A4: MIDDLE- UPPER DEVONIAN DEPOSITIONAL AND BIOTIC EVENTS IN WESTERN NEW YORK
Gordon C. Baird
Dept. of Geosciences
SUNY-Fredonia
Fredonia, NY 14063
D. Jeffrey Over
Dept. of Geological Sciences
SUNY-Geneseo
Geneseo, NY 14454
William T. Kirchgasser
Dept. of Geology
SUNY-Potsdam
Potsdam, NY 13676
Carlton E. Brett,
Univ. of Cincinnati
500 Geology/Physics Bldg
Cincinnati, OH 45221
INTRODUCTION
The Middle and Late Devonian succession in the Buffalo area includes numerous dark gray and black shale units recording dysoxic to near anoxic marine substrate conditions near the northern margin of the subsiding Appalachian foreland basin. Contrary to common perception, this basin was often not stagnant; evidence of current activity and episodic oxygenation events are characteristic of many units. In fact, lag deposits of detrital pyrite roofed by black shale, erosional runnels, and cross stratified deposits of tractional styliolinid grainstone present a counter intuitive image of episodic, moderate to high energy events within the basin. We will discuss current-generated features observed at field stops in the context of proposed models for their genesis, and we will also examine several key Late Devonian bioevents recorded in the Upper Devonian stratigraphic succession. In particular, two stops will showcase strata associated with key Late Devonian extinction events including the Frasnian-Famennian global crisis. Key discoveries made in the preparation of this field trip publication, not recorded in earlier literature, include: recognition of wave?-generated bedding and substrate channelization in styliolinid grainstone deposits of the Genundewa Limestone; discovery of a horizon in the lower Rhinestreet Shale with the chronozonally important goniatite cephalopod Naplesites and possibly dateable conodonts a few meters above a lag bed with Montagne Noire (MN) Zone 7 conodonts and a K-bentonite horizon presumably older than the Belpre Ash Bed of the southern Appalachian Basin (MN Zone 8); recognition of abundant phosphatic nodules in the Rhinestreet Shale cored by fish bones and scales; and discovery of a possible thin K-bentonite within the Pipe Creek Shale(= Upper Kellwasser Bed marking a global extinction-ecological disturbance event) allowing for potential absolute dating of that event.
This field trip differs from earlier ones in that it does not focus on any particular stratigraphic unit or problem. Rather we will provide somewhat of an ascending "Cook's tour" of units proceeding southwestward across Erie County from the lower medial Hamilton Group (STOP 1) to the Frasnian-Famennian mass extinction (STOP 7). This trip is, however, complimentary to our Sunday field trip (this volume) which focuses in more detail on the origin of the distinctive North Evans Limestone/Genundewa Limestone that we will see at STOP 2. For the benefit of participants, several of the newly-generated schematics are presented both in the Saturday and Sunday fieldtrip papers. In the tradition of NYSGA serving as a teaching forum, this fieldtrip is presented as "work in progress" and is designed to review controversies and ongoing questions. Although material covered is somewhat of an eclectic mix, this should lead to a broader array of issues to be addressed. Moreover, we have discovered several new features in several Late Devonian (Frasnian-Famennian) sections during field trip preparation that demand further investigation. These discoveries, discussed below, include the recognition of small-scale hummocky cross-stratification and substrate channelization in the Genundewa Limestone the finding of a new K-bentonite bed in the Pipe Creek Shale, the discovery of a geochronologically important occurrence of goniatites in the lower part of the Rhinestreet Formation, and the discovery of abundant phosphatic nodules containing fish bones and spines, also in the lower part of the Rhinestreet Formation. Thematic aspects of this trip will be: firstly, to examine evidence of current activity and bottom erosion in several basinal shale-dominated units intuitively viewed as "deep water" and "basinal," secondly, to look at distinctive facies and event horizons at different levels, and thirdly, to look at levels linked to key Late Devonian bioevents.

