Geologic Mapping in the Southern Pacific Border and Sierras provinces, California Active
San Andreas Fault
This project uses geologic and geophysical mapping to build an earth-science framework for scientific investigations that include assessments of critical resources, such as groundwater, and of hazards, such as those resulting from earthquakes, in California west of and including the Sierra Nevada and Cascade arc.
Questions of particular interest include:
What are the geometries, slip rates, and connectivity of faults throughout the broader San Andreas fault system? How do these faults affect resource quantity and quality? How do these factors contribute to the behavior of faults as earthquake sources?
How have basins and landscapes evolved through time? How has this evolution affected resource quantity and quality? Can we use this knowledge to better understand processes related to hazards and resources?
How are rocks and sediments of different properties distributed at the Earth’s surface and in the upper crust? How does this distribution affect resource quantity and quality? How does this distribution affect propagation of seismic energy and ground shaking?
Science Issue and Relevance
Earthquakes, Faulting and Tectonics
Determining how fast faults move through time, how they are connected at depth and at the surface, the style of deformation, and the distribution of rocks with different densities and seismic velocities relate directly to societally relevant questions of how to forecast shaking damage, the size of potential earthquakes, and where faults may rupture.
Basin stratigraphy, structure, and resources
Basins preserve the record of the tectonic evolution, unroofing and sedimentation of California; their structural and stratigraphic underpinnings are essential components for understanding availability and quality of natural resources, particularly water, oil, and gas, as well as understanding how seismic energy propagates in the subsurface and basin effects that concentrate shaking in certain areas.
Surface and Groundwater Resources
Surface water and groundwater serve as water supplies for urban populations, agriculture, and native habitats within California. The combination of rapid population growth, high water use, and arid climate has led to an increased dependence on groundwater resources, resulting in locally severe groundwater depletion and declining groundwater levels. Management of surface-water and groundwater resources in the province requires knowledge of the groundwater system, which in turn requires an understanding of the configuration and properties of aquifers. Such understanding includes the delineation of water-bearing units on the basis of lithology and hydraulic properties, and the construction of 2D and 3D hydrogeologic frameworks.
Methodology to Address Issue:
New geologic mapping will build on previous studies to address topical research problems with collaborating partners. New mapping and compilation will be at various scales (from 1:24,000 to 1:400,000), chosen as appropriate for the purpose of the mapping. Geologic mapping will be augmented by a variety of supporting information including whole-rock geochemistry and paleomagnetic data. Geochronology, such as argon dating, uranium-lead dating, thermochronology, microstratigraphy, and cosmogenic techniques, is essential to date offset features that provide slip rates as well as document timing of uplift. Petrography and microstructural studies of fault and associated mélange rocks are critical methods to translate mapped units to properties that influence fault behavior.
To project these data into the subsurface, geologic cross sections and geophysical data (such as gravity, magnetic, microearthquakes, well data) are essential. For 3D geologic mapping focused on addressing ground-water issues, work will be at the basin scale and focused on water-bearing strata in the upper 1-2 km of the crust. This will involve such elements as defining basin stratigraphy, creating digital 3D distribution of permeabilities and other properties, predicting the location and influence of faults, and evaluating basin evolution within the overall tectonic framework of the region. Techniques used will include geophysical methods (such as gravity and magnetic), basin stratigraphic analysis, structural analysis, and the constraints of regional tectonostratigraphic settings. Digital 3D models can better use semiquantitative geologic data in a predictive sense to build a parameterized model of an aquifer system. GIS and 3D methods of data visualization and analysis will be employed for overlaying and interpreting multiple data sets.
For regional 3D geologic maps focused on addressing seismic hazards, we look to improve the standard methodology in several ways, including subdivision of basement using gravity/magnetic models, using additional stratigraphic horizons to guide and constrain seismic velocity interpolation, and creating seamless 3D models. To assess the robustness of the geologic and velocity models, we will develop ways to compare and analyze various tomographic and 3D seismic velocity models derived from the 3D geologic maps and make data-intensive calculations more efficient.
