ABSTRACT

The Smackover Formation, penetrated in three wells in Perry and Stone Counties, southeastern Mississippi, is approximately 900 feet thick and consists almost entirely of carbonate rocks. It can be divided into a lower carbonate member, which is predominantly mudstone (micrite), and an upper member, which is distinguished by grain supported rocks.

Eight carbonate lithofacies were defined by texture, fabric, and composition. The facies within the lower member are: laminated micrite, micrite, and dolomite. These rocks are inferred to have been deposited as shelf sediments below wave base, in the deeper part of the basin. A few of the thin diagenetically formed dolomite zones within this interval contain asphaltic hydrocarbons and may be economically important in other areas.

The upper member represents a different sedimentologic regime, and consists of five interbedded lithofacies. In ascending order, these are: intraclastic peloid, peloid mixed allochem, oncolite, mixed allochems-sparite, and oolitic peloid facies. The upper member facies indicate an increase in hydraulic energy and probably formed as a consequence of the intersection of a gently sloping sea floor and wave base. Paleoenvironmental reconstruction of these lithofacies indicate shallow-water marine conditions with major changes in the depositional environments controlled by topography of the basin margin and bathymetric irregularities in the sea bottom. The vertical sequence of lithofacies can best be explained by progressive shoaling and basinward progradation of environments.