Skip Links

USGS - science for a changing world

Open-File Report 99-35

Geologic Map of the East of Grotto Hills Quadrangle, California: A Digital Database

By Jane E. Nielson

Digital database by David R. Bedford

Thumbnail of and link to report PDF (2.5 MB)Introduction

The East of Grotto Hills 1:24,000-scale quadrangle of California lies west of the Colorado River about 30 km southwest of Searchlight, Nevada, near the boundary between the northern and southern parts of the Basin and Range Province. The quadrangle includes the eastern margin of Lanfair Valley, the southernmost part of the Castle Mountains, and part of the northwest Piute Range. The generally north-trending Piute Range aligns with the Piute and Dead Mountains of California and the Newberry and Eldorado Mountains and McCullough Range of Nevada. The southern part of the Piute Range adjoins Homer Mountain (Spencer and Turner, 1985) near Civil War-era Fort Piute. Adjacent 1:24,000-scale quadrangles include Castle Peaks, Homer Mountain, and Signal Hill, Calif.; also Hart Peak, Tenmile Well, and West of Juniper Mine, Calif. and Nev.

The mapped area contains Tertiary (Miocene) volcanic and sedimentary rocks, interbedded with and overlain by Tertiary and Quaternary surficial deposits. Miocene intrusions mark conduits that served as feeders for the Miocene volcanic rocks, which also contain late magma pulses that cut the volcanic section. Upper Miocene conglomerate deposits interfinger with the uppermost volcanic flows. Canyons and intermontane valleys contain dissected Quaternary alluvial-fan deposits, mantled by active alluvial-fan deposits and detritus of active drainages. The alluvial materials were derived largely from Early Proterozoic granite and gneiss complexes, intruded by Mesozoic granite, dominate the heads of Lanfair Valley drainages in the New York Mountains and Mid Hills (fig. 1; Jennings, 1961). Similar rocks also underlie Tertiary deposits in the Castle Peaks, Castle Mountains, and eastern Piute Range

First posted January 28, 1999

Data files

For additional information, contact:
Geology, Minerals, Energy, and Geophysics Science Center
U.S. Geological Survey
345 Middlefield Road, MS 901
Menlo Park, CA 94025-3591
http://geomaps.wr.usgs.gov/gmeg/

Part or all of this report is presented in Portable Document Format (PDF). For best results viewing and printing PDF documents, it is recommended that you download the documents to your computer and open them with Adobe Reader. PDF documents opened from your browser may not display or print as intended. Download the latest version of Adobe Reader, free of charge.


Suggested citation:

Nielson, J. E., Bedford, D. R., 1999, Geologic Map of the East of Grotto Hills Quadrangle, California: A Digital Database: U. S. Geological Survey Open-File Report 99-35, 9 pp., https://pubs.usgs.gov/of/1999/0035/.


Accessibility FOIA Privacy Policies and Notices

USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: https://pubs.usgs.gov/of/1999/0035/
Page Contact Information: Contact USGS
Page Last Modified: Wednesday, December 07, 2016, 05:50:20 PM