21 D1. Advances in Geomorphology and Quaternary Geology (Posters)

Sunday, 15 October 2023
8:00 AM - 5:30 PM
Hall B

COMBINING REMOTE SENSING AND IN SITU OUTCROP DESCRIPTION TO PRODUCE GEOLOGICAL MAPS OF DENSELY VEGETATED AREAS. LAY DAM FORMATION, CHEAHA STATE PARK

Paper number: 21-4
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

The Appalachian Mountains stretch from the island of Newfoundland all the way down to Alabama. Our focus lies on the southernmost section that traverses Alabama, specifically within Cheaha State Park, which has not undergone a geological survey since 1988. Our objective was to document the stratigraphic record of the area, primarily observing the low-grade metamorphism of sedimentary rocks from the Talladega group. This group is a part of the thrust sheet of the southern Appalachians in Alabama, overlaying rocks of the Valley and Ridge province. Most units within the study area belong to the Lay Dam formation, featuring abundant outcrops of interlayered sandstones, siltstones, slates, and phyllites. The most prominent rock unit is the Cheaha quartzite, comprising massive beds of quartzite and conglomerates that form the summits of the Talladega Mountains. This unit gradually thins along the strike to the southwest and reaches a maximum thickness of 2000 ft. Phyllites were found in close association with the quartzite but at lower elevations. This can be attributed to the higher resistance of quartzite to weathering compared to phyllite. Consequently, areas where phyllite was abundant have been eroded down, contributing to the formation of valleys in the park. This observation is further supported by our drainage density and slope maps. Steep slope areas corresponded to the regions with the Cheaha Quartzite, while gentle slope areas matched those with phyllite outcrops. Similarly, the drainage density map indicated higher drainage in areas where phyllite was exposed due to its easier erosion compared to quartzite. Another noteworthy finding was the occurrence of phyllite at higher elevations than expected. After closely examining our drainage density map, we noticed higher elevation regions with increased drainage density, suggesting additional locations with phyllite outcroppings. By combining our outcrop observations, slope, and drainage density maps, we constructed a structural model for the area. This model revealed tight, upright to overturned asymmetric folding, indicating regional metamorphic events during the Paleozoic era. The metamorphic event is believed to have occurred during the Alleghenian orogeny, during which deep burial of rocks (approximately 12 km) led to their low-grade metamorphic signature within the metamorphic belt.

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

doi: 10.1130/abs/2023AM-394362

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