CONTROLS ON LARGE SCALE ARCHITECTURE AND DISTRIBUTION OF CARBONATE FACIES IN RAMP SETTINGS, SMACKOVER FORMATION, GULF OF MEXICO

The Upper Jurassic Smackover formation was deposited on a broad carbonate ramp or shelf along the central and eastern U.S. Gulf Coast region. The lateral and vertical distribution of facies appears heterogeneous at the regional scale, with the northeastern section of the Gulf, in eastern Mississippi, Alabama, and the Florida panhandle dominated by large microbialite mounds in mid-ramp settings developed during sea level transgression, and the western section of the Gulf region, in Texas, Louisiana, Arkansas, and western Mississippi, dominated by prograding, upper-ramp oolitic grainstone shoals deposited during regression. Lower ramp and basinal microlaminated lime mudstones are an important regional source rock that was deposited in both transgressive and regressive condensed units.

Carbonate production type and facies architecture are the result of complex interactions among several space and time dependent variables, including paleobathymetry, water chemistry, sediment influx, and accommodation. These factors affect the nature and rates of carbonate sediment production, and accumulation.

As the Smackover has been extensively studied at the prospect scale through a wealth of well and core data combined with scant seismic imaging, the quantitative evaluation of controls on the regional-scale stratigraphic architecture of carbonate ramp systems can be greatly advanced by the application of stratigraphic forward modeling.

Here we present stratigraphic forward modeling of regional transects for the Smackover. Our preliminary results reveal that a robust microbial factory is required in middle ramp settings of the Smackover to account for the observed extensive progradation. This observation suggests a strong water chemistry control on facies distribution.