EASTERN MISSISSIPPI DELTA - LATE WISCONSIN UNCONFORMITY, OVERLYING TRANSGRESSIVE FACIES, SEA-LEVEL AND SUBSIDENCE

Analysis of 92 engineering core logs located in the Balize sector of t he eastern Mississippi delta focuses on the late Wisconsin unconformit y and lithofacies of strata lying immediately below and above this str atigraphic horizon. This major sequence boundary is a key feature used to correlate strata across shelf and slope to the basin. Observations emphasize lithofacies distributions of the latest Pleistocene sedimen ts underlying the unconformity, the late Pleistocene to early Holocene transgressive facies, and the immediately overlying deltaic deposits. Maps and a cross-section compiled with this information highlight the critical relation between lithofacies distributions and late Wisconsi n sealevel oscillations. Core analysis reveals that the transgressive facies comprises distinct environments of deposition, offshore to onsh ore. Findings identify criteria to determine the approximate position of the shoreline at the late Wisconsin maximum sea-level lowstand and at the extent of early Holocene maximum marine inundation in the Baliz e complex. Mapping of lithologies along the late Wisconsin unconformit y serves to improve correlation of sediment facies with changes in aco ustic response along high-resolution seismic profiles. An estimate of long-term averaged land subsidence suggests lowering of at least 1 mm/ year near the shelfedge during the past similar to 18 000 years. This mapping also refines sea-level response models for the Mississippi del ta, including criteria to locate key paleogeographic features such as shelfedges and maximum flooding surfaces in other Recent marine deltas and in older, stacked deltaic sequences.