--> Abstract: Late Pleistocene Shelf-Edge Deltas and Growth Faulting in the Northeast Gulf of Mexico: The Early Development of Shelf Margin ; #90063 (2007)

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Late Pleistocene Shelf-Edge Deltas and Growth Faulting in the Northeast Gulf of Mexico: The Early Development of Shelf Margin Reservoir Systems

 

Fillon, Richard H.1, Harry H. Roberts2 (1) Earth Studies Group, New Orleans, LA (2) Coastal Studies Institute, Louisiana State University, Baton Rouge, LA

 

Seismically imaged clinoform sets in the northeast Gulf of Mexico define deltas that prograded to the shelf edge during periods of lowered sea level. Two shelf margin deltas, one associated with marine isotope stage 2 (~19 kaBP), and one associated with marine isotope stage 8 (~270 kaBP) are especially well imaged and have been cored by research boreholes. The architecture of this delta complex is calibrated to corrected radiocarbon age, marine isotope stages, biostratigraphic markers, paleoecologic water depth estimates, and sediment properties. The clinoform tops of the younger delta lie at about -90 m water depth, covered only by a thin veneer of transgressive deposits, while the clinoform tops of the older delta lie beneath 185 m of water and 50 m of sediments, downthrown ~145 m to a shelf edge growth fault.

 

Using this high-resolution dataset we are investigating how growth faulting affects the post depositional geometry and sourcing of shelf margin sand bodies, a major and very prolific reservoir type in the northern Gulf of Mexico. While located near the surface these sand bodies are relatively leaky, receiving large volumes of fluids from downdip sources, via linked thin distal turbidite beds. Fortuitously, the stacking relationship of growth faulted shelf-edge deltas places the leaky portions of older deltas beneath thick accumulations of vertically sealing prodeltaic strata related to middle shelf deltas of intermediate age. Further, it appears that the overlying prodeltaic strata are prevented from transmitting fluids laterally updip into coeval, and potentially leaky, middle shelf deltaic facies by displacement on the growth fault.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California