ABSTRACT

Traditional benthic biofacies models for the Gulf of Mexico show a two-dimensional cross section from shelf to abyssal plain divided into 5 to 7 zones based on benthic foraminifer associations. These models are generalized and somewhat oversimplified and are derived from an actualistic-uniformitarian approach. The new proposed models are based on three-dimensional Plio-Pleistocene benthic biofacies maps contoured at calcareous nannofossil and planktic foraminifer last appearance "time" surfaces. Proposed models differ from traditional ones primarily in the following aspects: (1) Tradtional models consider water depth as the primary control on benthic foraminifer biofacies. Theoretically, this is only partially applicable because benthic foraminifer communities are restricted to specific environments. Restricting environmental conditions are a combination of physical (e.g., sediment supply and type, physical consistency of the sea bottom), chemical (e.g., oxygen, concentration of biolimiting chemicals), biological (e.g., competition, food availability), and thermal parameters. Biofacies are an indication of paleoenvironments, not only of water depth. In addition, baleobathymetry of the Gulf of Mexico has been and still is highly complex. The new model shows how benthic biofacies can form islands entirely surrounded by different biofacies in places not considered in traditional models. Some of these islands correlate with paleotopographic highs caused by salt domes. (2) The new model considers the effects of differential sediment supply as being of major importance in determining the type of biofacies. (3) The new model is three-dimensional. Several examples from the Green Canyon area of northern Gulf of Mexico will illustrate new models. Proposed models have important implications for the interpretation of the stratigraphic and structural (salt) evolution of a region.

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