LITHOSPHERIC STRUCTURE OF THE SOUTH-CENTRAL UNITED-STATES

Recent seismic data in the Ouachita Mountains area and the Gulf of Mexico make it possible to construct a lithospheric-scale cross section (transect) from the midcontinent region to the gulf. We constructed a transect in the form of a gravity model, but it incorporates all available seismic, drill hole, and geologic data as constraints. The thrust sheets or the Ouachita orogenic belt appear as a thin veneer covering the southern part of the Arkoma basin and the preserved Paleozoic continental margin. Mesozoic rifting is evident in three areas: (1) southern Arkansas and northern Louisiana where extension was minor, (2) the vicinity of the Texas-Louisiana coastline where modification of the lithosphere and subsidence were considerable, and (3) the deep Gulf of Mexico where rifting was successful. A significant variation in the average density of the mantle, which could delineate the North American craton as a lithospheric feature, was detected near the Paleozoic continental margin.