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Earth Science Applications, National Training Center, Fort Irwin

Program Information

The U.S. Army maintains Fort Irwin primarily as a mock battleground to prepare troops for tank combat in desert settings. Some of the earth science needs of the Army at Fort Irwin are:

 

 

 

In addition, part of the base is occupied by NASA's Goldstone Deep Space Antenna array. These immense satellite dishes require stable footings in fault-free locations.

Information being collected
Bedrock Geology gives information on the rocks and their ages, as wells for the sources of sediment and sources of natural contamination. Bedrock maps depict young faults that may pose seismic hazards. Digital bedrock geologic maps for part of southwestern Fort Irwin are completed.
Surficial Geology gives information on surface materials and is especially valuable for estimating how young faults are, assessing flood hazards, and identifying changes in the environment. Digital surficial geologic maps for part of southwestern Fort Irwin are completed.
Aeromagnetic Data give information on the amount of magnetic minerals in bedrock at and beneath the surface, providing a valuable adjunct to the bedrock geologic map and predictor of the third dimension. Data covering southwestern Fort Irwin have been obtained.
Gravity Data provide information on the density of materials at and beneath the surface, and provide a powerful tool for determining thickness of potentially water-bearing sediment. High-quality gravity data are available for part of the western part of the base but data elsewhere are sparse.
Hydrology Data provide information on the amount and quality of water in the basins, the rate at which that water can be used, and the flow paths of water and contaminants. Data are well developed for Fort Irwin basin and are sparse for Bicycle Lake and Langford Well Lake basins.
Water resources activities
Geohydrologic assessment of water resources and water quality is aimed at three water basins: Fort Irwin, Bicycle lake, and Langford Well Lake basins.
These basins are initially studied by geologic mapping and by collecting and interpreting gravity and aeromagnetic data. These initial studies give rough descriptions of the extent and depth of potentially water-bearing sediment and result in GIS products including geology, aeromagnetic, and gravity data; three-dimensional depictions of the basins; and cross-sections of the basins.
Detailed hydrologic studies include drilling wells to collect and analyze information such as water levels and permeability of sediment in order to estimate the size of the water resource, and to collect water quality information. Multiple-well monitoring sites will be developed for these purposes and to provide a long-term monitoring network. The studies will result in GIS products describing well data, giving three-dimensional depictions of the basins, and giving detailed cross-sections of the basins.

Water contamination studies
Water quality is comprised in some places as a result of natural and introduced contaminants. Detailed chemical analysis of water in several parts of each basin is used to describe contamination and identify its sources, dispersal patterns, and rates of dispersal. This information leads to wiser use of the limited water resources and wiser strategies for waste-water disposal, which is a common source for contamination.

Flood hazard studies
Flood hazards can be predicted from the kinds of Quaternary sediment and their distribution. Distinctive sediments in canyons and washes indicate high-volume destructive floods, whereas sediments on alluvial fans show that less destructive sheetwash flooding occurs. Standing water is a threat near toes of fans and on playas.

Earthquake hazard studies
Although most current seismic activity is over ten miles west of Fort Irwin, young faults are common on the base and require evaluation for their potential to rupture or move by creep. In general, faults that moved during last ~10,000 years are considered to have potential for rupture. Concealed faults can be defined by geophysical studies. Cracks that formed during 1993 may have been caused by creep on several faults as a result of increased force on those faults after the Landers earthquake in the southern Mojave Desert. Although the cracking is unlikely to disrupt most facilities, it could disrupt sensitive communications lines and it indicates that these faults are potentially still active.

Windblown dust and sand hazards
Blowing dust and sand create potential health hazards and may block roads and other facilities. Geologic studies can identify the erosional sources of dust and sand and identify and predict where the dust and sand will be deposited.

Sensitivity of the environment
Examining historic changes in the environment such as increased dust and sand erosion can be done by comparing historic photographs with modern ones. For instance, preliminary studies indicate that playas and sand washes are undergoing increased erosion by wind and water, and that wind-deposited sand and dust is building at a an increased rate along the west side of Tiefort Mountain.

Resources
Geologic mapping identifies several potential resources, such as iron skarn deposits, collectible minerals (obsidian, opal), building materials (gravel, sand, coarse aggregate), and rip-rap.

Geologic framework
General-purpose geologic and geophysical data bases are produced in GIS (ARC/INFO) format for Fort Irwin and surrounding areas of interest. The goals are to collect field data to establish baseline information that can be used to address a variety of problems, such as (1) establishing the framework of water basins north of Bicycle lake basin (Nelson Lake and Drinkwater Lakes), (2) establishing geologic controls on migration of wastes and other hazardous materials, (3) establishing probable seismic hazards on faults capable of rupturing and creeping, (4) examining historic changes in the environment such as increased dust and sand erosion, and associated health hazards. An important aspect of geologic framework studies is that they provide baseline data that are critical to future, unforeseen, applications.
U.S. Army environmental programs
U.S. Army resource management programs
U.S. Geological Survey geological mapping programs
U.S. Geological Survey water resources programs

References to some published earth-science studies


Studies at Fort Irwin:
Byers, F.M., 1960, Geology of the Alvord Mountain quadrangle, San Bernardino County, California: U.S. Geological Survey Bulletin 1089-A, 71 p.

