CHAPTER 3: THE PORT JERVIS, ORISKANY, ESOPUS, AND SCHOHARIE FORMATIONS, AND EQUIVALENTS: PRAGIAN AND EMSIAN STRATA OF NEW YORK

Middle to upper Lower Devonian strata in New York (Pragian and Emsian stages) comprise seven formations, in four distinct vertical packages. They were deposited over ~18 million years (412.4-394.3 Ma; Becker et al., 2020). The lowest unit, the lower Pragian Port Jervis Limestone, occurs only in the Tristates area, southeastern NY. Overlying upper Pragian units are the ~coeval Oriskany Sandstone, Glenerie Cherty Limestone and Connelly Conglomerate. These strata were deposited during a period of quiescence, late in a first tectophase of the Acadian Orogeny (Ver Straeten, 2010).

Overlying siliciclastics of the lower Emsian Esopus Formation are restricted to eastern to east-central NY. Overlying upper Emsian strata of the coeval Schoharie and Bois Blanc formations comprise mixed siliciclastic-carbonate and carbonate strata, respectively. These three Emsian NY units correlate with lower and middle parts of the Needmore and Huntersville formations, central PA to southwestern VA and adjacent WV. Deposition was associated with early to middle stages of a second Acadian tectophase.

Across NY, some to all of these strata are absent at the Wallbridge Unconformity. The Tristates area, at the meeting of NY, NJ, and PA, is the only area where deposition was continuous through this time. To the north and west, a major Paleozoic sea level lowstand +/- crustal flexure during the Acadian Orogeny led to an amalgamated series of unconformities, bounding the sub-Oriskany Wallbridge Unconformity. Maximum development of the unconformity occurs in ~west-central NY, where Middle Devonian Onondaga Limestone overlies Upper Silurian strata. The entire succession comprises six or seven major, third order depositional sequences. This includes two likely Pragian sequences, and five distinct Emsian sequences; all appear to be global. A series of altered airfall volcanic tephras occur in the lower Esopus Formation; a few additional tephras are known in the Schoharie Formation. Three distinct faunas characterize Pragian and Emsian strata – the Oriskany, Esopus and Schoharie Ecological Evolutionary Subunits (Brett et al., 2009). Too little biostratigraphic data, and the provinciality of Pragian-Emsian faunas of the Eastern Americas Realm, limit the accuracy of stage boundaries in New York/Appalachian Basin strata.