LARGE-MAGNITUDE EROSION EVENTS AND ANOMALOUS, SPARSELY FOSSILIFEROUS, LATE FAMENNIAN SEDIMENTARY RECORD IN OHIO: REGIONAL PROXIES FOR GLOBAL BIOCRISES AND ASSOCIATED PALEOCLIMATIC PERTURBATIONS ON THE END-DEVONIAN EARTH

The topmost time-slice of the Catskill Delta clastic wedge, inclusive of the upper part of the black Cleveland Member and the succeeding Bedford – Berea formation section in Ohio, corresponds to the end-Devonian praesulcata international conodont Zone, a time of faunal extinction pulses and inferred rapid paleoclimatic changes, including glaciation events. In Ohio, this interval is characterized by major erosion surfaces, thick, deeply channeled sandstone deposits, as well as unusual, unfossiliferous, marine deposits not found in the lower Devonian section.

Although the top of the Cleveland Member is marked by a significant erosional disconformity below the Bedford Formation in most localities, work by the present authors shows no erosional break between these rock divisions in the inferred basin center in central Ohio, allowing for potential complete zonal and geochemical characterization of the Hangenberg biocrisis interval within the otherwise, lithologically monotonous Cleveland Member succession.

Although a sparse, neritic fauna is present at the top of the Cleveland and a more abundant and diverse community at the base of the Bedford Formation, succeeding Bedford-Berea strata essentially lack shelly faunas and yield meager, soft-sediment trace fossil assemblages. The medial Bedford is regionally dominated by a faunally barren, red-brown mudrock interval (red Bedford lithofacies) that is variably structurally sheared and microcleaved. This anomalous unit, interpreted earlier, both as a marine or nonmarine facies, is herein suspected to be an important signature of paleoclimate degradation following the initial Hangenberg event. Paleovalley development, preceding deposition of the Cussewago – Berea sandstone succession in Ohio and PA, is increasingly understood to be the signal of “icehouse Earth”-driven ice sheet expansion on Gondwana and in the Appalachian region.