SPATIAL EVOLUTION OF A PALEO-LANDSCAPE ACROSS THE MISSISSIPPIAN-PENNSYLVANIAN BOUNDARY: FACIES ANALYSIS OF THE MAUCH CHUNK AND POTTSVILLE FORMATIONS, EAST CENTRAL PENNSYLVANIA

The Mississippian-Pennsylvanian transition is a period of changing climate in Earth’s history. This transition from predominantly arid in the late Mississippian to semi-humid in the early Pennsylvanian is reflected in the sediments of the late Mississippian Mauch Chunk and early Pennsylvanian Pottsville Formations. The Mauch Chunk Formation consists of interbedded conglomeratic sandstones and mudstones. Many of these mudstones are paleosols with features similar to modern Aridisols and Vertisols. In contrast, the Pottsville Formation consists of very coarse-grained conglomerates, cross bedded sandstones, shales and coal. Conglomerate clast diameters range from 1-17 cm, indicating a shift from relatively low to high energy depositional environments across the Mississippian-Pennsylvanian boundary. This study analyzed these formations at two East-Central Pennsylvania sites with 600+ m of exposed stratigraphic section. These sites were chosen for their exposure as well as their relative position to one another on the paleo-landscape. One site was proximal to the sediment source and the other was distally located to the west of the source area. The objective of this study was to evaluate the spatial evolution of this landscape across the Mississippian-Pennsylvanian boundary. Variability in grain size are evaluated to characterize the energy of each of the depositional environments between the study sites. Paleoflow measurements are taken at both study sites and plotted on rose diagrams to assess potential changes in fluvial form. Evaluating lateral changes in lithofacies can provide possible insight on the proximal to distal relationship of this landscape as climate changed across the Mississippian-Pennsylvanian boundary.