The discovery of the supergiant oil fields of the Caspian region has focused attention on eustatic, tectonic, and climatic controls on Lower Carboniferous facies. This paper documents the development of a highly complex, mixed carbonate-siliciclastic ramp succession of the Lower Mississippian (Upper Osagean-Lower Meramecian) Fort Payne-Salem interval, Kentucky, that formed peripheral to an abandoned delta system (Borden Formation) following drowning of the paleoshelf, during a time of arid climate and tectonic quiescence. The antecedent Borden deltaic-marine paleoshelf stood 100 m above the starved basin plain to the southwest and had marginal slopes of less than 0.5°.
The succession is a supersequence (0 to 150 m thick, approximately 5 to 10 My duration) composed of two Upper Osagean (Fort Payne) and two Lower Meramecian (Warsaw-Salem) depositional sequences which correlate with the global sea-level cycles of Ross and Ross (1988). The supersequence lowstand systems tract on the basin floor consists of the lower part of a unit of green shale-and-mounds. Mound growth appears to have continued during supersequence transgression, culminating in some mounds up to 60 m thick. On the Borden paleoshelf, the supersequence transgressive systems tract is a condensed glauconite horizon(s). The supersequence highstand tract consists of marine quartz sandstone and shale, peritidal carbonates, high-energy crinoidal-bryozoan grainstone banks, and deep ramp and slope siliceous calcisiltite.
Third-order sequences have local lowstand-transgressive sand bodies; those in sequence 2 are clinoformed strike sand lobes up to 50 m thick, while those in the younger sequences are discontinuous sheets-dip oriented lobes. The siliciclastic units appear to be associated with a paleodrainage system off the Borden paleoshelf. In Upper Osagean sequences 1 and 2, third-order highstand systems tracts are aggradational on the paleoshelf and prograded to the southwest as a series of clinoforms into the starved basin. Lower Meramecian sequences 3 and 4 highstand systems tracts are relatively layer-cake, reflecting loss of accommodation during Late Osagean basin filling, and they prograded more to the west into the subsiding Reelfoot Graben-Illinois Basin. The extremely complex facies relations reflect the interaction of the antecedent shelf-slope-basin topography, the mixed carbonate and siliciclastic systems, mounded basin-floor topography, the highly channeled margin morphology, eustasy, and relatively stable tectonics.