The Permian(?) of the Central Appalachian Basin
Characteristics of Dunkard Group strata are indicative of the following: 1) tectonic control on basin configuration, 2) restricted chemical weathering and a long-term dry subhumid paleoclimate, 3) depositional systems decoupled from sea level, 4) lake levels and water chemistry controlled by cyclic variations in rainfall, 5) decreasing occurrence of coal and increasing numbers of calcic paleosols up-section indicative of progressive long-term drying, 6) base level and sedimentary cycles driven solely by climate.
Stratigraphic patterns within the Dunkard Group appear to be consistent with the better understood Pennsylvanian climate cycles. Tectonic uplift and/or low sea levels induced by Permian ice volume decoupled water levels within the basin from eustatic sea level fluctuations. Thus, dry periods associated with high stands and reduced ice volume, as in the Pennsylvanian, resulted in dry subhumid climates and calci paleo-Vertisols in the Dunkard when the basin dried and lakes disappeared. In contrast, pluvial periods associated with increases in ice volume resulted in lacustrine conditions. Rain shadow effects, induced by the rising ancestral Appalachian Mountains in the Early Permian(?), resulted in progressive climate drying in the Appalachian basin.