CORRELATION OF THE LOWER AND UPPER KELLWASSER EXTINCTION EVENTS (LATE DEVONIAN) IN THE APPALACHIAN BASIN

The Frasnian-Famennian mass extinction occurred in two pulses, the Lower and Upper Kellwasser Events (LKW and UKW), which were identified in deep-water paleoenvironments of western New York using conodont biostratigraphy (Over 1997). The Pipe Creek Shale is temporally equivalent to the LKW, and a shale bed just below the base of the Dunkirk Shale correlates to the UKW. Shallow-water facies containing an abundant benthic fauna are preserved farther to the east in New York, and the Pipe Creek and Dunkirk were correlated into these settings many decades ago based on lithostratigraphy. Here, we revise these correlations based on biostratigraphic, lithostratigraphic, and subsurface data. Previous correlations placed the Pipe Creek Shale above the Nunda Sandstone and the Dunkirk above the Wiscoy Sandstone in this field area. We argue that the shale above the Wiscoy actually correlates with the Pipe Creek; Dunkirk-equivalent strata occur further upsection above the Canaseraga Sandstone. The LKW (not the UKW) thus lies above the Wiscoy Sandstone, and we have traced this event into northern Pennsylvania. The UKW event and Frasnian-Famennian boundary lie within the Canaseraga Sandstone. We correlate the Canaseraga with the Pound Sandstone Member (Foreknobs Formation) of West Virginia and surrounding states, and the Wiscoy with the Briery Gap Member. These new correlations permit improved understanding of the dynamics of the Frasnian-Famennian extinction in shallow, siliciclastic-dominated paleoenvironments. For example, strophomenid brachiopods and rugose corals were regionally extirpated in the LKW, and the last atrypid brachiopod persisted to the UKW.