Latest Quaternary Outer Shelf and Slope Deposits, Northern Gulf of Mexico, USA: Industry Research Consortium

WINN, R. D., JR., Marathon Oil Co., Littleton, CO, et al.

A consortium of oil companies is undertaking a multiyear shallow coring and high-resolution seismic investigation of the outer shelf-slope deposits of the northern Gulf of Mexico. The program's objective is to reconstruct the depositional, seismic stratigraphic, biostratigraphic, isotopic, and organic geochemical record of the latest Quaternary of a portion of the Gulf margin. Results will serve as an analog to deeper hydrocarbon reservoirs and to help in understanding sedimentation with glacial-interglacial sea-level changes. Nearly continuous cores up to 850 ft long from Main Pass Blocks 303, 242, 288 and Viosca Knoll Block 774 are being described and analyzed. Main Pass 303 core samples Holocene to Oxygen Isotope Stage 6 deposits and as old or older strata are expected to have been penetrated in the other boreholes. Three or four sea level cycles are represented. Seismic acquisition is planned for late 1990.

The outer shelf and slope of the northern Gulf is an area of active growth faulting, high sedimentation rate, diapirism, and slumping. Recent work, including this study, shows that near-surface stratigraphy consists of coarse clastics alternating with carbonate-rich mud. Sands and gravels are inferred to have been deposited mostly during lowstands and rising sea level in deltas and valley-fill systems. Delta clinoforms on high-resolution seismic may represent shelf-margin wedges, prograding wedges, or highstand systems tracts. Highstand deposits are characterized largely by thin, continuous intervals of bioturbated muds containing abundant diagenetic carbonate and pyrite. Precise dating and correlation of outer shelf-upper slope facies to magnitude and direction of sea level change is intended during the project.

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