Abstract: Influence of Platform-Derived Sediment on Facies, Diagenesis, and Deformation in Slope and Basinal Deposits, Tongue of The Ocean, Bahamas

Wolfgang Schlager, R. N. Ginsburg

Narrow and elongate, the Tongue of The Ocean (TOTO) is a modern intraplatform trough resembling many ancient troughs. Because the steep slopes of TOTO are capped by shallow platform with high rates of sediment production, considerable platform sediment is delivered to the slopes and basin floor.

Carbonate sand from thick, unstable accumulations on the platform rim funnels down the steep slopes 1,200 m to the basin where it forms an apron of coarse-grained, thick beds at the toe of slope and thin, graded beds basinwide. Carbonate mud, aragonite, and magnesian calcite, winnowed from the platform, augment the rain of pelagic carbonate material giving high rates of deposition on the slopes and basin floor. These more soluble carbonate deposits help promote cliffs 10 m high of late Pleistocene chalks.

High rates of deposition in TOTO may explain the small-scale but extensive deformation of basinal sediments. Swells and swales on the seafloor, 4 to 10 km long and 3 to 15 m high, appear in seismic profiles as low-amplitude folds. Faults, a few meters high, downthrown basinward, are common near the toe of the slope. These faults and folds resemble the high rates of deposition on the periphery of TOTO.

These examples of the interconnections between sediment from the platform and the facies, diagenesis, and deformation of slope and basin deposits may prove useful in developing models of platform margins with predictive value.

AAPG Search and Discovery Article #90961©1978 AAPG Annual Convention and Exhibition, Oklahoma City, Oklahoma