Middle to Upper Devonian Stratigraphy and Faunas of ...

Field Trip NE GSA March, 30th, 2008

Middle to Upper Devonian Stratigraphy and Faunas of Erie County, Western New York Jörg Maletz Department of Geology, University at Buffalo, SUNY, 772, Natural Science Complex, Buffalo, New York 14260-3050, U.S.A., Email: [email protected].

Introduction Devonian rocks are widely distributed in western New York and represent the remains of the Catskill Delta sequence of the Middle and Upper Devonian. The sediments were deposited in an epicontinental basin, the Kaskaskia Sea, covering the central part of North America, west of the mountain-forming Acadian Orogeny, that produced the sediment infill. The Acadian Orogeny and the closure of the Iapetus Ocean to the east is a complex event including subduction of the oceanic crust of the Iapetus and the collision between continental blocks, forming a long belt of strongly deformed continental crust, the Acadian Mountains. The collision involved in the North the eastern coast of Greenland and the western coast of Baltica (Proto-Scandinavia). Further to the South, the southeastern parts of Canada and the New England states of the U.S. collided with a small continent called Avalonia, which was subsequently attached to the eastern side of North America. Remains of this paleocontinent are now found in the easternmost part of New England, eastern Canada and form large parts of Newfoundland. The western New York area did not suffer from intense subsequent tectonic deformation and the sedimentary succession is even now in a more or less undisturbed position with comparably few faults indicating the tectonic activity to the east. Fault systems in western New York were, however, active in the Silurian and Devonian across the Appalachian Basin (Beinkafner 1983, Jacobi & Fountain 1993, 1996). The tectonic effects visible in the Devonian of western New York are mainly restricted to the input of erosional debris from the Acadian

Mountains, shed into the formerly quiet, carbonatedominated inland sea, drowning the carbonates and reefs teeming with life under a carpet of mud and extinguishing rich and diverse faunal communities. In the Lower and lower Middle Devonian, the successions are dominated by shallow water carbonate rocks, indicating a low sedimentation rate and quiet, tropical environment with widely distributed growth of bioherms and reefs. This environment started to change in the later part of the Middle Devonian, when suddenly dark shales, deposited under anoxic conditions appear in the succession, covering the shallow water carbonates and terminating the reef growth during the onset of the Acadian Orogeny. During the later part of the Middle Devonian, the mountain uplift in the east caused the deposition of large amounts of clastic sediments into the shallow tropical sea. The basin was deepening through the enormous amounts of clastic sediments delivered from the uplifted and eroding Acadian Mountains in the east and its load shed into the shallow western seas. In the Upper Devonian clastic sedimentation continued in New York State. The shorelines prograded from a position east of the Hudson Valley towards the west and a foreland basin evolved. A large delta complex, the Catskill Delta formed at the shoreline. It was produced by a number of smaller to medium sized rivers contributing sediments to form the large and widespread delta complex, not by a single large river as does the modern Mississippi River. The shoreline migrated towards the west during the Upper Devonian and the Catskill Delta Complex reached western New York in the Mississippian Period (Gates 2000, Woodrow 1985, Woodrow & Sevon 1985). This laterally western migration of the Devonian succession can be seen easily by examining a geological map of New York State (Fig. 1). The Devonian rocks crop out in a laterally continuous band approximately 50 miles wide from the Hudson Valley in the east to western New York. On this field trip we will see the

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strata of this succession and its faunas in the Buffalo Region, especially in Erie County, that

will help us to understand the complex history of the region.

Figure 1. Simplified geological map showing the Devonian rocks outcropping in New York State. Paleontological Research The Devonian successions of New York State were the center of many paleontological investigations, of which the most important outcome probably is the concept of coordinated stasis by Brett et al. (1990) and Brett & Baird (1992, 1995). Many environments show distinct patterns of appearance and disappearance of fossils and recurrence of particular faunal assemblages through relatively long time intervals, punctuated by rapid changes is common, expressed as a regional phenomenon. This is the bases for the concept of coordinated stasis. The authors found about fourteen intervals of coordinated stasis, each about 3-7 Million years long, in an interval of ca. 60 Million years, from the base of the Silurian to the Middle Devonian (Brett et al. 1996). During the intervals of stasis, the majority of the species lineages (ca. 60-80%) remained stable and did show only minor anagenetic, nondirectional changes. The whole species associations are nearly constant with little change in species richness, taxonomic membership, dominance and guild structure. During the intervening episodes of rapid change, often more than 70%

of the faunas became extinct There are numerous examples of rapid speciation and successful immigration of new taxa. The causes for coordinated stasis remain poorly known, but may partly being the result of tracking of environments. Temporary changes in environmental conditions lead to incursion of immigrants, but as soon as the original environment is reestablished, faunas return. Some faunal turnovers clearly occur at unconformities or are associated with sedimentological changes, but a number of distinct faunal turnovers are not consistent with any facies changes at all.

The Upper Silurian In western New York the Upper Silurian succession is fairly incomplete. The uppermost Silurian is referred generally to the Bertie Group, often called “Waterlimes”. It is a cyclic succession of ca. 16-18 m of buff grey, slightly argillaceous dolostones (Brett et al. 2008). The succession represents a sabkha to estuarine and brackish environment, close to hypersaline shallow seas, but also normal marine, lagoonal environments are recognized . The most famous fossils of New York, the eurypterids, including the New York

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State Fossil Eurypterus remipes, originate from this Upper Silurian interval (Clarke & Ruedemann 1912, Ciurca 1973, 1982, 1990, 2005).

The Devonian The Devonian succession is about 1000 m thick in western New York. It is represented by a succession of shales with intercalated limestone indicating times of slowing of the sedimentation rate and even of intervals dominated by erosional features. In western New York, a distinct unconformity separates the Silurian and Devonian successions. This unconformity shows its’ largest extent in western New York, where the Devonian starts with Middle Devonian carbonates above the

unconformity. Lower Devonian rocks crop out further to the east, in the eastern part of the Allegheny Plateau, roughly from the Hudson River in the east to Cayuga Lake in the west (Fig. 1). This major unconformity marks the boundary between the Tippecanoe and Kaskaskia sequences (Sloss 1963, Dennison & Head 1975). The unconformity is commonly called the Wallbridge Unconformity. The surface of the unconformity is marked by karst features and represents a major sea-level drop through which the older, Silurian, carbonate and evaporite succession was exposed sub-aerially and eroded (Brett et al. 2000). While in some regions sediments of Lower Devonian age are represented even further west, in western New York the Lower Devonian has been eroded and the Middle Devonian follows directly above the unconformity on Upper Silurian strata (Fig. 2).

