Abstract

Sequence stratigraphic interpretations of carbonate platform margins are based to a large degree upon concepts of variable timing and nature of deposition relative to fluctuations in sea level. Quaternary platform margins in the Bahamas provide an exceptional opportunity to calibrate the sedimentary record because of the well-constrained nature of sea-level history during this period. Recent studies have shown that the steep (35-45°) marginal slopes surrounding the Bahama Platform consist of laterally heterogeneous lenses of coarse-grained skeletal material that were deposited during the transgressive phase of the latest sea level rise. The high initial porosity and permeability of some of the foreslope deposits, however, was rapidly occluded by precipitation of marine, pore-filling botryoidal aragonite and Mg-calcite cements. Precipitation of these cements has been shown to occur within a few hundred years of deposition, and may affect further diagenetic modification of these deposits. The sedimentary fabric, geometry, and scale documented in the lateral heterogeneity of foreslope deposits in the Bahamas, coupled with localized rapid occlusion of primary porosity and permeability, are both significant findings for development of hydrocarbon reservoirs in these types of deposits, as the reservoirs may be characterized by discontinuous flow units of high porosity and permeability separated by low permeability barriers to flow.