Ford, J.P., MacConnell, D.F., and Dokka, R.K., 1992, Neogene faulting in the Goldstone-Fort Irwin area, California: A progress report, in Richard, S.M., ed., Deformation associated with the Neogene eastern California shear zone, southeastern California and southwestern Arizona: San Bernardino County Museum Special Publication 92-1, p. 32.

McCulloh, T.H., 1960, Geologic map of the Lane Mountain quadrangle, California: U.S. Geological Survey Open-File Report.

Miller, D.M., Yount, J.C., Schermer, E.R., and Felger, T.J., Preliminary assessment of the recency of faulting at southwestern Fort Irwin, north-central Mojave Desert, California: Special Publication 94-1, San Bernardino County Museum Association.

Miller, E.L., and Sutter, J.F., 1982, Structural geology and 40Ar/39Ar geochronology of the Goldstone-Lane Mountain area, Mojave Desert, California: Geological Society of America Bulletin, v. 93, p. 1191-1207.

Yount, J.C., Schermer, E.R., Felger, T.J., Miller, D.M., and Stephens, K.A., 1994, Preliminary geologic map of Fort Irwin basin, north-central Mojave Desert, California: U.S. Geological Survey Open-File Report 94-173, 27 p.

Studies of the region in and around Fort Irwin:
Dibblee, T.W., Jr., 1961, Evidence of strike-slip movement on northwest-trending faults in the western Mojave Desert, California: U.S. Geological Survey Professional Paper 424-B, p. B197 B199.

Dokka, R.K., 1983, Displacements on late Cenozoic strike-slip faults of the central Mojave Desert, California: Geology, v. 11, p. 305-308.

Dokka, R.K., 1992, The eastern California shear zone and its role in the creation of young extensional zones in the Mojave Desert region, in Craig, S.D., ed., Structure, Tectonics, and Mineralization of the Walker Lane: Geological Society of Nevada, p. 161-186.

Dokka, R.K., and Travis, C.J., 1990a, Role of the eastern California shear zone in accommodating Pacific-North American plate motion: Geophysical Research Letters, v. 17, p. 1323-1326.

Dokka, R.K., and Travis, C.J., 1990b, Late Cenozoic strike-slip faulting in the Mojave Desert, California: Tectonics, v. 9, p. 311-340.

Garfunkel, Z., 1974, Model for the late Cenozoic tectonic history of the Mojave Desert, California, and its relation to adjacent areas: Geological Society of America Bulletin, v. 85, p. 1931-1944.

Jennings, C.W., Burnett, J.L., and Troxel, B.W., 1962, Geologic map of California; Trona sheet: California Division of Mines and Geology, scale 1:250,000.

Schermer, E.R., 1993, Mesozoic structural evolution of the west-central Mojave Desert, in G. Dunne and K.A. MacDougall, eds., Mesozoic Paleogeography of the Western United States-II: Pacific Section, Society of Economic Paleontologists and Mineralogists, p 307-322.

Walker, J.D., Martin, M.W., Bartley, J.M., and Coleman, D.S., 1990a, Timing and kinematics of deformation in the Cronese Hills, California, and implications for Mesozoic structure of the south-western Cordillera: Geology, v. 18, p. 554-557.

Studies of earthquakes in the Mojave Desert:

Brune, J. N. and Anderson, J.G., 1996, Precarious Rocks and Seismic Risk in the Las Vegas Region: Abstract from Nov. 14-16, 1996 conference: Seismic Hazards in the Las Vegas Region.

Brune, J.N., Bell, J.W., Anooshehpoor, Rasool, Liu, Tanzhuo, and Zreda, Matek, 1995, Precarious Rocks and Earthquake Hazard in Southern California: EOS, American Geophysical Union Transactions.

Du, Y., and Aydin, A., 1996, Is the San Andreas big bend responsible for the Landers earthquake and the eastern California shear zone?: Geolgoy, v. 24, p. 219-222.

Hauksson, E., Jones, L.M., Hutton, K., and Eberhart-Phillips, D., 1993, The 1992 Landers earthquake sequence: Seismological observations: Journal of Geophysical Research, v. 98, p. 19835-19858.

Nur, A., Ron, H., and Beroza, G., 1993, Landers-Mojave earthquake line: A new fault system?: GSA Today, v. 3, no. 10, p. 253-258.

Zachariasen, J., and Sieh, K., 1995, The transfer of slip between two en echelon strike-slip faults: A case study from the 1992 Landers earthquake, southern California: Journal of Geophysical Research, v. 100, p. 15281-15301.

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Last revised: 29 June, 1998