Geological Studies on the Great Bahama Bank
Southeast of Florida, outliers of the continental shelf form submerged limestone plains covering nearly 60,000 square miles. These are the Bahamian platforms which, for the most part, are covered by only a few feet of clear sea water. Conditions of sedimentation here must closely resemble those of the limestone shelf seas of the Paleozoic and Mesozoic. Nearly three miles of carbonate deposits have been laid down in the Bahamas since the early part of the Cretaceous period, indicating that there has been a high sustained rate of deposition. Doubtless this has contributed to the persistent subsidence of the area. This area is one of the most instructive in the world for studies of the origins of marine limestones. Calcium carbonate sediments virtually free from terrigenous materials are being formed in easily accessible sites and under a variety of conditions. Oolite and aragonite ooze are being formed on a scale probably unequaled elsewhere. Abundant sediments are also being formed by accumulation of skeletal remains of calcareous algae and invertebrates. Vigorous, newly established coral reefs dominate the scene in places and provide valuable clues about the origins of these structures. Although the region provides many of the conditions supposed by some to be favorable for the formation of primary dolomite, this rock is being formed here only at considerable depth, and the circumstances suggest only a secondary origin. Because of shallowness and clarity of the waters over the platforms, this area is unexcelled for direct visual examination of the sea floor by shallow diving and for documentation on aerial and submarine photographs.
This work was undertaken as an introduction to the marine geology and environments of the Great Bahama Bank, and emphasis has been laid on those relationships and processes which might be of value to the historical geologist intent on the general problems of ecological interpretations of fossils and sedimentary rocks. Particular attention was given to the celebrated Andros reefs and lagoon, and about 1000 square miles of this part of the area was mapped and studied at some length. Regional data are presented with respect to conditions under which the various calcareous sediments are being formed.
Figures & Tables
Regional Aspects of Carbonate Deposition
It was customary during many recent years for the Research Committee of the Society of Economic Paleontologists and Mineralogists (SEPM) to sponsor research symposia on special topics at the annual meetings. In addition to the regular Research Committee Symposium presented in 1954 at the St. Louis meeting, a special symposium was also held on Regional Aspects of Carbonate Deposition. This carbonate symposium was organized in response to a special request by H. N. Fisk, who was president of SEPM at that time. During the symposium, special question cards were distributed to the audience and collected after each paper. These questions, together with questions and comments from the floor, formed the basis for the Panel Discussion which followed the symposium. The panel consisted of Moore, Ginsburg, Rodgers, and Walter Bucher, who presented the paper on the Bahamas in the absence of Newell. In addition, two authorities in the field of carbonate deposition, L. V. Illing and R. W. Fairbridge, were invited to join the panel and participate in the discussion.