A4: MIDDLE- UPPER DEVONIAN DEPOSITIONAL AND BIOTIC EVENTS IN WESTERN NEW YORK

STOP 1. Charles E. Burchfield Art Museum and Nature Center
Town of West Seneca (see Figs. 4, 5).
When one of us (Baird) originally included this locality as a stop for a 1999 NYSGA fieldtrip (Baird et al., 1999), the present-day park was a vacant lot. The park has improved the access to this classic cutbank section along Buffalo Creek immediately upstream from Union Road. This stop is included, partly due to its relevance to our understanding of basinal submarine erosion processes, but also due to the fact that this stop was skipped owing to lack of time on the earlier fieldtrip. To reach the bank section we must wade across Buffalo Creek to the south-facing shale bank directly opposite the center. In the case of recent rains, the creek may be high, preventing our crossing. However, small, low exposures of the same channels are displayed at creek level on the south bank. These can be accessed in a high water scenario. At the bank, a prominent undulating contact is visible, separating gray to beige, calcareous mudstone below (lower division of the Levanna Member) from fissile, black shale above (medial part of Levanna Member; Figs. 4, 5). The undulating contact is an erosion surface which links eastward to a shell bed division of the Pompey Member of the Skaneateles Formation in central New York sections (see Baird et al., 2000). At this locality, conspicuous channel-like features are developed into the erosion surface which trend north-south, nearly perpendicular to the bank trend (Fig. 5). The channels range from a few decimeters to 1.5 meters width and up to 0.5 meters in depth. The dark shale fills in channels sometimes show smaller, nested channels within larger ones (Fig. 5c) indicating that channel formation was a continuous process during formation and burial of the contact. Parallel, north-south alignment of channels suggests a prevailing current direction during channel formation (Fig. 5b). Axes of channels sometimes contain concentrations of brachiopod and trilobite debris admixed with fish teeth and bones. The channels are interpreted by Baird and Brett (1991) to be ancient examples of submarine, erosional furrows, sensu Flood (1983); furrows form from sustained, unidirectional currents and can form in a variety of aqueous settings. However, they are found to be particularly common at modern continental slope breaks (Flood, 1983). We believe that the lenticular outcrop profiles of Leicester- and other detrital pyrite accumulations are the lateral perspective view of similar, debris-filled channels where surrounding mudrock has dewatered and flattened out channel relief.

Lake Erie visible to the right.
Low shale bluffs along shore are exposures of the Ledyard Member of the Ludlowville Formation (Middle Devonian).

Bridge over Eighteenmile Creek.
Upstream cutbank to the left shows the Middle Devonian Hamilton Group divisions unconformably overlain by Late Devonian strata of the Genesee Group.

Fishermen parking area
Fishermen parking area below pull-off to the left immediately south of the Lake Shore Road bridge over Eighteenmile Creek and small roadcut on Lake Shore Road to the right. This is STOP 1 of tomorrow's B3 Genesee Formation field trip (this volume).

Entrance to Frank Lloyd Wright Estate ("Graycliffs")
Entrance to Frank Lloyd Wright Estate ("Graycliffs") on the right. This newly restored attraction in the Buffalo area was a major access route to the shore cliffs along the lake in the 1980s before the great ladder below the estate fell into disrepair.

STOP 2. Lake Erie bluffs adjacent to the mouth of Pike Creek
Near Derby, Erie County (see Fig. 6). Proceed from end of long private driveway north of Pike Creek across yard to beach. Follow the beach southwest past Pike Creek to the beginning of a long bedrock cliff section bordering the beach. This section is in the southwestern part of a nearly continuous outcrop extending from Eighteenmile Creek almost to Sturgeon Point (STOP 4). Visible to the northeast are high cliffs exposing a long section, extending from the Wanakah Shale in the Hamilton Group, upward into the Frasnian Rhinestreet black shale. Units visible in the cliff south of Pike Creek, include: in ascending order, 2 meters of the Middle Devonian (Late Givetian) Windom Member, approximately 45 cm of lower Late Devonian (Frasnian) North Evans-Genundewa strata, 2.5 meters of gray and black shales of the West River Formation, and 2 meters of black Middlesex Formation. At this stop we will focus on the North Evans-Genundewa interval (Fig. 6).
