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

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At least 1,603 records · Page 89Linked to original sources

USGS1974

Palaeomagnetism and magnetic–polarity zonation in some Oligocene volcanic rocks of the San Juan Mountains, south–western Colorado

Palaeomagnetic results have been obtained from thirty sites in intrusive and extrusive rocks of Oligocene age from the San Juan Mountains, south-western Colorado. All specimens from each site were subjected to af demagnetization, and the reliability of each site determined. Twenty-three sites gave reliable results. Because five sites from the thick intracaldera part of the La Jara Canyon Member of the Treasure Mountain Tuff appear to have become magnetized during the same small interval of geological time, their results were combined and their mean pole and direction used in the final calculations. The eighteen remaining reliable sites yielded an average Oligocene palaeomagnetic pole at 85·6° N and 298·0° E (δ p = 8°, δ m = 11°, k = 24·1). A stratigraphic sequence is given for the major San Juan ash-flow sheets and selected additional units with their corresponding magnetic polarities and mean K-Ar ages.

Colorado↗

USGS2020

Micro-geographic variation in burrow use of Agassiz’s desert tortoises in the Sonoran Desert of California

Little has been published regarding the burrowing habits of Agassiz’s desert tortoises ( Gopherus agassizii ) in the Sonoran Desert of California. We monitored the interactions of tortoises with their burrows, and other tortoises, via radio-telemetry at two nearby sites between the Cottonwood and Orocopia Mountains, from 2015-2018. We examined how annual cycles of drought and non-drought years, behaviourally affected how tortoises use their burrows (i.e., burrow fidelity, cohabitation, and location), including the timing of the tortoise brumation period. Burrow locations were strongly dependent on local geology and topography, with a tendency to orientate in conformance with the general aspect of the landscape. The timing of brumation was similar to records for G. agassizii throughout their range (with a few exceptions). There was no difference in the estimated number of burrows used per 30 days between the active seasons (2017 and 2018) at the Orocopia site, despite the occurrence of drought in 2018.

California↗

USGS1986

Bibliography on ground water in glacial-aquifer systems in the Northeastern United States

The U.S. Geological Survey established the Regional Aquifer-System Analysis (RASA) program to evaluate major interconnected aquifers or groups of aquifers that share similar characteristics within a region. One of the objectives of the Northeastern Glacial RASA is to provide information on the occurrence and quality of ground water in glacial deposits in ten States: Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, Ohio, Pennsylvania, and New Jersey. To help meet the objectives of the RASA program, an automated bibliographic data base was developed. The data base contains references to ground-water resources of glacial-aquifer systems in the ten States listed above. This bibliography contains more than 700 ground-water related references that date from 1839 through 1984. The bibliography lists books, journal articles, conference proceedings, government and other technical reports, theses, and maps. Unpublished manuscripts, publications in press, newspaper articles, and book reviews are omitted from the bibliography.

Circular↗

USGS2026

The USGS Rotating X-ray Computed Tomography (RXCT) Coral-Core Archive: Scope, access, and standardization

We announce the U.S. Geological Survey (USGS) Rotating X-ray Computed Tomography (RXCT) Coral-Core Archive, a digital resource derived from ~400 coral reef cores curated at the USGS Pacific and St. Petersburg Coastal and Marine Science Centers. The archive de-livers calibrated 3-D image volumes that enable reproducible values of skeletal density, linear extension, and calcification from decadal-to-centennials scale records of coral growth and bioerosion. Cross-study comparability within the archive is supported by a unified RXCT workflow that minimizes imaging artifacts. This includes rejecting im-age-intensity–density regressions with r² < 0.95, back-calculating standard densities to verify a ±10% target precision, and confirming that band-averaged density values fall within published species- and site-specific ranges. Given global coral-reef decline and the rarity of physical archives, we release data under FAIR (Findable, Accessible, Interopera-ble, Reusable) principles. Calibrated imagery and scan metadata are distributed through CoralCache/CoralCT for analysis (DeCarlo et al., 2025), while core locations and collection metadata are published through the USGS Geologic Core and Sample Database (DOI: 10.5066/F7319TR3) with links to CT slice imagery in a USGS ScienceBase repository (DOI: 10.5066/P139Y9H4). This archive provides a powerful dataset for evaluating environ-mental controls on coral growth, establishing restoration baselines, and improving coastal-hazard assessments in the face of global coral-reef declines.