Figure 2. The Lower to Middle Devonian succession in New York State (from Cassa & Kissling 1992).

The Lower Devonian Sequence The Lower Devonian sequence of New York State is characterized by a succession of shallow water carbonates and to a lesser amount of darker shales. The dark shales may be interpreted as deposits of a deep-water region, along the axis of the Lower Devonian marine basin. This interpretation is also consistent with the location of the mountaneous highlands of the eroding Taconic Mountains to the east. The presence of shallow water carbonates close to the region,

however, indicates that these were already strongly eroded and did not represent an important source of extensive amounts of clastic sediments any more. The Lower Devonian is represented in the Buffalo Region by the Bois Blanc Formation of Emsian age (Oliver 1967). The Bois Blanc Formation is a thin unit of dolomitic wackestones and packstones, representing a normal marine environment. It contains a distinctive suite of brachiopods, corals, and trilobites. In southern Ontario, the base of the Bois Blanc Forma-

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tion is sandy and contains spheroidal, phosphatic sandstone concretions (Brett et al. 2008). It is interpreted to represent a time of reworking of the otherwise not preserved Lower Devonian Oriskany Formation in the region (Oliver 1967).

The Middle Devonian Sequence Towards the end of the Lower Devonian, the shallow inland sea covering western New York became very shallow and even sub-aerial exposure can be recognized as the sedimentary succession became exposed and erosion took place in the region, removing most of the sedimentary record of the uppermost Silurian and Lower Devonian rocks. When the seas returned in the Middle Devonian, a tropical paradise was again established and the region teemed with life as formerly in the Upper Silurian. The area saw the growth of reefs and the incursion of a multitude of tropical and warm water organisms thriving in the shallow marine environments. The transgression was quite extensive and basically all of New York State was covered by a blanket of carbonates, produced by the skeletons of marine organisms like crinoids, brachiopods, trilobites, corals and many more. The Middle Devonian rocks of western New York State show a similar depositional history to those of the Lower Devonian further to the east. Onondaga Limestone represents a shallow water, high energy environment, rich in fossils. Then suddenly, the depositional environment changes in the later part of the Middle Devonian. Black shales of the Marcellus Group cover the tropical shallow water carbonates. This succession of dark shales on carbonates is the first indication of the onset of the Acadian Orogeny in the east.

The Onondaga Formation The Onondaga (Limestone) Formation is a carbonate unit, differentiated into four members, the Edgecliff, Nedrow (Clarence), Moorehouse and Seneca members (Oliver 1954, Ozol 1964). The Onondaga Limestone is a widely distributed unit in New York State and, due to its resistance to weathering, it forms the Onondaga Escarpment, an east-west oriented cliff face that can be followed for long distances in New York State, where it more or less parallels the southern shore of Lake Ontario. The Onondaga Limestone is

quarried frequently in New York, mainly for crushed stone used in concrete, but also for other purposes. The reef facies in the Onondaga Limestone with its high porosities makes it a potential source for oil and gas exploration in the region. The Edgecliff Member (Oliver 1954) of the Onondaga Limestone is the lowest member of the Onondaga Limestone Formation. It is a light-gray, coarsely crystalline, crinoidal and coralline limestone, about 1-6 m thick in western New York. The Edgecliff Member contains at least thirty irregularly distributed smalll bioherms (Crowley & Poore 1974). The faunas and facies relationships of the bioherms of the Onondaga Limestone were studied by Oliver (1954, 1956a, 1956b, 1966), Mercarini (1964), Bamford (1966), Poore (1969) and Woloz (1990) among others. The structure and development of the Edgecliff bioherms are best illustrated by the Leroy bioherm, exposed in an abandoned quarry near LeRoy, New York. The Leroy bioherm was studied in some detail by Crowley & Poore (1974), who differentiated nine biofacies. The bioherm is about 4 m high, but the top is not preserved due to post-Devonian erosion. Thus, the final size of the bioherm remains unknown. The bioherm is largely composed of tabulate (favositid) and rugose corals. The base of the Edgecliff member is a ca. 0.5 m thick transgressive limestone, on which the reef ultimately grew during an interval of a slowly rising sea-level (Ver Straeten & Brett 2000). In the Upper Middle Ordovician, the Edgecliff bioherms finally drowned through the increasing subsidence and were buried by mud. Overlying Onondaga sediments of the Moorehouse and Seneca members are crinoid and small coral rich cherty packstones reflecting slightly shallowing conditions. In the exposed bioherm a “core” of fine-grained darker limestone is seen. It can be interpreted as being deposited as fine lime mud. In this ‘core’ the fossil composition differs from that of the surrounding reef. Delicate branching tabulates and other corals occur with a few other fossils. The main part of the reef consists of a coarse crinoidal-coraline facies. Bedding is lacking or visible only at contacts between superimposed coral colonies. This facies surrounds the “core” facies. The outer facies changes into bedded limestones of the reef flanks. The material is more fine grained and interfingers with the normal Edgecliff Member. In eastern New York the post-Edgecliff members are draped over the considerable thicker reefs. The lower units pinch out and the upper units thin over the reefs. The reef thickness reaches 23 m in regions, where the normal Edgecliff Member is 6-10 m thick. In the

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western New York region, however, the original thickness of the reefs is unknown, as all known reefs are strongly eroded. Their maximum hight was estimated at about 15 m. The reefs in general are rounded or elliptical structures with a diameter of 30 to 400 m. In the bioherm facies, colonial rugose corals described from the Leroy Reef include Actinophyllum segregatum, A. stramineum, Cyathocylindrium opulens, Heliophyllum coalitum and Synaptophyllum arundinaceum (Oliver 1976). In addition, solitary Cystiphylloides and Heliophyllum, and the tabulate corals Favosites and Cladopora are common. The favositid corals with distinctly dimorphic corallites is Lecfedites canadensis. Brachiopods, bryozoans, gastropods and trilobites occur in the bioherm facies, but are not common.

The top of the Moorehouse Member is defined by an up to 10 cm thick clay layer, the Tioga Ash Bed. This layer represents a volcanic eruption somewhere to the east during the Acadian Orogeny and can be used as an important tracer horizon and time line for local correlation (Oliver 1954). It has also been used for regional correlations as far as into the central Appalachians to the west into Illinois (Dennison 1961, Meents & Swann 1965). The Seneca Member is the uppermost member of the Onondaga Limestone Formation. Oliver (1954) claimed that this member is not recognizable in Erie County and is not mentioned by Buehler & Tesmer (1963).

