Sequence Stratigraphy of the Smackover Formation in the Northern Half of the Manila Embayment, Southwestern Alabama

Abstract

ABSTRACT The Smackover Formation in the northern half of the Manila Embayment, southwestern Alabama, ranges from 100 to 540 ft (30 to 165 m) thick and encompasses two genetic packages of facies. These genetic packages developed within a single cycle of relative sea-level change during the Late Jurassic (specifically late early Oxfordian to early Kimmeridgian) and comprise parts of a single depositional sequence. The base of the lower genetic package is the sharp contact between terrestrial clastic facies of the underlying Norphlet Formation and shelf carbonate facies in the Smackover. The lower Smackover genetic package (=transgressive systems tract) includes high-energy grainstones, shelf packstones and wackestones, and shelf-margin and patch-reef algal boundstones. The contact between the upper and lower genetic packages is a maximum-flooding surface delineated by a sharp facies change to a set of ramp carbonate facies. The upper genetic package (=prograding highstand systems tract) includes, in stratigraphic order, ramp packstones and wackestones, lagoon al wackestones and mudstones, and high-energy grainstone and clastic tempestite facies. The top of the upper genetic package is the sharp transition to anhydritic sabkha facies in the overlying Buckner Anhydrite Member of the Haynesville Formation.