Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “California Geology”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 865 records · Page 48Linked to original sources
USGS2002

Report for borehole explosion data acquired in the 1999 Los Angeles Region Seismic Experiment (LARSE II), southern California: Part II, data tables and plots

The Los Angeles Region Seismic Experiment (LARSE), a joint project of the U.S. Geological Survey (USGS) and the Southern California Earthquake Center (SCEC), was conducted to produce seismic images of the subsurface in the Los Angeles region. Primary targets were major fault systems and sedimentary basins; the goal of the project was to address the earthquake hazard posed by these geologic features. The first phase of data collection (LARSE 1) was completed in 1994; the second phase (LARSE 2) was completed in 1999. A description of the 1999 survey and an overview of both phase I and II is given in Fuis and others (2001). In this report, we present the technical details for the explosion data collected in 1999.

California↗
USGS2007

U.S. Geological Survey assessment concepts for conventional petroleum accumulations: Chapter 24 in Petroleum systems and geologic assessment of oil and gas in the San Joaquin Basin Province, California

Conventional petroleum accumulations are discrete fields or pools localized in structural or stratigraphic traps by the buoyancy of oil or gas in water; they float, bubble-like, in water. This report describes the fundamental concepts supporting the U.S. Geological Survey “Seventh Approximation” model for resource assessments of conventional accumulations. The Seventh Approximation provides a strategy for estimating volumes of undiscovered petroleum (oil, gas, and coproducts) having the potential to be added to reserves in a 30-year forecast span. The assessment of an area requires (1) choice of a minimum accumulation size, (2) assignment of geologic and access risk, and (3) estimation of the number and sizes of undiscovered accumulations in the assessment area. The combination of these variables yields probability distributions for potential additions to reserves. Assessment results are controlled by geology-based input parameters supplied by knowledgeable geologists, as opposed to projections of historical trends.

Professional Paper↗
USGS2009

Bathymetry and acoustic backscatter: Northern Santa Barbara Channel, Southern California

In the summer of 2008, as part of the California Seafloor Mapping Program (CSMP) the U.S. Geological Survey, Coastal and Marine Geology mapped a nearshore region of the northern Santa Barbara Channel in Southern California (fig 1). The CSMP is a cooperative partnership between Federal and State agencies, Universities, and Industry to create a comprehensive coastal/marine geologic and habitat basemap series to support the Marine Life Protection Act (MLPA) inititive. The program is supported by the California Ocean Protection Council and the California Coastal Conservancy. The 2008 mapping collected high resolution bathymetry and acoustic backscatter data using a bathymetric side scan system within State waters from about the 10-m isobath out over 3-nautical miles. This Open-File Report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and FGDC metadata.

California↗
USGS1987

The crustal structure of the axis of the Great Valley, California, from seismic refraction measurements

In 1982 the U.S. Geological Survey collected six seismic refraction profiles in the Great Valley of California: three axial profiles with a maximum shot-to-receiver offset of 160 km, and three shorter profiles perpendicular to the valley axis. This paper presents the results of two-dimensional raytracing and synthetic seismogram modeling of the central axial profile. The crust of the central Great Valley is laterally heterogeneous along its axis, but generally consists of a sedimentary section overlying distinct upper, middle, and lower crustal units. The sedimentary rocks are 3-5 km thick along the profile, with velocities increasing with depth from 1.6 to 4.0 km/s. The basement (upper crust) consists of four units: 1. (1) a 1.0-1.5 km thick layer of velocity 5.4-5.8 km/s, 2. (2) a 3-4 km thick layer of velocity 6.0-6.3 km/s, 3. (3) a 1.5-3.0 km thick layer of velocity 6.5-6.6 km/s, and 4. (4) a laterally discontinuous, 1.5 km thick layer of velocity 6.8-7.0 km/s. The mid-crust lies at 11-14 km depth, is 5-8 km thick, and has a velocity of 6.6-6.7 km/s. On the northwest side of our profile the mid-crust is a low-velocity zone beneath the 6.8-7.0 km/s lid. The lower crust lies at 16-19 km depth, is 7-13 km thick, and has a velocity of 6.9-7.2 km/s. Crustal thickness increases from 26 to 29 km from NW to SE in the model. Although an unequivocal determination of crustal composition is not possible from P-wave velocities alone, our model has several geological and tectonic implications. We interpret the upper 7 km of basement on the northwest side of the profile as an ophiolitic fragment, since its thickness and velocity structure are consistent with that of oceanic crust. This fragment, which is not present 10-15 km to the west of the refraction profile, is probably at least partially responsible for the Great Valley gravity and magnetic anomalies, whose peaks lie about 10 km east of our profile. The middle and lower crust are probably gabbroic and the product of magmatic or tectonic underplating, or both. The crustal structure of the Great Valley is dissimilar to that of the adjacent Diablo Range, suggesting the existence of a fault or suture zone throughout the crust between these provinces.

