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Caicos Platform Models of Quaternary Carbonate Deposition Controlled by Stronger Easterly Trade Winds - Applications to Petroleum Exploration

Jeffrey J. Dravis1 and Previous HitHaroldTop R. Wanless2
1Dravis Interests, Inc., Houston, TX
2Geological Sciences, University of Miami, Coral Gables, FL

Strong easterly trade winds on Caicos Platform, southeast Bahamas, promote widespread development of Holocene shallow-marine, platform-interior oolitic grainstones and isolated patch reefs. Sand bodies assume wind-parallel or wind-perpendicular orientations depending on preexisting topography and water depth; shoreline oolitic grainstones are common. Isolated patch reefs develop up to 40 kilometers inboard of open platform margins, and coalesce in seaward directions. Reefs and oolitic sands coexist because of wind-wave agitation. Trade winds also enhance the maturity of open-ocean, platform margin reefs. Isolated, kilometer-scale reef complexes exist along leeward platform margins when protected from off-bank sediment stress, with back-reef debris converted to oolite by wind-wave agitation. Grainstones are shed off leeward margins and may be potential reservoirs. Most of these Holocene relationships are reflected in outcropping and cored Late Pleistocene sequences on Caicos Platform, where a leeward margin barrier reef complex thrived coevally with oolitic grainstones. On Caicos Platform, reservoir potential exists over much of the platform, in contrast to classical northern Bahamian models, where the potential is confined to margins.

Carbonate sedimentation driven by stronger easterly paleotrade winds, influenced by preexisting topography, creates potential for hydrocarbon plays in settings historically considered low-energy and nonprospective. The Caicos models now explain why Paleozoic and Mesozoic reef and/or oolitic reservoirs occur well inboard of platform margins (James Limestone Fairway Field in East Texas, for example). Observations from Caicos Platform also explain why ancient leeward margin reefs developed and shed substantial quantities of carbonate sand from their margins (Golden Lane/Poza Rica Fields in Mexico).


AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas