By Carter Bussey

Faculty Mentor: Prof. Sarah Morealli

Abstract

Oasis Valley, NV, is located within the Basin and Range Province of the United States, part of a zone of continental rifting. This region is distinguished by alternating mountain ranges and valleys that form as blocks of rock drop due to the crust stretching. Valleys formed by extension act as basins where sedimentary rock accumulates. In Oasis Valley, this stretching peaked approximately 24-11 million years ago. Extensive breccia units are present within Oasis Valley; interpreted by Fridrich et al (2007) as landslide breccias. However, field mapping by Morealli (2010) suggests a different origin for some units. This study attempts to determine the origin of six breccias mapped within Oasis Valley using hand sample and thin section analysis. Structural features within samples suggest multiple different formation methods. In particular, thin section analysis of one sample provides evidence of secondary fracture formation and displacement along microfaults, indicating a tectonic origin. Evidence signals that reclassification of some units to describe diversity of rocks more accurately may be necessary. In turn, understanding of each breccia’s formation is critical to understanding groundwater flow in the region, as groundwater can flow faster though fault-related breccias.