Abstract: Petrology of Smackover Formation (Jurassic): Perry and Stone Counties, Mississippi
Brian D. Wakelyn
The Smackover Formation, penetrated in three wells in Perry and Stone Counties, southeastern Mississippi, is approximately 900 ft (274 m) 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 have been 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 seafloor and wave base. Paleoenvironmental reconstruction of these lithofacies indicates shallow-water marine conditions with major changes in the depositional environments controlled by topography of the basin margin and bathymetric irregularities in the seafloor. The vertical sequence of lithofacies can best be explained as the result of progressive shoaling and basinward progradation of environments.
AAPG Search and Discovery Article #90967©1977 GCAGS and GC Section SEPM 27th Annual Meeting, Austin, Texas