Results:
2-D geologic map compilations
2-D geologic map compilations integrate the best available mapping across a large area of regional interest. This integrated depiction of the distribution and orientation of geologic materials and structures at the Earth's surface provides vital input into both the basin-scale and the upper-crustal scale 3-D geologic maps, as well as directly informing regional questions of fault interconnectivity, long-term slip history, and sense of offset.
3-D hydrogeologic frameworks:
3-D hydrogeologic frameworks include the shape of the groundwater basin (often modeled using gravity data), faults that bound and pass through the basin deposits, and stratigraphic and textural information. Examples of hydrogeologic frameworks produced from an earlier incarnation of this project include the Cuyama Basin (north of Santa Barbara) and the Santa Rosa Plain (northern San Francisco Bay area). Because of the Sustainable Groundwater Management Act (SGMA) passed by the California state legislature in 2014, increased demand for these frameworks for groundwater modeling has led to work that spans much of California from the Eel River basin near Eureka in the north to the San Antonio basin near Vandenberg Air Force base in the south.
Using mapping to understand how certain rock types affect how faults slip:
Along the boundary between the Central Valley and the northern California Coast Ranges, rocks have been uplifted to expose old fault zones that are lined with highly sheared serpentinite (the state rock of California). Elsewhere, undeformed and unserpentinized parent rock (which once underlaid an ancient ocean) is exposed. By mapping the textures of these rocks one can infer how these rocks became weaker as the rocks were dissolved, broken up and crushed, and began to shear and slip, with implications of how this process changes the strength of the fault through time.
Where does right-lateral slip go east of the Sierra Nevada?
The San Andreas fault is the most famous member of a system of faults that accommodate right-lateral slip between the North America and Pacific tectonic plates, but other faults can be just as important, especially when they cause large earthquakes. On the east side of the Sierra Nevada is a system of right-lateral and extensional faults called the Walker Lane. Where this slip goes north of Lassen volcano is the subject of debate. We use remote sensing of the magnetic properties of rocks to look the amount of right-lateral offset, such as for the area north of Burney Falls (shown in map below).
Development of 3D geologic and property models:
In the Sacramento Delta of northern California, bringing together relationships of geologic units mapped at the surface, descriptions of rock types encountered in gas wells, logs of electrical and seismic velocity, and geophysical data such as gravity and magnetic data lays a foundation for building a 3D model of the geology. Such a model consists of surfaces of major faults (top panel) and various geologic map units into various flavors of basin fill and basement rocks (middle panel). The 3D model becomes the framework for assigning seismic velocities (how fast sound energy propagates through these rocks) to the subsurface (bottom panel) that can be used to predict ground shaking from future earthquakes.
Below are data or web applications associated with this project.
Digitized sonic velocity and density log data of Sacramento Valley, California
Sonic velocity and density well logs in the Sacramento Valley in California were digitized by hand. These logs are available as scanned files (pdfs and tiffs) on the California Division of Oil, Gas, and Geothermal Resources website and the data consist of transit times and bulk density measured downhole in oil and gas wells in the region. Sonic velocity and density data were also compiled from a n
Data supporting the construction of the Three-Dimensional Geologic Map and Geology-based Seismic Velocity Model of the Sacramento-San Joaquin River Delta and surrounding region, California
Geologic Map Schema (GeMS) version of Wentworth, C.M., Knudsen, K.L., and Witter, R.C., 2023, Quaternary deposits of the 9-county San Francisco Bay Region
Digital database for the geologic map along the southern Bartlett Springs fault zone and adjacent area between Cache Creek and Lake Berryessa, Northern Coast Ranges, California
Gravity, aeromagnetic, magnetic potential, and physical property data of the Bartlett Springs fault zone and surrounding areas, California
Quaternary deposits of the 9-county San Francisco Bay Region: an areally continuous digital map database prepared from Knudsen and others (2000) and Witter and others (2006)
Gravity data of southern Washoe County and adjacent areas, Nevada and California
Aeromagnetic and derivative gridded data, and magnetization boundaries of northeastern California
Digitized sonic velocity and density log data of Central Coast Ranges, California
Gravity and physical property data, basin depth of the Hayfork graben, and horizontal gradient maxima of the southern Klamath Mountains, California
Hydrogeologic Framework data and models for the Eel River groundwater basin, Humboldt County, California
Hydrogeologic data of the Russian River Watershed, Sonoma and Mendocino Counties, California (ver. 1.1, July 2023)
Below are maps associated with this project.