American Somoa, Guam, Florida, Hawaii, U.S. Virgin↗

USGS2019

Lethal infection of wild raptors with highly pathogenic avian influenza H5N8 and H5N2 viruses in the USA, 2014–15

An outbreak of highly pathogenic avian influenza (HPAI) led to heavy losses of poultry in commercial farms in North America in 2014–15. Enhanced surveillance by virologists and pathologists at the US Geological Survey National Wildlife Health Center and its partners resulted in the identification of lethal infections with clade 2.3.4.4 subgroup icA2 H5N8 and novel reassortant H5N2 viruses in diverse wild raptor species that died concomitant with the poultry epizootic in the US. A range of pathologic abnormalities were present in dead raptors, including necrotizing encephalitis and myocarditis, pancreatic necrosis, and pulmonary congestion and edema. Raptors are highly susceptible to disease caused by infection with HPAI clade 2.3.4.4 viruses.

Journal of Wildlife Diseases↗

USGS2018

Multiple stacked plays to drive continued Permian development

The exploitation of unconventional (continuous) resource plays with horizontal drilling and fracturing techniques continues to spur renewed development in mature producing basins in the US. The Permian basin of west Texas has emerged as a particularly strong prospect due to the potential for multiple stacked resource plays in formations such as the Wolfcamp shale and Spraberry and Bone Spring formations. Production began in the Permian basin in the early 1920s, and more than 116,000 wells have been drilled in Midland basin alone. 1 2 In 2017, total Permian basin oil production climbed to nearly 1.7 million b/d. 3 The US Geological Survey (USGS) conducts geologic-based assessments of undiscovered, technically recoverable domestic hydrocarbon resources. The USGS recently assessed the Wolfcamp shale in the Midland basin portion of the Permian basin for continuous (unconventional) oil and gas resources, and completed a reassessment of the Spraberry formation for both continuous and conventional oil and gas. 4 5 Combined, the assessments of the Spraberry formation and underlying Wolfcamp shale in Midland basin comprise the largest domestic continuous oil assessment in the contiguous US (Fig. 1).

Texas↗

USGS2013

Geologic effects on groundwater salinity and discharge into an estuary

Submarine groundwater discharge (SGD) can be an important pathway for transport of nutrients and contaminants to estuaries. A better understanding of the geologic and hydrologic controls on these fluxes is critical for their estimation and management. We examined geologic features, porewater salinity, and SGD rates and patterns at an estuarine study site. Seismic data showed the existence of paleovalleys infilled with estuarine mud and peat that extend hundreds of meters offshore. A low-salinity groundwater plume beneath this low-permeability fill was mapped with continuous resistivity profiling. Extensive direct SGD measurements with seepage meters ( n = 551) showed fresh groundwater discharge patterns that correlated well with shallow porewater salinity and the hydrogeophysical framework. Small-scale variability in fresh and saline discharge indicates influence of meter-scale geologic heterogeneity, while site-scale discharge patterns are evidence of the influence of the paleovalley feature. Beneath the paleovalley fill, fresh groundwater flows offshore and mixes with saltwater before discharging along paleovalley flanks. On the adjacent drowned interfluve where low-permeability fill is absent, fresh groundwater discharge is focused at the shoreline. Shallow saltwater exchange was greatest across sandy sediments and where fresh SGD was low. The geologic control of groundwater flowpaths and discharge salinity demonstrated in this work are likely to affect geochemical reactions and the chemical loads delivered by SGD to coastal surface waters. Because similar processes are likely to exist in other estuaries where drowned paleovalleys commonly cross modern shorelines, the existence and implications of complex hydrogeology are important considerations for studies of groundwater fluxes and related management decisions.

