Mojave Desert Region Research Articles

Morphology of Calcite Crystals in Clast Coatings From Four Soils in the Mojave Desert Region

AbstractPedogenic calcite‐crystal coatings on clasts were examined in four soils along an altitudinal gradient on Kyle Canyon alluvium in southern Nevada. Clast coatings were studied rather than matrix carbonate to avoid the effects of soil matrix on crystallization. Six crystal sizes and shapes were recognized and distinguished. Equant micrite was the dominant crystal form with similar abundance at all elevations. The distributions of five categories of spar and microspar appear to be influenced by altitudinally induced changes in effective moisture. In the drier, lower elevation soils, crystals were equant or parallel prismatic with irregular, interlocking boundaries while in the more moist, higher elevation soils they were randomly oriented, euhedral, prismatic and fibrous. There was little support for the supposition that Mg2+ substitution or increased (Mg + Ca)/HCO3 ratios in the precipitating solution produced crystal elongation.

Celadonite and its Transformation to Smectite in an Entisol at Red Rock Canyon, Kern County, California

AbstractA green, Lithic Torriorthent soil derived from a celadonite-rich, hydrothermally altered basalt immediately north of the Mojave Desert region in southern California was studied to investigate the fate of the celadonite in a pedogenic weathering environment. Celadonite was found to be disseminated in the highly altered rock matrix with cristobalite, chalcedony, and stilbite. X-ray powder diffraction (XRD) showed the soil material to contain celadonite having a d(060) value of 1.510 Å, indicative of its dioctahedral nature. Very little smectite was detected in the parent material, whereas Fe-rich smectite was found to be abundant in the soil. The Fe-smectite and celadonite were identified as the sole components of the green-colored clay fraction (<2 µm) of all soil horizons. The soil clay showed a single d(060) value of 1.507 Å, indicating that the smectite was also dioctahedral and that its b-dimension was the same as that of the celadonite. Mössbauer spectroscopy showed that the chemical environments of Fe in the rock-matrix celadonite and in the smectite-rich soil clay were also nearly identical. These data strongly suggest a simple transformation of the celadonite to an Fe-rich smectite during soil formation.Supporting evidence for this transformation was obtained by artificial weathering of celadonite, using sodium tetraphenyl boron to extract interlayer K. The intensity of the 001 XRD peak (at 10.1 Å) of celadonite was greatly reduced after the treatment and a peak at 14.4 Å, absent in the pattern of the untreated material, appeared. On glycolation of the sample, this peak expanded to 17.4 Å, similar to the behavior of the soil smectite. The alteration of celadonite to smectite is a simple transformation requiring only the loss of interlayer K. The transformation is apparently possible under present-day conditions, inasmuch as the erosional landscape position, shallow depth, and lack of significant horizonation indicate that the soil is very young.

Neogene clockwise tectonic rotation of the eastern Transverse Ranges, California, suggested by paleomagnetic vectors

Results from a paleomagnetic study of Neogene volcanic rocks situated within and around the Pinto basin region of the eastern Transverse Ranges suggest that the ranges have undergone a clockwise tectonic rotation of ∼41.4° ± 7.7° since late Miocene time. Both normal and reversed polarities are observed, and inclination data indicate no significant flattening. The rotation was accompanied by progressive sinistral slip on the several east-west–trending faults which bound and transect the eastern Transverse Ranges. A computation using the observed amount of cumulative left slip on the east-west–trending faults of the eastern Transverse Ranges (∼50 km) and the spacing between the Pinto Mountain and Salton Creek faults which bound the region (∼70 km) indicates that ∼35° of clockwise rotation is required, which roughly agrees with the paleomagnetic data. Removal of the eastern Transverse Ranges rotation in a reconstruction shows that the distributed dextral shear across the Mojave Desert region to the north must have been on the order of 100 km since late Miocene time. From the results of this study, we infer that crustal rotation of the eastern Transverse Ranges began later and is of less magnitude than that of the western Transverse Ranges.

