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Four shallow cores taken in Hogsty Reef Atoll, southeast Bahamas, reached the early Pleistocene at a depth of 30 m (98 ft) (below sea level). Unlike other banks of the Bahamas, Hogsty Reef Limestone consists of carbonate grains and cements that have maintained their original mineralogy. Five types of cements were found in the Pleistocene limestones of Hogsty Reef: (1) micritic magnesian calcite which predominates in all four cores; (2) bladed magnesian calcite which occurs in several thin (< 1 m) intervals, where it is associated with (3) fibrous aragonite, which also is found in Holocene cemented crust; (4) blocky low magnesian calcite, which occurs in several thin intervals underlying subaerial exposure horizons; and (5) an unusual type of blocky magnesian calcite ce ent, which consists of clear anhedral crystals, 25 to 100 microns in size, which contain less than 10% MgCO3. This cement is found together with bladed magnesian calcite and aragonite.
Preservations of the cements and grains original mineralogy may be attributed to a minor influence of fresh water resulting from the semi-arid climate of the southeastern Bahamas and the unlikely formation of a permanent freshwater lens during periods of emergence.
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