Aeromagnetic map of northeastern California
Geologic and geophysical maps of the Stockton 30’ × 60’ quadrangle, California
Geologic and geophysical maps of the Santa Maria and part of the Point Conception 30'×60' quadrangles, California
Below are publications associated with this project.
Neogene faulting, basin development, and relief generation in the southern Klamath Mountains (USA)
Development and evaluation of models for tectonic evolution in the Cascadia forearc require understanding of along-strike heterogeneity of strain distribution, uplift, and upper-plate characteristics. Here, we investigated the Neogene geologic record of the Klamath Mountains province in southernmost Cascadia and obtained apatite (U-Th)/He (AHe) thermochronology of Mesozoic plutons, Neogene graben
Integrated geologic and geophysical modeling across the Bartlett Springs fault zone, northern California (USA): Implications for fault creep and regional structure
The rate and location at depth of fault creep are important, but difficult to characterize, parameters needed to assess seismic hazard. Here we take advantage of the magnetic properties of serpentinite, a rock type commonly associated with fault creep, to model its depth extent along the Bartlett Springs fault zone, an important part of the San Andreas fault system north of the San Francisco Bay,
Geology along the Yuba Pass and Highway 70 corridors: A complex history of tectonics and magmatism in the northern Sierra Nevada
Achieving sub-nanoTesla precision in multirotor UAV aeromagnetic surveys
Insights into the geometry and evolution of the southern San Andreas Fault from geophysical data, southern California
Hydrologic and geochemical characterization of the Petaluma River watershed, Sonoma County, California
Hydrogeologic characterization of the San Antonio Creek Valley watershed, Santa Barbara County, California
Geologic framework of Mount Diablo, California
Global biotic events evident in the Paleogene marine strata of the eastern San Francisco Bay area, California
Comment on ‘New insights on Franciscan Complex geology, architecture, depositional age, and provenance for the western Mt. Tamalpais area, Marin County, California’ by Bero et al. (2020)
Implementation plan for the southern Pacific Border and Sierra-Cascade Mountains provinces
Aeromagnetic map of Burney and the surrounding area, northeastern California
gravmagsubs: Gravitational and magnetic attraction of 3-D vertical rectangular prisms
Below are partners associated with this project.
- Overview
This project uses geologic and geophysical mapping to build an earth-science framework for scientific investigations that include assessments of critical resources, such as groundwater, and of hazards, such as those resulting from earthquakes, in California west of and including the Sierra Nevada and Cascade arc.
Questions of particular interest include:
What are the geometries, slip rates, and connectivity of faults throughout the broader San Andreas fault system? How do these faults affect resource quantity and quality? How do these factors contribute to the behavior of faults as earthquake sources?
How have basins and landscapes evolved through time? How has this evolution affected resource quantity and quality? Can we use this knowledge to better understand processes related to hazards and resources?
How are rocks and sediments of different properties distributed at the Earth’s surface and in the upper crust? How does this distribution affect resource quantity and quality? How does this distribution affect propagation of seismic energy and ground shaking?