California↗
USGS1962

Aquifer-test compilation for the San Joaquin Valley, California

This report is the first of a series the purpose of which is to make available in standard tabular form the results of aquifer tests that have been made by various private and public agencies in California. The scope of the compilation is to describe systematically, in a form agreed upon by the California Department of Water Resources and the Geological Survey, the (1) test location, (2) pumping data, (3) well data, and (4) summary of results. The results of these tests sometimes have been published but most frequently have been used only as a step in obtaining other information, consequently the results and even the location of aquifer tests have not been readily available. This report has been prepared by the Geological Survey under the immediate supervision of Fred Kunkel, district geologist for California, in cooperation with the California Department of Water Resources, and tabulates through October 1962 all tests analyzed by the Geological Survey for the San Joaquin Valley. The report is designed to be expanded when additional tests are analyzed or new tests are made.

California↗
USGS2022

Remote sensing and mapping Miocene paleovalleys of the Marble, Bristol, and Old Dad Mountains in the Trilobite and Bristol Mountain Wildernesses, California

Wilderness areas in the Mojave Desert, California, are remote and rugged terrain, but they contain important geology for understanding faults of the eastern California shear zone (ECSZ), and remote sensing offers techniques that can optimize mapping. The Bristol–Granite Mountain fault zone (BGMFZ) is the easternmost fault of the ECSZ with the Marble, Bristol, and Old Dad mountains on either side of the fault, as are the Trilobite and Bristol Mountain Wildernesses. In the northern Marble Mountains, a west-trending Miocene paleovalley has been proposed to have a correlative in the Old Dad Mountains and provides a constraint for right-lateral separation across the BGMFZ; however, this correlation is based on the premise that there was a unique paleovalley with a well defined geometry. In the northern Marble Mountains, a paleovalley was mapped by the distribution of (1) thickness and facies within the Lost Marble gravel (LMg) and 18.8 Ma Peach Spring Tuff (PST), and (2) adjacent highlands where the PST was deposited on basalt and dacite lava flows. Whether this paleovalley is unique, or there are other paleovalleys farther south in the Marble Mountains, requires mapping of the entire 5 by 28 km area of Miocene volcanic rocks. In the south Bristol and Old Dad mountains, there is a similar 12 by 22 km area of Miocene basalt and dacite with deposits of PST and local sedimentary rocks, including the proposed offset Lost Marble paleovalley, but the entire range needs to be mapped to establish a unique correlate. The mountains are in the Mojave Trails National Monument, and the Trilobite and Bristol Mountains wilderness areas, so access is limited. Remote sensing data, including aerial photography and hyperspectral images, are important for identification and characterization of rocks. Airborne hyperspectral Mako data can distinguish the distinctive spectral characteristics of the PST as well as several more map units identified by detailed field mapping in the Bristol Mountains. Reconnaissance maps derived from high spatial resolution Mako data can guide the detailed mapping needed to identify paleovalley or paleohighland deposits and can be used to optimize field time.

California↗
USGS2013

Geologic map of the Lead Mountain 15’ quadrangle, San Bernardino County, California

