REMOTE GEOLOGIC MAPPING UTILIZING AIRBORNE LIDAR: A CASE STUDY FROM PENNSYLVANIA’S VALLEY AND RIDGE PROVINCE

Our project utilizes new topographic data derived from airborne LiDAR, and provided by the state of Pennsylvania for free, to map geologic units, folds, and faults in the fold and thrust belt of Pennsylvania’s Valley and Ridge. We loaded the LiDAR data into a GIS software, manually sketched distinctive beds, and grouped rocks according to topographic expression. Because of the wide variation in rock resistance to erosion, some beds are readily etched in relief across the landscape. We take advantage of these revealed layers to extract strike and dip using a coordinate-based vector solution to the three point problem. We tabulate the thickness of mappable units, and compare these to other locations along strike to identify potential thrust faults. We test the validity of our method by comparing our results to a published geologic map and by additional field investigation at select locations where rocks are well exposed. We focus on layer orientations and structural features provided by the geologic map as a test bed for our computed orientations. We hope this exercise emphasizes the high value of detailed high resolution topographic data, in that a great deal of information can be extracted over a broad swath of territory—territory to which access is often limited, and which vegetation obscures.