Crustal Framework of the Eastern U.S., and Its Influence on Hydrocarbon Development
Robert D. Hatcher, Jr., Department of Earth & Planetary Sciences, University of Tennessee, Knoxville, TN, 37996-1410
Eastern U.S. crust records Neoproterozoic breakup of supercontinent Rodinia, development of a Neoproterozoic to Early Cambrian rift-to-drift sequence, then an early Paleozoic platform. The Middle Ordovician Knox unconformity resulted from withdrawal of the sea from the eastern two thirds of Laurentia. Immediately following renewed inundation of the Appalachian foreland the diachronous Taconian orogeny produced foredeep sedimentation during the Middle (southern) and Late (central) Ordovician. This event was probably related to dynamic loading produced by obduction of volcanic arcs and ophiolites onto the outer margin, producing the foredeep and a peripheral bulge farther west.
The Devonian Acadian (and latest Devonian-early Mississippian Neoacadian) orogeny produced the Devonian Catskill delta, and Devonian shale, which propagated southwest from a source in New England. These events are related to accretion of the Carolina-Avalon terrane to Laurentia. They produced folding and some faulting far into the southern Appalachian foreland, later truncated by the pre-Chattanooga Shale unconformity. Chattanooga Shale and younger Mississippian clastics form the Neoacadian clastic wedge.
The late Mississippian to Permian Alleghanian orogeny uplifted the internal parts of the Appalachians, spreading sediment in a large late Mississippian to Early Permian delta complex from the Appalachian chain into the Midwest. The delta was deformed as Africa collided with North America propagating thrust faults through the crystalline crust and into the foreland. Deposition continued farther west as the eastern foreland was being deformed. These events provide the structural and depositional framework within which Appalachian petroleum systems and hydrocarbon traps developed.
AAPG Search and Discovery Article #90059©2006 AAPG Eastern Section Meeting, Buffalo, New York