic cephalopods cap a bench in this quarry. These layers, designated the Slate Rock beds (Baird et al., 1999), mark the uppermost part of a shale-dominated interval that we believe correlates to a unit that we designate the Marietta Cycle in central New York localities (see text; Fig. 3): Shale deposits below the Slate Rock beds yield several levels rich in the distinctive ambocoeliid brachiopod Microclypeus (Goldman and Mitchell, 1990) and auloporid corals often in association with discoidal concretions.
The top 2.5 meters of the Levanna Member below the Centerfield is a dark gray to near -black shale unit yielding Eumetabolotoechia ("Leiorhynchus"), Styliolina and few other fossils. We believe that this is a major highstand unit that is correlative with the Butternut Member in central New York sections. The top of the dark shale interval is abruptly overlain by richly fossiliferous, calcareous shale deposits of the Centerfield Member.

Small Onondaga Limestone exposure
Small Onondaga Limestone exposure to right south of the intersection.

STOP 3. STAFFORD MEMBER, CAYUGA VALLEY MERIDIAN
This newly discovered shale pit on the Ray Lockwood Dairy Farm and the nearby roadcut section on Route 326 display essentially a complete section of the Stafford Member as well as 2-3 meters of the underlying Oatka Creek Formation. The Stafford at this locality, though expressed as a ridge-forming impure carbonate unit, is surprisingly depauperate in fossils at most levels. Most fossils, including the brachiopods Cupulorastmm, Emanuella, and Devonochonetes, auloporid corals, the gastropod Bembexia and orthoconic cephalopods, are found near the base of the unit. We believe that this fossiliferous condensed interval correlates to the Mason Hill and Cedarvale beds in the equivalent Mottville Member. Above the Emanuella-rich "A" limestone at this locality is a 1.7 meter-thick interval of thin-bedded lenticular limestone layers yielding sparse fossils. At the top of the section is a 0.7 meter-thick massive limestone bed yielding hard, dolomitic? nodules and occasional chert. This unit, yielding Zoophycos and sparse body fossils, is designated the "B" limestone bed of the Stafford (Meyer, 1985; Baird et al., 1999). It is well developed between Erie County and Cayuga Lake. This bed dramatically thickens eastward to approximately 8 meters at Smiths Falls on the other side of Auburn (Figs. 2, 4) before rapidly thinning again to form the fossil-rich Case Hill Coral Bed in Onondaga County sections. The low fossil diversity of limestone beds at this locality is believed to reflect the "double whammy" of low oxygen conditions coupled with soft, turbid substrate conditions.

Mottville Member of Skaneateles Formation
Outcrop of Mottville Member of Skaneateles Formation to left on the southeast side of Route 326

STOP 4. MEDIAL-UPPER DIVISIONS OF LEVANNA MEMBER, OWASCO VALLEY MERIDIAN.
Small shale exposure on east side of Rockefeller Road; park vehicles on wide shoulder area opposite outcrop.
Visible in this roadcut are two shell bed bundles respectively capping Pompey Member-equivalent Levanna strata and "Marietta Member" -equivalent Levanna beds (Fig. 5). The lower shell bed bundle; visible in the lower end of this cut is represented by two main shell beds which are 1.2 meters apart and minor lower beds which are now concealed. These correlate eastward to the Nyassa arguata shell-rich zone which we will see at STOP 5A. In this cut the shell layers yield Devonochonetes, occasional Protoleptostrophia and Mucrospirifer, pelmatozoan debris, Phacops, auloporid corals and nuculoid bivalves. The small rugosan Stereolasma occurs in both shell beds. Reworked concretions are observed at the level of the lower shell bed in the nearby gully above Long Point signifying localized erosion below this layer (Fig. 5). Above the lower shell bed bundle is a 4.6 meter-thick fissile shale interval yielding minor shell-rich layers, dispersed ambocoeliid brachiopods and discoidal concretions. We believe that this unit is equivalent to the lower and middle parts of the "Marietta Member" in the Otisco Valley-Cazenovia region (Fig. 3).
The upper bundle of shell beds includes three subequal fossil-rich layers in a 0.8 meter-thick interval near the upper end of this roadcut. This bundle corresponds to the "Slate Rock beds" interval that caps the Marietta cycle across western and central New York. Key Slate Rock fossils include ambocoeliids, Mucrospirifer, pelmatozoan debris, auloporid corals, occasional Stereolasma and nuculoid bivalves. As with the lower shell bed bundle mollusks are typically preserved as flattened composite molds. This condition changes to the east of this locality where Levanna shell beds begin to yield mollusk fossils preserved as shells of black calcite (see text; STOP 5).
Above the Slate Rock beds shell bundle is an abrupt change into dark gray, highly fissile shale yielding few fossils. This part of the Levanna corresponds to the Butternut Member at localities east of here. The Butternut records a major transgression with development of near-anoxia during late Skaneateles time. Less than a meter of the dark shale can be seen here.

