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Victoria Langenheim

Publications and source records attributed to Victoria Langenheim.

17 recordsLinked to original sources
USGS2026

Controls on natural hydrogen generation during serpentinization of mantle rocks

Mantle rocks undergoing serpentinization can generate significant amounts of natural hydrogen, yet the rates and controlling processes remain poorly understood. Here, we constrain the possible hydrogen generation rates in two distinct mantle rock types, the fertile lherzolites of the Western Pyrenees and the depleted harzburgites of Northern California, to relatively low rates of ~0.1 to ~0.5 tonnes H₂ yr⁻¹ km⁻³ of reactive rock. When integrated over the full reactive volumes, this corresponds to total production rates of ~300 to ~600 tonnes H₂ yr⁻¹. By combining three-dimensional geophysical inversion with numerical modelling of fluid-rock processes, we show that hydrogen generation rates are mainly limited by H₂ saturation in the fluid and reaction kinetics. Under these constraints, hydrogen generation in mantle-derived serpentinization systems proceeds slowly, making rapid large-scale replenishment unlikely and suggesting that large, economically relevant accumulations, would require timescales of thousands to tens of thousands of years to develop.

northern California, western Pyrenees↗
USGS2025

Relationship of basin structure and bedrock lithology to faulting in the 2019 Ridgecrest earthquake region, California, from gravity and aeromagnetic data

We investigate patterns of cumulative offsets on the faults that ruptured in 2019 and along the Garlock Fault in the Ridgecrest region, California using recently published gravity and aeromagnetic data. We also examine the relationship of basin structure and bedrock structure to the 2019 M7.1 Ridgecrest earthquake ruptures (Fig. 1A), which were primarily along a dextral northwest-striking fault system, and along a sinistral northeast-striking fault, which ruptured hours earlier with a M6.4 event.

California↗
USGS2024

Site response in the Walnut Creek–Concord region of the San Francisco Bay, California: Ground motion amplification in a fault-bounded basin

Thirty‐seven portable accelerometers were deployed in the eastern San Francisco Bay communities of Walnut Creek and Concord to study site response in a fault‐bounded, urban, sedimentary basin. Local earthquakes were recorded for a period of two years from 2017 to 2019 resulting in 101 well‐recorded events. Site response is estimated by two methods: the reference site spectral ratio method and a source‐site spectral inversion method. The reference site spectral ratio method allows investigation of the variability of site amplification with source azimuth and frequency. The source‐site spectral inversion method yields the best least‐squares fit to site response for a database of ground‐motion records. Both methods show substantial amplification in the Walnut Creek–Concord basin below 2 Hz indicating strong surface‐wave development. Greater amplification is seen for sources aligned along the long axis of the basin. Inversion using close‐in sources at short distances yields lower amplification at longer periods than the entire data set due to reduced surface‐wave generation for steeper angles of incidence. Inversion of site response spectra for shallow shear‐wave velocity using a global search algorithm yields V S30 values consistent with generalized mapping results based on geology and topography but with greater variability due to local site variations. 3D finite‐element modeling shows greater amplification in the Walnut Creek–Concord basin with a basin‐edge effect likely contributing to higher ground motions. Topography is also seen to lead to increased scattering and shadowing effects.

