GEOLOGICAL INVESTIGATIONS OF BEDROCK AND SURFICIAL GEOLOGY IN THE SOUTHERN HALF OF THE RAWLEY SPRINGS QUADRANGLE, VIRGINIA

This field mapping project studied the southern half of the 7.5’ Rawley Springs Quadrangle in western Virginia in order to improve understanding of the North Mountain thrust fault system and structural and fluvial features in the area. The project identified lithologic contacts, structural fabrics, and surficial features in a region where existing geologic maps are at the 1:100,000 scale (Rader and Wilkes, 2000). The project also filled gaps in knowledge of the region where data was either lacking or needed to be reanalyzed and updated. Field data from this project was used to create new bedrock and surficial geologic maps at the 1:24,000 scale, which compliments ongoing mapping in the adjacent Singers Glen and Briery Branch Quadrangles (D. Doctor, M. Heller, R. Orndorff, personal communications). This project provided a capstone experience for senior undergraduate geology students. Early career undergraduate students also participated in the project as field assistants and gained hands-on experiences with fieldwork and geologic map preparation.

Field observations documented four formations in the region: the Hampshire, Price, Greenland Gap and Brallier Fms. Field data was collected using the StraboSpot app. Preliminary strike and dip data were used to infer lithologic contacts, which were subsequently evaluated in the field. Field data indicates shallowly southeast dipping sedimentary rocks throughout the majority of the quadrangle. However, in the southeast portion of the quadrangle, the bedrock is oriented subvertically and synclinally folded and complexly faulted in the footwall of the North Mountain thrust fault system. Surficial mapping used aerial LiDAR data to identify potential landforms with field checking to verify the presence of landforms and associated deposits. The surficial data shows dendritic drainage in the western part of the mapping area that exhibits subhorizontal bedding, which shifts to a trellis drainage pattern across the vertical beds in the southeast. Using field data collected with StraboSpot and aerial imagery, final maps were prepared using ArcGIS. Ongoing mapping continues to refine our geologic understanding of the Mid Atlantic Valley and Ridge region.