Timing and tectonic setting of Tertiary low‐angle normal faulting and associated magmatism in the southwestern United States

Major episodes of Tertiary low‐angle normal faulting in the southwestern United States south of latitude 37°N moved northward with time, occurring about 25 million years ago in southern Arizona, 20 million years ago in the Mojave Desert region, and 10 to 15 million years ago in the Las Vegas area. In most areas, faulting and associated volcanism occurred when the Mendocino triple junction lay to the west. This correspondence probably resulted from the unstable configuration of the triple junction. East‐west to northeast‐southwest horizontal stretching, as plates pulled apart at the triple junction, prevented development of a hole in the lithosphere at the triple junction. The regional strain history predicted by this model is consistent with observed Tertiary low‐angle faults, strike‐slip faults, and folds.

Correlation of metamorphosed Paleozoic strata of the southeastern Mojave Desert region, California and Arizona: Discussion and reply

Research Article| December 01, 1984 Correlation of metamorphosed Paleozoic strata of the southeastern Mojave Desert region, California and Arizona: Discussion and reply: Discussion HOWARD J. BROWN HOWARD J. BROWN 1Pluess-Staufer (California) Inc., P.O. Box 825, Lucerne Valley, California 92356 Search for other works by this author on: GSW Google Scholar Author and Article Information HOWARD J. BROWN 1Pluess-Staufer (California) Inc., P.O. Box 825, Lucerne Valley, California 92356 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1984) 95 (12): 1482–1485. https://doi.org/10.1130/0016-7606(1984)95<1482:COMPSO>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation HOWARD J. BROWN; Correlation of metamorphosed Paleozoic strata of the southeastern Mojave Desert region, California and Arizona: Discussion and reply: Discussion. GSA Bulletin 1984;; 95 (12): 1482–1485. doi: https://doi.org/10.1130/0016-7606(1984)95<1482:COMPSO>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract No Abstract Available. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Correlation of metamorphosed Paleozoic strata of the southeastern Mojave Desert region, California and Arizona: Discussion and reply

Correlation of metamorphosed Paleozoic strata of the southeastern Mojave Desert region, California and Arizona: Discussion and reply

Correlation of metamorphosed Paleozoic strata of the southeastern Mojave Desert region, California and Arizona

Isolated outcrops of deformed, regionally metamorphosed Paleozoic strata are scattered within the southeastern Mojave Desert region of California and western Arizona. These strata unconformably overlie a basement of Proterozoic crystalline rocks and are overlain in turn by metamorphosed Mesozoic sedimentary rocks. The strata can be correlated lithostratigraphically with the classic cratonal Paleozoic section of the western Grand Canyon, Arizona, and with nonmetamorphosed Paleozoic sections transitional between cratonal and miogeoclinal in the Ship, Marble, and Providence Mountains, California. The strata evidently were once continuous with Paleozoic epicontinental strata exposed throughout the southern Great Basin and Colorado Plateau. Outcrops of Paleozoic strata and of the underlying Proterozoic basement in the southeastern Mojave Desert region define a terrane that has been disrupted by Mesozoic thrust faults and by Tertiary detachment faults but that nevertheless retain a gross paleogeographic coherence. This coherent terrane extends at least as far west and southwest as the Big Maria, Palen, and Calumet Mountains, and possibly beyond to include Paleozoic exposures in the San Bernardino Mountains and near Victorville. Poorly understood tectonic boundaries separate the area of paleogeographic coherence from known or suspected allochthonous terranes in the western Mojave Desert and the eastern Transverse Ranges.

Stratigraphy of Northeastern Cady Mountains and Its Implications for Cenozoic Volcanic Evolution of Mojave Desert: ABSTRACT

