Abstract: Sequential Development of the Appalachian Foreland Along Seismic Transects

T. H. Wilson, R. C. Shumaker

Subsidence of the Appalachian foreland during the Paleozoic is chronicled by basement-block displacement and rotation recorded in the Paleozoic sedimentary cover. The foreland basement is dissected by a system of basement faults associated with the Cambrian-aged Eastern Interior aulacogen (Rome Trough). The geometry of the Trough changes from a narrow asymmetrical graben in the southwest to a broader basin, floored by a series of fault-bounded blocks.

The history of fault displacement and block rotation reveals the presence of from two to four periods of tectonic activity. These include: (1) continuous displacement of blocks down into the Trough from Cambrian through Middle Ordovician, (2) slight increase of displacement during the Middle Ordovician with some inversion, (3) relative quiescence during the Silurian and Early Devonian, (4) inversion from the Middle Devonian to at least the Middle Pennsylvanian. Reactivation histories vary from west-to-east across the foreland.

Possible interrelationships of basement faults to reservoir formation within the Paleozoic sedimentary cover are illustrated by a detailed seismic study of a field along the Trough margin. Production in this field appears to be in part controlled by reactivated basement and late stage detached structures, which developed during the Alleghenian orogeny. Detachment occurs over a basement block that dropped relative to adjacent blocks during deposition of the detachment interval. The chronology of structural events believed to effect reservoir formation is interpreted as follows: (1) basement growth during the Middle and Late Devonian, (2) formation of detached structures during the Alleghenian, which were accompanied or followed by (3) uplift of basement blocks along the west margin of ield.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994