Delaware↗

USGS2002

Concordant paleolatitudes for Neoproterozoic ophiolitic rocks of the Trinity Complex, Klamath Mountains, California

New paleomagnetic results from the eastern Klamath Mountains of northern California show that Neoproterozoic rocks of the Trinity ophiolitic complex and overlying Middle Devonian volcanic rocks are latitudinally concordant with cratonal North America. Combining paleomagnetic data with regional geologic and faunal evidence suggests that the Trinity Complex and related terranes of the eastern Klamath plate were linked in some fashion to the North American craton throughout that time, but that distance between them may have varied considerably. A possible model that is consistent with our paleomagnetic results and the geologic evidence is that the Trinity Complex formed and migrated parallel to paleolatitude in the basin between Laurasia and Australia–East Antarctica as the Rodinian supercontinent began to break up. It then continued to move parallel to paleolatitude at least through Middle Devonian time. Although the eastern Klamath plate served as a nucleus against which more western components of the Klamath Mountains province amalgamated, the Klamath superterrane was not accreted to North America until Early Cretaceous time.

California↗

USGS2003

Athena Mars rover science investigation

Each Mars Exploration Rover carries an integrated suite of scientific instruments and tools called the Athena science payload. The primary objective of the Athena science investigation is to explore two sites on the Martian surface where water may once have been present, and to assess past environmental conditions at those sites and their suitability for life. The remote sensing portion of the payload uses a mast called the Pancam Mast Assembly (PMA) that provides pointing for two instruments: the Panoramic Camera (Pancam), and the Miniature Thermal Emission Spectrometer (Mini‐TES). Pancam provides high‐resolution, color, stereo imaging, while Mini‐TES provides spectral cubes at mid‐infrared wavelengths. For in‐situ study, a five degree‐of‐freedom arm called the Instrument Deployment Device (IDD) carries four more tools: a Microscopic Imager (MI) for close‐up imaging, an Alpha Particle X‐Ray Spectrometer (APXS) for elemental chemistry, a Mössbauer Spectrometer (MB) for the mineralogy of Fe‐bearing materials, and a Rock Abrasion Tool (RAT) for removing dusty and weathered surfaces and exposing fresh rock underneath. The payload also includes magnets that allow the instruments to study the composition of magnetic Martian materials. All of the Athena instruments have undergone extensive calibration, both individually and using a set of geologic reference materials that are being measured with all the instruments. Using a MER‐like rover and payload in a number of field settings, we have devised operations processes that will enable us to use the MER rovers to formulate and test scientific hypotheses concerning past environmental conditions and habitability at the landing sites.

Journal of Geophysical Research E: Planets↗

USGS2012

Gravity model and structural implications of the Goddard Pendant, Sierra Nevada, California

A subsurface model for the Goddard pendant is constructed from a residual gravity high of about 7 mGal over the pendant. The model, which is the simplest and most geologically reasonable possibility, shows a metamorphic block that tapers with depth and extends about 3.5 km below the surface. The structures in the Goddard pendant are similar in style and orientation to those in other Sierra Nevada pendants, indicating that the country rock was neither deformed nor rotated during pluton emplacement. Consequently, emplacement must have been a passive rather than a forceful process. The pendant itself represents a piece of country rock trapped between plutons which are dome shaped in cross section.

Journal of Geophysical Research Solid Earth↗

USGS1992

The role of atomic absorption spectrometry in geochemical exploration

In this paper we briefly describe the principles of atomic absorption spectrometry (AAS) and the basic hardware components necessary to make measurements of analyte concentrations. Then we discuss a variety of methods that have been developed for the introduction of analyte atoms into the light path of the spectrophotometer. This section deals with sample digestion, elimination of interferences, and optimum production of ground-state atoms, all critical considerations when choosing an AAS method. Other critical considerations are cost, speed, simplicity, precision, and applicability of the method to the wide range of materials sampled in geochemical exploration. We cannot attempt to review all of the AAS methods developed for geological materials but instead will restrict our discussion to some of those appropriate for geochemical exploration. Our background and familiarity are reflected in the methods we discuss, and we have no doubt overlooked many good methods. Our discussion should therefore be considered a starting point in finding the right method for the problem, rather than the end of the search. Finally, we discuss the future of AAS relative to other instrumental techniques and the promising new directions for AAS in geochemical exploration.