STOP 5A NYASSA ARGUATA-RICH LAG BED AT TOP OF POMPEY CYCLE.
Turn vehicles around at drive-way loop of David Robinson residence at end of lane and park along lane part way back from loop.
Although the section of this creek is generally discontinuous and sloughy, the top of the Pompey Member-equivalent part of the Levanna Member, marked by Nyassa arguata-rich shell beds is fortuitously well exposed near the private lane. Similarly, the Slate Rock beds interval is well exposed 10 meters higher along this creek above the Route 41A overpass (see STOP 5B; Fig. 5).
At this locality the base of the Nyassa arguata-rich shell bed interval is a 14-18 centimeter-thick shell layer which is profusely fossiliferous. Brachiopods including Devonochonetes, Protoleptostrophia, ambocoeliids and occasional Mucrospirifer are present. Stereolasma and auloporid corals, Phacops, nuculoid bivalves and orthoconic cephalopods are also common. Both at and east of the Skaneateles Valley meridian, molluscan fossils are preserved as shells of black calcite, a condition that we will also see in the lower Delphi Station Member at STOP 7. The bivalve Nyassa arguata, a rare component of this interval west of the Skaneateles Valley is present and conspicuous at this level from Skaneateles Lake eastward. Typically the anterior of this clam is beautifully reinforced by thick black calcite while the posterior displays only a thin, often corroded, veneer of the carbonate. Reworked concretions are abundant in this bed at this locality; these are heavily bored and may yield a variety of encrustors (see Baird, 1981; Baird and Brett, 1981 for detailed study of this phenomenon). Exhumation of nodules below this bed in the Owasco and Skaneateles Valley region is consistent with our belief that this layer is correlative with the erosive Wadsworth Bed in western New York (see text; Baird et al., 1999; Fig. 3).

STOP 5B "SLATE ROCK BEDS'-INTERVAL. TOP OF MARIETTA CYCLE.
Proceed straight (west) across Route 41A into private driveway of James Garrison residence on the west side of Route 41A. Park vehicles near barn and proceed on foot to outcrop upstream from previous stop.
The creek bed just above the Route 41A overpass exposes the upper part of the "Marietta Member"-equivalent part of the Levanna, including the Slate Rock beds, as well as the base of the Butternut Member-equivalent part of the Levanna (Fig. 5). The Slate Rock beds interval is represented by a bundle of closely-spaced shell beds in association with discoidal concretions. The shell beds contain abundant ambocoeliid brachiopods, numerous Mucrospirifer and occasional Protoleptostrophia and Rhipidomella. Other fossils include auloporids and occasional Stereolasma, nuculoid bivalves and orthoconic cephalopods. As with the Nyassa arguata bed downstream, mollusks in the Slate Rock interval display black calcite preservation.

Axis of the deep glacially scoured Tully Valley
Junction of US Route 20 and Tully Farms Road in axis of the deep glacially scoured Tully Valley. The recent Tully Valley landslide (sec Fakundiny and Brett, 1997; Negussy et al., 1997) occurred south of this road junction.

