ABSTRACT

In eastern Mississippi, the upper member of the Smackover Formation and the lower member of the Buckner Formation represent a major regression of the Jurassic shoreline. The upper Smackover carbonate strata were deposited under shallow open-marine conditions, and the vertical sequence of lithofacies indicates progressive shoaling and basinward progradation of environments. The overlying lower member of the Buckner Formation consists of thick units of nodular anhydrite with interbedded dolomite, and is inferred to be the supratidal equivalent of the upper Smackover marine carbonates.

The principal reservoir rocks in the Smackover Formation are oolitic grainstones with primary depositional interparticle porosity. The high energy oolitic deposits formed by tidal action on shoals which were aligned roughly parallel to the coastline. An understanding of the structural and sedimentologic factors which controlled the location of the oolite shoals is critical to exploration in adjacent areas. The oolitic deposits appear to have built up as a consequence of the intersection of wave base and a gently sloping sea floor as there is no indication of a controlling shelf break. There is strong evidence of penecontemporaneous growth of salt-cored anticlines during deposition of the upper Smackover sediments, but these structures are not thought to be the principal factor in controlling the location of the high energy shoals.