Abstract

Hurricane-generated, thinly bedded grainstones are the dominant style of stratification on the carbonate tidal-flat complex on Caicos Platform, British West Indies. This is in dramatic contrast to the winter-storm-generated millimeter-thick laminae which dominate stratification on the northwest 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 18 November 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 layer of fine to very fine peloidal grainstone 0.5-2 cm in thickness across significant portions of the extremely broad, low-relief shore and channel levees and the inland algal marsh. These storm layers are interbedded with organic-rich layers which represent prolonged periods of growth of Scytonema algal mat between hurricanes. Recognition that centimeter-thick grainstone layers dominate entire tidal-flat complexes necessitates both a thorough modification of criteria for defining ancient carbonate tidal-flat deposits and a reevaluation of supposedly subtidal, thinly bedded limestones.

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