POSSIBLE BEDROCK LITHOLOGY AND FRACTURE PATTERN CONTROLS ON GEOMORPHOLOGY OF THE GOLDEN VALLEY HILLS, RENO, NV

A study was conducted on the Golden Valley Hills north of Reno—an area of rapid suburban expansion to accommodate the rising population of the Reno metro area. The bedrock of the region is made of Mesozoic porphyritic granitic rock that is highly-fractured and cut by epidote veins. Orientations of fractures and epidote veins were taken from multiple rock outcrops in the region and samples of bedrock were collected for thin section analysis.

Preliminary results suggest two generations of fractures. The first set strikes approximately to the east and has substantial epidote deposits and propylitic alteration of surrounding rock. The second is oriented roughly parallel to the Peavine Fault System and has little evidence of hydrothermal activity. We interpret the second set to be of recent tectonic origin while the first is interpreted to be either from post-emplacement cooling of the granitic magma during the Mesozoic or from hydrothermal activity and deformation by nearby volcanic activity during the Tertiary. Both sets of fractures appear to have heavily-influenced the geomorphology of the Golden Valley Hills—a consideration for geotechnical engineers building in the region..