Geologic Map of the Hiller Mountains Quadrangle, Clark County, Nevada, and Mohave County, Arizona by Keith A. Howard, Simon J. Hook, Geoffrey A. Phelps, and Debra L. Block, 2003, 1:24,000 scale

The Hiller Mountains Quadrangle straddles Virgin Canyon in the eastern part of Lake Mead. Proterozoic gneisses and granitoid rocks underlie much of the quadrangle. They are overlain by upper Miocene basin-filling deposits of arkosic conglomerate, basalt, and the overlying Hualapai Limestone. Inception of the Colorado River followed deposition of the Hualapai Limestone and caused incision of the older rocks. Fluvial gravel deposits indicate various courses of the early river across passes through highlands of the Gold Butte-Hiller Mountains-White Hills structural block. Faults and tilted rocks in the quadrangle record tectonic extension that climaxed in middle Miocene time.

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Map 137, 28.5x30-inch color plate, 8 pages of text, $15.00