The Eastern California Shear Zone (ECSZ) Mapping project, funded by the National Cooperative Geologic Mapping Program, combines surficial and bedrock geologic mapping, geophysical surveys, and high-resolution topographic data analysis with neotectonic, geomorphic, structural, volcanic, and geochronologic studies to better understand the tectonic framework and landscape evolution of the ECSZ in the central and eastern Mojave Desert, California. We are using these approaches to address the following map-based research questions: What are the timing and spatial distribution of fault slip across the northern portion of the ECSZ, and how do faults interact with one another, particularly at fault intersections? What is the imprint of early Mesozoic compression and Cenozoic extension on the Quaternary and active tectonics of the region? What are the distribution and geometry of groundwater basins in the northern Mojave Desert, what are the tectonic controls, and how do they fit into the context of the ECSZ? What are the characteristics of contemporaneous Quaternary depositional units between the northern Mojave Desert and the Lower Colorado River Corridor?
Scientific & Societal Relevance:
Landscape Evolution
Erosion and tectonic uplift have profoundly shaped the Mojave Desert region. The weathering, transport, and deposition that shaped the topography also govern the enrichment and availability of many critical mineral deposits, the extent of groundwater resources, and the distribution of nutrients critical to ecosystems. Understanding how surface processes have been influenced by tectonics and past climate variability will improve managers’ ability to make effective land-use decisions related to the utilization and conservation of natural resources. High-resolution topographic data enable coupling of quantitative surface process models to the geologic record, facilitating the use of geologic maps and databases to characterize natural resources and to mitigate natural hazards.
Magmatism
The Mojave Desert Region has been significantly affected by myriad ages and styles of igneous activity that are associated with different suites of mineral deposits, including those recently identified as “critical” for the United States’ national and economic security. Igneous rocks also provide important dateable stratigraphic markers for delineating the temporal evolution of basin formation, tectonic deformation, and sedimentary provenance. Better understanding the history of magmatism through geologic mapping can also be combined with 3D data to characterize potential geothermal energy resources.
Surface and Ground Water
Surface water and groundwater within the Mojave Desert serve as water supplies for population centers, National defense infrastructure, and native habitats of endangered species. The combination of rapid population growth, high water use, and arid climate has led to an increased dependence on groundwater, resulting in locally severe groundwater depletion and declining groundwater levels. Management of surface water and groundwater resources requires knowledge of the groundwater system, which in turn requires an understanding of the configuration and properties of aquifers.
Tectonic Evolution and Plate Boundary Kinematics
The geology and physiography of the northern and central Mojave Desert record all of the major episodes of orogeny, magmatism, continental extension, and basin formation that have shaped the Pacific-North American plate boundary since the Early Paleozoic. Active crustal deformation continues to shape the region, with direct consequences for geologic hazards, earth surface processes, and water resources. Increasingly sophisticated models of the tectonic evolution of the intermountain west require integrated regional geologic synthesis, subsurface geologic characterization, and quantitative description of geologic processes.
Integrated, Regional-Scale Geologic Map Database
Existing geologic map coverage of the ECSZ is inconsistent, mismatched across administrative borders, and lacks adequate surficial geologic detail, preventing comprehensive regional characterization of hazards associated with recent and active tectonic deformation. Seamless, multi-scale surficial and bedrock geologic mapping is essential for land management decisions. Complementary subsurface interpretations provide the template for regional geologic framework models of the earth’s composition, structure, and evolution. Geochronology, geochemistry, geophysics, and numerical modeling of Earth’s physical systems provide the analytical framework for understanding the timescales and physical properties of processes critical to mineral, water, and energy resource management, environmental health, hazard mitigation, and ecosystem impact.
