16-16 Relationships Between Structural Geology and Karst Features in Sinking Valley, PA

Session: From Thin Section to Outcrop: Exploration of Undergraduate Research (Posters)

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The orientation of fractures, faults, and bedding planes can play a critical role in controlling the development and spatial distribution of secondary permeability within karst aquifers. Permeability within these systems is heterogenous, resulting from both primary permeability and secondary permeability, which can make the flow of groundwater through karst aquifers difficult to predict. This study aims to improve our understanding of the development of flow paths within karst aquifers by comparing the characteristics of geologic structures with karst features within Sinking Valley, PA.

Sinking Valley is a folded and faulted carbonate valley located within the Appalachian Valley and Ridge physiographic province. This study’s field investigations focused on the Ordovician-aged carbonates on the southern end of the valley: the Bellefonte, Loysburg, Hatter, Snyder, Linden Hall, Nealmont, Salona, and Coburn Formations. Structural data was collected in Tytoona Cave and surrounding outcrops, within the Union Furnace Quarry, and along several roadcuts. The orientation and attitude of structural features were collected using a combination of Brunton compass and digital data collection methods (i.e. StraboField, StereonetMobile), with locations obtained using handheld GPS. Both inventory and scanline methods were employed to characterize fault, fracture, vein orientations, and densities. These data were compared with mapped karst features, including cave passages, sinkholes, and spring locations, and evaluated in conjunction with an ongoing dye-tracing study of springs feeding the Little Juniata River.

Preliminary results indicate correlations between dominant fracture sets, bedding orientations, and the alignment of karst features, suggesting that structural anisotropy impacts karst evolution and groundwater flow pathways in Sinking Valley. For example, in Tytoona Cave, two dominant fracture sets were identified, and these fracture sets align with the orientations of cave passages. These findings highlight the importance of integrating structural geology with karst hydrogeology to better predict subsurface flow behavior in deformed karst terrains.

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