REVISED STRATIGRAPHY OF THE UPPER MIDDLE DEVONIAN WINDOM SHALE-TULLY LIMESTONE INTERVAL (GIVETIAN), SUBSURFACE OF WESTERN NEW YORK AND NORTHWESTERN PENNSYLVANIA

摘要

Analysis of more than 600 geophysical well logs from the Appalachian Basin of western New York, northwesternPennsylvania, and northeast Ohio reveals a localized tectonic imprint that occurred over ~ 2 MY in the latter half of the Givetian Stage ('Middle Devonian), This activity, initiated prior to deposition of the Tully limestone, resulted in the erosion of as muah as 30 m of the yindom Shale Member of the Moscow Formation in the northeastern Chautauqua County - Cattaraugus County region of western New York, This was followed by accumulation of a shaly limestone unit interpreted to be a lower interval of the Tully Limestone over theeioded Windom Shale Soon after this, a second erosional event removed much of the lower Tully Limestone and perhaps more of the underlying Windom shale. The upper Tully Limestone was deposited over the eroded lower Tully Limestone and Windom Shale and locally on the underlying Tichenor Limestone, The final phase of erosion resulted in the loss of the upper Tully Limestone over much the same region of the basin that the Windom Shale had been most deeply eroded. The upper Tully Limestone and its equivalent upper bounding unconformity is sharply overlain by deposits of the Genesee Formation, notably the organic-rich Geneseo Member, which are interpreted to mark the onset of Tectophase III of the Acadian Orogeny and related collapse of the basin. However, this study suggests.that the western New York - northwestern Pennsylvania region of the Acadian foreland basin experienced the effects of thrust load-induced dynamics (i.e., development of a flexural welt) prior to widespread basinal subsidence and associated deposition of the GeneseeFormation,