Methodology:
We use a variety of techniques for building on recent 1:100k scale geologic mapping in the region. These include everything from traditional “boots on the ground” type field work to the application of geophysical and other remote sensing techniques, and targeted geochronology. These efforts are coordinated and compiled in a way that will contribute to a seamless, multi-scale geologic map database of the ECSZ. Specific approaches include:
Interpretation of remote sensing, including aerial and satellite imagery, DEM’s (including LiDAR and Structure for Motion), and spectral imagery. Many contacts and faults are visible on photo-imagery in the desert environment and can be accurately mapped as an aid to fieldwork.
Field mapping of contacts, faults, and folds, measurement of bedding and foliation attitudes, making detailed lithologic observations, and collecting samples for petrographic, geochemical, and geochronologic analysis. Most of this mapping is done directly on air photos or on field tablets with user-configured base maps, aided by the collection of many spot observations that are recorded using GPS.
Collection, analysis, and modeling of gravity and aeromagnetic data. This includes standard techniques such as depth-to-basement modeling and gradient and frequency analysis, as well as novel forward modeling techniques. These analyses yield models of subsurface geologic structure, which can be integrated with both surface and 3D mapping.
Digital compilation of geologic mapping as field mapping progresses. As needed, field mapping is modified in a GIS, based on digital imagery and GPS-based locality information. This is conducted in cooperation with other USGS geologic mapping projects in order to build towards a seamless geologic map database of the region.
Analytical work, including appropriate numeric chronology and geochemistry from both sedimentary and igneous rocks is used to correlate map units and to constrain the timing and rate of offset of faults of the ECSZ.
Below are data or web applications associated with this project.
Tabular geochronologic and geochemical data from metasedimentary and associated rocks in the Lane Mountain area, San Bernardino County, California
Aeromagnetic Data and horizontal gradient maxima of Blythe, California, and Surrounding Areas in California and Arizona
Aeromagnetic Data and horizontal gradient maxima of Garlock, California, and Surrounding Areas in California
Data release for cosmogenic beryllium-10 exposure ages of moraine boulders in the Stura Valley, Maritime Alps, northwestern Italy
Zircon U-Pb data for volcanic ash beds in the Barstow Formation, California probe data 2022
Data release for luminescence: Edwards Air Force Base (CA) and CA Water Science Center report including luminescence data and ages
Surface Displacement Observations of the 2019 Ridgecrest, California Earthquake Sequence
Pre-existing features associated with active faulting in the vicinity of the 2019 Ridgecrest, California earthquake sequence
Gravity data of the Hinkley area, southern California
Below are publications associated with this project.
Last Glacial Maximum and early deglaciation in the Stura Valley, southwestern European Alps
Mississippian sedimentary facies patterns in east-central California and implications for development of the Permian last chance thrust
Geochronologic, isotopic, and geochemical data from pre-Cretaceous plutonic rocks in the Lane Mountain area, San Bernardino County, California
Geomorphic history of Lake Manix, Mojave Desert, California: Evolution of a complex terminal lake basin
Geologic and geophysical maps of the Newfoundland Mountains and part of the adjacent Wells 30' x 60' quadrangles, Box Elder County, Utah
Documentation of Surface Fault Rupture and Ground‐Deformation Features Produced by the 4 and 5 July 2019 Mw 6.4 and Mw 7.1 Ridgecrest Earthquake Sequence
Evidence of previous faulting along the 2019 Ridgecrest, California earthquake ruptures
Surface displacement distributions for the July 2019 Ridgecrest, California earthquake ruptures
Correlations along a 140 km transect in the westernmost Peach Spring Tuff, and tracing changing facies through depositional environments
Depth to bedrock based on modeling of gravity data of the eastern part of Edwards Air Force Base, California
Geochronologic, isotopic, and geochemical data from igneous rocks in the Lane Mountain area, San Bernardino County, California
Below are partners associated with this project.