This section shows the Windom Member-North Evans Limestone contact as a knife-sharp boundary separating chippy gray Windom shale rich in the small brachiopod Emanuella praeumbona, from dark, dysoxic beds of the Genesee Group (Fig. 6). The North Evans is anomalous in this area in that it is very thin and characterized by more detrital pyrite than typically found in sections closer to Buffalo. Furthermore, above the thin North Evans bed, and separating it from the overlying Genundewa Limestone, is a 25 cm-thick brownish black, flaggy shale unit that is unnamed (Fig. 6). This shale, containing flattened Styliolina, Pterochaeni, and wood debris, is very localized in distribution. At the North Evans type section on Eighteenmile Creek, adjacent to-, but immediately downstream from, the Amtrak railroad overpass, about four km east of STOP 2, the North Evans Limestone is a 6-12 cm thick lag accumulation dominantly composed of crinoidal debris, but also characterized by abundant conodonts, glauconitic grains, fish debris, and reworked concretions (Fig. 6). At the overpass bridge, the North Evans grades directly into styliolinid grainstone facies of the overlying Genundewa, and no dark shale is present. However, further downstream from that bridge to the northwest, a succession of creek bank sections shows dramatic thinning of the North Evans Limestone with the appearance of the feather edge of the dark shale as a nodular parting above the lag unit. Moreover, the North Evans undergoes a lateral, spectral change from a thick crinoidal unit to a thin layer of mixed carbonate grains and detrital pyrite that is distinctly more "Leicester"-like (Fig. 6). In the next key section (Fig. 6) along the Old Lakeshore Road (to be seen by participants of the Sunday fieldtrip B3: this volume), the intervening shale is 10-11 cm thick and the North Evans Limestone is only about 2-3 cm-thick. This intervening shale unit is herein interpreted as being a local basinal facies of the Genundewa Limestone in that its upper contact is conformable (non erosional) with the Genundewa Limestone. The westward North Evans allochem transition from dominantly calcareous to largely insoluble grains, accords closely to the appearance of the overlying dark shale, and it suggests that carbonate dissolution of the exposed lag was more intense in the more basinal subenvironment of STOP 2 than at localities further to the northeast.
At STOP 2, the North Evans Limestone rests on the Taghanic Composite Unconformity, a disconformity of large time-magnitude. Based on comparison with more continuous Devonian sections further east, the section at Lake Erie is severely truncated; approximately one third of the Windom Member, the entire overlying Tully Formation, and all of the succeeding Geneseo and Penn Yan formation successions are absent at STOP 2 (Fig. 2). The North Evans Limestone is a complex lag blanket famous for its fish material (Hussakoff and Bryant, 1918, Bryant, 1921, Turner, 1998) and conodonts (Hinde, 1879, Bryant, 1921, Huddle, 1974, 1981). North Evans conodonts are exceedingly abundant and diverse in species and types of elements. Elements of the North Evans fauna, both its fish debris and conodonts, can be traced from Erie County to the Genesee Valley. Preservation of the conodont elements is distinctive and varies from complete and pristine (light amber-colored) to broken, dark (almost black), and degraded (Color Alteration Index is 2 to 3). Colors of some of the fish debris are red, orange, gray and blue. The taphonomic history of the North Evans debris is complex and tests the limits of chronostratigraphic resolution (Kirchgasser and Koslowski, 1996; Kirchgasser and Vargo, 1998; Kirchgasser, 1994, 1998, 2001, 2002, 2004). The final taphonomic (burial age) of the North Evans material correlates to the youngest zone conodont in the mix, which is Ancyrodella recta of the upper part of Lower Frasnian MN Zone 2 (Kirchgasser, 1994); early whorls of the Lower Frasnian goniatite Koenenites (also MN 2 age) have been recovered from North Evans conodont residues at the type section at Eighteen mile Creek (Fig. 6a) and in lenses within the Genundewa Limestone at Linden in Genesee County (see Sunday illustrations). The North Evans, as with most lag beds, poses a depositional paradox; even though the lag content records an enormous span of time, the actual final depositional event producing the bed may have been geologically instantaneous.
