Geology of southeastern Ventura basin, Los Angeles County, California
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Professional Paper↗
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Geologic and hydrologic features of Indian Wells Valley, California
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Water Supply Paper↗
Geology and saline resources of Danby Playa, southeastern California
No abstract available
Book chapter↗
Preliminary geology of the Bristol Lake region, Mojave Desert, California
No abstract available.
Conference Paper↗
A review of geology and mining in the Marble Mountains, southeastern California
Mining in the Marble Mountains of southeastern California was active in the earliest 1900s and gradually declined to very few active mines by 1959. Most mining consisted of hard-rock prospects and mines, with a few soft-rock prospects and one mine. The Marble Mountains are a 10 km by 30 km, gently NE-dipping dipping structural block composed of Proterozoic plutonic and metamorphic rocks, Paleozoic sedimentary rocks, and Jurassic granitoids exposed along the western anti-dip slopes, and Miocene volcanic and sedimentary rocks exposed along the crest of the range and eastern dip slopes. Mineralization occurred in metamorphic aureoles of intrusions, along dikes, as contact metasomatic replacement bodies in carbonate rocks, or adjacent to or along thrust faults. Mineralization locally formed gold, copper, malachite, azurite, bornite, chalcopyrite, magnetite, specularite, limonite, quartz, epidote, actinolite, and garnet. Hard-rock prospects and mines are clustered into five locations. The mines are small open pits, a few consist of a shaft or two with a few adits, most are just a single shaft or adit. There are a few small open-pit marble mines, and one is an open pit fossil mine. Eight prospects were developed in the Miocene tuffaceous deposits; three in the northwest and five prospects, and a single adit, in the south. Most of the Marble Mountains are now in the Trilobite Wilderness or adjacent Areas of Critical Environmental Concern, and the area of the Golden Cycle district (Castle Mine area) and prospect areas in the southern part of the range are in the Mojave Trails National Monument. The Iron Hat mine, several nearby areas, and the Trilobite mine area are privately owned. No rock or mineral mines are currently active, but the Trilobite mine in the south end of the range is still open to the public.
California↗
Preliminary geologic map of the Hemet 7.5' quadrangle, Riverside County, California
The Hemet 7.5' quadrangle is located near the eastern edge of the Perris block of the Peninsular Ranges batholith. The northeastern corner of the quadrangle extends across the San Jacinto Fault Zone onto the edge of the San Jacinto Mountains block. The Perris block is a relatively stable area located between the Elsinore Fault Zone on the west and the San Jacinto Fault Zone on the east. Both of the fault zones are active; the San Jacinto being the seismically most active in southern California. The fault zone is obscured by very young alluvial deposits. The concealed location of the San Jacinto Fault Zone shown on this quadrangle is after Sharp, 1967. The geology of the quadrangle is dominated by Cretaceous tonalite formerly included in the Coahuila Valley pluton of Sharp (1967). The northern part of Sharp's Coahuila Valley pluton is separated out as the Hemet pluton. Tonalite of the Hemet pluton is more heterogeneous than the tonalite of the Coahuila Valley pluton and has a different sturctural pattern. The Coahuila Valley pluton consists of relatively homogeneous hornblende-biotite tonalite, commonly with readily visible large euhedral honey-colored sphene crystals. Only the tip of the adjacent Tucalota Valley pluton, another large tonalite pluton, extends into the quadrangle. Tonalite of the Tucalota Valley pluton is very similar to the tonalite of the Coahuila Valley pluton except it generally lacks readily visible sphene. In the western part of the quadrangle a variety of amphibolite grade metasedimentary rocks are informally referred to as the rocks of Menifee Valley; named for exposures around Menifee Valley west of the Hemet quadrangle. In the southwestern corner of the quadrangle a mixture of schist and gneiss marks a suture that separated low metamorphic grade metasedimentary rocks to the west from high metamorphic grade rocks to the east. The age of these rocks is interpreted to be Triassic and the age of the suturing is about 100 Ma, essentially the same age as the adjacent Coahuila Valley pluton. Rocks within the suture zone consist of a mixture of lithologies from both sides of the suture. Gneiss, schist, and anatectic gneiss are the predominate lithologies within the rocks on the east side of the suture. Lesser amounts of metalithic greywacke and lenticular masses of black amphibolite are subordinate rock types. Biotite, biotite-sillimanite and lesser amounts of garnet-biotite-sillimanite