The Cenozoic rocks of the northeastern Cady Mountains can be divided into two separate sequences--an unnamed volcanic succession in the eastern Cady Mountains, and the volcanic and sedimentary strata of the Hector Formation in the northern Cady Mountains. In the eastern Cady Mountains, approximately 3,280 ft (1,100 m) of volcanic flows, flow breccias, domes, and laharic breccias overlie a basement complex of Mesozoic quartz diorite and quartz monzonite. These volcanic rocks have a continuous compositional variation from basaltic andesite to rhyodacite, although dacites and rhyodacites predominate. The age of this sequence is probably Oligocene and/or Miocene. In the northern Cady Mountains, approximately 2,395 ft (730 m) of strata assigned to the Hector Formation (Oligocene? to Miocene) lie unconformably on a basement complex of Mesozoic quartz monzonite and metamorphic rocks. The upper part of the Hector Formation also unconformably overlaps the volcanic rocks of the eastern Cady Mountains. The Hector Formation consists of alluvial sandstone and conglomerate plus lacustrine and paludal sandstone, siltstone, mudstone, and limestone. Laharic breccias, ash-flow and air-fall tuffs, and andesitic to basaltic lava flows are interbedded with the sedimentary rocks. Geochemical data indicate that the volcanic rocks from both areas are part of a calc-alkalic suite. The model proposed by various authors for the Cenozoic tectonic evolution of the western United States suggests that there should have been a transition from andesitic-type volcanism to basaltic-type volcanism, concurrent with the termination of subduction and the initiation of regional faulting. No such volcanic transition, however, can be identified within the northeastern Cady Mountains, nor has one been clearly identified in other late Oligocene to Miocene volcanic sequences within the Mojave Desert region. If this type of transition did take place within the Mojave Desert, it must have occurred after 18.6 ± 0.2 m.y.B.P. This is the date obtained from the youngest dated volcani rock that is unquestionably part of the calc-alkalic suite observed in the northeastern Cady Mountains. End_of_Article - Last_Page 1695------------

Geology of the Victorville Region, California

Late Precambrian and Paleozoic strata of the Cordilleran continental margin (miogeocline) form a westward-thickening wedge of sedimentary rocks in the southern Great Basin region (Stewart, 1970). Facies boundaries and isopachs of these rocks can be traced across this region into the eastern Mojave Desert, southeastern California, where these older trends are crosscut by the younger, Mesozoic-age magmatic arc terrane (Fig. 1). Miogeoclinal rocks involved in the Cordilleran fold-and-thrust belt in the eastern Mojave Desert become more highly deformed and metamorphosed southwestward as the magnatic arc is approached. The geologic complexity of the central and western Mojave Desert, however, has posed a major stumbling block in attempts to reconstruct the paleogeography and tectonic history of the southern part of the Cordilleran orogenic belt. In the central and western Mojave Desert, bed-rock exposures consist chiefly to Tertiary volcanic rocks and Mesozoic granitic rocks. Because of the lack of exposure of older rocks in this terrrane, the southwestward continuation of miogeoclinal facies and isopach trends and the timing and nature of structural events in this region are very poorly known in comparison to what is known about the eastern Mojave Desert region.

Effects of Day Length, Temperature, and Green Food on Testicular Development in a Desert Pocket Mouse Perognathus formosus

Coordination of reproductive condition in male pocket mice (Perognathus formosus) by environmental factors limits the season of reproduction to a time associated with the springtime peak in availability of dietary resources that are critical to reproduction. This optimal time for reproduction follows winter hibernation and precedes summer drought. Responsiveness of reproductive function to environmental influences was studied in male P. formosus of the Mojave Desert region by bringing freshly captured animals into the laboratory at different seasons and exposing them to a variety of experimental manipulations. Long days (16 h light/day) stimulated or maintained seasonal testicular function, whereas short days (8 h light/day) were nonstimulatory or inhibitory. However, because natural reproductive development begins while the mice hibernate underground in total darkness, it is not yet clear how day length might influence this pattern of reproductive development in nature. Reproductive development was great...

Tropospheric ozone distributions measured with an airborne laser absorption spectrometer

Measurements of tropospheric ozone have been made in the southern and middle California regions and over the Pacific Ocean during two series of flights in February and May 1977. The data were obtained by using a laser absorption spectrometer, a nadir‐viewing instrument which remotely measures the ozone column abundance between ground level and aircraft altitude by interacting with ozone at specific wavelengths near 9.5 μm. The measurements indicate significantly lower ozone abundances above the Mojave Desert region as compared with farm, forest, and urban areas. The average tropospheric column density was found to be 2.7 × 10−3 atm cm/km over the California region and 3.5 × 10−3 atm cm/km over the Pacific Ocean region 1000–2000 km west of the coast of Mexico.