The Genundewa Limestone at STOP 2 is a 30-40 cm-thick ledge composed of styliolinid grainstone-packstone carbonate (Fig. 6). It is typically brownish gray, massive to nodular, limestone which sometimes weathers into thinner, flaggy beds. Aside from Styliolina and the small bivalve Pterochaenia, fossils are scarce, usually small, and of low diversity. The goniatites Koenenites, Acanthoclymenia, and Tornoceras, as well as Manticoceras at the very top, occur in the Genundewa, but are rare or poorly preserved here; the conodont Ancyrodella recta of upper MN Zone 2 occurs in the North Evans Limestone and at the base of the Genundewa Limestone at Linden in Genesee County (see Sunday illustrations). As noted, the Genundewa is a pelagic limestone that probably represents oxygen-stressed, sediment-starved, basin slope conditions. However, at this locality, local erosional channelization is evident locally within the limestone (Fig. 6). These channels, as well as pervasive small-scale hummocky crossbedding and widespread alignment of Styliolina throughout the Genundewa, attest to significant current activity at the substrate, probably caused by deep-storm waves. The top of the Genundewa is gradational with the overlying shaley West River Formation; the topmost Genundewa becomes shaley and flaggy before giving way to the typical alternation of thin black and gray shale normally seen in the West River (Fig. 6). We herein interpret the interval from the sub-North Evans disconformity upward into the lower medial West River Formation is a Transgressive Systems Tract, starting with an erosional lowstand event recorded by the disconformity. The succeeding Genundewa is a condensed interval recording transgressive deepening within the basin and sediment-starvation on slope. A possible Maximum Flooding Surface is represented by a recurrent conodont-glauconite-bearing styliolinid bed within the basal West River Shale (Fig. 6); this conodont-rich bed has been traced westward from the Genesee Valley and is Huddle (1981) sample horizon 8122SD at Fall Brook, Geneseo (Kirchgasser et al., 1994, A-4, STOP I, fig. 10). Early highstand facies are represented by succeeding alternations of black and gray shale. This overall transgression probably represents a hybrid eustatic and flexural event within the basin.

STOP 3. Rhinestreet Formation at Lake Erie shore bluffs
Below at Seascape (private residence), 2 km northeast of Sturgeon Point near Derby, Erie County (see Fig. 7).
Near-vertical shore cliffs between STOPS 2 and 3 prevent our seeing units (Middlesex, Cashaqua formations) between the West River shale and the Rhinestreet shale. We will, however, see the top of the Cashaqua at STOP 5. STOPS 3-5 are directed to features in the lower part of the Rhinestreet Formation. Proceed across private yard to steps leading down the shore cliff. Turn right and proceed northward (down-section) along the beach to exposure of basal Rhinestreet strata.
