18 D11. Structural Geology and Tectonics (Posters)

Sunday, 20 March 2022
1:30 PM - 5:30 PM
Freedom Hall A

EVALUATING THE ATTITUDE OF RATTLESNAKE ROCK FROM THE PINE CREEK GORGE, LYCOMING COUNTY, PENNSYLVANIA

Paper number: 18-4
Program: Technical Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

Rattlesnake Rock is a coarse block located approximately 2.8 km downstream of the Pennsylvania Grand Canyon (PAGC) in Lycoming County, Pennsylvania. Rattlesnake Rock is characterized as a poorly-sorted, cross-bedded sandstone from the Late Devonian Catskill Formation, which is interpreted as a paleo-channel deposit. We hypothesize that Rattlesnake Rock was translocated during the formation of the PAGC, as opposed to being an in situ outcrop of autochthonous bedrock exposed by differential weathering. To test this hypothesis, a Brunton compass was used to collect attitude data on bedding-plane surfaces from Rattlesnake Rock and the surrounding bedrock for comparison (n=232). Trend and plunge values were analyzed using Fisher Vector Distribution in Stereonet-11 (v.11.3.1). Results demonstrate that Rattlesnake Rock exhibits a northern-orientation paleo-flow direction (009.5, 3.4; a99=1; n=52). In contrast, the nearby surrounding bedrock at the same stratigraphic level indicates a northeastern orientation (059.6, 6.3; a99=1.7; n=180). These results suggest that the orientation of Rattlesnake Rock is significantly different with no overlapping values with the in situ surrounding bedrock. These results support the hypothesis of Rattlesnake Rock being an allochthonous block that was moved/rotated, likely during the formation of the PAGC. Future work will involve ground-penetrating radar (GPR) to image and delineate the margins of Rattlesnake Rock that are currently buried under modern alluvium.

Geological Society of America Abstracts with Programs. Vol. 54, No. 3

doi: 10.1130/abs/2022NE-374904

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