schist and metaquartzite-metalithic greywacke lithologies occur west of the suture. Pleistocene continental beds, termed the Bautista beds occur east of the San Jacinto Fault Zone in the northeast corner of the quadrangle. Most of the Bautista beds were derived from the San Jacinto pluton that is located just to the east of the sedimentary rocks. Along the northern part of the quadrangle is the southern part of a large Holocene-late Pleistocene fan emanating from Baustista Canyon. Sediments in the Bautista fan are characterized by their content of detritus derived from amphibolite grade metasedimentary rocks located in the Bautista Canyon drainage. Between the Holocene-late Pleistocene Bautista fan and the Santa Rosa Hills is the remnant of a much older Bautista Canyon alluvial fan. A pronounced Holocene-late Pleistocene channel was developed along the south fringe of the very old alluvial fan and the Santa Rosa Hill. A now dissected late to middle Pleistocene alluvial complex was produced by the coalesced fans of Goodhart, St. Johns, and Avery canyons, and Cactus Valley. Pleistocene continental beds, termed the Bautista beds occur east of the San Jacinto Fault Zone in the northeast corner of the quadrangle. Most of the Bautista beds were derived from the San Jacinto pluton that is located just to the east of the sedimentary rocks. Along the northern part of the quadrangle is the southern part of a large Holocene-late Pleistocene fan emanating from Baustista Canyon.
California↗
Geologic map of the Lassen Peak, Chaos Crags, and Upper Hat Creek area, California
This digital publication contains all the information used to publish U.S. Geological Survey Geologic Investigations Series I-2723 (Christiansen and others, 2002). The map shows the distribution and relationships of volcanic and surficial-sedimentary deposits in an area of Lassen Volcanic National Park and vicinity. Emphasis is on products of the 1914-1917 eruptions of Lassen Peak and the approximately 1000-year-old eruptions of Chaos Crags. ArcInfo grids were prepared from scanned composite images of four U.S. Geological Survey 7.5' topographic quadrangle maps and were georeferenced and reprojected.
IMAP↗
Geologic map of the west half of the Blythe 30' by 60' quadrangle, Riverside County, California and La Paz County, Arizona
The Blythe 30' by 60' quadrangle is located along the Colorado River between southeastern California and western Arizona. This map depicts the geology of the west half of the Blythe quadrangle, which is mostly in California. The map area is a desert terrain consisting of mountain ranges surrounded by extensive alluvial fans and plains, including the flood plain of the Colorado River which covers the easternmost part of the area. Mountainous parts of the area, including the Big Maria, Little Maria, Riverside, McCoy, and Mule Mountains, consist of structurally complex rocks that range in age from Proterozoic to Miocene. Proterozoic gneiss and granite are overlain by Paleozoic to Early Jurassic metasedimentary rocks (mostly marble, quartzite, and schist) that are lithostratigraphically similar to coeval formations of the Colorado Plateau region to the east. The Paleozoic to Jurassic strata were deposited on the tectonically stable North American craton. These rocks are overlain by metamorphosed Jurassic volcanic rocks and are intruded by Jurassic plutonic rocks that represent part of a regionally extensive, northwest-trending magmatic arc. The overlying McCoy Mountains Formation, a very thick sequence of weakly metamorphosed sandstone and conglomerate of Jurassic(?) and Cretaceous age, accumulated in a rapidly subsiding depositional basin south of an east-trending belt of deformation and east of the north-trending Cretaceous Cordilleran magmatic arc. The McCoy Mountains Formation and older rocks were deformed, metamorphosed, and locally intruded by plutonic rocks in the Late Cretaceous. In Oligocene(?) to Miocene time, sedimentary and minor volcanic deposits accumulated locally, and the area was deformed by faulting. Tertiary rocks and their Proterozoic basement in the Riverside and northeastern Big Maria Mountains are in the upper plate of a low-angle normal (detachment) fault that lies within a region of major Early to Middle Miocene crustal extension. Surficial deposits of the flanking alluvial fans and plains range in age from late Miocene to Holocene. Among the oldest of these deposits are limestone and fine-grained clastic sediments of the late Miocene and (or) Pliocene Bouse Formation, which is commonly interpreted to represent an estuary or marine embayment connected to the proto-Gulf of California. Most of the surficial deposits younger than the Bouse Formation are composed of alluvium either derived from local mountain ranges or transported into the area by the Colorado River. Large parts of the area, particularly near the northern margin, are covered by eolian sand, and small parts are covered by playa sediments.
