T122 Hydrogeomorphic Processes in Hillslopes, Rivers, and Landscapes (Posters)

Monday, 1 November 2010
8:00 AM - 6:00 PM
Hall D

FRACTURE CORRELATION OF THE POTTSVILLE SANDSTONE WITH THE YOUGHIOGHENY RIVER COURSE, OHIOPYLE STATE PARK, PENNSYLVANIA

Paper number: T122-10
Program: Technical Sessions
Time: 8:00 AM – 6:00 PM

Authors

Abstract

The Youghiogheny River is a tributary of the Monongahela River and runs through Ohiopyle State Park in Pennsylvania for approximately fifteen miles. The geology of the area is dominated by resistant, fine to course grained sandstones and conglomerates, known as the Pottsville Sandstone or Pottsville Formation. The Pottsville is also known to contain shale and limestone in some sections. Much of the Pottsville Sandstone is exposed along the banks of the Youghiogheny throughout the park. This research in Ohiopyle State Park measures joint set orientations of the Pottsville in the vicinity of the river, as well as away from the river and even outside of park boundaries. The aim is to establish a relationship between the stream course of the Youghiogheny River and the orientation of fractures in the bedrock. The river runs generally southeast to northwest, crossing the Laurel Highlands, a broad, folded segment of Alleghenian Plateau running southwest to northeast. It is possible that the river’s course was well-established before uplift occurred in the region. Alternatively, the direction of the river is correlated to bedrock fractures, or structurally controlled.

Over 100 measurements of fracture orientations along the Youghiogheny River, within Ohiopyle State Park have been taken. Measurements from outside the park in other areas along the river in Pennsylvania are also included in the analysis. Due to the highly variable degree of jointing in the Pottsville’s various layers, only fractures with a length greater than 3 meters were included. In addition, several other parameters, including rock type and fracture characteristics such as weathering have been noted. The GPS locations of all measurements have been plotted using GIS software. The Youghiogheny River is evaluated through aerial analysis of the stream course in GIS using 30-meter segments. Individual and comparative analysis of fractures and the stream course are completed using rose diagrams. Initial analysis suggests a correlation of joint sets with regional tectonic stresses. However, the relationship between the Youghiogheny River and local fractures is initially unclear.