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Abstract: Morphology and Stratigraphy of Middle to Late Pleistocene Shelf Submarine Canyons, Central Offshore Louisiana

Thomas M. Kirkpatrick

Five submarine canyons exist in the Pleistocene section of central offshore Louisiana. These large features have depths up to 800 m and widths between 5 and 17 km, and were important sediment pathways to the Gulf basin. This study covers the shelf portion of the canyons and spans approximately 100 × 70 km, from the ancestral shelf margin to an onshore location in southern Louisiana. More than 3000 line km of 2-D seismic data were interpreted for this study as were data from 25 exploration wells consisting of digital well logs and information on lithology, biostratigraphy, and velocity. Canyon morphology was determined based on the unconformities between the canyon fill and the surrounding strata, and was mapped in time and depth. The stratigraphic position of the canyons indicate that they become progressively younger eastward, toward the present-day Mississippi Canyon. The canyons represent a hybrid type of submarine canyon with a complex origin referred to as delta-front troughs. Modern analogs can be found associated with the Mississippi, Indus, and Ganges-Brahmaputra deltas. The Miocene Markley Canyon of northern California and the Paleocene Yoakum Canyon of south Texas are also similar in morphology and paleogeographic setting. Data in the study area support the theory that canyon initiation may take place on the slope, followed by headward erosion onto the shelf and the focusing of turbidity and longshore currents through the canyon. It appears likely that canyon filling did not commence until well into the transgressive systems tract.

AAPG Search and Discovery Article #90983©1994 GCAGS and Gulf Coast SEPM 44th Annual Meeting, Austin, Texas, October 6-7, 1994