Recent Calcium Carbonate Facies of the Great Bahama Bank. 1. Petrography and Reaction Groups

The calcium carbonate sediments mantling the Great Bahama Bank have attracted the attention of a number of geologists seeking answers to problems of limestone genesis. This region has been the subject of several carbonate deposition studies, but many problems remain concerning the distribution, origin, and diagenesis of the carbonate grain types. The present study was initiated to quantitatively delineate calcium carbonate facies on the northwestern part of the Great Bahama Bank and to delineate the factors contributing to the origin and distribution of the various sedimentary constituents. Representative subsamples of 218 sediment samples collected on the northwestern part of the bank were impregnated in a polyester resin and then thin-sectioned. A point-count analysis of each thin section was made to determine the constituent composition of the sample fraction coarser than 1/8 mm. The weight percentage of the fraction smaller than 1/8 mm. was used as a measure of grain size. Statistical analysis of the accumulated data with a high speed digital computer resulted in the delineation of reaction groups that are defined as groups of sedimentary constituents that tend to react similarly to environmental changes.