Late Pleistocene geologic history of the outer continental shelf and upper continental slope, northwest Gulf of Mexico

Abstract

Integrated high resolution seismic and core data from the Texas outer continental shelf and upper continental slope were used to reconstruct the late Pleistocene geologic history of the area. Seismically aided correlation of paleoclimatic fluctuations determined with foraminifers indicates that the late Pleistocene-Holocene sequence was deposited during five cool-warm fluctuations. Correlation of these fluctuations with dated oxygen isotope curves serves as a basis for placing both paleoclimatic and sedimentary events into a time framework. Seismic pro files over the core sites allow the dating of seismic reflecting horizons and extension of the chronologic framework over most of the area. It appears that two major phases of shelf edge outbuilding occurred during the late Pleistocene. Both phases began with the development of shelf margin deltas during low stands of sea level. The deposition of these relatively coarse-grained sediments within the shelf-slope transition zone was accompanied by active growth faulting. Subsidence of the shelf edge also appears to have triggered up lift of elongate diapiric structures on the upper continental slope. Where the progradation of shelf margin deltas extended beyond the previously existing shelf break, large slid e masses are present on the adjacent continental slope. These slide masses appear to have associated with them active gas generation. Migration of gas into the surrounding sediments can greatly alter their seismic character. Sediment textural variations and fluctuations in the sediment accumulation rate also affect the character of individual reflecting horizons.