A GEOPHYSICAL CHARACTERIZATION OF THE TRANSITION BETWEEN THE GREAT VALLEY AND RIDGE AND VALLEY PROVINCES, PENNSYLVANIA

Pennsylvania is broadly divided into three physiographic provinces: the Appalachian Plateau, the Ridge and Valley, and the Piedmont. Each province has a distinct morphology, a result of tectonism. The Ridge and Valley is divided into subsets, including the Great Valley, Blue Mountain, and Anthracite Uplands. The Great Valley is a broad valley, underlain by carbonates in the southeast, transitioning to shales (and slate) towards the northwest. The Great Valley is bordered on the north by Blue Mountain and the broader Ridge and Valley Province.

An existing database of statewide gravity data provides an opportunity to examine the longer-wavelength trends of the gravity field in Pennsylvania, but, in most locations, is not of high enough resolution to observe a distinct transition between provinces. For this project, we are collecting high resolution gravity measurements across the Great Valley and Ridge and Valley province in the eastern part of the boundary in an attempt to better define the transition. Our analysis involves producing regional trend maps and residual trend maps from the observed gravity to see how the transition from the Great Valley to the Ridge and Valley is reflected in the gravity field. Through wavelength filtering, we can determine if the regional or residual trend better defines the transition, thus seeing if the provinces are better associated with deeper structural features or shallower features. Once these local maps are produced, the transition will be traced to the southwest, parallel to the strike of Blue Mountain. Through gravitational analysis, this work attempts to develop an understanding of the transition between physiographic provinces and how it might relate to shallow or deeper geologic features.