Science Issue and Relevance
Earthquakes, Faulting and Tectonics
Determining how fast faults move through time, how they are connected at depth and at the surface, the style of deformation, and the distribution of rocks with different densities and seismic velocities relate directly to societally relevant questions of how to forecast shaking damage, the size of potential earthquakes, and where faults may rupture.
Basin stratigraphy, structure, and resources
Basins preserve the record of the tectonic evolution, unroofing and sedimentation of California; their structural and stratigraphic underpinnings are essential components for understanding availability and quality of natural resources, particularly water, oil, and gas, as well as understanding how seismic energy propagates in the subsurface and basin effects that concentrate shaking in certain areas.
Surface and Groundwater Resources
Surface water and groundwater serve as water supplies for urban populations, agriculture, and native habitats within California. The combination of rapid population growth, high water use, and arid climate has led to an increased dependence on groundwater resources, resulting in locally severe groundwater depletion and declining groundwater levels. Management of surface-water and groundwater resources in the province requires knowledge of the groundwater system, which in turn requires an understanding of the configuration and properties of aquifers. Such understanding includes the delineation of water-bearing units on the basis of lithology and hydraulic properties, and the construction of 2D and 3D hydrogeologic frameworks.
Methodology to Address Issue:
New geologic mapping will build on previous studies to address topical research problems with collaborating partners. New mapping and compilation will be at various scales (from 1:24,000 to 1:400,000), chosen as appropriate for the purpose of the mapping. Geologic mapping will be augmented by a variety of supporting information including whole-rock geochemistry and paleomagnetic data. Geochronology, such as argon dating, uranium-lead dating, thermochronology, microstratigraphy, and cosmogenic techniques, is essential to date offset features that provide slip rates as well as document timing of uplift. Petrography and microstructural studies of fault and associated mélange rocks are critical methods to translate mapped units to properties that influence fault behavior.
To project these data into the subsurface, geologic cross sections and geophysical data (such as gravity, magnetic, microearthquakes, well data) are essential. For 3D geologic mapping focused on addressing ground-water issues, work will be at the basin scale and focused on water-bearing strata in the upper 1-2 km of the crust. This will involve such elements as defining basin stratigraphy, creating digital 3D distribution of permeabilities and other properties, predicting the location and influence of faults, and evaluating basin evolution within the overall tectonic framework of the region. Techniques used will include geophysical methods (such as gravity and magnetic), basin stratigraphic analysis, structural analysis, and the constraints of regional tectonostratigraphic settings. Digital 3D models can better use semiquantitative geologic data in a predictive sense to build a parameterized model of an aquifer system. GIS and 3D methods of data visualization and analysis will be employed for overlaying and interpreting multiple data sets.
For regional 3D geologic maps focused on addressing seismic hazards, we look to improve the standard methodology in several ways, including subdivision of basement using gravity/magnetic models, using additional stratigraphic horizons to guide and constrain seismic velocity interpolation, and creating seamless 3D models. To assess the robustness of the geologic and velocity models, we will develop ways to compare and analyze various tomographic and 3D seismic velocity models derived from the 3D geologic maps and make data-intensive calculations more efficient.
Results:
2-D geologic map compilations
2-D geologic map compilations integrate the best available mapping across a large area of regional interest. This integrated depiction of the distribution and orientation of geologic materials and structures at the Earth's surface provides vital input into both the basin-scale and the upper-crustal scale 3-D geologic maps, as well as directly informing regional questions of fault interconnectivity, long-term slip history, and sense of offset.
3-D hydrogeologic frameworks:
3-D hydrogeologic frameworks include the shape of the groundwater basin (often modeled using gravity data), faults that bound and pass through the basin deposits, and stratigraphic and textural information. Examples of hydrogeologic frameworks produced from an earlier incarnation of this project include the Cuyama Basin (north of Santa Barbara) and the Santa Rosa Plain (northern San Francisco Bay area). Because of the Sustainable Groundwater Management Act (SGMA) passed by the California state legislature in 2014, increased demand for these frameworks for groundwater modeling has led to work that spans much of California from the Eel River basin near Eureka in the north to the San Antonio basin near Vandenberg Air Force base in the south.
