Principal Facts for Gravity Stations and Physical Property Measurements in the Lake Mead 30' by 60' quadrangle, Nevada and Arizona

Introduction

The U.S. Geological Survey (USGS) collected 811 gravity stations on the Lake Mead 30' by 60' quadrangle from October, 1997 to September, 1999. These data were collected in support of geologic mapping of the Lake Mead quadrangle. In addition to these new data, gravity stations were compiled from a number of sources. These stations were reprocessed according to the reduction method described below and used for the new data. Density and magnetic susceptibility measurements were also performed on more than 250 rock samples. The Lake Mead quadrangle ranges from 360 to 360 30' north latitude and from 114° to 115° west longitude. It spans most of Lake Mead (see index map, below), the largest manmade lake in the United States, and includes most of the Lake Mead National Recreation Area. Its geology is very complex; Mesozoic thrust faults are exposed in the Muddy Mountains, Precambrian crystalline basement rocks are exhumed in tilted fault blocks near Gold Butte, extensive Tertiary volcanism is evident in the Black Mountains, and strike-slip faults of the right-lateral Las Vegas Valley shear zone and the left-lateral Lake Mead fault system meet near the Gale Hills. These gravity data and physical property measurements will aid in the 3-dimensional characterization of structure and stratigraphy in the quadrangle as part of the Las Vegas Urban Corridor mapping project.

First posted October 14, 1999