FRASNIAN AGE OF THE UPPER DEVONIAN UPPER WISCOY FORMATION AT THE TYPE SECTION ON WISCOY CREEK, WESTERN NEW YORK STATE

Johnson et al. (1985) described and delineated transgressive-regressive (T-R) cycles in Devonian strata that produced a framework for global correlation based on large scale eustatic sea-level changes. In the Upper Devonian offshore marine strata in the northern Appalachian Basin of New York the group-level strata fit within this framework where the widespread black shale strata represent the initial deeper setting of the T-R cycles. Biostratigraphy, primarily with conodonts and ammonoids, provides the zonal constraint for recognition of correlative lithology or cycles. The black organic-rich shales of the Java and Canadaway groups that span the Frasnian-Famennian boundary in the more nearshore facies of the succession exposed in the Genesee River Valley pose an interesting problem. The thick black shale that overlies the Wiscoy Sandstone at the type section exposed at the dam above Wiscoy Falls was originally considered to be the Dunkirk Formation that marks the start of T-R IIe in the lower Famennian. Bush et al. (2015) proposed that the black shale is the Pipe Creek Formation that marks the start of T-R IId2 in the upper Frasnian. Conodonts recovered from strata in the upper Wiscoy Formation and the overlying black shale are indicative of Frasnian Zone 13b (linguiformis Zone), which is younger than the Pipe Creek Formation, which is FZ 13a, and older than the Dunkirk Formation, which is Palmatolepis platys Zone. Lithologic correlation suggests that the 20 cm black shale in the upper Wiscoy Formation may be a thicker manifestation of the sub-Point Gratiot bed and that the thick black shale is the Point Gratiot Bed.