Using mapping to understand how certain rock types affect how faults slip:
Along the boundary between the Central Valley and the northern California Coast Ranges, rocks have been uplifted to expose old fault zones that are lined with highly sheared serpentinite (the state rock of California). Elsewhere, undeformed and unserpentinized parent rock (which once underlaid an ancient ocean) is exposed. By mapping the textures of these rocks one can infer how these rocks became weaker as the rocks were dissolved, broken up and crushed, and began to shear and slip, with implications of how this process changes the strength of the fault through time.
Where does right-lateral slip go east of the Sierra Nevada?
The San Andreas fault is the most famous member of a system of faults that accommodate right-lateral slip between the North America and Pacific tectonic plates, but other faults can be just as important, especially when they cause large earthquakes. On the east side of the Sierra Nevada is a system of right-lateral and extensional faults called the Walker Lane. Where this slip goes north of Lassen volcano is the subject of debate. We use remote sensing of the magnetic properties of rocks to look the amount of right-lateral offset, such as for the area north of Burney Falls (shown in map below).
Development of 3D geologic and property models:
In the Sacramento Delta of northern California, bringing together relationships of geologic units mapped at the surface, descriptions of rock types encountered in gas wells, logs of electrical and seismic velocity, and geophysical data such as gravity and magnetic data lays a foundation for building a 3D model of the geology. Such a model consists of surfaces of major faults (top panel) and various geologic map units into various flavors of basin fill and basement rocks (middle panel). The 3D model becomes the framework for assigning seismic velocities (how fast sound energy propagates through these rocks) to the subsurface (bottom panel) that can be used to predict ground shaking from future earthquakes.
- Data
Below are data or web applications associated with this project.
Filter Total Items: 26Digitized sonic velocity and density log data of Sacramento Valley, California
Sonic velocity and density well logs in the Sacramento Valley in California were digitized by hand. These logs are available as scanned files (pdfs and tiffs) on the California Division of Oil, Gas, and Geothermal Resources website and the data consist of transit times and bulk density measured downhole in oil and gas wells in the region. Sonic velocity and density data were also compiled from a n
Data supporting the construction of the Three-Dimensional Geologic Map and Geology-based Seismic Velocity Model of the Sacramento-San Joaquin River Delta and surrounding region, California
This report includes the previously unpublished primary and derivative data sets that underpin the construction of the three dimensional (3D) geologic map of the upper part of the Earth's crust beneath the Sacramento-San Joaquin River Delta, California. The primary data is X,Y,Z locations of stratigraphic horizons and, to a much lesser extent, geologic structures where penetrated by oil and gas weGeologic Map Schema (GeMS) version of Wentworth, C.M., Knudsen, K.L., and Witter, R.C., 2023, Quaternary deposits of the 9-county San Francisco Bay Region
This is a conversion of Wentworth and others (2023)[DAS1] to the Geologic Map Schema (GeMS) for inclusion in the National Geologic Map Database. The original publication was in the Alacarte schema commonly used for geologic map databases prior to the release of the now mandatory GeMS. The GIS layers in this release have the same scientific content as the source data release. The source data releasDigital database for the geologic map along the southern Bartlett Springs fault zone and adjacent area between Cache Creek and Lake Berryessa, Northern Coast Ranges, California
This geologic map database is comprised of new geologic mapping, at a 1:24,000 scale, along the southern Bartlett Springs fault in the northern California Coast Ranges. The map covers an area of 258 square miles in Lake, Napa, Colusa, and Yolo counties, work was undertaken between 2016 and 2021, and supported by the USGS National Cooperative Geologic Map Program. This geodatabase contains the mostGravity, aeromagnetic, magnetic potential, and physical property data of the Bartlett Springs fault zone and surrounding areas, California
