Mapping Benthic Biofacies at Biostratigraphic Tops, an Alternative Method to Evaluate Sediment Delivery: Examples from Northern Gulf of Mexico

Tomas Villamil, Claudia Arango, Paul Weimer, Mark Rowan, and Art Waterman

Traditional mapping of benthic biofacies considers average biofacies between biostratigraphic tops. This averaging causes biofacies boundaries to be diffuse, eliminating local bathymetric anomalies and anomalies of restricted duration. We have developed an integrated technique that consists of mapping biofacies at biostratigraphic tops. This new method preserves anomalies and shows well-defined boundaries which are generally more sinuous and variable than the ones determined by traditional methods. Results of this method resemble present-day, salt-influenced bathymetry.

We have interpreted benthic biofacies at approximately 26 levels of the Plio-Pleistocene of Green Canyon area, northern Gulf of Mexico using data from 180 exploration wells. Our analyses define a high-resolution interpretation of changing paleoenvironments at Villamil ^approx 0.2 Ma intervals. Most of the study area consists of bathyal environments. Extinction data were based on planktic taxa. Paleoenvironments were primarily affected by changes in sediment type and supply associated with the location of shelf depocenters, relative sea level oscillations, and the position/evolution of salt highs or minibasins. High rates of sediment input combined with relative sea level drop forced biofacies basinward. This basinward shift in biofacies happened more dramatically in regions of active ediment supply. Transgression and relative sea level rise caused biofacies to shift landward because of sediment trapping in nearshore regions. This technique allows increased biofacies resolution, and enhanced accuracy in paleoenviromental interpretations that best resemble geologic conditions at times of deposition.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California