The Lead Mountain 15’ quadrangle in the Mojave Desert contains a record of Jurassic, Cretaceous, Tertiary, and Quaternary magmatism. Small amounts of Mesoproterozoic(?) augen gneiss and Paleozoic and Mesozoic(?) metasedimentary rocks are preserved in small patches; they are intruded by voluminous Jurassic plutons of quartz diorite to granite composition and by Late Cretaceous granite of the Cadiz Valley batholith. Jurassic intrusive rocks include part of the Bullion Mountain Intrusive Suite and also younger dikes inferred to be part of the Jurassic Independence dike swarm. A contact-metamorphosed aureole 2 km wide in the Jurassic plutonic rocks fringes the Cadiz Valley batholith. Early Miocene dacitic magmatism produced a dense swarm of dikes in the eastern Bullion Mountains and the volcanic-intrusive remnant of a volcano at Lead Mountain. Tilting of the dike swarm from inferred vertical orientations may have resulted from Miocene tectonic extension. Conglomerate of Pliocene and (or) Miocene age is also tilted. Younger volcanism is recorded by Pliocene basalt of the Deadman Lake volcanic field, basalt of Lead Mountain (approximately 0.36 Ma), and the even younger basalt of Amboy. Quaternary sedimentation built alluvial fans and filled playas in the map area. Faulting in the dextral eastern California shear zone produced several northwest-striking faults in the quadrangle, some of them active into the Pleistocene and some that may have many kilometers of right-lateral offset.

California↗
USGS2006

Benthic habitat and geologic mapping of the outer continental shelf of north-central California

The Fanny Shoal area is located between North Farallon Island and Cordell Bank approximately 40 miles west of San Francisco, California. The area lies within the Gulf of the Farallones National Marine Sanctuary (GFNMS) which is located just a few miles from San Francisco. The waters within the GFNMS are part of a nationally significant marine ecosystem encompassing a diversity of highly productive marine habitats. Protection of the living and cultural resources at the sites are administered by the National Oceanic and Atmospheric Administration (NOAA). The U.S. Geological Survey (USGS) in cooperation with the Golden Gate National Recreation Area (GGNRA) and NOAA, including the GFNMS, and Monterey Bay National Marine Sanctuary (MBNMS), collected side-scanning sonar, and underwater video data over three cruises in July of 2003, and April of 2004. The data are consolidated into a geographic information system (GIS) to produce benthic habitat and geologic maps that provide researchers and those involved in decision making with crucial, georeferenced geologic information that will aid in preserving the area's environment.

California↗
USGS1995

Geologic map and structure sections of the Clear Lake Volcanics, Northern California

The Clear Lake Volcanics are located in the California Coast Ranges about 150 km north of San Francisco. This Quaternary volcanic field has erupted intermittently since 2.1 million years ago. This volcanic field is considered a high-threat volcanic system (Ewert and others, 2005) The adjacent Geysers geothermal field, largest power-producing geothermal field in the world, is powered by the magmatic heat source for the volcanic field. This report consists of three sheets that include the geologic map, one table, two figures, three cross sections, description of map units, charts of standard and diagrammatic correlation of map units, and references. This map supersedes U.S. Geological Survey Open-File Report 76-751. Descriptions of map units are grouped by geographic area. Summaries of the evolution, chemistry, structure, and tectonic setting of the Clear Lake Volcanics are given in Hearn and others (1981) and Donnelly-Nolan and others (1981). The geology of parts of the area underlain by the Cache Formation is based on mapping by Rymer (1981); the geology of parts of the areas underlain by the Sonoma Volcanics, Franciscan assemblage, and Great Valley sequence is based on mapping by McLaughlin (1978). Volcanic compositional map units are basalt, basaltic andesite, andesite, dacite, rhyodacite, and rhyolite, based on SiO2 content. Included in this report are maps showing the distribution of volcanic rocks through time and a chart showing erupted volumes of different lava types through time. A table gives petrographic data for each map unit by mineral type, abundance, and size. Most ages are potassium-argon (K/Ar) ages determined for whole-rock samples and mineral separates by Donnelly-Nolan and others (1981), unless otherwise noted. A few ages are carbon-14 ages or were estimated from geologic relationships. Magnetic polarities are from Mankinen and others (1978; 1981) or were determined in the field by B.C. Hearn, Jr., using a portable fluxgate magnetometer. Thickness for most units is estimated from topographic relief except where drill-hole data were available.

California↗
USGS2017

The California stream quality assessment

In 2017, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) project is assessing stream quality in coastal California, United States. The USGS California Stream Quality Assessment (CSQA) will sample streams over most of the Central California Foothills and Coastal Mountains ecoregion (modified from Griffith and others, 2016), where rapid urban growth and intensive agriculture in the larger river valleys are raising concerns that stream health is being degraded. Findings will provide the public and policy-makers with information regarding which human and natural factors are the most critical in affecting stream quality and, thus, provide insights about possible approaches to protect the health of streams in the region.

