EVOLUTION OF A LATE JURASSIC CARBONATE EVAPORITE PLATFORM, CONECUH EMBAYMENT, NORTHEASTERN GULF-COAST, USA

Successive time-slice lithofacies maps of the Smackover /Haynesville depositional sequence, constrained by marker beds, an interpreted maximum flooding surface, and interpreted sequence boundaries, show an onlapping and retrograding sequence of lithologies characteristic of a transgressive systems tract (TST). The TST is followed by several prograding sequences characteristic of a highstand systems tract (HST) and stacked shelf margin wedges (SMW). Comparison of stratigraphic cross sections, lithofacies maps, and a "paleotopographic" map of the sub-Smackover transgressive surface shows that the distribution of lithofacies within the TST was strongly controlled by two types of sub-Smackover paleotopographic highs: (1) Norphlet dune fields and (2) eroded basement rock. As the TST became progressively buried during deposition, distribution of lithofacies within the HST and the SMWs was controlled less by these early paleotopographic features and more by (1) differential compaction around shoal-water facies in the TST, (2) early Louann salt movement, (3) basement-related faulting and (4) freshwater influx along the basin rim.