Shallow-Water Limestones from Slope off Grand Cayman Island

Abstract

Limestones of Oligocene age obtained from a submersible at two sites about 3,000 m deep on the Oriente Slope and from two shallow drill holes on nearby Grand Cayman Island were deposited in shallow marine waters. All samples contain calcareous algae and shallow-water foraminifera, but no deep-water remains were found. The limestone on the slope was lithified in fresh water, according to its petrography and stable isotopes. A third dive encountered massive beds presumed to be outcrops of limestone that dip southward down the slope. We conclude that the region began to subside along a hinge line parallel to the Oriente Slope during Oligocene time and soon became too deep to generate a shallow-water carbonate deposit. This subsidence was associated with plate movements along the Cayman Trough.