RECONSTRUCTING HANGENBERG END-DEVONIAN EVENTS IN OHIO AND NORTHWEST PENNSYLVANIA: CHANGING PERSPECTIVES AND NEW OPPORTUNITIES FOR FILLING IN THE PIECES

New zonal age determinations obtained from Late Famennian glacial diamictites in Maryland, as well as strata enclosing a large granite lonestone within topmost black shale deposits of the Cleveland Member in Kentucky, serve to place the onset of regional glacial and periglacial conditions, near the end of Cleveland Member deposition (LE palynozone). This is at a significantly lower stratigraphic level than that projected earlier by several workers at the regionally conspicuous, disconformable base of the Cussewago-Berea Sandstone.

These findings suggest that the Cleveland Member records an internal greenhouse-to-icehouse (Dasberg transgression-to-Hangenberg event) signal that remains to be fully characterized. Moreover, the thick, post-Cleveland succession (marine shell-bearing basal Bedford Formation, enigmatic red Bedford claystone, base-Cussewago-Berea lowstand event, and succeeding Berea Sandstone), point to a succession of important sea-level and climatic changes between the inferred Hangenberg black shale event (top-Cleveland interval) and the end of the Devonian. As such, this interval may record end-Devonian events not observed elsewhere.

We are addressing the need for improved biostratigraphic control (conodonts, ammonoids) within the Cleveland-Bedford interval as well as better characterization of the Hangenberg ¹³C excursion. If the unusual red Bedford facies in Ohio is truly an offshore marine deposit, it should yield conodonts and palynomorphs confirming this origin. Bulk disaggregation of this unit is currently underway as is the completion of polished sections for the viewing of sedimentary structures. Recent work by the present authors shows that the Cleveland Member-into-Berea Sandstone succession in central Ohio appears to be depositionally continuous, suggesting that this section will serve as an important future end-Devonian marine stratotype for eastern North America.