We acknowledge Kenneth Parolski for his technical support during the three geophysical cruises that provided the data for this report.  We also acknowledge University of Nevada Las Vegas (UNLV) faculty members Brenda Buck and Andrew Hanson, former faculty member Mark Rudin, and former student Jonathan Zybala for their assistance in data collection, data analysis, and valuable discussions.  The original fieldwork and research were funded largely by a cooperative agreement between UNLV and the USGS, but additional funding was provided by the U.S. Bureau of Reclamation, Southern Nevada Water Authority, and UNLV.  Support for the interpretation presented with this report was provided by the National Park Service. We appreciate the helpful reviews provided by Elizabeth Pendleton, Jason Chaytor, and Lawrence Poppe.