The Hamilton Group In the Buffalo region, the Edgecliff Member is overlain by the Clarence Member of Ozol (1964), a local equivalent of the Nedrow Member of central New York. The Clarence Member is about 13-14 m thick and consists of finegrained limestone and dark chert. The Clarence Member contains a high amount of chert, up to 45-70% (Dunn & Ozol 1962), distinctly more than in any other member of the Onondaga Limestone. The correlation of the Clarence Member with the succession in central New York is unclear due to the poor fossil content. It might roughly be equivalent to the Nedrow Member, but may also include parts of the upper Edgecliff and lower Moorehouse members of central New York. Well-preserved fossils are not common in the Clarence. Brachiopod, bryozoan and trilobite fragments can be found frequently within the debris largely consisting of crinoid fragments, whereas corals are rare. Transport of the material is indicated by strong sorting and gradation of material in the individual layers as well as by current orientation of fossils. The Moorehouse Member consists of a ca. 18 m thick unit of medium grained, light medium gray, massive limestone with a distinct fauna including corals, trilobites and other invertebrates, while brachiopods are the dominant faunal elements. The Moorehouse Member contains a varying amount of chert, mostly light to dark grey in color. The unit thins towards the east and is only about 8 m thick at Syracuse.

The Hamilton Group can be differentiated into four formations, the Marcellus, Skaneateles, Ludlowville and Moscow formations from the base to the top. Cooper (1930), who introduced these subdivisions from his extensive research based on numerous exposures in New York State, provided the most comprehensive study of the Hamilton Group. The work was preceded by early investigations by Vauxem (1840, 1842) and Hall (1843) among others. Baird (1978, 1979), Brett (1974a,b, 1986), Baird & Brett (1981, 1983), Brett & Baird (1974, 1982, 1985, 1992, 1995) and Landing & Brett (1986) provided a modern revision of the stratigraphy and faunas of the Hamilton Group in western New York. The Hamilton Group is a succession of clastic, dark to black shales with distinct thin layers of carbonates, deposited in shallow offshore and nearshore environments (Cooper 1930, Rickard 1981, Dick & Brett 1981). The succession represents a basin fill related to the Catskill Delta Complex. New investigations show that the individual thin lithostratigraphic units can be correlated over large distances in an east-west direction (Dick & Brett 1981, and others). In Erie County the succession is fairly thin and a number of units found further east are not represented here. An unconformity at the base of the Hamilton Group was discussed by Cooper (1930), but appears to be unsubstantiated and the Onondaga/Hamilton contact is usually shown to be conformable and gradational in western New York. This contact is not exposed in Erie County, thus, detailed information is not available. The Hamilton Group is about 285 feet thick at Lake Erie (Cooper 1930, p. 121) and increases in thickness

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to the east to up to 1680 feet in the Schoharie Valley. It ranges from the base of the Marcellus Shale to the base of the Tully Limestone, where an unconformity of considerable extent exists. The Marcellus Formation The Marcellus Shale can be differentiated into the Union Shale Member, the Cherry Valley Limestone Member and the Oatka Creek Shale Member. The thickness of the Marcellus Shale is about 30-55 feet (Buehler & Tesmer 1963). The Marcellus Shale consists mainly of black, fissile shales, often with a distinct petroleum odor. Gray shales and layers of limestone concretions are present in the unit. The fossil content has been discussed by Wood (1901) and Buehler & Tesmer (1963). The Skaneateles Formation According to Buehler & Tesmer (1963) the Skaneateles Formation can be differentiated into the lower Stafford Limestone Member and the upper Levanna Shale Member. However, the Stafford Member has been included as the upper member of the Marcellus Shale by Cooper et al. (1942). The Skaneateles Formation is about 6090 feet thick in Erie County. The upper contact with the Ludlowville Formation is not exposed in the region. The Skaneateles Formation is a black, fissile shale with lighter colored layers in the upper part. The unit includes some calcaceous beds and pyritic layers. Grabau (1899) discussed and illustrated the fossils from this interval. The Ludlowville Formation The Ludlowville Formation (Hall 1839) comprises four member, the Centerfield Limestone Member, the Ledyard Shale Member, the Wanakah Shale Member and the Tichenor Limestone Member (Buehler & Tesmer 1963). It consists of gray, fissile shales and gray limestones with a thickness of about 65-130 feet. The Ludlowville Formation is exposed extensively along the shores of Lake Erie and along several creeks in Erie County. The Ludlowville Formation is rich in fossils and highly diverse faunas have been described (see Grabau 1899, Buehler & Tesmer 1963). The contact with the overlying Moscow Formation is taken at the top of the Tichenor Limestone Member. It is sharp and is represented by a distinct unconformity.

The Centerfield Limestone Member is a shale/limestone sequence marking the base of the Ludlowville Formation. Savarese et al. (1986) described the lithology and paleontology of the Centerfield Limestone in the Genesse Valley in some detail. The Centerfield Limestone represents a symmetrical cycle with a central limestone unit and surrounding gray calcareous claystones grading into dark to black shales. Savarese et al. (1986) interpreted the interval as regressive-transgressive cycle with the limestone representing the more shallow water deposition, while the surrounding shales indicate deeper water depositional environments. The unit is rich in brachiopods, corals, bivalves, gastropods and trilobites, differentiated into a number of associations by Savarese et al. (1986). The Centerfield Limestone is exposed in Erie County only in the Buffalo Creek section at Blossom (Stop 3). Buehler & Tesmer (1963) listed the faunas found in the Centerfield Limestone in Erie County. The Ledyard Shale Member (Cooper 1930) is between 30 and 80 feet thick in Erie County. It consists of a soft and fissile gray shale with thin limestone beds. Buehler & Tesmer (1963) provided an extensive list of the fauna found in this interval. The Wanakah Shale Member consists of medium gray, fissile shales with a low diversity fauna dominated by the brachiopods Mucrospirifer, Ambocoelia umbonata, Athyris spiriferoides and chonetids, small rugose corals such as Stereolasma, the trilobites Greenops and Phacops and numerous bivalves. A number of persistent limestone layers or calacreaous shale layers in this interval were called the trilobite beds by Grabau (1898). Common trilobites include Phacops rana, which may be found in enrolled specimens. The interval also bears intervals with limestone concretions and septarian limestones. The Wanakah Shale has a calcareous interval at its base in Erie County, in which the brachiopod Strophalosia and the coral Pleurodictyum are common. The type locality of the Wanakah Shale Member are the cliffs of Lake Erie at Wanakah (Stop 5). The Wanakah Shale at its type locality is 19.8 m thick, including several bands of calcareous mudstones and zones of larger and smaller carbonate concretions. Some concretions contain black sparry calcite and pyrite, associated with fossil accumulations. These concretions and the surrounding shales yield abundant fossils of a moderate diverse assemblage dominated by the small brachiopod Ambocoelia umbonata, which frequently occurs in exceedingly dense, localized clus-

