B2: UPPER DEVONIAN KELLWASSER EVENTS, DAY 2
D. Jeffrey Over
SUNY Geneseo
Geneseo, NY 14454
over@geneseo.edu
Andrew Bush
Center for Integrative Geosciences
University of Connecticut
Storrs, Connecticut, 06269
andrew.bush@uconn.edu
Gordon C. Baird
205 Jewett Hall
State University of New York at Fredonia
Fredonia, NY 14063
mason@fredonia.edu
James Andrew Beard
james.beard@uconn.edu
Introduction
Earth-system perturbations caused a series of mass extinction events during the Devonian Period, including the Taghanic event in the Givetian, the Lower and Upper Kellwasser events in the Frasnian, and the Hangenberg event in the Famennian (House, 2002; Bambach, 2006). These extinctions occurred against the backdrop of orbitally forced sea-level fluctuations, the Acadian Orogeny (Averbuch et al., 2005), the expansion of plants and animals on land (Algeo et al., 1995), and ecological changes in the marine biosphere (Signor and Brett, 1984; Bambach, 1999). The Frasnian-Famennian boundary in particular represents a significant global crisis, considered one of the “big five” mass extinctions (Raup and Sepkoski, 1982) that led to the demise of the widespread and diverse Devonian reef community (Copper, 2002).
The Appalachian Basin preserves a tremendous record of Devonian stratigraphy, and these rocks have been studied for about 200 years (Aldrich, 2000). They have been, in whole or in part, the inspiration for numerous advances and theories in geology and paleontology, including the concepts of facies (Chadwick, 1935), punctuated equilibrium (Eldredge, 1971), coordinated stasis (Brett and Baird, 1995), and considerable work on paleoecology (Sutton et al., 1970; Bowen et al., 1974; Thayer, 1974; McGhee, 1976; McGhee and Sutton, 1981; 1983; 1985; Sutton and McGhee, 1985; Stigall Rode and Lieberman, 2005). Critical faunas and floras document the invasion of land (Daeschler et al., 1994; Daeschler, 2000; VanAller Hernick, 2003).
In particular, foreland basin sediments provide an exceptionally thick and complete record of the Upper Devonian, and thus the opportunity to examine Late Devonian extinction events. Studies of the late-Frasnian Kellwasser events have been concentrated in the more offshore settings of western New York, where geochronology is well constrained by conodont biostratigraphy and carbon isotope chemostratigraphy (Over, 1997; Murphy et al., 2000; Over, 2002; Tuite and Macko, 2013; Lash, 2017). Specifically, the Pipe Creek Formation is temporally equivalent to the Lower Kellwasser Event (LKW), and a thin black shale bed in the upper Hanover Formation is equivalent to the Upper Kellwasser Event (UKW) (Over, 1997; 2002). Baird, Bush, and students have been investigating the Kellwasser events in shallower-water paleoenvironments further to the east, primarily in Steuben County, New York, and adjacent areas of Pennsylvania (Bush et al., 2015; Beard et al., 2017) (Fig. 1).

B2: UPPER DEVONIAN KELLWASSER EVENTS, DAY 2

Cowanesque Lake, Lawrenceville, PA
This outcrop of the Wiscoy Formation (Figs. 50-51) is similar to the numerous outcrops along I-99/Rt. 15 on either side of the New York-Pennsylvania border, but it is easier to access. The strata display hummocky and swaley cross-stratification, and appear similar to facies S2-S3 of Beard et al. (2017) (see Table 3). Facies S2 indicates medium- to thick-bedded, fine-grained sandstone with < 20% interbedded mudstones with abundant swales, and was interpreted as middle shoreface, and S3 is similar but with thin to medium beds and 20-50% interbedded mud, and was interpreted as lower shoreface.
Fossils are abundant and are easy to find in the float, particularly brachiopods, bivalves, and trace fossils. Brachiopods include Strophonelloides coelata, Whidbornella hirsuta, Spinatrypa cf. hystrix, “Cupularostrum” contractum, and chonetids.

