A seismic stratigraphic analysis of multifold reflection data from the deep water part of southeastern

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Gulf of Mexico basin (located between the Campeche Escarpment and the Florida Escarpment and north of Cuba) provides the basis for an interpretation of the geologic history of the area.

A prominent unconformity of middle Cretaceous age (middle Cenomanian, 97 m.y.) separates the sedimentary section into two major depositional sequences. The pre-middle Cretaceous sequence consists of about 2 to 3 km of Middle Jurassic through middle Cretaceous sedimentary rocks unconformably overlying rifted, attenuated continental crust containing inferred Triassic-Lower Jurassic rift basins. This major sequence is further subdivided into several depositional sequences defined by unconformities tentatively age-dated by correlation with the global sea-level chart. Seismic facies analysis suggests that this major sequence represents a gradation upward from nonmarine to shallow marine and then to deeper marine rocks, the offbank equivalent of the Lower Cretaceous carbonate sections formi g the adjacent Florida and Campeche Banks. Overlying the middle Cretaceous unconformity is a relatively thin sequence consisting mainly of pelagic and hemipelagic sediments mixed with carbonate debris eroded from adjacent banks (drilled in Deep Sea Drilling Project 97).

Two DSDP core holes will be drilled in this area in early 1981. Together, these two holes will sample a continuous section into the Jurassic, providing a valuable reference for extrapolating seismic data and unraveling the evolution of the southeastern gulf. In addition, these holes will test the principles of seismic stratigraphy as a tool for predicting depositional setting and age of sedimentary sequences ahead of the drill and will provide data for dating and understanding the origin of deep-sea unconformities.

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