Print this pagePleistocene Gulf Coastal Plain:
Regional Stratigraphic and Geomorphic Contrasts.
Intensive Erosion Related to Sea-Level Decline and Hinterland Uplift.
Ervin G. Otvos
Department of Coastal Sciences, University of Southern Mississippi,
703 E. Beach Dr., Ocean Springs, Mississippi 39564
ABSTRACT
The narrow Pleistocene–Holocene belt on the northeastern Gulf of Mexico contrasts sharply with the wide central and northwest coastal plain with three extensive Pleistocene terraces and the underlying thick sedimentary sequences. In addition to deposits of the last interglacial, but limited remnants of the penultimate terrace survive in the northeast. Only a thin Sangamon–early Wisconsin coastal complex, locally >10 km (6 mi) wide remains east of Mobile Bay. The complex correlates with nearshore seismic and engineering profiles. A thin (>30 m [100 ft]) late Pleistocene sequence directly overlies the Neogene in the shallow subsurface. Intensive erosive lowering of the land surface and valley entrenchment coincided with combined impacts of major glacial lowstands between the late Pliocene and Sangamon and, to a lesser extent during the Wisconsin glacial. In contrast with Louisiana and Texas, fewer major eastern coastal plain rivers delivered less sediment. Lowstands combined with tectonic rise resulted in a major hiatus between the late Pliocene and Sangamon. Unlike Pleistocene deposits, Holocene coastal units did not undergo major lowstand and uplift-related removal. Despite the much longer duration of the Pleistocene Epoch, the maximum thickness (6-24 m [20-80 ft]) of the uncompacted Holocene deposits compares well with the Pleistocene values on the eastern Gulf.
Otvos, E. G., 2009, Pleistocene Gulf Coastal Plain: Regional stratigraphic and geomorphic contrasts. Intensive erosion related to sea-level decline and hinterland uplift.: Gulf Coast Association of Geological Societies Transactions, v. 59, p. 585-600.
AAPG Search and Discover Article #90093 © 2009 GCAGS 59th Annual Meeting, Shreveport, Louisiana