California↗
USGS2023

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 sediment thickness, detrital zircon records from Neogene grabens, gravity and magnetic data, and kinematic analysis of faults. We documented three aspects of Neogene tectonics: early Miocene and younger rock exhumation, development of topographic relief sufficient to isolate Neogene graben-filling sediments from sources outside of the Klamath Mountains, and initiation of mid-Miocene or younger right-lateral and reverse faulting. Key findings are: (1) 10 new apatite AHe mean cooling ages from the Canyon Creek and Granite Peak plutons in the Trinity Alps range from 24.7 ± 2.1 Ma to 15.7 ± 2.1 Ma. Inverse thermal modeling of these data and published apatite fission-track ages indicate the most rapid rock cooling between ca. 25 and 15 Ma. One new AHe mean cooling age (26.7 ± 3.2 Ma) from the Ironside Mountain batholith 40 km west of the Trinity Alps, combined with previously published AHe ages, suggests geographically widespread latest Oligocene to Miocene cooling in the southern Klamath Mountains province. (2) AHe ages of 39.4 ± 5.1 Ma on the downthrown side and 22.7 ± 3.0 Ma on the upthrown side of the Browns Meadow fault suggest early Miocene to younger fault activity. (3) U-Pb detrital zircon ages ( n = 862) and Lu-Hf isotope geochemistry from Miocene Weaverville Formation sediments in the Weaverville, Lowden Ranch, Hayfork, and Hyampom grabens south and southwest of the Trinity Alps can be traced to entirely Klamath Mountains sources; they suggest the south-central Klamath Mountains had, by the middle Miocene, sufficient relief to isolate these grabens from more distal sediment sources. (4) Two Miocene detrital zircon U-Pb ages of 10.6 ± 0.4 Ma and 16.7 ± 0.2 Ma from the Lowden Ranch graben show that the maximum depositional age of the upper Weaverville Formation here is younger than previously recognized. (5) A prominent steep-sided negative gravity anomaly associated with the Hayfork graben shows that both the north and south margins are fault-controlled, and inversion of gravity data suggests basin fill is between 1 km and 1.9 km thick. Abrupt elevation changes of basin fill-to-bedrock contacts reported in well logs record E-side-up and right-lateral faulting at the eastern end of the Hayfork graben. A NE-striking gravity gradient separates the main graben on the west from a narrower, thinner basin to the east, supporting this interpretation. (6) Of fset of both the base of the Weaverville Formation and the cataclasite-capped La Grange fault surface by a fault on the southwest margin of the Weaverville basin documents 200 m of reverse and 1500 m of right-lateral strike-slip motion on this structure, here named the Democrat Gulch fault; folded and steeply dipping strata adjacent to the fault confirm that faulting postdated deposition of the Weaverville Formation.

California, Oregon↗
USGS2023

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, California (western United States). We model aeromagnetic and gravity anomalies using geologic constraints along 14 cross sections over a distance of 120 km along the fault zone. Our results predict that the fault zone has more serpentinite at depth than inferred by geologic relationships at the surface. Existing geodetic models are inconsistent and predict different patterns of creep along the fault. Our results favor models with more extensive creep at depth. The source of the serpentinite appears to be ophiolite thrust westward and beneath the Franciscan Complex, an interpretation supported by the presence of antigorite, a high-temperature serpent ine mineral stable at depth, in fault gouge near Lake Pillsbury.

California↗
USGS2023

Evolution of Miocene normal and dextral faulting in the lower Colorado River region near Blythe, California, USA

The evolution of strain in nascent continental plate boundaries commonly involves distributed deformation and transitions between different styles of deformation as the plate boundary matures. Distributed NW-striking faults, many with km-scale right-lateral separation, are prevalent near Blythe, California, and have been variably interpreted to have accommodated either Middle Miocene NE-SW extension as normal faults or Late Miocene to Pliocene dextral shear as strike-slip faults. However, with poor timing and kinematic constraints, it is unclear how these faults relate to known domains of Neogene deformation and the evolution of the Pacific–North America plate boundary. We present kinematic data (n = 642 fault planes, n = 512 slickenlines) that demonstrate that these faults dominantly dip steeply northeast; ~96% of measured faults record normal, dextral, or oblique dextral-normal kinematics that likely reflect a gradational transition between normal and dextral oblique kinematic regimes. We constrain fault timing with 11.7 Ma and 7.0 Ma 40 Ar/ 39 Ar dates of rocks cut by faults, and laser ablation–inductively coupled plasma–mass spectrometry U-Pb dating of calcite mineralized during oblique dextral faulting that demonstrates fault slip at ca. 10–7 Ma and perhaps as late as ca. 4 Ma. This Late Miocene dextral oblique faulting is best compatible with a documented regional transition from Early to Middle Miocene NE-directed extension during detachment fault slip to subsequent NW-directed dextral shear. We estimate 11–38 km of cumulative dextral slip occurred across a 50-km-wide zone from the Palen to Riverside mountains, including up to 20 km of newly documented dextral shear that may partly alleviate the regional discrepancy of cumulative dextral shear along this part of the Late Miocene Pacific–North America plate boundary.