The Rhinestreet Formation is one of the thickest Late Devonian black shale divisions in western New York. Hard, well-jointed, black shale makes up most of this section. Less organic-rich, recessive weathering dark gray shale intervals, as well as beds of greenish gray shale, can also be seen (Fig. 5). Conspicuous at several levels within the black shale intervals are large, often massive, septarial concretions. After walking northward on the beach, we will stop at a level displaying the largest concretions which occur about two meters below a 2.2 meter-thick gray shale unit (Fig. 7). The black shale facies within the Rhinestreet records intervals of severe dysoxia to near-anoxia within the Devonian basin associated with a broad time interval associated with global sea level highstand (Johnson et al., 1985). This organic-rich lithofacies accumulated in a relatively deep-water, stratified basin setting west of the prograding Catskill Delta in a foreland basin already maintained by collisional thrust loading (Ettensohn, 1998; see Fig. 1). Contemporaneity of Catskill Delta progradation is splendidly shown by the eastward splaying of Rhinestreet black shale divisions into the deltaic clastic wedge and by eastward passage of organic-rich basinal facies into shoreward, coarse, fossiliferous neritic facies and terrestrial red beds (Woodrow and Sevon, 1985; see deWitt, 1960; deWitt and Colton, 1959; Colton and deWitt, 1958; Sutton, 1963, and Kirchgasser et al., (1994) for evolution of correlations and unit terminology pertaining to eastern Rhinestreet and other West Falls Group subdivisions). The 2.3 meter to 2.4 meter-thick gray shale unit above the band of large concretions is the western distal "toe" of a progradational clastic pulse extending westward from the delta complex; this fine grained turbiditic or hemipelagic sediment was probably deposited during a sea level lowstand event which allowed prodelta muds to be exported far into the basin (Fig. 1). A turbiditic origin for part of this interval is suggested by the presence of a 2 - 5 cm thick siltstone bed at its basal contact at STOPS 3, 4, and 5 (Fig. 7); the basal surface (sole) of this layer displays erosional groove cast impressions and the top of the bed fines upward into featureless gray shale, suggestive of a turbiditic event. At STOP 3 (Seascape section), the basal lag of the siltstone bed yields conodonts of MN Zone 7 (Levin and Kirch gasser, 1994; Kirchgasser et al., 1994; Kirchgasser and Klapper, 1992). About one meter below the green-gray shale unit is a recessive notch that marks the position of a K-bentonite layer (Fig. 7). This altered ash bed is characterized by gray brown clays (kaolinite and mixed layered clays), bleached (pyroclastic?) micas, and secondary pyrite with minor quartz, calcite, plagioclase and ?apatite. The ash bed is graded with clay flakes in the upper part with even stronger parallel orientation than the clays in the overlying black shale. Lenses with the distinctive color and fabric of the ash occur intermittently for a few centimeters above the ash bed. As noted above, this ash bed is apparently not the Belpre Ash Bed of Tennessee (conodont MN Zone 8, Rotondo and Over, 2000) but an earlier event within the interval of MN Zone 7; the Belpre Ash has a radiometric date of 381.1 ± 3.3 Ma (Tucker et al., 1998; Kaufmann, 2006).

STOP 4. Rhinestreet Formation in Lake Erie shore bluff succession
Both to the northeast of-, and southwest of, the Sturgeon Point marina and car park complex near Derby, Erie County (see Fig. 7). We will, first, proceed on foot from the northeast end of the car park to the beach and follow the beach and continuous shale cliff section to a position near the outflow pipes from the Derby waterworks. The bluff section is nearly the same as that for STOP 3, except that most of the black shale interval below the gray shale unit is below lake level. The K-bentonite is not accessible here, but the gray shale unit is much easier to examine at this outcrop. Moreover, the black shale interval above the gray unit can be examined here (Fig. 7).
Within the gray shale unit in this locality are very thin, 0.2-6 cm-thick, black shale beds that often display sharp contacts and strong visual definition within the thicker gray succession. Buff gray concretions occur at two levels within the gray shale interval; these are concentrated closely below black shale bands and appear to be controlled by the presence of the bands. However, in a few places along the exposure, the thin, overlying black shale bands pinch out over the tops of the subjacent nodules. This suggests that concretion growth may have created differential paleorelief, perhaps due to early dewatering and differential settling of mud. The sharply defined thin, black bands pose an interesting question: Do they represent slow background deposition between turbiditic gray mud pulses, or do the thin black bands, themselves, represent some alternative type of rapid depositional event involving sedimentation, or resedimentation, of organic-rich sediment? Is it possible that the organic-rich sediment, instead, may have been originally pelletal, hence mobile and easily transported on the seafloor? This latter scenario, yet untested, could explain these sharp pinstripe bedforms as rapidly deposited, current-traction-generated features.
