SEDIMENTOLOGY AND PALEO-WEATHERING OF THE DEVONIAN-MISSISSIPPIAN CATSKILL, SPECHTY KOPF, AND POCONO FORMATIONS, APPALACHIAN BASIN, PENNSYLVANIA

The Late Paleozoic Ice Age (LPIA; late Devonian – late Permian) represents a relevant interval in Earth’s history because it serves as a paleoclimate analog for Earth’s current icehouse (low CO2, widespread glaciers). It was the last icehouse to greenhouse transition in Earth’s history and the only previous icehouse to occur on a fully vegetated Earth. Glaciation on the southern supercontinent of Gondwana is well documented, but alpine glaciation near the equator, on the continent of Euramerica, has been debated. The purpose of this study is to investigate late Devonian / early Mississippian sediments in the Appalachian Basin, Pennsylvania and assess their potential for glaciogenic deposition. A field visit was made to three sites (Wilkes-Barre, Duncannon, and Lehigh Gorge) to describe and sample the Catskill Formation, the diamictite-bearing Spechty Kopf Formation, and the Pocono Formation. Samples were collected, processed, and sent to Michigan State University to undergo X-ray fluorescence analysis for use in Chemical Index of Alteration (CIA) calculations. Sedimentology results indicate that diamictites are associated with soft sediment deformation features such as folds, sheared beds, slumps, and slides. Some dropstones were observed, possibly indicating ice rafting. Preliminary CIA results suggest a more chemically weathered landscape, which would be unusual if glaciers covered the study area for a prolonged period of time. These results, coupled with descriptions of the sedimentology of the units, has led to the interpretation that the Spechty Kopf diamictites in the study area were more likely deposited by a sub-aqueous debris flow than direct glacial activity. However, indirect glacial influence cannot be ruled out by the results of this study and further work needs to be completed over a wider area.