Scientific Investigations Map↗
Estimated ground-water discharge by evapotranspiration from Death Valley, California, 1997-2001
The U.S. Geological Survey, in cooperation with the National Park Service and Inyo County, Calif., collected field data from 1997 through 2001 to accurately estimate the amount of annual ground-water discharge by evapotranspiration (ET) from the floor of Death Valley, California. Multispectral satellite-imagery and National Wetlands Inventory data are used to delineate evaporative ground-water discharge areas on the Death Valley floor. These areas are divided into five general units where ground-water discharge from ET is considered to be significant. Based upon similarities in soil type, soil moisture, vegetation type, and vegetation density; the ET units are salt-encrusted playa (21,287 acres), bare-soil playa (75,922 acres), low-density vegetation (6,625 acres), moderate-density vegetation (5,019 acres), and high-density vegetation (1,522 acres). Annual ET was computed for ET units with micrometeorological data which were continuously measured at six instrumented sites. Total ET was determined at sites that were chosen for their soil- and vegetated-surface conditions, which include salt-encrusted playa (extensive salt encrustation) 0.17 feet per year, bare-soil playa (silt and salt encrustation) 0.21 feet per year, pickleweed (pickleweed plants, low-density vegetation) 0.60 feet per year, Eagle Borax (arrowweed plants and salt grass, moderate-density vegetation) 1.99 feet per year, Mesquite Flat (mesquite trees, high-density vegetation) 2.86 feet per year, and Mesquite Flat mixed grasses (mixed meadow grasses, high-density vegetation) 3.90 feet per year. Precipitation, flooding, and ground-water discharge satisfy ET demand in Death Valley. Ground-water discharge is estimated by deducting local precipitation and flooding from cumulative ET estimates. Discharge rates from ET units were not estimated directly because the range of vegetation units far exceeded the five specific vegetation units that were measured. The rate of annual ground-water discharge by ET for each ET unit was determined by fitting the annual ground-water ET for each site with the variability in vegetation density in each ET unit. The ET rate representing the midpoint of each ET unit was used as the representative value. The rate of annual ground-water ET for the playa sites did not require scaling in this manner. Annual ground-water discharge by ET was determined for all five ET units: salt-encrusted playa (0.13 foot), bare-soil playa (0.15 foot), low-density vegetation (1.0 foot), moderate-density vegetation (2.0 feet), and high-density vegetation (3.0 feet), and an area of vegetation or bare soil not contributing to ground-water discharge unclassified (0.0 foot). The total ground-water discharge from ET for the Death Valley floor is about 35,000 acre-feet and was computed by summing the products of the area of each ET unit multiplied by a corresponding ET rate for each unit.
