DEAN, STUART L., University of Toledo, OH; MARK T. BARANOSKI, Ohio Division of Geological Survey, Columbus, OH; and JOHN L. WICKS, Red Bird Producing, Wooster, OH

Abstract: Interpretation of Precambrian Geology along the Structurally Restored Ohio Consortium for Continental Reflection Profiling (COCORP) Seismic Lines

A structural restoration of reprocessed Ohio COCORP seismic lines has clarified the configuration and chronological development of the Fort Wayne rift (an arm of the East Continent Rift Basin) and a series of sediment-filled Precambrian foreland basins east of the previously accepted Grenville Front. Total shortening at the top of the Grenville sequence is about 13% across Ohio from the West Virginia border to the western boundary of the Grenville tectonic zone in west-central Ohio. Shortening appears to culminate within the tectonic zone at about 16.5%.

Grenville foreland basins are defined by (1) marked impedance contrasts between essentially horizontal basin fill and underlying Grenville metamorphic rocks, and (2) abnormally low interval velocities in basin strata. 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.

Thrusting occurred west of the Grenville Province and well into Indiana, involving fill strata of the East Continent Rift Basin, as well as underlying rocks of the Central Granite-Rhyolite Province. However, shortening decreases significantly westward; and fill strata show a maximum of 10% shortening at the eastern border of the East Continent Rift Basin and approximately 2% at the western end. 

AAPG Search and Discovery Article #90926©1999 AAPG Eastern Section Meeting, Indianapolis, Indiana