This data release contains principal facts of gravity measurements collected by the U.S. Geological Survey in 2020-2022, a compilation of existing and new density and magnetic susceptibility data, and gridded magnetic and magnetic potential data of the Bartlett Springs Fault Zone and surrounding areas, northern California. These data support modeling of gravity and magnetic anomalies to characteQuaternary deposits of the 9-county San Francisco Bay Region: an areally continuous digital map database prepared from Knudsen and others (2000) and Witter and others (2006)
This digital map database provides an areally continuous representation of the Quaternary surficial deposits of the San Francisco Bay region merged from the database files from Knudsen and others (2000) and Witter and others (2006). The more detailed mapping by Witter and others (2006) of the inner part of the region (compiled at a scale of 1:24,000), is given precedence over the less detailed mapGravity data of southern Washoe County and adjacent areas, Nevada and California
This data release provides principal fact information of gravity data collected and compiled in southern Washoe County, Nevada and adjacent areas in Nevada and California. These data were collected from 1983 to 2011. Data were collected as part of a larger effort by Washoe County, University of Nevada, Reno and the U.S. Geological Survey to investigate the crustal structure of the region as it relAeromagnetic and derivative gridded data, and magnetization boundaries of northeastern California
This data release contains gridded aeromagnetic data from a dataset that merges two aeromagnetic surveys of northeastern California. Data from the Alturas and Burney surveys were gridded and merged to provide a continuous, detailed aeromagnetic dataset of the region. The merged dataset was then corrected for the inclination of the Earth's magnetic field (reduced to pole or rtp); match-filtering ofDigitized sonic velocity and density log data of Central Coast Ranges, California
Sonic velocity and density well logs in the Central Coast Ranges in California were digitized by hand. These logs are available as scanned files (pdfs and tiffs) on the California Division of Oil, Gas, and Geothermal Resources website and the data consist of interval transit times and bulk density measured downhole in oil and gas wells in the region. Sonic velocity data were also compiled from a nGravity and physical property data, basin depth of the Hayfork graben, and horizontal gradient maxima of the southern Klamath Mountains, California
This data release contains principal facts of gravity measurements collected by the U.S. Geological Survey in 2013-2022, a compilation of existing and new density and magnetic susceptibility data, horizontal gradient maxima derived from gravity and magnetic potential fields, and depth of Cenozoic basin fill in the Hayfork basin from inversion of gravity data of the southern Klamath Mountains, CaliHydrogeologic Framework data and models for the Eel River groundwater basin, Humboldt County, California
This data release contains a geospatial database related to a digital 3D hydrogeologic framework model (3D HFM) of the Eel River Valley groundwater basin, California. The geospatial database contains two main data elements: (1) input data to the 3D HFM; (2) interpolated elevations and thicknesses of hydrogeologic units as a cellular array, which are a spatial representation of the 3D HFM results.Hydrogeologic data of the Russian River Watershed, Sonoma and Mendocino Counties, California (ver. 1.1, July 2023)
This data release contains digital data generated by the U.S. Geological Survey under cooperative agreements with Sonoma County Water Agency and the California State Water Resources Control Board to characterize the three-dimensional hydrogeology and water quality of the Russian River Watershed, located in the northern part of the California Coast Ranges section of the Pacific Border province. Thi - Maps
Below are maps associated with this project.