Water-Resources Investigations Report↗
Evaluation and application of the Purge Analyzer Tool (PAT) to determine in-well flow and purge criteria for sampling monitoring wells at the Stringfellow Superfund site in Jurupa Valley, California, in 2017
The U.S. Geological Survey and U.S. Environmental Protection Agency are developing analytical tools to assess the representativeness of groundwater samples from fractured-rock aquifers. As part of this effort, monitoring wells from the Stringfellow Superfund site in Jurupa Valley in Riverside County, California, approximately 50 miles east of Los Angeles, were field tested to collect information to assist in the evaluation and application of in-well flow as computed by the analytical model called the Purge Analyzer Tool, which computes in-well groundwater travel times for simple piston transport of inflowing groundwater from open intervals of a monitoring well to the pump intake and can provide insight into optimal purging parameters (duration, rate, and pump position) needed for the collection of representative groundwater samples. Field testing of wells included hydraulic, chemistry, and dye tracer analysis to investigate travel times in wells under pumping conditions. The Purge Analyzer Tool was able to replicate dye velocities (travel times) for one of three wells that had appreciable inflow from the aquifer but not the other two wells, which are screened in low-permeability sediments and rock, where flow was dominated by borehole storage. A set of criteria was established to help assess the ability to collect representative groundwater chemistry from monitoring wells; criteria included understanding the height of the static well water column and relative exchange rate between the aquifer and the well.
California↗
Using Landsat satellite data to support pesticide exposure assessment in California
Background The recent U.S. Geological Survey policy offering Landsat satellite data at no cost provides researchers new opportunities to explore relationships between environment and health. The purpose of this study was to examine the potential for using Landsat satellite data to support pesticide exposure assessment in California. Methods and Results We collected a dense time series of 24 Landsat 5 and 7 images spanning the year 2000 for an agricultural region in Fresno County. We intersected the Landsat time series with the California Department of Water Resources (CDWR) land use map and selected field samples to define the phenological characteristics of 17 major crop types or crop groups. We found the frequent overpass of Landsat enabled detection of crop field conditions (e.g., bare soil, vegetated) over most of the year. However, images were limited during the winter months due to cloud cover. Many samples designated as single-cropped in the CDWR map had phenological patterns that represented multi-cropped or non-cropped fields, indicating they may have been misclassified. Conclusions We found the combination of Landsat 5 and 7 image data would clearly benefit pesticide exposure assessment in this region by 1) providing information on crop field conditions at or near the time when pesticides are applied, and 2) providing information for validating the CDWR map. The Landsat image time-series was useful for identifying idle, single-, and multi-cropped fields. Landsat data will be limited during the winter months due to cloud cover, and for years prior to the Landsat 7 launch (1999) when only one satellite was operational at any given time. We suggest additional research to determine the feasibility of integrating CDWR land use maps and Landsat data to derive crop maps in locations and time periods where maps are not available, which will allow for substantial improvements to chemical exposure estimation.
California↗
Black abalone surveys at Naval Base Ventura County, San Nicolas Island, California—2020, annual report
The U.S. Geological Survey monitors a suite of intertidal black abalone sites at San Nicolas Island, California, in cooperation with the U.S. Navy, which owns the island. The nine rocky intertidal sites were established in 1980 to study the potential impact of translocated sea otters on the intertidal black abalone population at the island. The sites were monitored from 1981 to 1997, usually annually or biennially. Monitoring resumed in 2001 and has been completed annually since then. At the time of this report, the work is conducted by the Western Ecological Research Center’s Santa Cruz Field Station, Santa Cruz, California. The study sites became particularly important, from a management perspective, after a virulent disease decimated black abalone populations throughout southern California beginning in the mid-1980s. The disease, withering syndrome, was first observed on San Nicolas Island in 1992 and during the next few years, it reduced the population there by more than 99 percent. The species was subsequently listed as endangered under the Endangered Species Act in 2009. The subject of this report is the 2020 monitoring cycle of the sites and how the current status fits into the long-term data at San Nicolas Island. Since 2001, the monitored population has increased twelvefold to approximately 9.6 percent of the pre-disease level. This increase has resulted from generally higher levels of recruitment than seen in the first two decades of monitoring, punctuated by a few unexplained high recruitment events. Most of the population growth has been at two of the nine sites (sites 7 and 8). This pattern continued in 2020, but with increasing numbers at all sites and the highest number of abalone counted and measured island-wide since 1993. Recruitment rates have fallen since a peak in 2017, but 2020 continued to show moderate levels of additional recruitment. The distance between adjacent black abalone has decreased substantially since it was first consistently measured in 2005, potentially indicating that the abalone are close enough to one another to reproduce successfully. Sand burial can have devastating localized consequences to black abalone, but there is evidence suggesting that they may be able to escape periodic sand inundation if suitable refugia exist. These data suggest that monitoring can inform adaptive management of the resource by base resource managers.