McDonalds' Restaurant to the left
McDonalds' Restaurant to the left (rest stop for trip participants). Butternut Member of Skaneateles Formation visible on I -81 entrance ramp across US Route 20 from restaurant.

STOP 6A MEDIAL SKANEATELES FORMATION SUCCESSION EXPOSED AT PRATTS FALLS
Continue to large parking area by Pratts Falls. Park vehicles and proceed on foot to falls overlook.
The east and west forks of this creek display almost a complete view of the Skaneateles Formation. Pratts Falls itself provides a view of the upper part of the Delphi Station Member which is exposed in the lower part of the falls and the Pompey Member which makes up the upper part of the falls face and falls cap. Although strata are inaccessible from the overlook, one can clearly see that the upper part of the Pompey succession has coarsened to resistant siltstone and fine sandstone. This part of the succession is best viewed on the west fork of this creek (see STOP 6B).

STOP 6B DELPHI STATION, POMPEY, "MARIETTA" AND BUTTERNUT MEMBERS OF SKANEATELLES FORMATION
Park vehicles at parking area by small bridge over the creek west fork within the park.
Strata on the west branch include the Delphi Station, Pompey, "Marietta" and Butternut members. However, the Delphi Station and lower part of the Pompey members are difficult to observe here; we will focus on the capping sandstone beds of the Pompey Member between the road and the footbridge, the "Marietta Member" upstream from the road and the basal Butternut Member in the upstream waterfall.
Fossil-rich sandstone and siltstone beds yielding abundant moldic Nyassa arguata and spirifers can be viewed below the park road overpass; these most likely correspond, in part, to the Nyassa arguata-rich shell bed observed at STOP 5A and the lower shell bed bundle at STOP 4 (Fig. 3). This coarse facies represents the regressive capping part of the Pompey Member (and Pompey coarsening-up cycle). At Delphi Falls, south of this locality, the corresponding sandstone is 6.5 meter-thick attesting to coarse sediment progradation from the east or southeast. The underlying regressive top-Delphi Station interval at this locality, by contrast, is mainly a muddy siltstone suggesting that the Pompey cycle contains more proximal facies in this area.
Above the road is a short covered interval where the Pompey Member-"Marietta Member" contact is concealed. However, above this gap is a three and 1.3 meter-thick interval of soft gray fossiliferous shale succeeded by a 0.7 meter-thick falls-capping siltstone bed; this is the visible part of the 2.3 meter-thick "Marietta Member" succession at this locality. The soft shale below the siltstone bed is rich in ambococliids and an alate form of Mucrosirifer resembling M. arkonensis as well as many other taxa. The soft shale is much finer than corresponding shales in the basal part of the Pompey Member, suggesting that the Marietta cycle is part of a backstepping transgressive systems tract succession. Eastward thinning of the "Marietta Member" across this area, noted earlier, may reflect erosion and/or section condensation.
Above the small falls held up by the top-Marietta siltstone bed is a large falls displaying fissile dark gray shale and thin siltstone beds of the Butternut Member. In this region the Butternut has thickened to 75 meters and numerous tabular, flaggy siltstone beds are present in the middle and upper parts of the succession (Figs. 2, 4). The base of the Butternut is sharp and possibly erosional upon the top-Marietta siltstone; this contact is a classical maximum flooding surface associated with a major transgressive event.

