Controls on Passive Margin Stratigraphy: Seismostratigraphic and Basin Modeling Evaluation of Georges Bank Basin

SHUSTER, MARK W., and DAVID T. LAWRENCE, Shell Development Company, Houston, TX

Seismostratigraphic interpretations constrained by well data were coupled with 2-D stratigraphic forward and thermo-subsidence models to predict stratigraphy and to better understand the roles of tectonics, eustasy, and sedimentation in controlling sequence development in the Georges Bank basin. Seventeen late Middle Jurassic-Cretaceous depositional sequences and 13 types of seismically defined depositional facies were recognized and correlated within the basin. Subsidence histories constrained by seismic correlations, a modified Exxon sea-level curve, and iteratively determined sediment infill parameters were the primary input for 2-D stratigraphic modeling analyses of three

dip-oriented seismic lines. The sea-level curve was the same as that used in earlier modeling studies of Baltimore Canyon. The integrated seismostratigraphic interpretations and stratigraphic modeling results predict similar aggradational Jurassic-Cretaceous mixed clastic/carbonate platforms. However, the individual depositional sequences vary significantly in duration, geometry, facies distribution, and thickness from line to line. Because the same eustatic and nearly the same sedimentation parameters were used as input, the differences in the stratigraphic responses must be largely the result of subsidence and uplift and initial topographic control. The extent and rate of shelf margin progradation can be attributed to focused infilling associated with an embayment or possible salt o basement tectonism. Relative sea-level changes controlled gross reciprocal clastic/carbonate depositional patterns. Subtle differences in bathymetry are caused by compaction and clastic poisoning. A series of time sequential cutaway block diagrams and facies maps will be shown illustrating the computer-modeled and seismically interpreted Jurassic-Cretaceous sequence stratigraphic evolution of the basin. The Georges Bank stratigraphic evolution will be compared to that of Baltimore Canyon. Even though the two basins had differing subsidence and sedimentation histories, the observed facies distribution and stratal geometries could be simulated with a single sea-level curve.

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