Journal of Geochemical Exploration↗

USGS2003

Imaging spectroscopy: Earth and planetary remote sensing with the USGS Tetracorder and expert systems

Imaging spectroscopy is a tool that can be used to spectrally identify and spatially map materials based on their specific chemical bonds. Spectroscopic analysis requires significantly more sophistication than has been employed in conventional broadband remote sensing analysis. We describe a new system that is effective at material identification and mapping: a set of algorithms within an expert system decision‐making framework that we call Tetracorder. The expertise in the system has been derived from scientific knowledge of spectral identification. The expert system rules are implemented in a decision tree where multiple algorithms are applied to spectral analysis, additional expert rules and algorithms can be applied based on initial results, and more decisions are made until spectral analysis is complete. Because certain spectral features are indicative of specific chemical bonds in materials, the system can accurately identify and map those materials. In this paper we describe the framework of the decision making process used for spectral identification, describe specific spectral feature analysis algorithms, and give examples of what analyses and types of maps are possible with imaging spectroscopy data. We also present the expert system rules that describe which diagnostic spectral features are used in the decision making process for a set of spectra of minerals and other common materials. We demonstrate the applications of Tetracorder to identify and map surface minerals, to detect sources of acid rock drainage, and to map vegetation species, ice, melting snow, water, and water pollution, all with one set of expert system rules. Mineral mapping can aid in geologic mapping and fault detection and can provide a better understanding of weathering, mineralization, hydrothermal alteration, and other geologic processes. Environmental site assessment, such as mapping source areas of acid mine drainage, has resulted in the acceleration of site cleanup, saving millions of dollars and years in cleanup time. Imaging spectroscopy data and Tetracorder analysis can be used to study both terrestrial and planetary science problems. Imaging spectroscopy can be used to probe planetary systems, including their atmospheres, oceans, and land surfaces.

Journal of Geophysical Research E: Planets↗

USGS2012

Evolution of the caldera‐forming eruption at Crater Lake, Oregon, indicated by component analysis of lithic fragments

Crater Lake caldera (8 × 10 km), formed 6845 years B. P. ( 14 C age) during the climactic eruption of the volcanic edifice known as Mount Mazama, is intermediate in size between small calderas associated with central vent eruptions and large calderas that have ring fracture vent systems. Our quantitative study of lithic fragments in the ejecta confirms the existing model of changes in vent configuration during the climactic eruption of Mount Mazama. Initial activity was from a single vent that produced a rhyodacite pumice fall from a Plinian column. Altered preexisting volcanic rocks are the predominant lithic type in the Plinian deposit, and their extensive hydrothermal alteration is considered as evidence of their relatively deep origin. The Wineglass Welded Tuff lies atop the Plinian deposit and contains a higher proportion of fresh volcanic rocks, suggesting enlargement of the single vent by slumping of its walls. This same vent enlargement caused the Plinian eruption column to collapse and feed valley‐hugging pyroclastic flows that deposited the Wineglass Welded Tuff. When enough material was erupted from the shallow magma chamber that its roof was no longer adequately supported, Mount Mazama collapsed to form the caldera, while highly energetic pyroclastic flows produced the climactic ignimbrite. A lag breccia that represents the proximal facies of the compositionally zoned climactic ignimbrite lies atop the Wineglass Welded Tuff and contains predominantly altered volcanic rocks of deeper origin, accompanied by minor granitoids from the magma chamber walls. Azimuthal differences in lithic component proportions in the lag breccia correlate well with the geology of the caldera walls, indicating that the climactic ignimbrite was ejected by multiple vents along a ring fracture system. Systematic lithic component changes within the lag breccia suggest different quarrying levels that reflect waxing and waning of the discharge rate during the caldera collapse phase of the climactic eruption. Our lithic component analysis demonstrates that calderas that may be too small to experience structural resurgence, such as Crater Lake, nevertheless may form by syneruptive subsidence along ring fractures.

