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The northernmost central Appalachian fold-thrust belt is a classic example of a blind thrust system that abruptly changes orientation by nearly 90 degrees, and defines the Pennsylvania orocline. Previous research has quantified shortening distribution across the central Valley and Ridge Province, yet no such data has been collected at the easternmost extent of the arc in Pennsylvania. In the easternmost portion of the Pennsylvania orocline, folding in the Appalachian plateau is less pronounced than in the central and western extents, suggesting complications in the transition from the valley and ridge to Appalachian plateau that limit stress migration northward. Underlying this region in northeastern Pennsylvania (NEPA) are intrusions of high density rock, a product of a failed neoproterozoic rift, that contribute to a local gravity anomaly, or Scranton Gravity High (SGH). The Lackawanna Synclinorium, a structure formed by the removal of salt, geographically coincides with the SGH. These two features could have limited the development of strain northward by (1) constraining stress accumulation with denser material, and/or (2) accommodating stress through the migration of weak materials (salt).

​ in the case of the first hypothesis, grain-scale strain would be more pronounced south of the SGH than in the central parts of the orocline as stress builds up in the valley and fold system. For the second hypothesis, stress may have been preferentially accommodated by the migration of salt, resulting in no significant increase in strain within the orocline. To explore these hypotheses, we constructed a balanced cross-section and conducted microscopic strain analyses. Microscopic strain analysis was performed on three orthogonal thin-sections from oriented samples of quartz-rich competent rocks using normalized fry and Rf-O methods. 2D ellipses from the normalized fry method were then processed by Geological Programs for Mathematica to extract an oriented 3D ellipse for each sample, and ellipticity, axes orientation and Flinn diagrams for all samples were analyzed to more easily identify distinct microscopic deformation patterns in eastern PA. We present this strain data with a balanced cross-section to gain a better understanding of how pre-existing structures affect the development of strain in the Appalachians.

Presented at the GSA Conference in Portland, Maine 2018.

Fractures occur at various scales and are important in hydrogeology/hydrology as they may provide easy pathways for fluid flow (hydraulic conductor) by enhancing the flow rate through low permeable media, or directing the flow through a structure that otherwise would be a barrier to flow. As such, fractures contribute directly to permeability, and near-surface fractures play a significant role on surface water flow into the subsurface to enhance the migration of water and solutes into and out of subsurface reservoirs. A fractured subsurface reservoir is one with structural discontinuities resulting from a given paleostress history, where the orientations of historical principal stress axes can be understood, and current fracture orientations and densities can be used to construct flow models within such a reservoir. This project combines both geological and engineering perspectives to study fractures and their effect on the flow of water near Penobscot mountain. In this region, several streams seem to be directly influenced by the presence of fractures, and this study aims to better understand the complex hydrologic processes occurring in the area. In conjunction with field investigations on surface waters and materials, we mapped and analyzed fractures at various scales to better understand paleostress history, and the geospatial distribution and orientation of fractures in the region. Additionally, we conducted seismic (refraction and multi-channel attenuation of surface waves), electrical resistivity, and electromagnetic (ground penetrating radar) methods and generated a 3D model of the water table and compared it to fracture data to correlate the presence of fractures to fluid flow.

Presented at the AGU Conference in San Francisco, California (2019).