ROLE OF STORMS, OCEANIC SWELLS, PREVAILING ENERGY, AND SEA LEVEL IN DEFINING SEDIMENT BODY GEOMETRY, COMPOSITION, AND TEXTURE ON CAICOS PLATFORM, TURKS AND CAICOS ISLANDS (Invited Presentation)

Pleistocene and Holocene carbonate sediment bodies on Caicos Platform are created by a combination of major storm events and prevailing energy conditions. Major long-period oceanic swell events together with hurricane surges have built pronounced coastal beach ridges on exposed north-facing margins and create elongate reef-rubble lobes within back-reef lagoons. Major hurricane surges have defined the location and geometry of Holocene platform-interior sand shoals, an elongate leeward-margin shallow subtidal sand shoal, fanning longitudinal sand ridges extending in from leeward margins, and coarse skeletal gravels layers in and towards the base of the platform-interior grainstone sequence. Hurricane events of all scales also have built extensive south-facing tidal flats and defined the depositional texture and fabric of accumulating Callianassabioturbated platform-interior grainstones and packstones.

Within the framework of pre-existing and storm-generated topography/bathymetry, prevailing brisk easterly Trade Winds and prevailing oceanic swells provide agitation for growth and expansion of ooid grainstone shoals and beach strand plains on the platform interior and margins respectively. Prevailing conditions also define the distribution and productivity of coral, seagrass and other benthic communities.

Although tidal currents provide important water renewal and create local sediment bodies, it is hurricanes, large oceanic swell events and prevailing wind-wave and swell conditions that have defined sediment body forms, features, and textural components of Caicos Platform. Twenty to forty winter cold fronts pass through Caicos each year followed by brisk northerly winds. Their primary contribution is to leave the south flanks of islands leeward so that sandy strand plains and peri-tidal flats are not eroded.

Extensive shallowing of the platform margin and interior, progradation of coastal sand strand plains, and local evaporite sedimentation is the result of the gradual rate of sea level rise over the past 2,500 years, the warm tropical setting, good supersaturation of ocean water in this low rainfall setting, and good water renewal across the platform because the eastern margin is sufficiently open to the push from the Easterly Trade Winds across the platform.