PA 287, Tioga, PA
Outcrop of Wiscoy, Pipe Creek, and Canaseraga formations (Fig. 52). Location TGB of Bush et al. (2015) and Beard et al. (2017), and type section of the Hammond Member of the Canaseraga Formation.
Beard et al. (2017) provided a facies description of the Tioga sections, which is summarized below by stratigraphic interval (see Fig. 52 for section and Table 3 for facies descriptions). For other descriptions and interpretations of these sections, see Berg et al. (1981, pp. 153-158), Castle (2000), and Bush et al. (2015).
Wiscoy Formation: The lowermost portion of the TGB section consists of swaley, fine-grained sandstones with various amounts of interbedded mudstone, interpreted as lower to middle shoreface (facies S2-S3). The upper several meters of the Wiscoy are finer grained, consisting of interbedded mudstone and thin siltstone/sandstone beds, interpreted as inner shelf. Fossils include Strophonelloides coelata, Schizophoria amanaensis, Spinatrypa cf. hystrix, Douvillina arcuata, Cyrtospirifer inermis, rugose corals, other invertebrates, and trace fossils.
Pipe Creek Formation: Dark gray, silty shale, interpreted as a low-oxygen, offshore setting. However, depositional conditions could not have been permanently anoxic, because Beard et al. (2017) noted the presence of occasional trace fossils, small bivalves, and lingulid brachiopods.
Hammond Member, Canaseraga Formation: Beard et al. (2017) defined the Hammond Member at the TGB section as the basal portion of the Canaseraga Formation that directly overlies the Pipe Creek. It is considerably coarser-grained than the Pipe Creek and the overlying part of the Canaseraga, and Beard et al. (2017) interpreted it as represented a middle shoreface environment. At Tioga, the base is covered by large burrows, possibly Teichichnus isp. and Thalassinoides isp., which appear to have been mining the organic-rich sediments of the Pipe Creek once fully oxygenated conditions returned. Other beds of the Hammond at Tioga also contain abundant trace fossils. The coarsest sandstone beds at the base of the Hammond are capped by granule-rich, rippled bedform (Beard et al., 2017, fig. 6A,B) similar to those interpreted in the Appalachian Basin and elsewhere as transgressive ravinement surfaces (Castle, 2000; Plint, 2010; McClung et al., 2013).
The brachiopod Floweria chemungensis is extremely common in the Hammond Member, forming pavements at some horizons. The Hammond also contains the last representatives of a couple species that elsewhere have not been found above the Wiscoy, including Spinatrypa cf. hystrix and Schizophoria amanaensis. Trace fossils are also abundant, as well as the large bivalve Grammysia, as noted by Berg et al. (1981).
Undifferentiated Canaseraga Formation: The transition from the Hammond to the overlying undifferentiated portion of the Canaseraga represents a deepening. The remainder of this interval generally coarsens upward from primarily facies S3 (lower shoreface; approximately 20 to 30 m) to largely S2 (middle shoreface). The lower, slightly deeper portion of the undifferentiated Canaseraga has a diverse fauna, including several brachiopod species that first appear in this formation (“Thiemella” leonensis, “Athyris” angelica, and Spinatrypa planosulcata), but the upper reaches of the outcrop are dominated by Cyrtospirifer inermis. Glass sponges have also been found in the lower portion of the undifferentiated Canaseraga (Fig. 53).
Several noteworthy beds are marked in Fig. 52 as facies S4, which consists of muddy, fine grained sand characterized by dewatering structures and convoluted bedding. Beard et al. (2017) interpreted these beds as representing the rapid deposition of mud and sand that were loaded prior to dewatering. Brachiopods are often present in these layers.
