Paleoenvironmental clues archived in non-marine Pennsylvanian-lower Permian limestones of the Central Appalachian Basin, USA

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 packstones/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 103 to 104 yr-scale, which were likely climate-driven.