- Overview
The Eastern California Shear Zone (ECSZ) Mapping project, funded by the National Cooperative Geologic Mapping Program, combines surficial and bedrock geologic mapping, geophysical surveys, and high-resolution topographic data analysis with neotectonic, geomorphic, structural, volcanic, and geochronologic studies to better understand the tectonic framework and landscape evolution of the ECSZ in the central and eastern Mojave Desert, California. We are using these approaches to address the following map-based research questions: What are the timing and spatial distribution of fault slip across the northern portion of the ECSZ, and how do faults interact with one another, particularly at fault intersections? What is the imprint of early Mesozoic compression and Cenozoic extension on the Quaternary and active tectonics of the region? What are the distribution and geometry of groundwater basins in the northern Mojave Desert, what are the tectonic controls, and how do they fit into the context of the ECSZ? What are the characteristics of contemporaneous Quaternary depositional units between the northern Mojave Desert and the Lower Colorado River Corridor?
The core of the Manix Fault (dark band dipping to the left in the middle of the image), which is an east-trending left-lateral fault in the central Eastern California Shear Zone, separates two Pliocene sedimentary sequences near Afton Canyon, central Mojave Desert Scientific & Societal Relevance:
Landscape Evolution
Erosion and tectonic uplift have profoundly shaped the Mojave Desert region. The weathering, transport, and deposition that shaped the topography also govern the enrichment and availability of many critical mineral deposits, the extent of groundwater resources, and the distribution of nutrients critical to ecosystems. Understanding how surface processes have been influenced by tectonics and past climate variability will improve managers’ ability to make effective land-use decisions related to the utilization and conservation of natural resources. High-resolution topographic data enable coupling of quantitative surface process models to the geologic record, facilitating the use of geologic maps and databases to characterize natural resources and to mitigate natural hazards.
Magmatism
The Mojave Desert Region has been significantly affected by myriad ages and styles of igneous activity that are associated with different suites of mineral deposits, including those recently identified as “critical” for the United States’ national and economic security. Igneous rocks also provide important dateable stratigraphic markers for delineating the temporal evolution of basin formation, tectonic deformation, and sedimentary provenance. Better understanding the history of magmatism through geologic mapping can also be combined with 3D data to characterize potential geothermal energy resources.
Research Geologist Geoff Phelps measuring basalt flow thickness and magnetic susceptibility of individual basalt flows of the Broadwell Mesa Basalt in the central Mojave Desert near Ludlow, CA. Surface and Ground Water
Surface water and groundwater within the Mojave Desert serve as water supplies for population centers, National defense infrastructure, and native habitats of endangered species. The combination of rapid population growth, high water use, and arid climate has led to an increased dependence on groundwater, resulting in locally severe groundwater depletion and declining groundwater levels. Management of surface water and groundwater resources requires knowledge of the groundwater system, which in turn requires an understanding of the configuration and properties of aquifers.
Tectonic Evolution and Plate Boundary Kinematics
The geology and physiography of the northern and central Mojave Desert record all of the major episodes of orogeny, magmatism, continental extension, and basin formation that have shaped the Pacific-North American plate boundary since the Early Paleozoic. Active crustal deformation continues to shape the region, with direct consequences for geologic hazards, earth surface processes, and water resources. Increasingly sophisticated models of the tectonic evolution of the intermountain west require integrated regional geologic synthesis, subsurface geologic characterization, and quantitative description of geologic processes.
Lineations on a vertical fault strand of the Soda-Avawatz Fault Zone, exposed in the northern Soda Mountains, Mojave Desert, southern California. The fault can be seen cutting both late Tertiary sand and gravel units, but is buried by an overlying mid-Pleistocene alluvial gravel deposit. Integrated, Regional-Scale Geologic Map Database
Existing geologic map coverage of the ECSZ is inconsistent, mismatched across administrative borders, and lacks adequate surficial geologic detail, preventing comprehensive regional characterization of hazards associated with recent and active tectonic deformation. Seamless, multi-scale surficial and bedrock geologic mapping is essential for land management decisions. Complementary subsurface interpretations provide the template for regional geologic framework models of the earth’s composition, structure, and evolution. Geochronology, geochemistry, geophysics, and numerical modeling of Earth’s physical systems provide the analytical framework for understanding the timescales and physical properties of processes critical to mineral, water, and energy resource management, environmental health, hazard mitigation, and ecosystem impact.
