INFERRED END-DEVONIAN TECTONIC, SEA-LEVEL, AND PALEOCLIMATIC EVENTS AS OBSERVED IN NORTHERN OHIO AND ADJACENT PENNSYLVANIA
Ongoing work in Ohio shows a dynamic pattern of northwestward, progradational downlap of divisional units of the Bedford Formation towards the top-Cleveland Shale–basal Bedford Formation erosional contact across the greater Cleveland area. This culminated in deposition of enigmatic, red-brown mudstone deposits of the topmost Bedford succession, well within the zonal time-slice of the global Hangenberg biocrisis. This facies, indicative of either parallic deltaic conditions or an offshore, oligotrophic, marine setting, remains poorly understood. Post-Bedford sea-level drop is indicated by a widespread disconformity that floors the top-Devonian Cussewago-Berea Sandstone succession across the Ohio – northwest Pennsylvania region. The Cussewago fills a major lowstand paleovalley centered near the OH/PA state line; these gravelly, valley-fill deposits yield numerous basement clasts including granite and gneiss. This immaturity stands in marked contrast to other area conglomeratic units, which are quartz-dominated. Hence, the basal Cussewago is believed to record unusually rapid, dissection of sediment source terrains, consistent with reports of glacial and periglacial deposits in this time-slice by others.