Geology of the Mojave Desert Province

Geologic Framework of the Mojave River Channel Region

The USGS has been involved in geologic-mapping and subsurface investigations that will clarify the geologic setting and geologic history of sedimentary materials and faults in the vicinity of the Mojave River channel. Investigations include:

• 1:24,000-scale mapping of Quaternary deposits along the Mojave River corridor from Victorville to Afton Canyon, with emphasis on the Helendale, Hinkley, Nebo, and Harvard Hill (Calico Fault) areas;
• siting 4 exploratory wells near Daggett and Harvard Hill for water-resources studies and site studies of proposed percolation and ground-water recharge facilities (with USGS WRD, San Diego)
• recording about 40 seismic-refraction profiles variously located near Helendale, Barstow, Daggett, and Harvard Hill, using sledgehammer-powered seismographs for the first two sites and 8-ga. shotgun shells for energy at the second two sites, in order to locate changes in depths to rock associated with northwest trending faults that traverse the Mojave River corridor;
• trenching of a photolineament on the Marine Logistics Base at Nebo near the golf course in order to confirm the presence of a trace of the Camp Rock-Harper Lake fault trend, pursuant to the mapping of the fault zone by Cox and Wilshire (1993);

Much of these activities were conducted in support of regional studies of the Mojave River aquifer system. Mapping is being conducted to determine the surface and subsurface extent and thickness of various deposits that store and transmit ground water to wells along the Mojave River. In general, the seismic studies confirmed the presence of shallow bedrock at Nebo, Hinkley, and Helendale, and the absence of shallow bedrock near Daggett Road and the Mojave River; discontinuous zones of cementation in the shallow subsurface near Helendale yielded uneven results. The trenching at Nebo showed that a Pleistocene aggradational fluvial terrace and filled channel of the Mojave River was strongly deformed by folding and faulting along both high-angle and bedding-plane parallel shears. We will have an event chronology containing at least two and perhaps three events; there is adequate radiocarbon for time control on the latest event (Holocene, on the basis of soil development).

Recent Publications

Cox, B.F., and Tinsley, J.C., III, 1999, Origin of the late Pliocene and Pleistocene Mojave River between Cajon Pass and Barstow, California, in Reynolds, R.E., and Reynolds, Jennifer, eds., Tracks along the Mojave: A field guide from Cajon Pass to the Calico Mountains and Coyote Lake: San Bernardino County Museum Association Quarterly, v. 46, no. 3, p. 49-54.

Cox, B.F., and Wilshire, H.G., 1993, Geologic map of the area around the Nebo Annex, Marine Corps Logistics Base, Barstow, California: U.S. Geological Survey Open-File Report 93-568, 36 p., scale 1:12,000.

Cox, B.F., and Wilshire, H.G., 1994, Geologic map of the Yermo Annex and vicinity, Marine Corps Logistics Base, Barstow, California: U.S. Geological Survey Open-File Report 94-681, scale 1:12,000.

Cox,B.F., Hillhouse, J.W., Sarna-Wojcicki, A.M., and Tinsley, J.C.,III, 1998, Pliocene-Pleistocene depositional history along the Mojave River north of Cajon Pass, California-Regional tilting and drainage reversal during uplift of the central Transverse Ranges: Geological Society of America Abstracts with Programs, v. 30, no. 5, p. 11.

Densmore, J.N., Cox, B.F., and Crawford, S.M., 1997, Geohydrology and water quality of Marine Corps Logistics Base, Nebo and Yermo Annexes, near Barstow, California: U.S. Geological Survey Water Resources Investigations Report 96-4301, 116 p.

Tinsley, J. C., and Cox, B. F., 1994, Neotectonics and hydrologic influence of the Harper Lake-Camp Rock fault near the Nebo Annex of the Marine Corps Logistics Base, Barstow, California, in McGill, S.F., and Ross, T. M., eds., Geological investigations of an active margin: Geological Society of America, Cordilleran Section, guidebook, p. 169-171.