HACKBARTH, CLAUDIA J., Shell Western E & P, Inc., Houston, TX; and ROGER D. SHEW, Shell Development Company, Houston, TX

ABSTRACT: Interpretation of a Mid-Pleistocene Leveed Channel System Using High-Resolution Seismic Data, Cores, and Logs, Viosca Knoll, Northeastern Gulf of Mexico

The "Einstein" turbidite channel/levee system was first mapped from sparker seismic data and a 3-D seismic survey. We then shot 440 line-miles of high-frequency (500 Hz) multifold seismic data and cored and logged three boreholes in order to characterize the Einstein feature as an analog system to several older oil and gas prospects in the region. The channel extends for approximately 40 miles from the paleo-shelf edge to a downdip truncation by DeSoto Canyon. The associated levees are non-symmetrical and over 500 feet thick in places. The updip portion of the deposit occupies a pre-existing slump scar and has a strike width of over five miles. The Mobile/Tombigbee River system and associated small deltas are the probable source of the turbidite deposits, which were carried basinward uring a sea level lowstand.

The five seismic facies and their compositions are: (1) a high-amplitude, low-continuity seismic facies located in the base of the erosional channel and consisting of poorly sorted pebbly mudstones and sands; (2) a moderate-amplitude, upper channel-fill, seismic facies consisting of silty claystone to mudstone, deposited during waning flow and channel abandonment; (3) upper levees exhibiting a high-continuity, low-amplitude, seismic character and consisting of mudstone and claystone couplets that form a subtle thinning and fining upward sequence; (4) a transparent-to-chaotic seismic facies occurs locally along the channel margins, probably representing slumped levee material; (5) a high-amplitude, chaotic seismic facies at the base of the levee in the updip area consisting of sand and mudstone which probably represent early unconfined turbidite flows and slumped slope sediments. The system is bounded by pelagic and hemipelagic claystones.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.