Hurricane-Dominated Carbonate Tidal Flats, Caicos Platform, British West Indies

Harold R. Wanless, Kenneth M. Tyrrell, Lenore P. Tedesco

Hurricane-generated, thinly bedded grainstones are the dominant style of stratification throughout the carbonate tidal flat complex on Caicos Platform, BWI. This is in dramatic contrast to the winter storm-generated, millimeter laminae which dominate stratification on the Andros tidal flats and have become the general criteria for recognizing ancient carbonate tidal flat sequences.

Hurricane Kate, which passed directly across the Caicos tidal flats on November 18, 1985, provided an opportunity both to document the character and distribution of a specific storm sediment layer and to evaluate the role of hurricanes in molding the geometry of the tidal flat system.

Though moderate in strength and producing only incomplete flooding, Hurricane Kate deposited a 0.5-2-cm thick layer of fine peloidal grainstone across significant portions of the extremely broad low-relief shore and channel levees and minor sections of the sequence beneath both the channel levees and the inland algal marsh. These storm layers are interbedded with organic-rich layers which represent prolonged periods of Scytonema algal mat growth between hurricanes.

Recognition that centimeter-thick grainstone layers dominate entire tidal flat complexes necessitates both a thorough modification of criteria for defining ancient tidal flat deposits and a reevaluation of supposedly subtidal thinly bedded limestones.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.