Reprocessing and reinterpretation of COCORP southern Appalachian profiles

Abstract

Reprocessing of COCORP southern Appalachian data was focused on basic seismic evidence for continuation of sediments beneath a master decollement. The most important evidence is a nearly continuous series of subhorizontal reflections extending from the Valley and Ridge province into the Piedmont province. Continuity of subhorizontal reflections becomes tenuous in the Inner Piedmont. Careful reprocessing has yielded evidence for termination of strong reflections beneath the allochthon and the beginning of a relatively weak and complex series of “events”. Termination of sedimentary rocks beneath the Piedmont is interpreted from true amplitude seismic data. A zone of detachment continues southeast of the sediment termination as far as the master decollement root zone. Research on stacking velocities has indicated that complex velocity structures could create apparent low stacking velocities. This phenomenon may occur in the Charlotte belt of Georgia. Bouguer gravity can be modeled as a former craton of normal density with an accreted margin of very slightly higher density. Variation in crustal thickness also contributes to the Bouguer gravity gradient. No continuous large-scale overthrust is needed southeast of the interpreted master decollement root zone located beneath the Kings Mountain belt and Charlotte belt.