To the immediate northeast of the second waterworks outlet is a problematic structural displacement or offset at the level of the gray shale unit. At the lake edge, several fractures in the lower black shale division can be seen that are filled with gray shale that displays soft-sediment shearing and fracturing. Directly across from the area of shore fractures in the cliff face the gray shale unit thins to less than a third of its normal thickness across a distance of about 80 meters. However, debris on the beach conceals the intervening area and the full nature of this structure. The shore cliff and lake edge exposure displays excellent examples of joint networks, particularly for the black shale bands. These joints are believed by Gary Lash to have evolved during thermal-burial maturation of the black shale unit as the black shale units began to function as hydraulic top seals for moving fluids migrating up from below (see Lash, 2006; Lash and Blood, NYSGA Sunday trip B1, this volume). The different orientations of the various joint sets are believed to correlate to a series of far-field stress phases associated with the Allegheny orogeny (Lash and Blood, Sunday trip B1, this volume). This outcrop will be important as a stop on that Sunday trip.
Between 40 and 45 cm above the gray shale interval, within black shale facies, is a styliolinid-rich, hashy layer that is associated with widely-spaced, spheroidal concretions (Fig. 7). Close examination of the layer shows the presence of numerous, flattened goniatites (some partially pyritized), spotty concentrations of Styliolina, fish debris, large horizontal (arthropod?) trace fossils and scattered conodonts. The goniatites first identified during a survey of this section this past June, belong to the genus Naplesites in the family Beloceratidae. The lineage is characterized by compressed (discoidal), evolute shells with increasingly numerous, distinctly pointed lobes (and saddles) forming chevron-like patterns. The ancestor of the family is Probeloceras which in New York occurs below the Rhinestreet in the Cashaqua Shale (Sonyea Group; MN Zone 5); the group culminates with the extremely multi-lobed Beloceras, a genus still unknown in North America (Fig. 3). The discovery of the Naplesites horizon at Sturgeon Point (Stop 4) is important in that its presumed position in the lower Rhinestreet (House and Kirchgasser, 1993) is confirmed and the conodonts in the bed may prove to be datable. Naplesites is otherwise rare in New York and is known only from a few specimens (two species) described by Clarke (1898) far to the east from unspecified horizons and sections in the shales around Naples in Ontario County (Canandaigua Lake meridian). Probeloceras and Naplesites (as Mesobeloceras) are illustrated in Kirchgasser, Over and Woodrow, 1994, fig. 7).The close stratigraphic coincidence of useful conodonts, Naplesites, and the K-bentonite bed is important geochronologically and is the subject of ongoing work.
Return to vehicles and proceed by car around to the southwestern most parking area near the Sturgeon Point pier.
Proceed on foot to beach below car park and follow beach southwestward for approximately 120 meters to a low outcrop bench of black Rhinestreet shale at the lake edge.
This exposure of black shale is probably stratigraphically higher than the accessible beds northeast of the marina owing to regional dip effects, but the precise match of beds can not yet be made owing to the long covered interval between the two sections. Notable in this outcrop are several bands of concretions including a line of massive septarial concretions below the bench of very resistant black shale. At the top of the black shale bench are two closely-spaced horizons of small spherical to ellipsoidal, 0.3 - 4 cm-diameter, phosphatic nodules. Phosphatic nodules, well known from the upper part of the New Albany Shale and the Cleveland Shale, have not been reported from the Rhinestreet. The occurrence of nodules of this type has been interpreted as evidence of nutrient upwelling and high productivity in surface waters (see Robl and Barron, 1989). What is striking here is that many, if not most, of the nodules are nucleated by fish spines and scales. Small, sand-size grains within some of the nodules may be radiolarian tests.

