Stratigraphy and structure of Northeast Providence Channel, Bahamas

A comprehensive, continuous seismic-reflection-profile survey of the Northeast Providence Channel, Bahamas, was conducted. Seismic data were integrated with Deep Sea Drilling Project Site 98 data, piston cores, and rock dredge samples to facilitate stratigraphic correlations. Bottom samples obtained were all deep-water chalks of varied degrees of induration ranging in age from Late Cretaceous (early Maestrichtian) to Pleistocene-Holocene. Results of this study reveal four major stratigraphic units within the Northeast Providence Channel: (1) a middle Eocene to Holocene soft, deep-water chalk layer; (2) an early to middle Eocene siliceous, cherty, soft, deep-water chalk layer; (3) a hard, well-indurated deep-water chalk layer at least as old as Late Cretaceous-Paleocene; a lower layer which has not been sampled and is known only from the seismic profiles. These strata were deposited in a preexisting deep-water trough of pre-Late Cretaceous (late Santonian) age The Northeast Providence Channel appears to be controlled structurally by normal faults along its bank margins that may have been active sporadically since the inception of incipient faults 180 to 200 m.y. ago as a consequence of the rifting of North America and Africa. Cenozoic tectonic disturbances may have resulted in additional relief of parts of the Northeast Providence Channel. The bottom topography of the Northeast Providence Channel has undergone extensive modification by Pleistocene submarine erosion probably controlled by fluctuations of sea level during the Pleistocene. The origin of this erosion is uncertain, but may have been physical (turbidity currents) and/or chemical (carbonate dissolution). Constructional processes, which were controlled sedimentologically, biologically, hydrologically, and structurally, also appear to have been active in this channel. Such constructional processes have resulted in the buildup of deep-canyon flanks and the lateral growth of parts of the deep-bank margin.