LESSONS IN THE GEOLOGY AT CHIMNEY ROCK STATE PARK: INSIGHTS FROM THE DEFORMATION OF THE HENDERSON GNEISS

The Hickory Nut Gorge, which includes Chimney Rock State Park, lies within the Inner Piedmont of western North Carolina and consists of metamorphosed sedimentary and igneous rocks. The focus of this research was the deformation of the Henderson augen gneiss caused by emplacement of the overlying Poor Mountain Formation along the Sugarloaf Mountain thrust fault as visible within the park. This undergraduate research project was conducted as part of an expanded geology program intended for visitors to the park, as well as to provide an outline for future physical and structural geology courses taught at UNC Asheville. The Henderson gneiss is the predominant rock in the area, and the one that forms the “chimney” which gives the park its name. Rocks of the Poor Mountain Formation were emplaced above the Henderson gneiss and can now be found at the highest elevations within the park. The contact of these rocks is the Sugarloaf Mountain thrust fault, which creates a nearly horizontal line of separation between the different rock units and is clearly visible within the park. Chimney Rock State Park provides the unique opportunity to study the Henderson gneiss at different stages of deformation. The physical effect of shearing along the thrust fault is clearly visible through folds within the gneiss, and feldspar porphryoblasts that have been rotated, flattened, and/or sheared out. These effects increase in abundance and amount of strain approaching the fault. Through the use of optical micrographs, the deformational changes to the mineral structure of the gneiss can be illustrated. It is hoped that macroscopic and microscopic images of microstructures in samples collected from different elevations will give park visitors a new perspective into the forces which shaped this impressive geologic structure. The main outcomes of this project include: (1) valuable undergraduate field and research experience, (2) information gained combined with previous studies of the Henderson Gneiss will be incorporated into park educational programs that will be available to the general public, and (3) details from this research will be used to design a field trip guide and activity for Physical and Structural Geology courses at UNC Asheville.