Regional structural setting of Yucca Mountain, southwestern Nevada, and late Cenozoic rates of tectonic activity in part of the southwestern Great Basin, Nevada and California

Abstract

The southwestern Great Basin region surrounding Yucca Mountain is divisible into three major structural-physiographic subsections with different structural styles and chronology. Yucca Mountain is located in the tectonically least active of the subsections, the Walker Lane belt. The belt, however, contains a number of structural zones of northeast trend, some of which are moderately active, as shown by Quaternary fault scarps and persistent low-magnitude seismicity. Tectonic activity appears to be favored by northeast fault orientation with respect to the present stress field. In southwestern Nevada, the Walker Lane belt was the source of voluminous middle and late Miocene silicic volcanism, which was located mainly in an area of major right-steps in the northeastern belt margin. The belt originated as a shear and flexure zone in the Mesozoic, when the majority of lateral displacement probably occurred. Tertiary time was characterized by relatively small-scale lateral displacements, accompanied by west-northwest crustal spreading and volcanism. A distinct decrease in the rate of faulting occurred in nearly all areas 9 or 10 m.y. ago. Relatively little tectonic activity has occurred in the Walker Lane belt since about 6 m.y. ago, after silicic volcanism ceased and northwest-striking faults in the belt came under compression as a result of a change in the regional stress field. Gentle regional tilting to the south has probably occurred in the last 3 m.y.