PRECAMBRIAN STRUCTURE AND STRATIGRAPHY ACROSS CENTRAL OHIO, A DIFFERENT VIEW OF THE BASEMENT COMPLEX

Detailed interpretation of reprocessed Ohio COCORP seismic lines has clarified the configuration and chronological development of the East Continent Rift Basin (ECRB) and a series of sediment-filled Precambrian Grenville foreland basins deposited both west and east of the previously accepted Grenville Tectonic Front. Grenville-age thrusting can be demonstrated west of the Grenville Front and well into Indiana, involving fill strata of the East Continent Rift Basin, as well as underlying rocks of the Granite-Rhyolite Province. Pronounced unconformities on seismic reflection data define the chronological sequence of the provinces as: (1) Granite-Rhyolite, (2) ECRB, and (3) Grenville. Petrographic examination of Precambrian samples from oil and gas wells suggests that laterally continuous seismic reflectors are in part ash-flow tuffs of the ECRB. Grenville foreland basins are defined by (1) marked impedance contrasts between essentially horizontal basin fill and underlying Grenville metamorphic rocks, (2) abnormally low interval velocities in basin strata, and (3) linear, magnetically low contour trends. Structural restoration of fault displacements at the basin-fill/Grenville-metamorphic-rock unconformity reveals a geometry suggestive of three large foreland basins that were later progressively partitioned as Grenville thrusting advanced from east to west. Precambrian architecture had a strong influence on development of the Indiana-Ohio Platform and the Appalachian Basin during the Paleozoic.