The Petrography and Geochemistry of Some Californian Arkoses with Application to Identifying Gneisses of Metasedimentary Origin

Forty marine and continental Eocene and Oligocene arkosic sandstones and interbedded shales from the Santa Ynez Mountains, California and nine continental Holocene sands from the Salton Basin, California have been petrographically and chemically analyzed for 27 elements each. The arkoses and Holocene sands are composed of quartz and feldspar with minor amounts of clay, mica, and rock fragments. The shales are about 65% clay, 15% quartz, and 15% feldspar; Fe, Mg, Zn, K, Hb, Ti, Nb, Cr, and Ni are largely contained in the clay minerals with little detritai mafic rock or minerals. The data indicate a provenance of plutonio igneous and metamorphic rocks with minor volcanics; probably the Mojave Desert region. The composition of the sediments is roughly equivalent to an intermediate igneous rock minus dissolved material, particularly Na and Ca, plus diagenetically added sulfur. The sediments were derived by moderate weathering, in an area of high relief, as is shown by the abundance and relatively unaltered condition of the plagioclase and some of the unstable heavy minerals, but detrital basic rock is uncommon and the Fe, Mg, Ni, Co, Nb, and possibly Cr were contained in precipitated clay minerals derived from solution of basic rock. Chemical criteria are suggested that would enable a highly metamorphosed or migmatised arkosic sequence to be distinguished from primary injected granitic or partial melts of granitic composition. The diagnostic importance of Zr, Ni, Cr trends and abundances are emphasized; these elements, being relatively immobile, are likely to preserve original igneous or sedimentary trends.

Theory of plasticity applied to faulting, Mojave Desert, southern California

The Mojave Desert region, a triangle-shaped area in southern California, is bounded on the northwest by the left-slip Garlock fault and on the southwest by the right-slip San Andreas fault. Within the triangle partly defined by these two faults, right-slip northwest-trending and left-slip northeast-trending faults occur. The structural geology and fault pattern within the triangle are uniform and internally consistent and are markedly different from the structural geology and fault pattern of the areas to the north and south. To describe the pattern of faults and to interpret the mechanics of deformation of the triangle, a two-dimensional model from theory of plasticity is proposed wherein an analogy is made between the Mojave Desert triangle and L. Prandtl9s compressed cell. To simulate regional stresses, the cell is subjected to north-south compression. The maximum shear-stress trajectories developed in the theoretical model have the same orientation and sense of relative movement as the faults in the Mojave Desert area. The theoretical model may be used to predict the orientations and sense of movement along faults that might form in the future.

Model for the Late Cenozoic Tectonic History of the Mojave Desert, California, and for Its Relation to Adjacent Regions

The Mojave Desert region is crossed by young northwest-striking right-slip faults. Restoration of their displacement indicates that the over-all shape of this region has been considerably distorted. The assumption that the region was always in contact with the Sierra Nevada forms the basis for the following conclusions: (1) The slices between the faults, and the faults themselves, were rotated counterclockwise, possibly by as much as 30°; the precise magnitude and timing of the rotation can be checked by paleomagnetic studies. (2) Because of this deformation, the part of the San Andreas fault adjacent to the Mojave Desert was bent; originally the fault was much straighter. (3) The major deformation of the Mojave Desert was a west-trending left shear that was supplemented by the left slip on the Garlock fault. A similar deformation, without rotation of blocks, was accomplished in the eastern Transverse Ranges by left slip on approximately west-striking faults. This crustal shearing resulted from the position of the Mojave Desert between the regions of crustal spreading in the Great Basin and those in the continental borderland and the Salton Trough. The shearing of the Mojave Desert accommodated lateral variations of crustal spreading. These deformations distorted the shape of the margin of the North American plate during Neogene and Quaternary time. They mainly reflect movement normal to the plate boundary, whereas much larger movement occurred contemporaneously parallel to the plate boundary.

Effects of Waste Percolation of Groundwater in Alluvium Near Barstow, California: ABSTRACT

