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Climatic Controls on Reef Development and Distribution: Lessons Learned from Caicos Platform, Southern Bahamas

Jeffrey J. Dravis1 and Previous HitHaroldTop R. Wanless2
1 Dravis Geological Services, Houston, TX
2 University of Miami, Miami, FL

Reef systems on Caicos Platform are strongly controlled by a key climatic element, namely, energetic easterly trade winds. In concert with topography and bathymetry, these winds influence where reefs occur and their level of maturity.

Barrier reefs along the northern margin of Caicos Platform show the highest degree of maturity when facing directly into easterly trade winds. On the platform, isolated and coalesced patch reefs occur up to 40 kilometers inboard from open windward margins because winds deliver oceanic waters and provide agitation. Oolitic sands form in close association with these patch reefs. Where leeward margins swing slightly into the prevailing winds, smaller-scale linear reefs with mature reef flats develop. Otherwise, off-bank sand transport inhibits reef growth on leeward margins.

Several ancient reefal complexes, all developed in paleo-trade wind belts, reflect aspects of these Caicos models. Lower Cretaceous Black Lake Field (156 MMBOIP) in Louisiana and Fairway Field (395 MMBOIP) in East Texas initiated over 50 miles inboard of the Sligo platform margin. Conversion of skeletal sands to oolitic grainstones at Black Lake, and the orientation of grainstone belts at and near Fairway Field, confirm stronger paleo-trade wind influences. In Mexico, the Middle Cretaceous Poza Rica Field (2.7 BBOIP) represents shedding of voluminous amounts of platform-derived grainstones from rudist reefs on an open leeward margin, similar to that noted for Caicos Platform.

Those exploring for subsurface reef plays should factor in wind direction and intensity, since it expands the potential for reef development across many different parts of platforms.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005