California↗
USGS2023

Geology 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 on a single trip provides an opportunity to examine the progression of tectonic forces in this region since the Paleozoic Era. Inspiration for this trip is a 1:100,000-scale geologic map and geophysical maps of the Portola 30′ × 60′ quadrangle that integrate decades of published and unpublished mapping with new geophysical data. The quadrangle map will seamlessly depict a geologically complex region along the boundary between the Sierra Nevada and Basin and Range provinces, dominated by transtensional tectonics of the Walker Lane. This field trip highlights many of the major units of the geologic map and will also feature new geochronological data on plutonic rocks.

California↗
USGS2023

Geologic 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’ × 60’ quadrangle covers approximately 4,890 km 2 of Contra Costa, Alameda, San Joaquin, and Stanislaus Counties, California. From the rugged hillsides of the northern Diablo Range in the west to the San Joaquin Valley in the east, the map extends roughly 88 km across growing suburban communities of the eastern San Francisco Bay Area and Livermore Valley, grass-covered ranchlands along eastern slopes of the Diablo Range, and into the low farmlands of the San Joaquin Valley and Sacramento-San Joaquin River Delta (Figure 1). The elevation ranges from near sea level in the Delta to 1,173 meters on Mt. Diablo, the most prominent peak of the San Francisco Bay region.

California↗
USGS2022

Insights 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 (Coachella segment) coincide with the northeastern margin of a Cenozoic basin and are marked by prominent gravity and magnetic gradients that are consistent with these strands of the San Andreas fault having accommodated >160 km of right-lateral and 1–5 km of vertical displacement. These anomalies are best fit by a moderate to steep northeast dip. Such a geometry is further supported by seismicity, reflectivity, geodesy, and boundary-element modeling. We explore the possibility that these fault strands forming the margin of Coachella Valley were originally near vertical and have rotated into their present orientation by underplating of a localized high-velocity, lower-crustal prong within the Peninsular Ranges batholith. Reconstructions of San Andreas fault offset suggest that this crystalline body was translated into the San Gorgonio Pass area at the time of major fault reorganization at 1.1–1.3 Ma.

California↗
USGS2021

Influence of pre-existing structure on pluton emplacement and geomorphology: The Merrimac plutons, northern Sierra Nevada, California (USA)

In much of the western Cordillera of North America, the geologic framework of crustal structure generated in the Mesozoic leaves an imprint on later plutonic emplacement, subsequent structural setting, and present landscape morphology. The Merrimac plutons in the northern Sierra Nevada (California, USA) are a good example of the influence of pre-existing structure at a larger scale. This paper updates and refines earlier studies of the Merrimac plutons, with the addition of analysis of gravity and magnetic data and new 206 Pb/ 238 U zircon dates. The gravity and magnetic data not only confirm the presence of two different neighboring plutons, but also (1) support the presence of a third pluton, (2) refine the nature of the contact between the Merrimac plutons as being structurally controlled, and (3) estimate the depth extent of the plutons to be ∼4–5 km. The zircon 206 Pb/ 238 U dates indicate that the two main plutons have statistically different crystallization ages nearly 4 m.y. apart. Geomorphic analyses, including estimates of relief, roughness and drainage density and generation of chi plots, indicate that the two main plutons are characterized by different elevations with large longitudinal channel knickpoints that we speculatively attribute to possible reactivation of pre-existing structure in addition to lithologic variations influencing relative erosion susceptibility in response to prior accelerated surface uplift.

California↗
USGS2021

Geologic 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 composed of Cretaceous and Cenozoic strata overlying a compound basement made up of the Franciscan and Great Valley complexes. The rocks are folded and faulted by late Neogene and Quaternary compressional structures related to both regional plate-boundary–normal compression and a restraining step in the strike-slip fault system. The core of the mountain is made up of uplifted basement rocks. Late Neogene and Quaternary deformation is overprinted on Paleogene extensional deformation that is evidenced at Mount Diablo by significant attenuation in the basement rocks and by an uptilted stepped graben structure on the northeast flank. Retrodeformation of the northeast flank suggests that late Early to early Late Cretaceous strata may have been deposited against and across a steeply west-dipping basement escarpment. The location of the mountain today was a depocenter through the Late Cretaceous and Paleogene and received shallow-marine deposits periodically into the late Miocene. Uplift of the mountain itself happened mostly in the Quaternary.

