THE FIRST GREAT DEVONIAN FLOODING EPISODES IN WESTERN NEW YORK: REEXAMINATION OF UNION SPRINGS, OATKA CREEK, AND SKANEATELES FORMATION SUCCESSIONS (LA TEST EIFELIAN- LOWER GIVETIAN) IN THE BUFFALO-SENECA LAKE REGION Baird, G.C., Department of Geosciences, State University of New York College at Fredonia, Fredonia, New York 14063; Brett, C.E., Department of Geology, University of Cincinnati, 500 Geology/Physics Building, Cincinnati, Ohio 45221; Ver Straeten, C., Department of Geology, University ofWisconsin: Oshkosh, Oshkosh, Wisconsin 54901 INTRODUCTION The lower (sub-Ludlowville Formation) part of the Hamilton Group in western New York has received little attention by geologists owing to poor exposure and to the perception that it is composed essentially of drab, unfossiliferous deposits. Reexamination of numerous sections and several subsurface cores of Onondaga Group and lower Hamilton Group strata by Brett and Ver Straeten (1994) and Ver Straeten et al. ( 1994) has led to significant revisions of published correlational schemes (Rickard, 197 5, 1984). In particular, the old formational division of the lower Hamilton Group (Marcellus Formation) has been elevated to subgroup status and is now understood to include two formational entities (Ver Straeten et al., 1994); the Union Springs Formation (Bakoven Member-Hurley Member-succession) comprises the lower part of the Marcellus subgroup and the Oatka Creek Formation (Cherry Valley Member through Chittenango Member-succession) represents the upper part (Fig. 1). The above terminology of Ver Straeten et al. (1994) is employed herein (Figs. 1, 2). Two of us (Baird, Brett) are involved in ongoing revision of the Union Springs-through-Skaneateles formational successions across central and western New York as, well as central Pennsylvania. Only a small portion of this work has yet been set in print; Meyer, working under supervision of Baird, revised the stratigraphy of the Stafford Member (basal Skaneateles Formation) and elucidated its relationship with the Mottville Member (Meyer, 1985). A spectacular erosionally furrowed discontinuity surface (see STOP 6) has been described from the lower medial part of the Levanna Member in Erie County (Brett and Baird, 1990; Baird and Brett, 1991). The stratigraphic relationships of basinal Chittenango Member and Levanna Member facies in western New York with coarser, shoreward deposits in central New York are the subject of detailed scrutiny by Brett and Baird. The present paper advances an overview of the stratigraphy of the topmost Onondaga Group and sub-Centerfield Hamilton interval between the Seneca Lake meridian and Lake Erie noting revisions to date. We also tentatively explain vertical and lateral lithologic changes in terms of an inferred sea level curve and the sequence stratigraphy paradigm. Key background sources on the stratigraphy of this interval by earlier workers include: Cooper (1930); Smith (1935); Rickard (1975, 1984); Grasso (1986); Linsley (1991); Brower and Nye (1991); Brett and Ver Straeten (1994); and Ver Straeten et al. (1994). Because the Union Springs, Oatka Creek, and, especially, the Skaneateles Sat. Al (/) :::J I Ledyard Mbr. (.) ~ I co I ::J > I::J Centerfield Mbr. ~ lo CD 1'- Q) ~ 0) ~ 0 1:/) c ~ +-'co I 0 Q) (/) ..... I +-'co .0 ? I E E I ~ Q) "Wadsworth Bed" * IC 0 pyrite lag-floored LL ~ * ~ black shale unit (/) fE :::J "Papermill Limeston: c +-' Bed" co (/) co (/) ~ co +=i c ol CD c Q) co :::11 CD c > e1 co Q) > (.!) E I -c Q) CD I co _J ..c ~ 1'-Q) I (/) 5 I Stafford Mbr. * ---"Cardiff Mbr." -; Q) Chittenango Mbr. 0) +-'co (/) * cco :S2 Bakoven Mbr. UJ 1 ~-F--.-ft;o:::J:O:X::o::t:r8&::e:J:~~ Seneca Mbr. 7 1:I:IJ:I:D:I:IJ:I~ Moorehouse Mbr. Figure 1. Generalized succession of lithologic and zonal units in the uppermost · Onondaga Fonnation-through-basal Ludlowville Formation interval in western New York. Numbers denote: 1, base-Bakoven Member discontinuity; 2, Cabrieroceras plebieforme zone; 3, Haplocrinites zone; 4, Agoniatites vanuxemi zone; 7, Onondaga Indian Nation (OIN) K-bentonite; 8, Tioga "F" K-bentonite. SaL A2 Buffalo Geneseo Tully Cooperstown Valley ~ -~. OE 'OLL ~'0'(_ . .3 centerfield c 0 :;:; <1:1 E,_ 0 LL 90m ~ <D 60 ,_<D () 30 10 20 30 40 50 km 0 5 10 25 50mi A Figure 2. Generalized stratigraphy and unit relationships in the lower part of the Hamilton Group along the east-west outcrop belt across New York State. Conspicuous eastward thickening of units reflects major clastic influxes associated with the second tectophase of the Acadian Orogeny and coincident deepening of the Devonian foreland basin. SaL A3 formational successions are poorly exposed, we can only focus on a few key beds and distinctive intervals in the present report. STRATIGRAPIDC-IDSTORICAL OVERVIEW Onondaga Group and Union Springs Formation The uppermost Emsian?