STOP 5. Cashaqua Shale/Rhinestreet Shale contact
And overlying Rhinestreet strata exposed on Eighteenmile Creek and on access road leading to that creek, town of North Evans, Erie County (see Fig. 7). Enter access path opposite from North Evans Cemetery. Proceed on foot down sloped path to valley bottom. Cross flat area to edge of Eighteenmile Creek.
The Cashaqua Shale Formation of the Sonyea Group in southern Erie County is characteristically composed of gray fissile shale with a rhythmic succession of discoidal concretion bands (Buehler and Tesmer, 1963; Kirchgasser et al., 1997, fig. 9). The fauna of this unit consists of small mollusks and brachiopods, indicative of a dysoxic setting. Most notable, is the occurrence of numerous, often poorly preserved, goniatites belonging to the genera Manticoceras and Probeloceras which are flattened outside of the concretions and variably three dimensional inside of them (conodont Zone MN 5). Probeloceras is the ancestral genus of the family Beloceratidae and is followed by the genus Naplesites in the Rhinestreet Shale seen at Sturgeon Point, Lake Erie (Stop 3; see Kirchgasser, Over and Woodrow, 1994, fig. 7 for illustrations of Sonyea and West Falls Group goniatites). The prominent concretion layer with MN Zone 6 conodonts in the dark shales of the upper Cashaqua Shale is a septarian band with white or pink barite filling the shrinkage cracks and in places east of the Genesee Valley in Livingston County, replacing the shells of a rich molluscan fauna including the goniatites Manticoceras, Prochorites, Acanthoclymenia and Aulatornoceras; conodonts in the bed indicate MN Zone 6. The Prochorites is a species (P. alveolatus) known elsewhere only in Western Australia.
We will see the contact of this unit with the overlying Rhinestreet Formation of the West Falls Group in the bed of Eighteenmile Creek. The base of the Rhinestreet is sharp and marked by a seam of diagenetic pyrite which weathers to a rusty band in bank sections. No detrital pyrite has been found on the contact, but a rich association of conodonts is reported from the basal few centimeters of black Rhinestreet shale (Huddle, 1968; Kirchgasser and Klapper, 1992; Klapper et al., 1995).
Ascending the access path as we return to the vehicles, we pass the same lower Rhinestreet gray shale division that we examined at STOPS 3 and 4. Along the path this section is weathered and slumped, but, on the other side of Eighteenmile Creek, an excellent profile through this interval can be seen on a side tributary waterfall (Fig. 7).

STOP 6. Section of Pipe Creek Formation ("lower Kellwasser Bed")
And synjacent units at waterfall along south branch of Eighteenmile Creek, southeast of Eden, Erie County (see Figs. 8, 9). Proceed on foot from the vehicles to the lip of the large waterfall. The gray, silty, bioturbated unit in the falls face is the top part of the shaley Angola Formation of the West Falls Group. This is abruptly capped by the resistant, black, and well jointed Pipe Creek Formation of the Java group (Fig. 8) that forms the erosional lip of the waterfall. The 1.6 meter-thick Pipe Creek succession is followed upstream in the floor of the creek by softer, nodule-rich, gray and black shale facies of the Hanover Formation (Fig. 8).
The black Pipe Creek shale consists of massive, organic-rich facies that contrasts markedly with both the underlying Angola and overlying Hanover. The base of the Pipe Creek is abrupt on the Angola with the development of abundant diagenetic pyrite in the uppermost Angola. No erosional, detrital pyrite has been found at the contact, but a profound change in micro-texture is seen as one passes from the bioturbated, pyrite- suffused, uppermost Angola, into the laminated, black Pipe Creek (Fig. 9). As noted in the text, this unit has now been found to correlate to the "Upper Kellwasser Bed" which marks a major ecological reorganization and extinction event in global sections.
