Print this pageSequence Stratigraphic Framework of Early Mississippian Mound-Bearing, Ramp Margin Fades, Fort Payne-Warsaw-Salem, Kentucky
KHETANI, AMY B., and J. FRED READ
Early Mississippian ramp carbonates in Kentucky (top of Borden to base of Renfro/St. Louis) provide a well exposed analog of mound reservoirs in the Williston Basin. Outcrop sections and cores show that the succession is a single large scale depositional supersequence (0 to 500 feet thick, 15 m.y. duration). It formed on and in front of the emergent Borden delta, which had up to 300 feet of relief above the adjacent black shale basin. Major facies consists of marine quartz sandstones, rare tidal flat laminites and lagoonal mudstones, high energy ramp margin crinoidal-bryozoan grainstones and local bryozoan and mud mounds, dark gray, cherty, laminated quartz-carbonate silty slope, with depositional dips of 2 to 10 degrees locally, and local channel-form grainstones. The supersequence is composed of approximately 6 depositional sequences (30 to 60 feet thick). The lowest sequence rests on and interfingers with the deeper water shale, and is characterized by low-stand mounding, related to a major sea level fall. Sequences 2 and 3 show marked backstepping. Sequences 4 to 6 show major offlap/shingled progradation of ramp margin grainstone and local mounds onto deeper water slope silts. Sequences show local development of low-stand marine sand units in front of incised canyons on the delta. Rare sands can be traced updip into unconformities. Rare grain stone bodies occur in extreme downdip positions, and may be toe-of-slope carbonate sand bodies, or perhaps low stand buildups.