Barstow is 96 mi northeast of Los Angeles in the Mojave Desert region of southern California, adjacent to the normally dry Mojave River. Groundwater in alluvial fill is the only reliable source of water for the main water purveyors (the city of Barstow and the U.S. Marine Corps Supply Center). The alluvial aquifer near Barstow has been subjected to contamination from percolation of industrial and municipal sewage for nearly 60 years. The contamination has forced the abandonment of several domestic wells because of taste, odor, and foaming, and it threatens the well field serving the U.S. Marine Corps Supply Center. An intensive investigation was made to determine (1) the nature of groundwater degradation; (2) the areal and vertical extent of the degradation; (3) the rate nd direction of movement of the degraded water; and (4) the effects of several proposed management practices designed to alleviate the problem. A series of 53 observation wells was installed within the 10-sq-mi study area to supplement data from existing domestic and irrigation wells. Groundwater samples were analyzed for the usual chemical constituents plus arsenic, hexavalent and total chromium, dissolved organic carbon, detergents, ammonia, phosphates, and oil and grease. Concentration gradient for dissolved solids and several individual constituents were defined in 3 dimensions. The dispersive characteristics were investigated by use of a 2-well tracer-dilution test. The chemical stratification found within the aquifer indicates that an old plume of degraded water (produced by percolation from sewage facilities near Barstow) occupies the lower part of the alluvial aquifer. Since 1910 this plume has moved down gradient about 4 mi. A more recent overlying plume of degraded water occurs near the downstream edge of the deeper plume. This recent plume is produced by effluent from sewage-treatment facilities installed in 1968. Detergent concentrations beneath this site reflect the current use of LAS-type detergents in contrast to the ABS types that are found in the deeper zones of degradation. End_Page 1596------------------------------ Distribution of nitrogen and chloride has indicated that the gradual increase in dissolved-solids concentrations in the Marine Corps wells is caused by the use of treated sewage effluent on a local golf course. Areal and vertical mapping of the degraded water indicates that the water supply at the Marine base will be affected if no measures are taken to avoid contamination. A digital water-quality model of the aquifer was built to aid in evaluating the effects of several alternative ground-water management practices. The model first was verified by comparison with existing hydrologic data and then used to calculate the water-level and water-quality conditions that might occur in the aquifer within the next 20 years. Model results indicated that by 1991 present sewage-percolation practices would result in dissolved-solids concentrations exceeding 900 mg/l in the Marine Corps well field. Two of the alternative water-quality management practices that were evaluated with the model are: (1) The oxidation ponds could be lined to prevent further percolation, and the effluent piped out of the study area. The model indicated that this would cause water-level declines in excess of 70% of the saturated thickness of the aquifer in the vicinity of the Marine Corps well field. This is probably unacceptable. (2) The percolation of treated sewage effluent could be allowed to continue, and a line of barrier wells could be drilled between the sewage-treatment facility and the Marine Corps well field. The barrier wells would be pumped at a lesser rate than the rate of recharge from the oxidation ponds, to lessen the undesirable effects. The model indicated that by 1987 a constant rate of pumping from the barrier wells would effectively limit the movement of the degraded plume toward the well field. However, by 1991 the increasing quantities of percolation from the oxidation ponds would greatly exceed the barrier pumping rate and the highly concentrated parts of the degraded plume would approach the edge of the Marine Corps well field. Judicious choice of barrier pumping rates would probably e tend the effectiveness of the barrier beyond 1987. End_of_Article - Last_Page 1597------------

Post-Miocene Sedimentation and Possibilities of Oil and Saline Minerals in Newberry Basin, Mojave Desert: ABSTRACT

The name Newberry Basin is given to an area east of Barstow underlain by a large thickness of relatively unconsolidated continental sedimentary which lie upon Miocene or older The areal limits of the basin are roughly those given by Buwalda (1914) as that for Lake Manix and represent a present-day tectonically negative area. The mountain ranges bordering the basin have been structurally positive since at least the post-Miocene orogeny. Very large thicknesses of extrusive volcanic and continental sedimentary overlying pre-Tertiary basement rocks compose most of the mountain masses. The post-Miocene sedimentary filling the upper part of the basin are given the name Newberry formation and several facies of the formation can be recognized. The prominently exposed Lake Manix green clay represents deposition in a relatively long-lived Pleistocene desert lake. Coyote Lake, a present-day playa, had a short-lived period of Pleistocene pluvial sedimentation. A widespread sand unit is newly recognized as a deltaic facies of Lake Manix. The marginal facies deposited on the flanks of the basin are represented by fan deposits. Lateral gradations of all these facies can be seen in outcrop. Underlying this upper unit of Lake Manix time are older fluviatile and fan deposits. The unit proposed as the Yermo formation by McCulloh (in press) composes the lower part of the Newberry Basin fill. Only the marginal facies (sand and gravel) of the Yermo formation are exposed for certain in outcrop; however, fine-grained facies are suspected to exist in the basin subsurface. Additional information from well data allows an interpretation of continual filling of the basin with sediments since possibly Pliocene time. Early recognition of the nature of Newberry Basin sedimentation was made by Thompson (1929). Interruptions of any magnitude in the deposition have occurred along the margins of the basin only and represent structural adjustments of the basement rocks. Alvord Mountain has a history of renewed uplift since the beginning of Yermo deposition. Several major faults cross or border the basin. Recent movements have occurred along the Manix fault zone and the Cave (Afton) Canyon fault system. The latter caused damming of the Pleistocene Mojave River and formed the several stages of Lake Manix and possibly earlier pluvial lakes. Hydrocarbons are found in minute quantities in Miocene fresh-water shale concretions in the Calico Mountains and several test wells have reported oil and gas in the Newberry Basin. Modern knowledge of the origin of petroleum and the understanding of the environments of sedimentation in this region allow for reasonable explanations, but do not predict significant occurrences of oil or gas. Saline minerals, primarily borates, are being extensively sought in the Mojave Desert region. Additional occurrences in the Newberry Basin area besides those in the Calico Mountains are evaluated in the light of the present study. The possibility of buried borate-bearing beds of the Miocene Barstow formation is considered to warrant further exploration. End_of_Article - Last_Page 256------------