California↗
USGS2019

Depth 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 here as Cenozoic sedimentary and volcanic rocks). After removing the gravitational effect of the basin-fill deposits, the inversion also results in a gravity map that reflects variations in the bedrock density. The depth to bedrock is generally less than 1 kilometer in the map area, except for localized depressions north and south of Kramer Hills, northwest-trending pockets about 4 kilometers northeast of Rogers Lake, and a large depression southwest of Rogers Lake. In the area near Leuhman Ridge, depth to bedrock is shallow. The Spring and Leuhman faults do not coincide with large variations in basin-fill thickness or with prominent gravity gradients, suggestive of minor vertical displacement and minor horizontal displacement at their southeastern mapped extents where they project across a large gravity low.

California↗
USGS2019

Distributed fault slip in the eastern California shear zone: Adding pieces to the puzzle near Barstow, California

We investigate the dextral Lockhart and Mt. General faults, which are among four active structures in the northwestern portion of the eastern California shear zone (ECSZ). Early mapping depicts the Lockhart and Mt. General faults as discontinuous fault traces that continue northwest of the Lenwood Fault. Recent work indicates that the Lenwood Fault slips at ~0.2-1.0 mm/yr over the past ~8 ka and 0.8 ± 0.2 mm/yr since ~37 ± 7 ka. We reconstruct the record of fault slip for the Lockhart and Mt. General faults using high-resolution Structure-from-Motion built topography, field observations, geochronology, and gravity data. Geomorphic offsets along a Holocene-active trace of the Lockhart Fault indicate dextral displacement between ~4 and 6 m. A feldspar infrared stimulated luminescence (IRSL) age implies surface abandonment and at least one earthquake after 3540 ± 880 ka (2σ). The implied Holocene fault slip rate on the Lockhart Fault is between ~0.9 and 2.3 mm/yr. Holocene-active traces of the 19-km-long Mt. General Fault are marked by southwest-facing scarps and dextral offsets of ~4–5 m on alluvial fans, with down-to-the-southwest vertical offset of ~0.3 m. Summing dextral displacements across subparallel fault strands yields a maximum of ~7–8 m. A feldspar IRSL age indicates deposition of the alluvial fans since 11,380 ± 1700 ka (2σ). This results in a Holocene slip ~0.3–0.6 mm/yr, possibly ranging up to 1.0 mm/yr. Taken together, these observations imply a net Holocene dextral slip rate for active faults in Hinkley Valley at 1.2–3.3 mm/yr―higher than expected given published fault slip rates along-strike to the southeast.

California↗
USGS2018

Middle Pleistocene infill of Hinkley Valley by Mojave River sediment and associated lake sediment: Depositional architecture and deformation by strike-slip faults

Hinkley Valley in the Mojave Desert, near Barstow about 140 km northeast of Los Angeles and midway between Victorville Valley and the Lake Manix basin, contains a thick sedimentary sequence delivered by the Mojave River. Our study of sediment cores drilled in the valley indicates that Hinkley Valley was probably a closed playa basin with stream inflow from four directions prior to Mojave River inflow. The Mojave River deposited thick and laterally extensive clastic wedges originating from the southern valley that rapidly filled much of Hinkley Valley. Sedimentary facies representing braided stream, wetland, delta, and lacustrine depositional environments all are found in the basin fill; in some places, the sequence is greater than 74 m (245 ft) thick. The sediment is dated in part by the presence of the ~631 ka Lava Creek B ash bed low in the section, and thus represents sediment deposition after Victorville basin was overtopped by sediment and before the Manix basin began to be filled. Evidently, upstream Victorville basin filled with sediment by about 650 ka, causing the ancestral Mojave River to spill to the Harper and Hinkley basins, and later to Manix basin. Initial river sediment overran wetland deposits in many places in southern Hinkley Valley, indicating a rapidly encroaching river system. These sediments were succeeded by a widespread lake (“blue” clay) that includes the Lava Creek B ash bed. Above the lake sediment lies a thick section of interlayered stream sediment, delta and nearshore lake sediment, mudflat and/or playa sediment, and minor lake sediment. This stratigraphic architecture is found throughout the valley, and positions of lake sediment layers indicate a successive northward progression in the closed basin. A thin overlapping sequence at the north end of the valley contains evidence for a younger late Pleistocene lake episode. This late lake episode, and bracketing braided stream deposits of the Mojave River, indicate that the river avulsed through the valley, rather than continuing toward Lake Manix, during the late Pleistocene. Two dextral strike-slip fault zones, the Lockhart and the Mt. General, fold and displace the distinctive stratigraphic units, as well as surficial late Pleistocene and Holocene deposits. The sedimentary architecture and the two fault zones provide a framework for evaluating groundwater flow in Hinkley Valley.

