PRELIMINARY PETROGRAPHIC AND CATHODOLUMINESCENCE STUDY OF SAN SALVADOR, BAHAMAS STRATIGRAPHY

Lithologic samples were taken from seven locations on San Salvador, Bahamas in order to analyze the constituent grains from six stratigraphic units and to investigate the feasibility of using cathodoluminescence in determining cement histories. Both strategies are used to determine the possibility of defining another Grotto Beach unit, the Dixon Hill, creating a more accurate and detailed stratigraphy of San Salvador.

Petrographic samples from six of the localities are fine- to medium-grained ooid grainstones with varying amounts of bioclastic grains and peloids. One unit collected from near the mouth of the Dixon Hill Lighthouse Cave contains coarse grainstone composed primarily of marine red algae fragments and whole foraminifera. We postulate that this unit formed as sea level fell following the MIS 5e highstand of sea level that is responsible for the development of the Cockburn Town reef facies. This 5e marine incursion onto San Salvador likely created shallow, normal marine environments that supplied the abundant biotic clasts present in this coarse-grained facies during the sea-level fall. This coarser unit may help to identify an additional lithologic boundary, which may define an additional member. Future research will establish if this boundary is regionally extensive.

Preliminary cathodoluminescence on the youngest and the oldest samples, Hanna Bay Member and Owls Hole Formation, respectively, provides internal variability in Mg content and more detailed ooid structure than what petrographic studies show but details of cement history are not illuminated.