Geology of Mescal Range: ABSTRACT

The Mescal Range, approximately 33 miles east of Baker, is in the central Mojave desert region of southeastern California. Here exposed, are rocks ranging in age from Precambrian to Recent. There are, however, no known sedimentary rocks of Tertiary age. Paleozoic sedimentary rocks nearly 11,000 feet thick, complexly folded and faulted, are separated from granitic augen gneiss of Lower Precambrian age by the Clark Mountain normal fault. The Paleozoic formations include: Cambrian, Prospect Mountain quartzite and Pioche shale; Cambrian through Devonian, Goodsprings dolomite and Sultan limestone; Carboniferous, Monte Cristo limestone and Bird Spring formation; Permian, Kaibab formation. The Moenkopi and Chinle formations, of Triassic age, are nearly 850 feet thick. The Aztec sandstone and Delfonte dacite, of Jurassic age, aggregate approximately 1,100 feet. During late Cretaceous time all earlier rocks were deformed by east-west compression. The west-dipping Mescal, Mesquite, and White Line faults represent major thrust faults. Other thrust faults are of an imbricate nature and are exposed on both sides of the Piute Valley. Interphased normal fault movement occurred during the same time interval, as evidenced by the Clark Mountain, Aztec, Piute, and Iron Horse faults, and the Monte Cristo fault system. Widespread zones of breccia, ranging in thickness from 500 feet to a feather edge, probably were formed by tectonic activity. Plutonic rocks of acid and intermediate composition were emplaced during the late stage of the Laramide orogeny. Erosional surfaces may exist between: the Goodsprings dolomite and the Sultan limestone, the Monte Cri to limestone and the Bird Spring formation, the Kaibab formation and the Moenkopi formation, and the Moenkopi formation and the Chinle formation. In Tertiary (?) time a complex system of dikes, ranging in composition from rhyolite to basalt, was emplaced. Older alluvium of Pleistocene age, blankets the lower flanks of the Mescal Range. Recent alluvium occurs in the larger stream courses and as a veneer over the older alluvium in the Shadow and Piute valleys. Geomorphically, the Mescal Range represents a highly dissected upland terrane, which rises about 2,000 feet above a mature surface of moderate relief referred to by Hewett (1956) as the Ivanpah Upland. The maximum elevation found in the Mescal Range is 6,493 feet and is attained just north of the Piute valley on a peak cut in the Bird Spring formation. The area is noted for the Sulphide Queen carbonate body which occurs in the Lower Precambrian basement rocks 3/4 mile east of the settlement of Mountain Pass. This ore body represents the greatest concentration of rare-earth minerals known in the world. In addition, deposits of lead, zinc, End_Page 253------------------------------ silver, gold, and copper ore are found in mineralized zones in the Goodsprings dolomite. Building stone has been quarried from the Aztec sandstone and limestone from the Monte Cristo limestone. A nominal water supply, sufficient for domestic use, is available at Valley Wells Station, Windmill, Clark Mountain Station, the Mountain Pass Mine, and Wheaton Springs. End_of_Article - Last_Page 254------------