Aeromagnetic map of northeastern California
Aeromagnetic surveys were conducted to improve understanding of the geology and structure in northeastern California, a region predominantly covered by Quaternary and Tertiary, mainly Neogene, volcanic rocks including Medicine Lake volcano. New aeromagnetic data are a substantial improvement over existing data and reveal structural details not resolved by older surveys. Here we show how these dataGeologic and geophysical maps of the Stockton 30’ × 60’ quadrangle, California
This pamphlet and accompanying geologic and geophysical maps are the products of cooperative efforts by the California Geological Survey (CGS) and United States Geological Survey (USGS) to compile a comprehensive, digital representation of the bedrock geology, Quaternary surficial deposits, and potential-field anomalies within the boundaries of the Stockton 30’ × 60’ quadrangle. The Stockton 30’ ×Geologic and geophysical maps of the Santa Maria and part of the Point Conception 30'×60' quadrangles, California
This report presents digital geologic, gravity, and aeromagnetic maps for the onshore parts of the Santa Maria and Point Conception 30'x60' quadrangles at a compilation scale of 1:100,000. The map depicts the distribution of bedrock units, surficial deposits, paleontological data, geophysical data and structural features in the Santa Maria basin and the Santa Ynez Mountains to the south, an area cByNatural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Energy Resources Program, National Cooperative Geologic Mapping Program, Central Energy Resources Science Center, Geology, Minerals, Energy, and Geophysics Science Center, Geosciences and Environmental Change Science Center, Pacific Coastal and Marine Science Center - Publications
Below are publications associated with this project.
Filter Total Items: 21Neogene faulting, basin development, and relief generation in the southern Klamath Mountains (USA)
Development and evaluation of models for tectonic evolution in the Cascadia forearc require understanding of along-strike heterogeneity of strain distribution, uplift, and upper-plate characteristics. Here, we investigated the Neogene geologic record of the Klamath Mountains province in southernmost Cascadia and obtained apatite (U-Th)/He (AHe) thermochronology of Mesozoic plutons, Neogene graben
AuthorsMelanie J. Michalak, Susan M. Cashman, Victoria Langenheim, Taylor C. Team, Dana J. ChristensenIntegrated geologic and geophysical modeling across the Bartlett Springs fault zone, northern California (USA): Implications for fault creep and regional structure
The rate and location at depth of fault creep are important, but difficult to characterize, parameters needed to assess seismic hazard. Here we take advantage of the magnetic properties of serpentinite, a rock type commonly associated with fault creep, to model its depth extent along the Bartlett Springs fault zone, an important part of the San Andreas fault system north of the San Francisco Bay,
AuthorsVictoria Langenheim, Robert J. McLaughlin, Benjamin MeloshGeology along the Yuba Pass and Highway 70 corridors: A complex history of tectonics and magmatism in the northern Sierra Nevada
This field trip traverses a cross section of northern Sierra Nevada geology and landscape along two major corridors, Highway 49 (Yuba Pass) and Highway 70. These highways, and adjacent roadways, offer roadcuts, outcrops, and overviews through diverse pre-Cenozoic metamorphic rocks along the Laurentian margin, Mesozoic batholithic rocks, and Miocene volcanic rocks. Observing this array of rocks onAuthorsMichelle Roberts, Victoria Langenheim, Richard A. Schweickert, Richard E. HansonAchieving sub-nanoTesla precision in multirotor UAV aeromagnetic surveys
An uncrewed aerial vehicle (UAV) multirotor aeromagnetic system using a 5-m sling load for a magnetic sensor system is described and characterized. Four magnetic surveys with identical flight lines were completed, at two nominal altitudes of 25 and 40 m. The surveys were used to assess the repeatability of data collected with the described UAV aeromagnetic system, and comparison with a ground survAuthorsGeoffrey Phelps, Robert E. Bracken, John Spritzer, David S. WhiteInsights into the geometry and evolution of the southern San Andreas Fault from geophysical data, southern California