In the process of measuring this section for this field trip, we found an apparent K-bentonite bed 15 cm below the top of the Pipe Creek (Fig. 8, unit e). This layer consists of approximately 1 cm of soft clay rich in pyroclastic mica. The bed is currently being analyzed for its geochronostratigraphic potential (see text).
Above the Pipe Creek shale, there is an abrupt change to softer, gray shale that abounds in small concretionary nodules through an interval of about 1.5 meters (Fig. 8). One bed (Fig. 8, unit g), is packed with very small irregular nodules such that this layer somewhat resembles a muddy version of the classic condensed, gray, nodular limestone facies of European sections (Tucker, 1974; Tucker and Kendall, 1973). Fossils are common in the lower Hanover, but are usually very small. Diminutive gastropods, bivalves, and ostracodes make up most of the faunal trail mix. Goniatites, important as chronostratigraphic markers, occur sparingly in this interval at this section. However, at Java Village in Wyoming County, Delphiceras occurs just above the top of the Pipe Creek and somewhat higher in the section at Walnut Creek. At Silver Creek in Chautauqua County Sphaeomanticoceras and Crickites can be found, the latter genus being the highest zonal indicator of the Frasnian Stage (Fig. 3; House and Kirchgasser, 1993).

STOP 7. Upper part of Hanover Formation
Showing "Upper Kellwasser Bed" (Point Gratiot Bed) and basal contact of Dunkirk Formation on south branch of Eighteen mile Creek below New Oregon Road bridge, southeast of Eden, Erie County (see Figs. 10, 11). Exit vehicles and proceed to the downstream end of a long, west-facing cutbank along the south branch of Eighteenmile Creek below the New Oregon Road overpass. At this point gray shale of the upper middle part of the Hanover Formation are abruptly overlain by the black Point Gratiot Bed and succeeding gray and black shale beds of the upper part of the Hanover Formation (Fig. 10).
At this locality the Point Gratiot Bed is a black ledge that correlates to the "Upper Kellwasser Bed" of Late Devonian sections globally (see text). The topmost part of this ledge marks the actual Frasnian-Famennian extinction event of literature based on conodont work in western New York sections (see Over, 1997, 2002; Day and Over, 2002). Although the bed is composed of basinal black shale, fossils such as the probable anaptychus organ Spathiocaris, fish material, and wood debris can be found, particularly near the top of the bed. Moreover, elevated levels of Platinum Group elements occur at this level and other horizons in the boundary interval black shales (see Over et al., 1997).
Above the Point Gratiot Bed in this section is a 2.2 meter-thick upper Hanover succession of alternating gray and black shale beds that is capped by the black, well jointed Dunkirk Shale at the top of the bank (Fig. 10). The upper Hanover interval closely resembles the lower Rhinestreet gray shale unit owing to several discrete, thin, black shale bands which contrast sharply with the thicker gray lithology. Reworked pyritic burrow clasts and exhumed geopetally pyritized Tasmanites half-spheres (sensu Schieber and Baird, 2001) have been found in thin lags at the base of the thin black beds and at the base of the Dunkirk Shale. Immediately above the Point Gratiot Bed in this section is a thin, gray, bioturbated shale bed yielding small nodules (Fig. 10). Above this level, gray shale units become less visibly bioturbated and more non calcareous, suggestive of a long-term transgressive trend in the interval. Hanover deposits below the Point Gratiot Bed are markedly more calcareous, lighter colored, and more intensely bioturbated; upward changes across the Point Gratiot Bed probably reflect combined effects of transgressive deepening in the basin and adverse biological effects associated with the Frasnian-Famennian crisis. Participants should look for any sign of the fossiliferous "recovery bed" discovered by Jeff Over approximately one meter above the Point Gratiot Bed near Java Village (Day and Over, 2002). Although it is absent from many area sections, the STOP 7 outcrop has not yet been seriously checked for the presence or absence of this unit.