-Eifelian Onondaga Group records a subtidal carbonate shelf supportive of a variably diverse open marine biota comprising the "Onondaga Fauna" (see Oliver, 1956, Koch, 1981; Brett and Ver Straeten, 1994). Epeirogenic processes, presumably linked to the ongoing Acadian Orogeny in New England (Ver Straeten et al. 1994) explain a pattern of an eastwardly migrating backbulge basin within the medial Onondaga Limestone across western New York (Brett and Ver Straeten, 1995). In Pennsylvania, to the south of the Finger Lakes, Onondaga deposits accumulated in a carbonate-starved deeper part of the foreland basin under conditions that were more decidedly dysoxic (Koch, 1981; Brett and Ver Straeten, 1994). The end of Onondaga carbonate deposition, marked by packstone to lime mudstone facies of the Seneca Member, signaled the onset of a major deepening event within the Appalachian Basin, designated the "second tectophase" by Ettensohn, 1985, 1987; widespread deposition of organic-rich shales and ribbon limestones of the Bakoven Member of the Union Springs Formation marks the presumed collapse of the carbonate platform due to a major thrust loading pulse associated with terrain collision to the east. This was closely associated with the progradation of clastics from orogenic source areas to the east; the developing foreland basin was filled with sediment as it subsided and expanded leading to the long-recognized pattern of eastwardly thickening clastic wedges within the Hamilton Group (Fig. 2). Significantly, the post-Onondaga deepening event is closely associated with the "Tioga" cluster of k-bentonites that occur both within the upper Onondaga and basal Union Springs successions. Rapid eastward-southeastward thickening of the Bakoven shale in the vicinity of the Hudson Valley attests to initial development of foreland basin conditions timed with earliest Hamilton Group deposition (Ver Straeten et al., 1994). The Union Springs Formation marks an initial major flooding pulse partly of tectonic and partly of eustatic origin (see Ettensohn, 1985, 1987; Ver Straeten et al., 1994). Above the Bakoven Member interval, however, is evidence of a regression marked by the Stony Hollow Member-Chestnut Street Bed-interval (Ver Straeten et al., 1994) which is mostly eustatic origin but is influenced by the first coarse clastic pulse of the Hamilton succession. The thin Chestnut Street Limestone submember ("proetid bed") of the Hurley Member originally lumped within the Cherry Valley Member (Rickard, 1975; Cottrell, 1972), is now observed to be a distinct unit from the overlying Cherry Valley (Fig. 1). This bed, is the condensed cratonward equivalent of the much thicker, siliciclastic succession of the Stony Hollow Member in the Hudson Valley (Ver Straeten et al., 1994). Moreover, the Cherry Valley Member, "Agoniatites Limestone" of early workers, is observed to be a thin (condensed) transgressive drape over the top of the Stony Hollow Member in eastern Mohawk Valley and Hudson Valley sections (Ver Sat. A4 Straeten et al., 1994). Thus the Bak:oven-Stony Hollow-Chestnut Street succession respectively correspond to late highstand-regressive parts of the first great Hamilton sedimentary cycle, while the Cherry Valley marks the basal transgressive deposit of the second major cycle. The Union springs cycle also marks an incursion of a new faunal association that replaces the long-standing "Onondaga Fauna". This faunal change was part of a global or near­ global series of bioevents termed "Kacak-otomari" events by Chlupac and Kukal, 1986; Walliser, 1986; Truyols-Massoni et al., 1990 which are believed to be linked to a sea level highstand event timed with the late Eifelian. Distinctive taxa including: Variatrypa arctica, Pentamerella winteri, Schizophoria Sp., and Emmanuel/a Sp. characterize the Union Springs Formation. Kacak-Otomari immigrants are believed to be linked to warmer tropical water sources, perhaps in paleoenvironments recorded in deposits in present day arctic Canada. Oatka Creek Formation The Oatka Creek Formation, dominated by organic-rich basinal facies in central and western New York, records expansion of the foreland basin during the earliest Givetian. (Figs 1,2). A brief but widespread incursion of globally important cephalopods and dacryoconariids (Chlupac and Kukal, 1986; Walliser, 1986; Ver Straeten et al., 1994; Griffing and Ver Straeten, 1991) is reflected in the transgessive Cherry Valley facies. The Eifelian-Givetian zonal boundary probably lies slightly above the Cherry Valley Member-Berne Shale Member contact across the study area. The Berne Member, marked by a very thin, condensed interval of black, styliolinid-dacryoconariid-rich black shale in central and western