UPDATES CONCERNING END-DEVONIAN BIO-, SEQUENCE-, AND EVENT-STRATIGRAPHY, NORTHWEST PENNSYLVANIA AND NORTHEASTERN OHIO REGIONS

The latest Famennian (expansa Zone-praesulcata Zone interval) represents the last Devonian time-slice. In particular, the upper praesulcata Zone interval records the onset of a series of major, isotopic excursions, biotic disruptions, and climatic perturbations (= Hangenberg biocrisis interval). This time-rock interval occurs immediately south of the NY/PA state line and southwest into Ohio.

Time-slice 1 (Upper trachytera Zone-into-Lower expansa Zone interval): gray Chagrin Shale (offshore marine, outer-shelf-slope in Ohio), which grades eastward, respectively, into the Venango-Riceville succession (storm-influenced mid-shelf, with good neritic fauna) in northwest Pennsylvania, which, in turn, passes into Cattaraugus facies (inner shelf-paralic zone settings) in the Warren-Bradford area; time slice 2: basinal, black Cleveland Shale, temporally encompassing pre- and syn-Hangenberg zonal strata in Ohio, is overstepped by erosion in the vicinity of the OH/PA state line. However, marginally neritic deposits (West Mead bed and higher layers), yielding Middle expansa Zone conodonts, coeval to those at base of Cleveland Member, reappear in the Meadville-Oil Creek Valley region. The West Mead may be a western “feather edge” of the much-thicker Oswayo succession in the Warren-Bradford region. Higher Pennsylvania units (Drake Well formation-through- Corry Sandstone, or their eastward equivalent, the Knapp Formation), appear to largely fall within the praesulcata Zone and may be equivalent to the topmost Cleveland Member-through-Bedford Shale interval in Ohio. The coarse Cussewago-Berea succession (time-slice 3) and its basal regional, low-stand disconformity in Ohio are traceable eastward into the northern part of the Oil Creek Valley in Pennsylvania where they are apparently overstepped by younger, Carboniferous strata. Time slice 4 commences with the thin, condensed, basal Mississippian Bartholomew Bed across the Cleveland, Ohio-Oil Creek Valley region.