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ters. Concretions yield well preserved, frequently enrolled specimens of Phacops rana and Greenops boothi, as well as rare pyritized nautiloids (Michelinoceras) and the goniatite Tornoceras uniangulare. Immediately overlying shales (Unit B) are particularly rich in specimens of the spiriferid brachiopod Athyris spiriferoides, and were subsequently termed the Athyris Beds by Grabau (1899). The highest beds of the Wanakah Shale (Unit C) exposed just below the Tichenor Limestone contain a high diversity fossil assemblage termed the Demissa and Stictopora beds of Grabau (1898, 1899). These units yield over 80 species of macrofossils and are particularly rich in brachiopods (Nucleospira, Cyrtina, Douvillina, Strophodonta demissa, Spinocyrtia granulosa, Pseudatrypa sp. and chonetids) and bryozoans (fenestellids, Sulcoretepora). Auloporids, Stereolasma and rare larger cystiphylloid corals occur in the upper beds, suggesting an approach to a coral bed locally. The Stictopora beds contain scattered thin lenses of crinoid-brachiopod rich limestone. The Jaycox Shale Member is considerably thinned in the Erie County region and is about ca. 30 cm thick in the Bullis Road section (Stop 4), compared to its development further to the east, where it reaches a thickness of ca. 4 m. Baird (1979) defined the Jaycox Member at Jaycox Creek, where it starts with a thin limestone bed rich in brachiopods and gastropods, overlain by gray to dark gray shales, partly calacareous shales with diverse corals (Eridophyllum, Heliophyllum, Trachypora and favositids) in several beds (Baird & Brett in Oliver & Klapper 1981). The Jaycox Member can be recognized everywhere by its characteristically coral rich fauna. The shale is soft, bluish-gray, with prominent fossil-rich biostromal horizons. The fauna of the coral beds is similar to that of the older Centerfield Limestone, and includes a variety of large and small rugose corals such as Eridophyllum, Heliophylum halli, the colonial rugosan Heliophyllum confluens, numerous large favositids, and Trachypora. The Moscow Formation Three units of the lower Moscow Formation, the Deep Run, Meneth and Kashong members, present in the Finger Lakes region, are absent at Eighteenmile Creek due to non-deposition or erosion. A very thin upper Moscow Formation section is present comprising about 4.3 m of Windom Shale. This contrasts with a thickness

of almost 20 m of the Windom Shale in eastern Erie Co. Despite its thinness, the Windom Shale is stratigraphically complete (condensed), and can be divided into a number of persistent faunal assemblage zones (Grabau 1898, Brett 1974a). In Erie County the Moscow Formation starts with the Tichenor Limestone Member, overlain by the strongly reduced Deep Run Shale and the Menteth members at Buffalo Creek (Stop 4). It is followed by the Kashong Shale and Windom Shale members. The succession is relatively incomplete when compared with the much thicker successions in the eastern part of New York and shows distinct disconformities (Brett 1974, Brett & Baird 1974, Baird 1978). The Moscow Formation is fairly thin at the shores of Lake Erie, measuring about 11.5 feet, but increases in thickness to ca. 55 feet in the eastern part of Erie County (Buehler & Tesmer 1963). The top of the Moscow Formation is defined at the base of the Tully Limestone in the Seneca Lake region, but this unit is not represented in Erie County, where the Leicester Pyrite Bed and the North Evans Limestone represent the local base of the Genesseo Shale. The Tichenor Member, called the Encrinal Limestone by Grabau (1898, 1899), is an approximately 3060 cm thick, medium gray, buff to rusty weathering calcarenite, forming a single massive unit at the shores of Lake Erie. Baird (1979) redefined it as the basal unit of the Moscow Formation. It consists predominantly of echinoderm skeletal debris with a mixture of lime mud and sparry calcite cements. The lower surface of the unit is a distinct disconformity. Fossils from the upper part of the Wanakah Shale are often found incorporated into the base of the Tichenor Limestone. The top of the Tichenor Limestone is a discontinuity surface with a locally developed hardground. This surface shows a relief of up to 20 cm. Locally the upper surface of the Tichenor Limestone exhibits dark, possibly phosphatic staining, anchor-faceted fossils and directly cemented crinoid holdfasts, bryozoans, and auloporid corals. This suggests synsedimentary lithification of the Tichenor Limestone, forming a hardground prior to the deposition of the overlying Windom Shale (Brett 1974a). The Tichenor Limestone contains numerous large rugose corals (Heliophyllum, Eridophyllum) and heads of the tabulate coral Favosites hamiltoniae, up to 50 cm in diameter. The specimens are found frequently overturned and not in life position. Large crinoid columns, fenestellid bryozoans and brachiopods, particularly Tropidoleptus, Pustolatia, Cryptonella and the robust Spinocyrtia granulosa are common in the