California↗
Characterization of subsurface conditions and recharge at the irrigated four-plex baseball field, Fort Irwin National Training Center, California, 2018–20
The U.S. Geological Survey performed subsurface and geophysical site characterization of the irrigated four-plex baseball field in the Langford Valley–Irwin Groundwater Subbasin, as part of a research study in cooperation with the U.S. Environmental Protection Agency, the Agricultural Research Service, and the Fort Irwin National Training Center, California. To help meet future demands, the Fort Irwin National Training Center is evaluating the efficacy of gravity-fed drywells to enhance storm-water recharge into the Langford Valley–Irwin Groundwater Subbasin by bypassing fine-grained, less permeable deposits between land surface and the water table. The amount, rate, and location of recharge beneath an irrigated baseball field in the groundwater basin at the Fort Irwin National Training Center is not well understood, so data were collected using physical and geophysical techniques to characterize subsurface materials, geologic controls, and the vertical movement of water through the unsaturated zone to the water table near the drywell at the Fort Irwin National Training Center. Based on the data collected and interpreted from these techniques, several fine-grained deposits were identified. Although these deposits appear to impede the downward movement of water through the unsaturated zone locally, they are not laterally continuous, and water appears to continue to move downward when it reaches the edges of the deposits. These data will help managers evaluate recharge at the site and determine if the use of gravity-fed drywells enhances recharge from surface runoff.
California↗
A summary of geologic hazards for proposed OCS oil and gas lease sale 68, southern California
A geophysical survey, consisting of about 6,880 line-km of multisensor, high-resolution, seismic reflection data, was run in 161 of the 221 tracts tentatively selected by the U.S. Department of the Interior for inclusion in the southern California Outer Continental Shelf Oil and Gas Lease Sale 68. Geologic hazards identified in the study area for which stipulations are recommended are active faults, mass transport, steep slopes (>10?), and steep-walled submarine canyons. Geologic hazards whose effects can be mitigated through existing technology and design and are not considered cause for stipulation are shallow faults, buried and filled channels, shallow gas, gas-charged sediments, hydrocarbon seeps, and unstable fan deposits. The Minerals Management Service has recommended that a stipulation be applied to 83 tracts where there is evidence of existing or potential sea-floor instability over a significant portion of the tract. Further data acquisition and analysis on a more detail-ed grid will be required of lessees or operators before drilling will be permitted on leases issued as a result of the sale.
Open-File Report↗
Geologic and bathymetric reconnaissance overview of the San Pedro shelf region, southern California
This report presents a series of maps that describe the bathymetry and late Quaternary geology of the San Pedro shelf area as interpreted from seismic-reflection profiles and 3.5-kHz and multibeam bathymetric data. Some of the seismic-reflection profiles were collected with Uniboom and 120-kJ sparker during surveys conducted by the U.S. Geological Survey (USGS) in 1973 (K-2-73-SC), 1978 (S-2-78-SC), and 1979 (S-2a-79-SC). The remaining seismic-reflection profiles were collected in 2000 using Geopulse boomer and minisparker during USGS cruise A-1-00-SC. The report consists of seven oversized sheets: 1. Map of 1978 and 1979 uniboom seismic-reflection and 3.5-kHz tracklines used to map faults and folds on San Pedro Shelf. 2. Maps of multibeam shaded bathymetric relief with faults and folds, and bathymetric contours. 3. Isopach map of unconsolidated sediment, seismic-reflection profile across the San Pedro shelf, seismic-reflection profile across San Gabriel paleo-valley. 4. Seismic-reflection profiles across the Palos Verdes Fault Zone. 5. Geologic map and samples of Uniboom and 120-kJ sparker seismic-reflection profiles used to make the map. 6. Map showing thickness of uppermost (Holocene?) sediment layer. 7. Map of San Gabriel Canyon paleo-valley and associated drainage basins.