The lower 10 m of the TGB section represent an increase in water depth from the swaley sediments of the Wiscoy Formation to the offshore paleonvironments of the Pipe Creek. The transition from the Pipe Creek to the middle shoreface sediments of the base of the Hammond is abrupt, suggesting a forced regression. Additional large changes in water depth are suggested by the rippled bedform atop this basal sandstone, similar to transgressive ravinement surfaces (Castle, 2000; Plint, 2010; McClung et al., 2013), followed by mudstone, then the middle shoreface sediments of the upper Hammond Member. Facies changes are more subdued in the rest of the section, which generally coarsens upward. These patterns appear similar to those seen in the magnetic susceptibility data from further offshore shown in Fig. 3: large facies changes above the Pipe Creek, followed by smaller fluctuations.

US 15, Tioga, PA
Location TGA of Bush et al. (2015) and Beard et al. (2017). Upper Canaseraga (Mills Mills Member), Dunkirk, Candeadea, and Catskill formations. Stratigraphic units are described below in ascending order (Fig. 54; see Table 3 for facies descriptions). Also see Berg et al. (1981, pp. 148-152), Woodrow et al. (1989), Castle (2000), Oest et al. (2013), Bush et al. (2015).
Mills Mills Member, Canaseraga Formation: 10 m of the Mills Mills is exposed at the base of the section. It fines from facies S2 and S3 (middle to lower shoreface) to M1 (inner shelf). Fossils are abundant and include “Athyris” angelica, Tylothyris mesacostalis, Praewaagenoconcha sp., Floweria chemungensis, Schizophoria impressa, and “Cupularostrum”. Bivalves are also abundant. No Frasnian taxa have been found (e.g., Spinatrypa sp., Cyrtospirifer chemungensis), consistent with placement above the UKW event.
Dunkirk Formation: The Dunkirk Formation is the uppermost thick black shale unit in the Devonian of New York. At Tioga, it consists of a dark gray, silty shale, and we place the top of the unit at a package of silty-sandy interbeds. Fossils similar to those in the Mills Mills Member are found in the lowermost Dunkirk, although it becomes less fossiliferous above that. Beard et al. (2017) interpreted it as an offshore paleoenvironment, perhaps dysoxic, although the fossils near the base may indicate a gradual decrease in oxygen.
Caneadea Formation: The Caneadea is a thick interval of gray shale overlying the Dunkirk. At Tioga, there are frequent silty-sandy interbeds. It generally coarsens upward from the top of the Dunkirk to the base of the Catskill Formation. Beard et al. (2017) interpreted it mostly as facies M2 and M1 (outer and inner shelf), with increasing S3 (lower shoreface) toward the top. At 40 m, there is a thick sandstone interval with a scoured base, plane laminations, cross beds, ripples, and abundant plant material that Beard et al. (2017) interpreted as a shallow shelf channel. Fossils are generally similar to those in the Mills Mills Member, although above ~40 m, Cyrtospirifer, “Cupularostrum”, and Floweria become the dominant brachiopods.
Catskill Formation: We have not examined the Catskill Formation in detail. The lowermost Catskill consists of alternating red and gray strata that are similar to the Irish Valley Member described elsewhere in Pennsylvania, and the overlying strata are similar to the Sherman Creek Member (McLaurin, 2010) (Fig. 54, lower panel). Cotter and Driese (1998) discussed the depositional environments of these units at an outcrop further to the south in Selinsgrove, PA. Lingulids and Cyrtospirifer are occasionally present in the lower portion of the Catskill, and trace fossils are abundant in the float. Fish remains are also present, and tetrapods have been found in the Fammenian of the region (Daeschler et al., 1994; Daeschler, 2000).
The lower 10 m of the TGA outcrop represent an increase in water depth from the uppermost Canaseraga Formation into the offshore environments of the Dunkirk. Overall, the section coarsens upward from the Dunkirk into the Candeadea, although it remains mostly mudrock dominated. The transition to the lower Catskill Formation represents further decrease in water depth, culminating in the transition to terrestrial sedimentation.