STOP 7 MOTTVILLE AND DELPHI STATION MEMBERS, POMPEY HOLLOW SECTION
Large roadcut on US Route 20 that begins at upper end of long descending grade into the Limestone Creek Valley. Vehicles will park on level ground on west (upper) end of this roadcut. Participants will exit vehicles and proceed on foot to lower end of exposure.
This is a roadcut that has served as an important section for viewing lower Hamilton Group facies and collecting fossils. Recent widening of the road has both enlarged and lengthened the section (Fig. 6). Moreover, a year of exposure of the fresh rock face to the elements has served to loosen and release an enormous number of fossils.
The Mottville Member is now exposed in its entirety as well as 1.0 meter of underlying rock assignable to the Cardiff Member of the Oatka Creek Formation (Fig. 6). Above the 8 meter-thick Mottville succession is a 23 meter section including almost the entire succession of the Delphi Station Member. This latter interval includes 7 meters assignable to the Cole Hill cycle within the lower part of the Delphi Station Member and 10 meters comprising most of the main Delphi Station cycle succession within the middle and upper parts of the Delphi Station Member (Fig. 6).
The Mottville Member, at this locality, is marked by two prominent fossil-rich layers, the Mason Hill and Case Hill beds (see text). Between these markers is a 7.5 meter succession of calcareous silty mudstone marked by a prominent parting about 3.7 meters above the Mason Hill Bed(Fig. 6). Between the parting and the Case Hill Bed is mudstone rich in Tropidoleptus, Nucleospira and Mediospirifer. Above the Case Hill Bed is 2 more meters of softer mudstone rich in Ambocoelia and small mollusks.
The Mason Hill Bed yields abundant brachiopods including Mediospirifer as well as associated bryozoan debris and exuviae of Dipleura. The 0.3 meter-thick shell-coral-rich bed in the upper Mottville is clearly the Case Hill Coral Bed of Grasso (1986) and it corresponds to the Mottville "B" bed of Meyer (1985). We believe that a third key marker, the Cedarvale Bed is poorly developed in this section and corresponds to the bank reentrant below the Tropidoleptus-rich interval (Fig. 6). In sections within the Marcellus, South Onondaga and Jamesville 7.5' quadrangles, the Cedarvale Bed is a packstone-grainstone encrinite layer comparable to the higher Stone Mill and Tichenor limestones. It probably overlies a sequence boundary regionally; at this section the sequence boundary unconformity is probably represented by the reentrant below the Tropidoleptus interval.
The Case Hill Coral Bed yields large rugose and tabulate corals as well as diverse brachiopods. The upward change from the unit into soft, Ambocoelia-rich shale marks a significant deepening event within a larger transgressive systems tract succession above the sequence boundary reentrant. The top of the Mottville is typically marked by a bedding plane covered by small brachiopods as well as gastropods and orthoconic cephalopods displaying black calcite preservation. This maximum flooding surface, unfortunately, is poorly exposed in this section.
Above the Mottville interval is a 7 meter-thick interval of gray shale and gray silty shale that is bounded at the top by a shell bed yielding abundant phosphatic nodules associated with numerous Athyris cora and other fossils (Fig. 6). This shell bed marks a discontinuity that can be traced westward into the Levanna Member as far as Cayuga Lake (Fig. 4). Between Cayuga Lake and the Tully Valley, this layer is typically characterized by reworked concretions encrusted by auloporid corals in association with molluscan debris. East of the Tully Valley the reworked concretions are replaced by small phosphatic pebbles and a somewhat more diverse associated biota. We believe that this shell-phosphate layer projects to the top of the Cole Hill Sandstone bed near Sangerfield.
Between the top of the Mottville and the top-Cole Hill cycle shell-phosphate bed is an interval of shale yielding abundant clams, snails and cephalopods displaying black calcite preservation. Gastropods, including Bembexia and Palaeozygopleura, as well as nuculoid bivalves and cephalopods, are typically preserved three-dimensionally.
Above the shell-phosphate bed is a 16 meter-thick interval of silty shale grading upward to fine sandstone at the upper (west) end of the outcrop. This part of the section corresponds to the upper Delphi Station upward-coarsening cycle. The uppermost beds in this interval are considerably coarser than equivalent strata at Pratts Falls suggesting a trend to greater facies proximality towards the southeast. The coarse beds at the top of the section contain abundant bivalves and occasional large brachiopods such as Spinocyrtia. Three meters below the top of this section is a band of medium-size corals that is also observed at Pratts Falls and at a section near Delphi Station; this bed may correlate to the Papermill Bed-Roanoke Bed interval in western New York (Fig. 3).