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Nonmarine limestones are a key component of the upper Middle Pennsylvanian through lower Permian succession in the Appalachian Basin. Previous interpretations of their environments of deposition range from brackish coastal mudflats to hydrologically open freshwater lake complexes with peat-forming vegetated marshes to semi-closed or closed, possibly saline, shallow lakes developed on a distal alluvial plain.

Ostracode wackestones/packstones, some exhibiting laminations, and with fish debris, articulated ostracode shells and phosphatic clasts define the lower portions of limestone beds or benches, passing upward into ostracode-peloidal wackestones/packstones and intraclastic-skeletal-peloidal pacicstones/grainstones. Desiccation features and rooting structures, which are developed in the upper portions of the limestones, record subaerial exposure, pedogenic alteration and desiccation. Pseudomicrokarst and caliche-like vadose and early diagenetic phreatic cements suggest a seasonally dry subhumid to semi-arid regional climate. Many of the sedimentologic and diagenetic features of the limestones are characteristic of palustrine carbonates, which coupled with their stratigraphic relation to paleo-Vertisols, siliciclastics, and coals, indicate that they formed in broad seasonal wetland-pond complexes that developed on distal regions of a low-gradient, distal alluvial plain under seasonally dry subhumid to semi-arid climates. Integration of Sr isotopic compositions of shark teeth with previously published stable isotope compositions of the limestones suggests that these purely continental environments were hydrologically semi-closed to closed systems. Repeated stacking of these features at the bed- to limestone bench-scale defines repeated shallowing upward, drying cycles at the 10(3) to 10(4) yr-scale, which were likely climate-driven. Published by Elsevier B.V.