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Neogene Depositional Processes on the Texas-Louisiana Continental Slope Revealed by High-Resolution Seismic Studies

DAMUTH, JOHN E., and HILARY CLEMENT OLSON, Mobil Research and Development Corp., Dallas, TX, and DAVID C. TWICHELL, U.S. Geological Survey, Woods Hole, MA

Systematic interpretation of high-resolution seismic profiles (3.5-10 kHz echograms and 100 Hz Previous HitairNext Hit Previous HitgunTop) from the continental slope and rise of offshore Texas and Louisiana from the shelf break across the highly deformed zone of salt diapirs, folds, and intraslope basins to water depths greater than 3500 m seaward of the Sigsbee Escarpment

reveals the geometries, scales, distributions, and depositional processes of deep-water deposits in this region. The 3.5-10 kHz data indicate that redistribution of sediment by mass-transport processes is ubiquitous, and a wide spectrum of slumps, slide blocks, and debris flows are observed from small, isolated deposits in intraslope basins to large, complex deposits covering hundreds of kilometers. The reflection character (echo character) of many intraslope basin and canyon floors indicates sand-rich deposits; however, aggradational leveed-channel systems, characteristic of deep-sea fans, are not observed in the steep-walled intraslope basins. In contrast, some large submarine-fan channel-levee complexes do extend seaward from the mouths of these large canyons and basins at the base of the Sigsbee Escarpment to form one or more large deep-sea fans on the continental rise. Individual fan channels up to 160 m deep are perched atop levee systems greater than 100 km wide and are comparable in size to channel-levee systems of the nearby Mississippi fan. Apparently, large quantities of terrigenous sediments can be transported by turbidity flows through the intricate network of rugged intraslope basins and canyons to feed these fans. Evidence of sediment redistribution by bottom currents (contour currents) is also observed in the form of sediment waves and drift deposits across a large area of the continental rise seaward of the southeastern base of the Sigsbee Escarpment.


AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)