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Tichenor Limestone. The large bivalves Plethomytilus, Actinopteria, and Goniopora, are locally abundant in the upper surface of the Tichenor Limestone. Buehler & Tesmer (1963) produced a detailed list of the fauna found in the Tichenor Limestone. Conodonts obtained from the Tichenor Limestone suggest that a considerable percentage of the material in the limestone is reworked and that the unit incorporates a comparatively long time interval, condensed into a single, homogeneous bed. The Deep Run Shale Member. The Deep Run Member is is a hard, gray shale to shaly mudstone, forming a lensoid unit that thin out towards the west and is not present in the Lake Erie shore sections (Baird 1979). In the Canandaigua Valley the unit reaches a thickness of 17 m. In the Bullis Road section at Buffalo Creek (Stop 4) is is represented by a ca. 30 cm interval only. The shales of this unit are more calcareous and harder than those of the underlying Ludlowville Formation. However, they bear numerous small coral biostromal buildups, including a horizon well exposed within the creek that contains many large, in place coral heads of the tabulate coral Favosites. Bryozoans and large crinoid stems are common in the beds as well. The Deep Run Shale Member grades upwards into the prominent, rubbly ledge of the Menteth Limestone Member. The Menteth Limestone Member is a thin unit found in the area between the Cayuga Valley to Erie County, where it thins out completely (Baird 1979). It is a nodular limestone unit showing heavy bioturbation. The basal contact from the deep Run Shale is gradational, but the upper contact appears to be abrupt and formed by a clear unconformity. The westernmost outcrop of the Menteth Limestone is in the Bullis Road section on Buffalo Creek (Stop 4). Here, the Menteth Limestone Member forms the uppermost ledges of the series of riffles that cut across Buffalo Creek between the old and new bridges. They consist of about 10-15 cm of light gray, buff-weathering, irregularly bedded and strongly bioturbated limestone. It is richly fossiliferous with a diverse shelly and ichnofauna. Blue-gray soft shales with limestone lenses and concretions, often bearing fossil fragments and debris make up the Kashong Shale Member of

the Moscow Formation. The Kashong Shale is up to 26 m thick in Livingston County, but thins strongly towards the west and disappears in eastern Erie County due to a distinct erosional unconformity at the top (Baird 1978, 1979). The Kashong Shale is well exposed only in the eastbank cliffs down stream from the new bridge in the Bullis Road section on Buffalo Creek. It consists of relatively soft, medium to dark blue-gray, calcareous shales and mudstones. The unit is also abundantly fossiliferous with commonly preserved crinoid stems, brachiopods, trilobites (including Dipleura dekayi), bryozoans and corals. The contact with the overlying Windom Shale is disconformable and at this locality is marked by a thin zone of weathered pyrite nodules and phosphate nodules. The basal Windom Shale is medium gray, fissile, with abundant Ambocoelia umbonata and small Stereolasma corals. The Windom Shale Member is only 4.3 m thick in the Eighteenmile Creek section, but appears to be fairly complete and a number of faunal associations can be differentiated. The basal Windom Shale Member consists of about 50 cm of very soft, medium gray, richly fossiliferous shale. This unit contains an Ambocoelia umbonata – chonetid fauna, similar to the middle Wanakah Shale. Abruptly overlying the Ambocoelia rich basal shales is a 10-15 cm thick band of soft, blocky crumbly weathering gray mudstone containing an exceedingly rich and unique fossil assemblage, termed the Penn Dixie Coral Bed (Baird & Brett 1983). At Eighteenmile Creek this unit is expressed as a shell rich horizon containing abundant corals, bryozoans, brachiopods and crinoid debris. The spiriferid Mediospirifer audaculus, and Mucrospirifeer consobrinus, the atrypids Pseudatrypa sp. cf. P. devoniana and Spinatrypa spinosa are particularly common in this horizon. The Penn Dixie Coral Bed is gradationally overlain by bout 35 cm of light gray to medium gray calcareous shale and argillaceous limestone. It has been termed the Coral-Trilobite Bed (Brett 1974b) and is characterized by an abundance of the small rugose corals Amplexiphyllum and Stereolasma and complete and partial specimens of Phacops rana and Geenops boothi. Both trilobites occur in localized clusters of complete individuals. Clumps of over 100 specimens per square meter have been discovered from this bed in several localities, suggesting exceedingly rapid burial of local aggregates of trilobites. A band of calcareous mudstone occurs at about 1 m below the top of the Windom Shale, the Praeumbona bed of Brett (1974b). The Windom Shale is sharply and disconformably overlain by the North Evans Limestone of the Genesee Group (Rickard 1975).

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The Genesee Group In the Eighteenmile Creek area, the Upper Devonian Genesee Group is exceptionally thin and is represented by four units. A distinct regional disconformity is present on top of the Windom Shale in Erie County, where the North Evans Limestone is the oldest Upper Devonian unit. The Middle/Upper Devonian boundery interval, thus, cannot be defined easily and a considerable depositional gap is expected. Only in the Bullis Road section on Buffalo Creek is the Leicester Pyrite Bed present. Pyrite beds are common at certain levels in the Hamilton Group and indicate stagnation and depositional lacks (Dick 1982, Brett & Baird 1982, Dick & Brett 1986). The North Evans Limestone Member consists of lenses of 10-15 cm thick of crinoidal limestone, which shows sedimentary features like cross lamination, intraclasts and fossils, indicating considerable erosion and a derivation from the underlying Windom Shale. The North Evans Limestone was previously called the Conodont Bed by Grabau (1898). It contains a highly diverse conodont fauna of at least 41 species (Bryant 1921, Buehler & Tesmer 1963). The North Evans Limestone is a classic example of an erosion lag deposit or bone bed. The mixed conodont zone faunas indicates that the unit might represent a multiply reworked deposit, which accumulated over an exceptionally long time period spanning the Givetian-Frasnian boundary. The unit is also particularly rich in fish remains. Arthrodire and ptyctodont plates are very abundant and over 43 species have been reported from Erie County (Hussakof & Bryant 1918). The Genesseo Shale Member was originally described from Fall Brook, Geneseo. Its maximum thickness at Lake Erie is about 30 cm. The Geneseo Shale is a black shale, very petroliferous. The unit is also exposed in the Bullis Road section of Buffalo Creek (Stop 4). The Penn Yan Shale Member is a dark gray, concretionary shale with a thickness of only nine inches at the shore of Lake Erie (de Witt & Colton 1959). The Genundewa Limestone Member is a thin limestone unit, that is locally absent near Lake Erie (de Witt & Colton 1959). It has been called the Styliolina Limestone in the past. The Genundewa Limestone marks a break in sedimentation

(Cooper et al. 1942). Styliolina fisurella is the most common fossil in the Genundewa Limestone. Buehler & Tesmer (1963) provided a complete list of the rich conodont and fish fossils from the unit. The West River Shale Member is about 2.5 m thick at the Lake Erie shore. It consists of dark gray, fissile shale with calcareous concretions and beds of argillaceous siltstone. The West River Shale has a conformable contact to the underlying Genundewa Limestone. It grades into the Sonyea Formation.

