Character, Distribution and Timing of Latest Quaternary Mass-Transport Deposits in Texas—Louisiana Intraslope Basins Based on High-Resolution (3.5 kHz) Seismic Facies and Piston Cores

Abstract

Systematic mapping of 3.5 kHz seismic facies (echo character) reveals the geometry, scales and distribution of Late Quaternary mass-transport deposits (MTDs) within the northern Gulf of Mexico (GOM) intraslope basin province and adjacent Sigsbee Abyssal Plain. The 3.5 kHz seismic facies indicate that localized MTDs are common in the intraslope mini-basins. MTDs of larger scale occur on the upper continental slope (e.g. East Breaks Slide Complex) and seaward from the eastern base of the Sigsbee Escarpment. Approximately 120 piston cores from these deposits “ground truth” the seismic facies interpretations and reveal that the sedimentary facies of the MTDs in intraslope basins contain a spectrum of slumps, slides and debris flows. Most MTDs are muddy deposits, but sandy MTDs are also common. The presence of sandy debris flows suggests that similar, more deeply buried MTDs may constitute significant reservoir sands. Many piston cores containing MTDs were biostratigraphi-cally and chemically zoned using G. menardii complex and calcium carbonate fluctuations to determine the timing and sourcing of MTDs in relation to glacio-eustatic sea-level changes associated with the Last Glacial and Holocene. This stratigraphic analysis indicates that the majority of downslope transport (including sandy turbidites, sandy and muddy debris flows, and slumps) occurred during the Last Glacial cycle. Downslope transport of MTDs during the Holocene Interglacial was rare.