California↗
Environmental Setting of the Lower Merced River Basin, California
In 1991, the U.S. Geological Survey began to study the effects of natural and anthropogenic influences on the quality of ground water, surface water, biology, and ecology as part of the National Water-Quality Assessment (NAWQA) Program. As part of this program, the San Joaquin-Tulare Basins study unit is assessing parts of the lower Merced River Basin, California. This report provides descriptions of natural and anthropogenic features of this basin as background information to assess the influence of these and other factors on water quality. The lower Merced River Basin, which encompasses the Mustang Creek Subbasin, gently slopes from the northeast to the southwest toward the San Joaquin River. The arid to semiarid climate is characterized by hot summers (highs of mid 90 degrees Fahrenheit) and mild winters (lows of mid 30 degrees Fahrenheit). Annual precipitation is highly variable, with long periods of drought and above normal precipitation. Population is estimated at about 39,230 for 2000. The watershed is predominately agricultural on the valley floor. Approximately 2.2 million pounds active ingredient of pesticides and an estimated 17.6 million pounds active ingredient of nitrogen and phosphorus fertilizer is applied annually to the agricultural land.
Scientific Investigations Report↗
California's restless giant: The Long Valley Caldera
Scientists have monitored geologic unrest in the Long Valley, California, area since 1980. In that year, following a swarm of strong earthquakes, they discovered that the central part of the Long Valley Caldera had begun actively rising. Unrest in the area persists today. The U.S. Geological Survey (USGS) continues to provide the public and civil authorities with current information on the volcanic hazard at Long Valley and is prepared to give timely warnings of any impending eruption.
California↗
Crustal structure in the western United States; study of seismic propagation paths and regional traveltimes in the California-Nevada region
The U.S. Geological Survey, with the assistance of United ElectroDynamics, Inc., completed ten weeks of seismic-refraction field work during the summer of 1962 in the southwestern part of the United States. This work was a continuation of a program initiated in 1961 to study traveltimes and seismic propagation paths in the earth?s crust and upper mantle in the western United States. A total of 761 seismograms were recorded along 10 profiles from 86 explosions at 18 shotpoints. Analysis of the data is continuing, but a few conclusions can be made from a preliminary study: (1) Variations in traveltimes in the Basin and Range province are large but measurable, and perhaps predictable. (2) Traveltimes of seismic waves in adjacent geologic provinces are usually significantly different. (3) The velocity of P g along all of the profiles recorded in 1962 ranges from 5.0 to 6.5 km/sec, and averages 6.0 km/sec. (4) The average velocity of P g in extreme northern Nevada and southern Idaho is 5.6 km/sec, and it is 6.1 km/sec in most of Nevada and California. (5) The average velocity of P n is 7–9 km/ sec and ranges from 7.85 to 7.95 km/sec on reversed profiles where the true P n velocity could be computed. (6) A shallow "intermediate" layer with a velocity of approximately 6.8 km/sec was found in the Snake River Plain. (7) Refraction arrivals from the mantle (P n ) were recorded in the Sierra Nevada. They indicate that the thickness of the crust in the Sierra Nevada is much greater than that in the Basin and Range province. (8) Many refinements in field techniques were made during the 1962 field season.
California;Nevada;Idaho↗