Determining the Location and Magnitude of Basin and Range and Laramide Faulting, Southern Nevada

Wednesday, 17 December 2014
Chelsea Elizabeth Brundrett1, Melissa A Lamb1 and Sue Beard2, (1)University of St Thomas, St. Paul, MN, United States, (2)USGS, Flagstaff, AZ, United States
Southern Nevada records two recent periods of deformation; the Laramide orogeny and Basin and Range extension. Our research focuses on these events to understand the history of faulting in this area and the resulting landscape.

First, we have advanced an on-going research project in the Lake Mead region of Nevada, which was deformed by extension that began around 17 Ma. We are currently working in the White Basin, near Lake Mead. The White Basin is comprised of the Lovell Wash Member, ~14-12 Ma, of the Horse Spring Formation. The Lovell Wash Member contains siliciclastic and carbonate units that vary laterally and vertically throughout this area. This is a change from the fairly homogenous Bitter Ridge Limestone Member below and suggests a change in the style of faulting. To determine the faulting history, we mapped out marker beds, focusing on tuffs and limestone beds that form continuous, well-exposed outcrops in the area. We found abrupt stratigraphic thickening of ~50% across faults, documenting syndepositional faulting. We used dated tuffs to determine that this faulting developed from ~13.7-13.2 Ma.

Secondly, we are working on a Laramide uplift project. We are testing the hypothesis that an area in the Kingman Uplift region was deformed by a Laramide age fault, prior to Miocene extensional deformation. We are using U-Th/He Apatite and K-Spar Multiple Diffusion Domain thermochronology, to determine the cooling histories of rocks on either side of the proposed fault.

Both of these on-going research projects highlight the complex geology that is found in the Basin and Range province in the United States. Understanding this complex geology will help answer questions about the timing, driving forces, and processes associated with extensional and compressional events.