ABSTRACT: A New Look at the Distribution and Geochemistry of Surface Sediments from the Bahamas
Since the pioneering work of Illing, Ginsburg, Newell, and Purdy, the Great Bahama Bank (GBB) and its surface sediments has served as an analogue for the study of ancient carbonate platforms. These studies have formed basis for much of the current understanding of facies distribution on carbonate platforms. As these studies were originally carried out without the benefit of modern navigation and many types of sedimentary and geochemical analyses were not conducted on the original samples, we have initiated a five year study to re-characterize the surface sediments of GBB, in terms of the grain types and inorganic and organic characteristics. Our sampling protocol utilizes a inter-sample spacing of 10 km and involves collection of sediment samples with minimal loss of the mud fraction. The new facies maps reveal significant variations in sedimentary characteristics, not recognized in the original studies. In particular the distribution of facies are not directly related to proximity to the platform margin or Andros Island. Such variations also suggest some control on the facies distribution may be exerted by an underlying topography which trends towards the north-western portion of GBB. Sediment types appear to be related to geochemical differences, with muddier facies containing higher concentrations of high-Mg calcite (HMC). Such controls have been recognized in other carbonate lagoonal environments such as Belize and Mayotte (Comoro Islands). When finished, the new data set will enable more realistic interpretations of facies and geochemical patterns in ancient carbonate platforms.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.