CARBON CYCLE PERTURBATIONS ALONG AN ONSHORE-OFFSHORE GRADIENT DURING THE KELLWASSER MASS EXTINCTION EVENTS, UPPER DEVONIAN, NORTHERN APPALACHIAN BASIN

The Kellwasser extinction events during the late Frasnian (Late Devonian) are globally associated with organic-rich deposition and 3-4‰ positive δ¹³C excursions. In the siliciclastic-dominated Catskill Delta Complex of the Northern Appalachian Basin, both the Lower and Upper Kellwasser events (LKW and UKW respectively) are associated with black to grey shales and silty-shales. Our study sites (from Wiscoy, NY to Tioga, PA) span a depth gradient from onshore-offshore, east to west. We have previously revised the stratigraphic correlations in this region and have recovered high-resolution δ¹³C_org signals through the intervals hypothesized to contain the LKW and UKW. We see a progressive shift to more depleted baseline values with increasing distance from shore and a change in the magnitude of the δ¹³C_org excursions through the LKW and UKW.

The LKW in the northern Appalachian Basin is characterized by a 3-5‰ positive excursion; in many locations, a negative excursion precedes or is superimposed upon the positive excursion, typically in the most organic-rich sediments. For example, prior to the positive excursion associated with the LKW at Big Creek near Hornell, NY, there is a rapid negative shift (~3‰) from the baseline associated with a change in lithology from the sands and silts of the Wiscoy Formation to the finer grained silty-shales of the Pipe Creek Formation.

In Western New York, the UKW is observed in a thin black shale in the upper Hanover Formation. According to our revised correlations, the Canaseraga Formation is the onshore equivalent of the Hanover. At two different localities in New York (Mills Mills along Wiscoy Creek and Cameron) we observe a 3-3.5‰ positive δ¹³C_org excursion in the upper Canaseraga Formation. The geochemical placement of the LKW and UKW are consistent with faunal sampling that indicates a major extinction at the LKW and the last known occurrence of atrypid brachiopods just below the UKW.