The Sonyea Formation The Sonyea Formation is differentiated into the Middlesex and the Cashaqua members in the Lake Erie shore sections of Erie County. It consists mostly of dark gray to black shales and is about 12 m feet thick. While the lower contact is gradational, the top of the Sonyea Formation sharp at the base of the black shales of the West Falls Formation. The Middlesex Shale Member consists of black shales and is 2.9 m thick. A few gray bands and concretionary layers are present in the unit. It shows a fairly low fossil content (Buehler & Tesmer 1963). The Cashaqua Shale Member has a gradational lower contact to the Middlesex Shale Member. It consists of olive-gray, soft shale with few fossils (Buehler & Tesmer 1963) and reaches a thickness of 9.1 m.

West Falls Formation The West Falls Formation is a variable unit including black and gray shales, light gray siltstones and intervals with calcareous concretions and nodules. Its thickness reaches ca. 400 feet. The Rhinestreet Shale Member is about 150 feet thick. It is largely a thick unit of massive black shales with a distinct oil content (Jaffe 1950). In the upper part of the Rhinestreet Shale lighter colored shales appear. Ther are a few thin gray siltstone beds and thin-bedded argillaceous limestones inthe succession. Limestone concretions are common at many levels and reach diameters of up to 2 m. They often contain pyrite, but fossils are rare. The limestone corncretions may be septarian limestones with veins filled with calcite, dolomite, abrite and siderite. The Rhinestreet Shale is only sparsely fossiliferous. Conodonts have been reported from the lower part of the unit. Buehler & Tesmer (1963) provided a long list of species reported from this unit.

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The Angola Shale Member is a more than 220 feet thick interval of gray and black shales with impure limestones and calacareous siltstone beds. It is characterized by about 50 levels with calacareous concretions and limestone nodules of up to 1 m in diameter. The base of the Angoila Shale is defined at a layer of pyrite concretions called the “scaggy layer”.

Acknowledgements Buffalo Crushed Stone, Inc. and their geologist Gary Nelson provided access to the Como Parks Stone Quarry in Cheektowaga.

References Baird, G. C. 1978. Pebbly phosphorites in shale: a key tor ecognition of as widespread sedimentary discontinuity in the Middle Devonian of New York. Journal of Sedimentary Petrology 48, 545-555. Baird, G. C. 1979. Sedimentary relationships of Portland Point and associated Middle Devonian rocks in central and western New York. New York State Museum Bulletin 433, 24 pp. Baird, G. C. & Brett, C. E. 1981. Submarine discontinuities and sedimentary condensation in the Upper Hamilton Group (Middle Devonian): examination of marine shelf and paleoslope deposits in the Cayuga Valley. New York State Geological Association Guidebook, 53rd Annual Meeting, SUNY at Binghamton, 115-145. Baird, G. C. & Brett, C. E. 1983. Regional variation and paleontology of two coral beds in the Middle Devonian Hamilton Group of western New York. Journal of Paleontology 57, 417-446. Beinkafner, K. J. 1983. Deformation of the subsurface Silurian and devonian rocks of the southern tier of New York State. Ph.D. thesis, Syracuse University, Syracuse, N.Y. 332pp. Bamford, R. 1966. Paleoecology of the Albrights Reef Onondaga Limestone (Devonian), eastern New York, Masters Thesis, Univ. Nebraska. Brett, C. E. 1974a. Contacts of the Windom Member (Moscow Formation) in Erie County, New York. New York State Geology Association Guidebook 46th Annual Meeting, SUNY College at Fredonia, C1-C122. Brett, C. E. 1974b. Biostratigraphy and paleoecology of the Windom Shale Member (Moscow Formation) in Erie County, N.Y. – New York State Geological Association Fieldtrip Guidebook, 46th Annual Meeting, SUNY Fredonia, G1-G15. Brett, C. E. 1986 (ed.). Dynamic stratigraphy and depositional environments of the Hamilton Group (Middle Devonian) in New York State, Part I. New York State Museum Bulletin 457. Brett, C. E. & Baird, G. C. 1974. Late Middle and early Upper Devonian disconformities and paleoecology of the Moscow Formation in western Erie County, New York State. New York State Geology Association Guidebook 46th Annual Meeting, SUNY College at Fredonia, C23C29. Brett, C. E. & Baird, G. C. 1981. Stop 9 – Jaycox Run, Geneseo. pp. 28-31. In . Oliver, W. A. & Klapper, G. (eds.) De-

vonian Biostratigraphy of New York Part 2. Stop Descriptions. International Union of Geological Sciences, Subcommission on Devonian Stratigraphy. Washington, D. C. 1981. Brett, C. E. & Baird, G. C. 1982. Upper Moscow-Genesse stratigraphic relastionships in western New York: evidence for regional erosive beveling in the late Middle Devonian. New York State Geological association Guidebook, 54th Annual Meeting, SUNY at Bugffalo, 19-63. Brett, C. E. & Baird, G. C. 1985. Carbonate-shale cycles in the Middle Devonian of New York: an evaluation of models for the origin of limestones in terrigenous shelf sequences. Geology 13, 324-327. Brett, C. E. & Baird, G. C. 1992. Coordinated stasis and evolutionary ecology of Silurian-Devonian biotas in the Appalachian basin. Geological Society of America, Abstracts with Programs 24, A139. Brett, C. E. & Baird, G. C. 1995. Coordinated stasis and evolutionary ecology of Silurian-Devonian faunas in the Appalachian Basin, In Erwin, D. H. & Anstey, R. L. (eds.) New Approaches to Speciation in the Fossil Record pp. 285-315.. Columbia University Press, New York. Brett, C. E., Ivany, L. C. & Schopf, K. M. 1996. Coordinated stasis: an overview. Palaeogeography, Palaeoclimatology, Palaeoecology 127, 1-20. Brett, C. E., Miller, K. B. & Baird, G. C. 1990. A temporal hierarchy of paleoecologic processes within a Middle Devonian epeiric sea. In Miller III, W. (ed.). Paleocommunity Temporal Dynamics: The long-term development of multispecies asemblies. Paleontological Society Special Publication 5, 178-209. Brett, C. E., Ver Straeten, C. A. & Baird, G. C. 2000, Anatomy of a composite sequence boundary: The Silurian-Devonian contact in western New York State. New York State Geological Association 72nd Annual Meeting Field Trip Guidebook, 39-74. Bryant, W. L. The Genesee conodonts. Buffalo Geological Society of Natural Sciences Bulletin 21, No. 3. Buehler, E. J. & Tesmer, I. H. 1963. Geology of Erie County, New York. Buffalo Society of Natural Sciences Bulletin 21, No. 3, 118 pp. Cassa, M. R. & Kissling, D. L. 1982. Carbonate facies of the Onondaga and Bois Blanc formations, Niagara Peninsula, Ontario. New York State Geological Association, 54th Annual Field Trip Guidebook, Buffalo, NY, 65-97. Ciurca, S. J. 1973. Eurypterid horizons and the stratigraphy of the Upper Silurian and ?Lower Devonian of western New York State. New York State Geological Association, 45th Annual Meeting Field Trip Guidebook, Brockport, NY, D-1-D-14. Ciurca, S. J. 1982. Eurypterids, stratigraphy, late Silurian – early Devonian of western New York State and Ontario, Canada. pp. 99-120. In Buehler, E. J. & Calkin, P. E. (eds.) Guidebook for field trips in western New York, northern Pennsylvania and adjacent, southern Ontario. New York State Geological Association 54th Annual Meeting, Amherst, N.Y. Ciurca, S. J. 1990. Eurypterid biofacies of the Silurian-Devonian evaporite sequence: Niagara Peninsula, Ontario, Canada and New York: New York State Geological Association, 62nd Annual Meeting Field Trip Guidebook, Fredonia, NY, pp. D1-D23. Ciurca, S. J. 2005. Trip B-4. Eurypterids and facies changes within Silurian/devonian ‘eurypterid beds’ of New York State. pp. 113121. In Valentino, D. W. (ed.) New York State Geological Association. 77th Annual Meeting Field Trip Guidebook. Oswego 2005. Clarke, J. M. & Ruedemann, R. 1912. The Eurypterida of New York: New York State Museum Memoir 14, Volumes 1 and 2.

