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THE STRUCTURE OF THE JAMAICAN REEF COMMUNITIES. GEOLOGICAL ASPECTS
NEW YORK ZOOLOGICAL SOCIETY BROOKLYN
Bathymetric surveys were made on the north coast of Jamaica to determine major geomorphic characteristics of the inshore platform and its relation to the modern reef. A portable recording fathometer, mounted in a small boat, was used. The fathograms show that the modern reef framework on that coast averages about 15 to 20 ft., but can reach a maximum thickness of about 35 feet. These reefs rest unconformably on the antecedent platform, and are believed to be less than 7000 years old. A particularly interesting feature, located first by echo-sounding, is the sill-like elevation found at the edge of the 90 ft. level. Investigations by diving have shown that this rim is made up of a series of low rock mounds between 5 and 25 ft. high which appear to be the remnants of an old eroded coral reef. Several drowned Pleistocene reefs were located by echo sounding and investigated by diving. The relationship of the old reefs suggests that the reef building in some localities was not completely interrupted during the rapid Pleistocene rise in sea level. Author