Methodology:
We use a variety of techniques for building on recent 1:100k scale geologic mapping in the region. These include everything from traditional “boots on the ground” type field work to the application of geophysical and other remote sensing techniques, and targeted geochronology. These efforts are coordinated and compiled in a way that will contribute to a seamless, multi-scale geologic map database of the ECSZ. Specific approaches include:
Interpretation of remote sensing, including aerial and satellite imagery, DEM’s (including LiDAR and Structure for Motion), and spectral imagery. Many contacts and faults are visible on photo-imagery in the desert environment and can be accurately mapped as an aid to fieldwork.
Field mapping of contacts, faults, and folds, measurement of bedding and foliation attitudes, making detailed lithologic observations, and collecting samples for petrographic, geochemical, and geochronologic analysis. Most of this mapping is done directly on air photos or on field tablets with user-configured base maps, aided by the collection of many spot observations that are recorded using GPS.
Research Geologist Kevin Schmidt and Geoff Phelps examine satellite imagery on tablet computers during geologic mapping field work near Broadwell Mesa while supported by mule pack train. Collection, analysis, and modeling of gravity and aeromagnetic data. This includes standard techniques such as depth-to-basement modeling and gradient and frequency analysis, as well as novel forward modeling techniques. These analyses yield models of subsurface geologic structure, which can be integrated with both surface and 3D mapping.
Simplified geologic, gravity, and aeromagnetic maps of the eastern most fault of the Eastern California Shear Zone showing the locations and geometries of pull-apart basins. The locations, shapes and sizes of these basins provide constraint on fault step-overs and total offset along the Soda-Avawatz - Bristol-Granite Mountains Fault Zone. Red lines - faults; dashed blue lines - playas; dark blue lines - 0.5 km contours of basin thickness; plus signs - locations of maximum horizontal gradients, with smaller symbols denoting gradient values below the mean value and larger symbols denoting gradient values above the mean value. Digital compilation of geologic mapping as field mapping progresses. As needed, field mapping is modified in a GIS, based on digital imagery and GPS-based locality information. This is conducted in cooperation with other USGS geologic mapping projects in order to build towards a seamless geologic map database of the region.
Analytical work, including appropriate numeric chronology and geochemistry from both sedimentary and igneous rocks is used to correlate map units and to constrain the timing and rate of offset of faults of the ECSZ.
- Data
Below are data or web applications associated with this project.
Tabular geochronologic and geochemical data from metasedimentary and associated rocks in the Lane Mountain area, San Bernardino County, California
This dataset provides geochronologic and geochemical data for selected metasedimentary and associated rock samples collected in the Lane Mountain area about 20 kilometers northwest of Barstow, California. Geochronologic data were obtained for 24 samples, and geochemical data were obtained for 5 of these. The dataset consists of four tables in csv (comma separated values) format: (1) sample localitAeromagnetic Data and horizontal gradient maxima of Blythe, California, and Surrounding Areas in California and Arizona
This data release provides access to an aeromagnetic survey and magnetization boundaries over Blythe, California and surrounding areas in southern California and western Arizona. The survey extends east of Joshua Tree National Park across the Colorado River and west over the Dome Rock, Trigo, and Plomosa Mountains in Arizona. The survey was flown north of the Chocolate Mountains Gunnery Range overAeromagnetic Data and horizontal gradient maxima of Garlock, California, and Surrounding Areas in California
This data release provides access to an aeromagnetic survey and magnetization boundaries over Garlock, California and surrounding areas in southern California. The survey extends from the city of Bakersfield across the southern Sierra Nevada and Tehachapi Mountains and west over Indian Wells Valley and the towns of Mojave and Rosamond to just northwest of the town of Barstow. These data were acquiData release for cosmogenic beryllium-10 exposure ages of moraine boulders in the Stura Valley, Maritime Alps, northwestern Italy