Hinkley Valley↗
USGS2012

The utility of gravity and magnetic methods for understanding subsurface hydrogeology in large alluvial watersheds: Examples from urbanized basins of the Western United States

Population continues to grow rapidly within the large alluvial watersheds associated with structural basins of the Basin and Range Province and the Rio Grande rift of the western United States. Increasing demands on ground‐water resources in these basins, combined with water‐rights disputes, have amplified the need for improved understanding of subsurface hydrogeology. Gravity and magnetic methods provide cost‐effective information critical to the understanding of the subsurface geology that controls hydrology at watershed scales. Gravity models are used to estimate the variations in the overall thickness of basin‐fill aquifers and to define major subbasin boundaries that partition flow systems. High‐resolution aeromagnetic surveys can be used to map the distribution of volcanic and other crystalline rocks in the shallow subsurface that impede flow. In certain geologic settings, the aeromagnetic data can be used to infer the base of basin aquifers or reveal buried, shallow paleotopography. In addition, the utility of high‐resolution aeromagnetic data to locate partially or wholly concealed faults within basin sediments is a non‐conventional application that has gained prominence in recent years. Examples of these uses of gravity and magnetic methods come from studies of basins within the Albuquerque‐Santa Fe, NM, urban corridor, the Virgin Valley in the tristate area of NV, AZ, and UT, the upper Verde River watershed near Prescott, AZ, and the San Luis Valley surrounding Alamosa, CO.

Conference Paper↗
USGS1999

Cenozoic basins of the Death Valley extended terrane as reflected in regional-scale gravity anomalies

The contrast in density between basin-filling deposits and underlying basement rocks in the Basin and Range province produces a distinctive pattern of gravity anomalies that roughly correlates with basin-and-range topography. This is especially apparent in the Death Valley extended terrane, where minima in residual gravity closely correspond to well-known extensional basins, such as Owens Valley, Saline Valley, Pahrump Valley, and Death Valley itself. A three-dimensional calculation of the thickness and shape of Cenozoic deposits throughout the Basin and Range based on digital gravity, geologic, and topographic information is here interpreted in terms of the depths and shapes of extensional basins in the Death Valley region. In most basins, the gravity inversion predicts a much more complex basement than might be assumed from the surface topography. Death Valley itself is, to first order, a two-dimensional feature; as reflected by the topography of the bounding ranges down to 400–800 m below the valley floor, it is a long, narrow, and continuous valley along its entire length of 200 km. This apparent uniformity, however, belies a complex basement surface beneath the Cenozoic cover as revealed by the gravity inversion. The floor of Death Valley is pockmarked with four deep (3–5 km), steep-sided depressions that may have formed as relatively small pull-apart structures superimposed on the more uniform extension that created the twodimensional aspects of Death Valley. Lateral dimensions of these subbasins suggest a minimum of 10 km of northwest extension across Death Valley. If a regionally continuous detachment surface lies beneath Death Valley, it must lie deeper than the subbasins, that is, below a depth of 3–5 km. Similar deep, steep-sided subbasins are seen elsewhere in the Death Valley extended terrane, notably at Saline Valley, Panamint Valley, Pahrump Valley, the Amargosa Desert, and Fremont Valley, but are noticeably absent from the Mojave Desert block south of the Garlock fault zone where extensional rates are lower. The floor of the caldera complex at the southwest Nevada volcanic field is predicted by the gravity inversion to be extraordinarily deep (>8 km) and rugged. Deep, linear basins that branch out of the caldera complex may reflect modification of extensional strain due to massive injections of magma into the middle and upper crust.

California, Nevada↗