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Cooper, G. A. 1930. Stratigraphy of the Hamilton Group of New York, Parts 1& 2. American Journal of Science 19, 5th Series, 116-134, 214-236. Cooper, G. A. et al. 1942. Correlation of the Devonian sedimentary formations of North America. Geological Society of America Bulletin 53, 1729-1793. Crowley, D. J. and Poore, R. Z. 1974, Lockport (Middle Silurian) and Onondaga (Middle Devonian) patch reefs in western New York. NY State Geological Association, 46th Annual Meeting Field Trip Guidebook., A-1-A-41. Dennison, J. M. 1961. Stratigraphy of Onesquethaw Stage of Devonian in West Virginia and bordering states. West Virginia Geological Survery, Bullwetin 22, 1-87. Dennison, J. M. and Head, J. W. 1975, Sea level variations interpreted from the Appalachian Basin Silurian and Devonian. American Journal of Science 275, 1089-1120. de Witt, W. & Colton, G. W. 1959. Revised correlations of lower Upper Devonian rocks in western and central New York. American Association of Petroleum Geologists Bulletin 43, 2810-2828. Dick, V. B. 1982. Taphonomy and depositional environments of the Middle Devonian (Hamilton Group)m pyritic fossil beds in western New York. Master’s thesis, University of Rochester, 115 pp. Dick, V. B. & Brett, C. E. 1981. Petrology, taphonomy and sedimentary environments of pyritic fossil beds from the Hamilton Group (Middle Devonian) of western New York. New York State Musem Bulletin 457, 102-127. Gates, A. E. 2000. Chapter 3 Continents Adrtift. The Plate tectonic history of New York State. pp. 11-20. In Isachsen, Y. M., Landing, E., Lauber, J. M., Rickard, L. V. & Rogers, W. B. (eds.) Geology of New York. A simplified account. New York State Museum Educational Leaflet 28. Grabau, A.W. 1898-1899. Geology and paleontology of Eighteenmile Creek and the lake shore sections of Erie County, New York. – Buffalo Society of Natural Sciences Bulletin 6, Pt. I, Geology, Pt. II, Paleontology, 403 pp. (reprinted 1974: Hamburg Natural History Society, Inc., Persimmon Press, Buffalo, N. Y.) Hall, J. 1843. Geology of New York, Part IV. comprising the survey of the Fourth Geological District. Nat. Hist. N. Y. Div. 4, Geology v. 4. Hussakof, L. & Bryant, W. L. 1918. Catalog of the fossil fishes in the Museum of the Buffalo Society of Natural Sciences. Buffalo Society of Natural Sciences Bulletin 12. Jacobi, R. D. & Fountain, J. C. 1993. The southern extension and reactivations of the Clarendon-Linden fault system. Geographie Physique et Quarternaire 47, 285-302. Jacobi, R. D. & Fountain, J. C. 1996. Determination of the seismic potential of the Clarendon-Linden fault system in Allegany County, final report. Albany, New York State Energy research and development Authority, 2106 pp. & 31 oversized maps. Jaffe, G. 1950. A field and laboratory investigation of the oil bearing Rhinestreet Shale. M.A. Thesis, University at Buffalo. Landing, E. & Brett, C. E. 1986 (eds.). Dynamic stratigraphy and depositional environments of the Hamilton Group (Middle Devonian) in New York State, Part II. New York State Museum Bulletin 469. Martini, I.P., 1971, Regional analysis of sedimentology of the Medina Formation (Silurian) in Ontario and New York: American Association of Petroleum Geologists Bulletin, v. 55, p. 1249-1261.

