Paleosol Stratigraphy of the Eskridge Formation; Early Permian Pedogenesis and Climate in Southeastern Nebraska

Abstract

ABSTRACT At least five Aridisol- and Vertisol-like paleosols are developed within the Eskridge Formation (Lower Permian) in Richardson County, Nebraska; these soils are recognized by their prominent soil structure (peds, nodules and filled cracks), micromorphology (oriented clay fabrics, and iron cutans), and well-developed carbonate-enriched horizons. Eskridge paleosols represent significant decreases or cessations in terrestrial sedimentation during long-term subaerial exposure; direct evidence for drowning of three out of the five paleosols (by subsequent marine transgressions) indicates strong marine influence on the duration of pedogenesis. Stratigraphic fluctuations in the 13C and 18O values of Eskridge pedogenic micrites are potentially compatible with climatic fluctuations between wetter and drier conditions during the Permian, based on comparisons with isotope values from Cenozoic paleosols. Occurrence of fossil plants and coals, along with evaporites, as well as the different paleosol types, tends to support an interpretation of varying climate. Recognition of paleosols within the Eskridge improves the understanding of cyclic sedimentation and sea level change by recording several episodes of low terrestrial sedimentation and geomorphic stability; these episodes probably correspond to peak marine regressions.