T91 Paleozoic Stratigraphic and Tectonic Evolution of the Appalachian Foreland: In Honor of Frank Ettensohn

Monday, 16 October 2023
8:00 AM - 12:10 PM
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SEDIMENTOLOGY AND PALEOWEATHERING TRENDS OF DEVONIAN/MISSISSIPPIAN BOUNDARY STRATA, NORTHEAST/CENTRAL PENNSYLVANIA: IMPLICATIONS FOR GLACIATION IN THE APPALACHIAN BASIN

Paper number: T91-6
Program: Technical Sessions
Time: 9:25 AM – 9:40 AM

Authors

Abstract

The Late Paleozoic Ice Age (LPIA, late Devonian – late Permian) serves as the best deep time paleoclimate analog for the current Cenozoic icehouse (similarly low atmospheric CO2, widespread glaciers and forests, last complete transition from icehouse to greenhouse climate). The sedimentary record of LPIA glaciation on Gondwana is well documented, but evidence for glaciation in Euramerica is rare and remains disputed. Diamictites, rhythmites, striated clasts, and dropstones in the Appalachian Basin have been attributed to alpine glaciation in the paleotropics, coinciding with initial LPIA cooling during the Famennian. This study investigates the depositional processes and paleoweathering history of late Devonian/early Mississippian sediments in the Appalachian Basin, Pennsylvania to test for a glacial influence. Fieldwork was completed at sites across northeast and central Pennsylvania to describe and sample the Catskill Formation, the diamictite-bearing Spechty Kopf/Rockwell Formations, and the Pocono/Burgoon Formations. Samples were analyzed for major elements using X-ray fluorescence (XRF) for use in paleoweathering indices. Sedimentology results indicate that diamictites are closely associated with mass transport processes (slumps/slides) and sediment gravity flows (debris flows and turbidites). Soft sediment folds, load and flame structures, and sheared beds are common. Some lonestones were observed, possibly indicating ice rafting. Paleoweathering indices indicate relatively high chemical weathering throughout the latest Devonian into the Mississippian, which would be unusual if glaciers covered the study area for a prolonged period of time. These results, coupled with the sedimentology, has led to the interpretation that the Spechty Kopf diamictites in our study area were likely deposited by subaqueous debris flows rather than direct glacial emplacement. 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 to test the extent and timing of the hypothesized glaciation.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-394883

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