Regional Controls from Temporal and Spatial Distribution of Continental Slope and Abyssal Plain Reservoir Systems of the Gulf of Mexico Basin
William E. Galloway, Tim Whiteaker, and Patricia E. Ganey-Curry
Institute for Geophysics, University of Texas at Austin, Austin, TX
By the beginning of Cenozoic time, the Gulf of Mexico had assumed its general configuration as a small ocean basin. Clastic sediment entered a basin with a continental slope and extensive abyssal plain. In the late 20th Century, exploration began to test the hydrocarbon potential of these deep-water depositional systems. A succession of major plays ensued, beginning with the Plio-Pleistocene “Flex Trend” discoveries in slope apron turbidite reservoirs, and culminating in giant-field discoveries in Paleocene abyssal fan systems. Regional mapping reveals several key attributes of the deep Gulf reservoir systems. 1. Approximately two-thirds of the sediment entering the Gulf was ultimately deposited in continental slope and abyssal plain settings. 2. The principal accumulation phases of deep-water strata, particularly sand-rich intervals, correspond closely to major phases of sediment influx into the basin from tectonically uplifted and/or erosionally rejuvenated sources on the North American continent. 3. The geographic location of slope and basin depocenters was determined by the sites where major extra-basinal rivers draining those sources entered the Gulf. 4. Reservoir systems deposited by various gravity mass transport processes accumulated widely within offlapping continental slope aprons and as large submarine fan systems on the paleo-abyssal plain. 5. Contemporaneous gravity tectonic domains further accentuated partitioning of sediment between slope and basinal systems. 6. Regional seismic lines show that basin-scale, sand-rich deep slope and abyssal systems remain untested by drilling, particularly in the western Gulf. 7. Both seismic facies mapping and ODP drilling of the Quaternary Mississippi fan demonstrate that fan systems are quite capable of and have repeatedly distributed sand hundreds of kilometers beyond the contemporaneous shelf margin.
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