California↗
USGS2021

Aeromagnetic map of Burney and the surrounding area, northeastern California

An aeromagnetic survey was conducted to improve understanding of the geology and structure in the area around Burney, northeastern California. The new data are a substantial improvement over existing data and reveal a prominent north northwest-trending magnetic grain that allows extension of mapped faults, delineation of plutons within the Mesozoic basement in the northern Sierra Nevada, and linear anomalies that limit the amount of strike-slip offset along various faults in the area.

California↗
USGS1980

Geology and ground water in north-central Santa Cruz County, California

North-central Santa Cruz County is underlain mainly by folded sedimentary rocks of Tertiary and Cretaceous age that have been highly fractured by movements in the San Andreas fault system. Ground water is stored in fractures within shale and mudstone formations and in intergranular pore spaces within fine- to very fine-grained sandstone and siltstone formations. Fewer than 10% of the wells yield more than 15 gallons of water per minute. The water in most wells is moderately hard to very hard, is generally of a sodium bicarbonate or calcium bicarbonate type, and commonly has excessive concentrations of iron or manganese. Of the many geologic units in the study area, only the Purisima Formation of Pliocene age has the potential to sustain well yields greater than 100 gallons per minute. (USGS)

California↗
USGS1979

Comparison of Miocene provincial foraminiferal stages to coccolith zones in the California Continental Borderland

Biostratigraphic ages determined by planktic coccoliths and benthic foraminifera for the same core samples from the California Continental Borderland suggest that a significant overlap exists among provincial Miocene stages of California and that some of the benthic foraminifera commonly used to recognize these stages are time-transgressive. For example, samples assigned to the middle Miocene Discoaster exilis Zone of coccoliths (∼ 14 ± 1 m.y.) are also assigned to the Relizian, Luisian, and lower Mohnian Stages on the basis of benthic foraminifera. Significantly, most past and current geologic interpretations of Cenozoic marine sequences in California rely heavily on provincial benthic foraminiferal stages and zones. Thus, the apparent overlapping of provincial stages has serious implications for geologic studies of the California Cenozoic and should be further investigated in sections onshore.

California↗
USGS1980

Earthquake alarm; operating the seismograph station at the University of California, Berkeley.

An alarm bell rings at the seismographic station and at the office of the campus police. It is 3:00 on a foggy San Francisco morning. Somewhere in the world an earthquake has occurred. The police telephone the duty seismologist at home telling him that the alarm has triggered. He makes his way into the seismograph station, bathrobe and all, to locate the earthquake and determine its magnitude. In this way, many seismology graduate students have been initiated into the responsibilities of running a seismographic station. At the University of California seismographic stations, the task of locating and determining magnitudes for both local and distant earthquakes is a continuous one. Teleseisms must be located rapidly so that events that occur in the Pacific can be identified and the Pacific Tsunami Warning System alerted. For great earthquakes anywhere, there is a responsibility to notify public agencies such as the California Office of Emergency Services, the Federal Disaster Assistance Administration, the Earthquake Engineering Research Institute, the California Seismic Safety Commission, and the American Red Cross. In the case of damaging local earthquakes, it is necessary to alert also the California Department of Water Resources, California Division of Mines and Geology, U.S Army Corps of Engineers, Federal Bureau of Reclamation, and the Bay Area Rapid Transit. These days, any earthquakes that are felt in northern California cause immediate inquiries from the news media and an interested public. The series of earthquakes that jolted the Livermore area from January 24 to 26 1980, is a good case in point.

Earthquake Information Bulletin (USGS)↗
USGS2021

Geologic influences on the quality of groundwater used for domestic supply in the northern Sierra Nevada Foothills

Approximately 2 million California residents depend on groundwater from domestic wells for their drinking-water supply. The State of California, in collaboration with the U.S. Geological Survey, created the Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP) to assess the quality of groundwater used for domestic supply throughout the state and determine regional vulnerabilities to drinking-water resources. Many rural households in the northern Sierra Nevada foothills (hereafter referred to as “the foothills”) use domestic wells that pump water from fractured-bedrock aquifers. In the foothills, complicated and varied regional bedrock geology can cause substantial variation in groundwater chemistry and quality over relatively short distances. This factsheet presents findings from the GAMA-PBP assessment that highlight influences of geologic factors on groundwater quality in the foothills.