Mecarini, G. 1964. Ecological succession in a Middle Devonian bioherm. Masters Thesis, Brown University, Rhode Island. Meents, W. F. & Swann, D. H. 1965. Grand Tower Limestone (Devonian) of southern Illinois. Illinois geological Survey, Circular 389, 34. Oliver, W. A. 1954. Stratigraphy of the Onondaga Limestone (Devonian) in central New York. Geological Society of America Bulletin 65, 621-652. Oliver, W. A. 1956a. Stratigraphy of the Onondaga Limestone in eastern new York. Geological Society of America Bulletin 67, 1441-1474. Oliver, W. A. 1956b. Biostromes and bioherms of the Onondaga Limestone in eastern New York. New York State Museum and Science Service, Circular 45, 1-23. Oliver, W. A. 1966. The Bois Blanc and Onondaga Formations in western New York and adjacent Ontario. New York State Geological Association, Guidebook, 38th Meeting, 32-43. Oliver, W. A. 1967. Stratigraphy of the Bois Blanc Formation in NewYork. United States Geological Survey Professional Paper 584A, 1-18. Oliver, W. A. 1976. Noncystimorph colonial rugose corals of the Onesquethaw and Lower Cazenovia Stages (Lower and Middle Devonian) in New York and adjacent areas. U.S. Geological Survey Professional Paper 869, 156 pp. Ozol, M. A. 1964. Alkali reactivity of cherts and stratigraphy and petrology of cherts and associated limestones of the Onondaga Formation of central and western New York. Dissertation Abstracts, Ann Arbor 24 (10), 4144-4145. Poore, R. Z. 1969. The Leroy bioherm: Onondaga Limestone (Middle Devonian) western New York. Master’s Thesis, Brown University, 69 pp. Rickard, L. V. 1975. Correlation of the Silurian and Devonian rocks in New York State. New York State Museum and Science Service Map and Chart Series No. 24. Rickard, L. V. 1981. The Devonian System of New York State. In Oliver, W. A. Jr. & Klapper, G. (eds.). Devonian biostratigraphy of New York. Subcommission on devonian Stratigraphy. International Union of Geological Sciences, Washington, D. C., pp. 522. Savarese, M., Gray, L. M. & Brett, C. E. 1986. Faunal and lithologic cyclicity in the Centerfield Member (Middle Devonian: Hamilton Group) of western New York: a reinterpretation of depositional history. New York State Museum Bulletin 457, 32-56. Sloss, L.L. 1963. Sequences in the cratonic interior of North America. Geological Society of America Bulletin 74, 93-114. Vauxem, L. 1840. Fourth Annual report of the geological Survey of the Third District. N. Y. State Geological Survey Ann. Rep. 4, 355-388. Vauxem, L. 1842. Geology of New York. Part III, comprising the Third Geological District. Nat. Hist. N. Y. Div. 4, Geology v. 3. Ver Straeten, C. A. & Brett, C.E. 2000. Forebulge migration and pinnacle reef development, Devonian Appalachian foreland basin. Journal of Geology 108, 339-352. Wolosz, T. H. 1990. Shallow water reefs of the Middle Devonian Edgecliff Member of the Onondaga Limestone, Port Colbourne, Ontario, Canada. New York State Geological Association, 62nd Annual Meeting Field Trip Guidebook, Fredonia, NY, E1-E17. Wood, E. 1901. Marcellus (Stafford) Limestones of Lancaster, Erie County, New York. New York State Museum Bulletin 49, 139181. Woodrow, D. L. 1985. Paleogeography, paleoclimate, and sedimentary processes of the late Devonian Catskill Delta. pp. 51-63. In

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Woodrow, D. L. & Sevon, W. D. (eds.). The Catskill Delta. Geological Society of America Special Paper 201. Woodrow, D. L. & Sevon, W. D. 1985 (eds.). The Catskill Delta. Geological Society of America Special Paper 201, 246 pp.

Stop descriptions

During this field trip, a number of sections in Erie County, New York, will be visited depending on weather and water level conditions. Thus, changes or adjustments in the schedule might be necessary. A general succession of the Middle to Upper Devonian stratigraphic units is shown in Fig. 4 with information of the position of the visited sections.

Figure 3. Stratigraphic units in the Middle to lower Upper Devonian (Eifelian to Frasnian) of Erie County, western New York State and ranges of stratigraphic units in the visited localities.

Stop 1. Como Park Quarry, Cheektowaga 500 Como Park Blvd, Cheektowaga, N.Y.

Onondaga Limestone including the Edgecliff, Clarence and Moorehouse members and the Tioga Ash bed.

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Stop 2. Charles E. Burchfield Nature & Art Center 2001 Union Road, West Seneca, N. Y. Close to the corner of Clinton Street/Union Road. The Stafford Member of Skaneateles Formation is exposed in Buffalo Creek.

Stop 3. Buffalo Creek, near Blossom The Centerfield Limestone is exposed in the Buffalo Creek at low water level. The section was described and illustrated by Buehler & Tesmer (1963: pl. 8). It is the only exposure of this unit in Erie County.

Stop 4. Buffalo Creek section at Bullis Road, Elma, New York Exposures in creek bed and along west banks of Buffalo Creek, beneath the new bridge and on east bank about 300-400 m northwards (downstream) from bridge. The exposures provide a nearly continuous succession of the upper Ludlowville and Moscow formations. The Ludlowville Formation at this locality includes the Wanakah Shale and the Jaycox Shale members. They are unconformably overlain by the Moscow Formation. Uppermost Moscow units, the Windom Shale and the Geneseo Shale are exposed upstream of the old Bullis Road Bridge along the east bank of the creek. A view down from the old bridge shows the patterns of fractures in the shale unit exposed upstream. The fractures are easily visible in the stream and in the facing cliff section, where they are enhanced by weathering and erosion.

sion of western New York. The lithological successions and faunas were described in some detail by Grabau (1898, 1899) and was the subject of many studies since then. Grabau (1898) described eight sections along the Creek along a stretch of about 3 km. Even though many of the lithostratigraphic and biostratigraphic units described by Grabau (1898) are not in use any more, the work provides a vivid picture of the exposures and their geological and paleontological potential and value. The second part of Grabaus’ monograph (Grabau 1899) provides a detailed description of the faunas found in the strata.

Stop 6. Eighteenmile Creek, North Evans, New York Cliff exposure along east side of Eighteenmile Creek, 0.2 km northwest of bridge for N.Y. Rt. 5 and 0.3 km southeast of Lakeshore Road Bridge, Hamburg, Erie County, N.Y. This classic Eighteenmile Creek section (section 7 in Grabau 1898) exposes portions of the Middle Devonian (Givetian) Hamilton Group and the Upper Devonian (Frasnian) Genesee and Sonyea Groups (Fig. 5). We intend to visit several sections along Eighteenmile Creek and at the mouth of Eighteenmile Creek at the shore of Lake Erie (Grabau sections 1,6,7,8, shore section).

Stop 6. Sturgeon Point, shore of Lake Erie, N.Y. Cliff exposure on Lake Erie shore of the Upper Devonian Rhinestone Shale.

Stop 5. Eighteenmile Creek, Hamburg, New York We will visit a number of sections along Eighteenmile Creek and on the shore of Lake Erie, representing the famous localities described by Grabau (1998, 1899) in some detail. The Eighteenmile Creek region in Erie County is long known to include some of the best exposures of the Middle to Upper Devonian succes-

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Figure 4. Buffalo Creek Section showing the contact between the Ludlowville and Moscow formations (from Baird & Brett).

Figure 5. Ludlowville/Moscow contact in the Eighteenmile Creek section (from Baird & Brett).

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