Mark T. Baranoski and Ronald A. Riley, Ohio Division of Geological Survey, 2045 Morse Road, Building C, Columbus, OH 43229.

The tectono-stratigraphic architecture of eastern North America, and the geometry of the Central Appalachian Basin, during Middle Paleozoic time were controlled dominantly by regional tectonic stresses impinging on the Laurentian continent. Pre-existing Precambrian Proterozoic terranes and Neoproterozoic/Cambrian rifts affected sedimentation and structure throughout the Paleozoic. Significant volumes of clastic and carbonate sediments accumulated during Cambrian time, notably along the Rome Trough trend. Sediment removal across the region during the Late Cambrian/Early Ordovician Sauk unconformity partially masked pre-existing structural features. Middle Ordovician Black River time marked the position of elongate, north-northeast-trending depo-center geometries, which remained throughout the Paleozoic. Black River time was dominated by a broad, stable, shallow-water carbonate ramp along the northwest margin of the basin. Thick, shaley carbonates were deposited along the southeast margin of the ramp, defining the western edge of the Central Appalachian Basin approximately along the western edge of the underlying Rome Trough. Further to the east and southeast, thick shale and clastics accumulated in the Sevier Basin foredeep along the Laurentian continental margin. Craton-wide transgression continued after Black River time with deposition of relatively clean Trenton platform carbonates to the northwest and north, and argillaceous Lexington platform carbonates to the south, thereby marking significant changes in regional tectonics and global paleoclimate. Low-relief carbonate buildups on these extensive platforms surrounded an interplatform sub-basin where brown and black shale of the Utica Shale/Point Pleasant were deposited. Shaley carbonates accumulated in the depo-centers to the east, while further east at the continental margin, an extensive volcanic island system supplied wind-borne sediments to the region. Over time, shaley carbonate deposition in basin depo-centers gave way to shale deposition as continent-wide transgression continued. As the basin subsided during Late Ordovician time, carbonate platforms were completely drowned by Utica Shale and equivalents.

AAPG Search and Discovery Article #90059©2006 AAPG Eastern Section Meeting, Buffalo, New York