California↗
USGS2001

Selected ground-water data for Yucca Mountain region, southern Nevada and eastern California, through December 1999

The U.S. Geological Survey, in support of the U.S. Department of Energy, Yucca Mountain Site Characterization Project, collects, compiles, and summarizes hydrologic data in the Yucca Mountain region. The data are collected to allow assessments of ground-water resources during studies to determine the potential suitability of Yucca Mountain for storing high-level nuclear waste. Data on ground-water levels at 34 wells and a fissure (Devils Hole), ground-water discharge at 5 springs and a flowing well, and total reported ground-water withdrawals within Crater Flat, Jackass Flats, Mercury Valley, and the Amargosa Desert are presented for calendar year 1999. Data collected prior to 1999 are graphically presented and data collected by other agencies (or as part of other Geological Survey programs) are included to further indicate variations of ground-water levels, discharges, and withdrawals through time. A statistical summary of ground-water levels at seven wells in Jackass Flats is presented to indicate potential effects of ground-water withdrawals associated with U.S. Department of Energy activities near Yucca Mountain. The statistical summary includes the number of measurements, the maximum, minimum, and median water-level altitudes, and the average deviation of measured water-level altitudes for selected baseline periods and for calendar years 1992-99. At two water-supply wells median water levels for calendar year 1999 were unchanged from their respective baseline periods. At a nearby observation well, the 1999 median water level was slightly lower (0.1 foot) than its baseline period. At the remaining four wells in Jackass Flats, median water levels for 1999 were slightly higher (0.2 foot to 1.6 feet) than for their respective baseline periods.

Open-File Report↗
USGS1994

Selected ground-water data for Yucca Mountain region, southern Nevada and eastern California, through December 1992

Tne U.S. Geological Survey. in support of the U.S. Department of Energy, Yucca Mountain Site- Characterization Project, collects, compiles, and summarizes water-resource data in the Yucca Mountain region. The data are collected to document the historical and current condition of ground-water resources, to detect and document changes in those resources through time, and to allow assessments of ground-water resources during investigations to determine the potential suitability of Yucca Mountain for storing high-level nuclear waste. Data on ground-water levels at 36 sites, ground- water discharge at 6 sites, ground-water quality at 19 sites, and ground-water withdrawals within Crater Fiat, Jackass Flats, Mercury Valley, and the Amargosa Desert are presented. Data on ground-water levels, discharges, and withdrawals collected by other agencies or as part of other programs are included to further indicate variations through time. A statistical summary of ground-water levels and median annual ground-water withdrawals in Jackass Flats is presented. The statistical summary includes the number of measurements, the maximum, minimum, and median water-level altitudes, and the average deviation of a11 water-level altitudes for selected baseline periods and for calendar year 1992. Data on ground-water quality are compared to established, proposed, or tentative primary and secondary drinking-water standards, and measures which exceeded those standards are listed for 18 sites. Detected organic compounds for which established, proposed, or tentative drinking-water standards exist also are listed.

California, Nevada↗
USGS1996

Selected ground-water data for Yucca Mountain region, southern Nevada and eastern California, through December 1994

The U.S. Geological Survey, in support of the U.S. Department of Energy, Yucca Mountain Site Characterization Project, collects, compiles, and summarizes hydrologic data in the Yucca Mountain region. The data are collected to allow assessments of ground-water resources during studies to determine the potential suitability of Yucca Mountain for storing high-level nuclear waste. Data on ground-water levels at 36 sites, ground-water discharge at 6 sites, and ground-water withdrawals within Crater Flat, Jackass Flats, Mercury Valley, and the Amargosa Desert are presented for calendar year 1994. Data collected prior to 1994 are graphically presented and data collected by other agencies (or as part of other programs) are included to further indicate variations of ground-water levels, discharges, and withdrawals through time. A statistical summary of ground-water levels at seven wells in Jackass Flats is presented. The statistical summary includes the number of measurements, the maximum, minimum, and median water-level altitudes, and the average deviation of measured water-level altitudes for selected baseline periods and for calendar years 1992-94.

Open-File Report↗