Two new joint gravity-magnetic models in northern Coachella Valley provide additional evidence for a steep northeast dip of the Mission Creek strand of the southern San Andreas fault (southern California, USA). Gravity modeling indicates a steep northeast dip of the Banning fault in the upper 1–2 km in northern Coachella Valley. The Mission Creek strand and its continuation to the southeast (CoachAuthorsVictoria Langenheim, Gary S. FuisHydrologic and geochemical characterization of the Petaluma River watershed, Sonoma County, California
Executive SummaryThe objectives of the study are to (1) develop an updated assessment of the hydrogeology and geochemistry of the Petaluma valley watershed (PVW) and (2) develop an integrated hydrologic model for the PVW. The purpose of this report is to describe the conceptual model of the hydrologic, hydrogeologic, and water-quality characteristics of the PVW and a numerical groundwater-flow modAuthorsJonathan A. Traum, Nicholas F. Teague, Donald S. Sweetkind, Tracy NishikawaHydrogeologic characterization of the San Antonio Creek Valley watershed, Santa Barbara County, California
The San Antonio Creek Valley watershed (SACVW) is located in western Santa Barbara County, about 15 miles south of Santa Maria and 55 miles north of Santa Barbara, California. The SACVW is about 135 square miles and encompasses the San Antonio Creek Valley groundwater basin; the SACVW is separated from adjacent groundwater basins by the Casmalia and Solomon Hills to the north, and the Purisima HilAuthorsGeoffrey Cromwell, Donald S. Sweetkind, Jill N. Densmore, John A. Engott, Whitney A. Seymour, Joshua Larsen, Christopher P. Ely, Christina L. Stamos, Claudia C. FauntGeologic framework of Mount Diablo, California
The basic stratigraphic and structural framework of Mount Diablo is described using a revised geologic map, gravity data, and aeromagnetic data. The mountain is made up of two distinct stratigraphic assemblages representing different depocenters that were juxtaposed by ~20 km of late Pliocene and Quaternary right-lateral offset on the Greenville-Diablo-Concord fault. Both assemblages are composedAuthorsRussell Graymer, Victoria LangenheimGlobal biotic events evident in the Paleogene marine strata of the eastern San Francisco Bay area, California
Paleogene marine strata in the eastern San Francisco Bay area are exposed in discontinuous outcrops in the various tectonic blocks. Although there are many missing intervals, the strata were previously thought to span most of the Paleocene and Eocene. Revision of biochronology and calibration to the international time scale as well as to the global oxygen isotope curve and sea-level curves indicatAuthorsKristin McDougall-ReidComment on ‘New insights on Franciscan Complex geology, architecture, depositional age, and provenance for the western Mt. Tamalpais area, Marin County, California’ by Bero et al. (2020)
Serious errors and inconsistencies in the article undermine many of its interpretations to the point that principal conclusions are not valid. Much dependence is placed on the maximum depositional age (Dmax) of sandstone units based on zircon analysis of 10 samples, but calculation of those Dmax values is flawed, and their use confuses maximum with actual depositional ages and makes age distinctioAuthorsRussell Graymer, Trevor A. Dumitru, Robert J. McLaughlin, Carl M. WentworthImplementation plan for the southern Pacific Border and Sierra-Cascade Mountains provinces
IntroductionThe National Cooperative Geologic Mapping Program (NCGMP) is publishing a strategic plan titled Renewing the National Cooperative Geologic Mapping Program as the Nation’s Authoritative Source for Modern Geologic Knowledge (Brock and others, in press). The plan provides a vision, mission, and goals for the program during the years 2020–2030, which are:Vision.—Create an integrated, threeAuthorsVictoria E. Langenheim, Russell W. Graymer, Robert E. Powell, Kevin M. Schmidt, Donald S. SweetkindAeromagnetic 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 lineaAuthorsVictoria E. Langenheim - Software
gravmagsubs: Gravitational and magnetic attraction of 3-D vertical rectangular prisms
gravmagsubs is a software package for the R language that provides tools for forward modeling gravity and magnetic anomalies from 3-D right rectangular prisms. The gravity anomaly is defined as the vertical component of gravitational acceleration, while the magnetic anomaly includes the effects of both induced and remanent magnetization. The package can model the total anomaly from a collection - Partners
Below are partners associated with this project.