This report summarizes the cosmogenic beryllium-10 (10Be) geochronologic results from boulders deposited on moraines in the Stura Valley of the Maritime Alps, the southwestern most extent of the European Alpine mountain chain, northwestern Italy. Within this report are detailed the methodologies used to collect samples of whole rock, determine the concentrations of cosmogenic 10Be in purified quarZircon U-Pb data for volcanic ash beds in the Barstow Formation, California probe data 2022
Zircon grains separated from altered ash beds were analyzed to better understand the ages of the beds. Isotopic analyses for U-Pb geochronology and trace element geochemistry were performed simultaneously by secondary ion mass spectrometry using the Stanford-USGS SHRIMP-RG ion microprobe housed at Stanford University, USA. Analyses followed the analytical protocol and data acquisition conditions dData release for luminescence: Edwards Air Force Base (CA) and CA Water Science Center report including luminescence data and ages
The following report summarizes the dating results from Aeolian deposits within and around Edwards Air Force Base in California. Within this report, we detail the methodology used by the USGS Luminescence Geochronology Laboratory to obtain ages including sample preparation methods, luminescence measurement, equivalent dose determination, and dating related calculations. We recommend that this repoSurface Displacement Observations of the 2019 Ridgecrest, California Earthquake Sequence
Surface rupture associated with the 2019 Ridgecrest, California earthquake sequence includes the dominantly left-lateral and northeast-striking M6.4 rupture and dominantly right-lateral and northwest-striking M7.1 rupture. This data release includes surface-displacement observations of these ruptures made by teams of federal, state, academic, and private sector geologists between July and NovemberPre-existing features associated with active faulting in the vicinity of the 2019 Ridgecrest, California earthquake sequence
This dataset is composed of linear active tectonic and other relevant features (scarps, deflected drainages, and lineaments and contrasts in topography, vegetation, and ground color) mapped based on high-resolution topography, aerial/satellite imagery, and field observations. The mapping covers the area surrounding the 2019 Ridgecrest, California earthquake surface ruptures. Point locations of fieGravity data of the Hinkley area, southern California
This dataset contains gravity data collected in the HInkley area in the Mojave Desert of southern California. - Publications
Below are publications associated with this project.
Last Glacial Maximum and early deglaciation in the Stura Valley, southwestern European Alps
We combined data from geomorphologic surveys, glacial modelling, and 10Be exposure ages of boulders on moraines, to investigate the Last Glacial Maximum (LGM) and the early retreat glacial phases in the Stura Valley of the Maritime Alps. We used the exposure ages to reconstruct the timing of standstills or readvances which interrupted the post-LGM withdrawal, initiated ∼24 ka. We mapped and datedMississippian sedimentary facies patterns in east-central California and implications for development of the Permian last chance thrust
Mississippian sedimentary facies belts in east-central California, occurring primarily in the autochthon (lower plate) of the Last Chance Thrust, are consistently oriented in a northeast–southwest direction. The boundary of one belt is marked by the depositional limit of the Osagean to Meramecian Santa Rosa Hills Limestone; a second belt farther to the northwest is bordered by the erosional truncaGeochronologic, isotopic, and geochemical data from pre-Cretaceous plutonic rocks in the Lane Mountain area, San Bernardino County, California
Pre-Cretaceous, predominantly dioritic plutonic rocks in the Lane Mountain area, California, intrude metasedimentary and metavolcanic rocks considered part of the El Paso terrane. New geochronologic (uranium-lead zircon), geochemical, and isotopic data provide a reliable basis for dividing these pre-Cretaceous plutonic rocks into two mappable suites of Permian–Triassic and Late Jurassic ages. TheGeomorphic history of Lake Manix, Mojave Desert, California: Evolution of a complex terminal lake basin
The US Environmental Protection Agency's short-term freshwater effluent test methods include a fish (Pimephales promelas), a cladoceran (Ceriodaphnia dubia), and a green alga (Raphidocelis subcapitata). There is a recognized need for additional taxa to accompany the three standard species for effluent testing. An appropriate additional taxon is unionid mussels because mussels are widely distributeGeologic and geophysical maps of the Newfoundland Mountains and part of the adjacent Wells 30' x 60' quadrangles, Box Elder County, Utah
The Newfoundland Mountains map area (Newfoundland Mountains and adjacent part of Wells 30' x 60' quadrangles) is located in Box Elder County, northwestern Utah. The map encompasses broad expanses of the Great Salt Lake Desert as well as several picturesque mountain ranges (figures 1, 2, and 3). The geology of the area was last mapped and summarized by Doelling (1980). Since that landmark study, muDocumentation of Surface Fault Rupture and Ground‐Deformation Features Produced by the 4 and 5 July 2019 Mw 6.4 and Mw 7.1 Ridgecrest Earthquake Sequence
The MwMw 6.4 and MwMw 7.1 Ridgecrest earthquake sequence occurred on 4 and 5 July 2019 within the eastern California shear zone of southern California. Both events produced extensive surface faulting and ground deformation within Indian Wells Valley and Searles Valley. In the weeks following the earthquakes, more than six dozen scientists from government, academia, and the private sector carefullyEvidence of previous faulting along the 2019 Ridgecrest, California earthquake ruptures
The July 2019 Ridgecrest earthquake sequence in southeastern California was characterized as surprising because only ~35% of the rupture occurred on previously mapped faults. Employing more detailed inspection of pre-event high-resolution topography and imagery in combination with field observations, we document evidence of active faulting in the landscape along the entire fault system. Scarps, deSurface displacement distributions for the July 2019 Ridgecrest, California earthquake ruptures
Surface rupture in the 2019 Ridgecrest, California, earthquake sequence occurred along two orthogonal cross faults and includes dominantly left‐lateral and northeast‐striking rupture in the Mw 6.4 foreshock and dominantly right‐lateral and northwest‐striking rupture in the Mw 7.1 mainshock. We present >650 field‐based, surface‐displacement observations for these ruptures and synthesize our resultsCorrelations along a 140 km transect in the westernmost Peach Spring Tuff, and tracing changing facies through depositional environments
Tephrochronology is the correlation of tephra beds and tuffs by various means, and it is an important tool in refining stratigraphic and structural interpretations. The 18.78 Ma Peach Spring Tuff (PST) is a large-volume ignimbrite that was deposited across a ~200 km x 360 km area of southeastern California, northwestern Arizona, and southern Nevada. The PST is a valuable stratigraphic marker inDepth to bedrock based on modeling of gravity data of the eastern part of Edwards Air Force Base, California
We describe a gravity survey acquired to determine the thickness of basin-fill deposits (depth to bedrock) and to delineate geologic structures that might influence groundwater flow beneath the eastern part of Edwards Air Force Base, California. Inversion of these gravity data combined with geologic map and well information provides an estimate of the thickness of basin-fill deposits (defined hereGeochronologic, isotopic, and geochemical data from igneous rocks in the Lane Mountain area, San Bernardino County, California
We present new geochronologic, isotopic, and geochemical data for selected igneous rocks in the Lane Mountain area, California. We determined SHRIMP-RG U-Pb zircon ages for the following units: (1) Larrea complex (~253 Ma and ~149–146 Ma); (2) Daisy granodiorite (~151 Ma); (3) Jack Spring quartz monzonite (~85–82 Ma); (4) unnamed porphyritic dikes and stocks (~80–73 Ma); and (5) Lane Mountain volc - Partners
Below are partners associated with this project.