Oregon↗

USGS1997

Predicting travel time and dispersion in rivers and streams

The possibility of a contaminant being accidentally or intentionally spilled in a river is a constant concern to those using the water. Methods are developed to estimate: (1) the velocity of a contaminant in a river; (2) the rate of attenuation of the peak concentration of a conservative contaminant; and (3) the time required for a contaminant plume to pass a point. The methods are based on data collected by the U.S. Geological Survey in almost a hundred different rivers representing a wide range of sizes, slopes, and geomorphic types. Although the accuracy of the predictions can be greatly increased by performing time-of-travel studies, the emphasis of this paper is on providing methods for making estimates where few data are available. It is shown that the unit-peak concentration is well correlated with travel time and that the travel time of the leading edge averages 89% of the travel time of the peak concentration.

Journal of Hydraulic Engineering↗

USGS2005

Applying petrophysical models to radar travel time and electrical resistivity tomograms: Resolution-dependent limitations

[1] Geophysical imaging has traditionally provided qualitative information about geologic structure; however, there is increasing interest in using petrophysical models to convert tomograms to quantitative estimates of hydrogeologic, mechanical, or geochemical parameters of interest (e.g., permeability, porosity, water content, and salinity). Unfortunately, petrophysical estimation based on tomograms is complicated by limited and variable image resolution, which depends on (1) measurement physics (e.g., electrical conduction or electromagnetic wave propagation), (2) parameterization and regularization, (3) measurement error, and (4) spatial variability. We present a framework to predict how core‐scale relations between geophysical properties and hydrologic parameters are altered by the inversion, which produces smoothly varying pixel‐scale estimates. We refer to this loss of information as “correlation loss.” Our approach upscales the core‐scale relation to the pixel scale using the model resolution matrix from the inversion, random field averaging, and spatial statistics of the geophysical property. Synthetic examples evaluate the utility of radar travel time tomography (RTT) and electrical‐resistivity tomography (ERT) for estimating water content. This work provides (1) a framework to assess tomograms for geologic parameter estimation and (2) insights into the different patterns of correlation loss for ERT and RTT. Whereas ERT generally performs better near boreholes, RTT performs better in the interwell region. Application of petrophysical models to the tomograms in our examples would yield misleading estimates of water content. Although the examples presented illustrate the problem of correlation loss in the context of near‐surface geophysical imaging, our results have clear implications for quantitative analysis of tomograms for diverse geoscience applications.

Journal of Geophysical Research B: Solid Earth↗

USGS2012

Reconciliation of stress and structural histories of the Tharsis region of Mars

We present a new compilation of the structural and stratigraphic evolution of the Tharsis region of Mars that incorporates recent advances in understanding its stratigraphy, and we introduce a lithospheric deformation model that can account for the observations. The first period in the formation of Tharsis occurred in Late Noachian/Early Hesperian time with the deposition of volcanic plains materials throughout the surrounding highlands (e.g., Lunae Planum) and on the Tharsis rise (which includes the giant volcanoes and surrounding, elevated lava fields). Extensive radial normal faulting occurred on the rise, locally extending outward at Valles Marineris and Tempe Terra, and concentric wrinkle ridges formed along the edge of the rise. This regional deformation appears to have been modulated by a global compressional stress field due to rapid planetary cooling and contraction. The second period occurred during the Late Hesperian/Amazonian with Tharsis volcanism centered on the rise and radial extensional deformation that extended from the center of the rise for thousands of kilometers. We propose a model in which the lithosphere beneath Tharsis consists of a thin elastic crustal cap on the rise that is mechanically detached from the strong upper mantle by a volcanically thickened, hot, weak lower crust. These layers merge into a single cooler, strong lithospheric layer around the edges of the rise. This model is capable of generating large extensional hoop stresses throughout much of the western hemisphere, in agreement with observations. The tectonic interpretation of the stresses predicted by this model requires the reconciliation of extensional strain within narrow grabens and compressional strain within wrinkle ridges with (1) processes in the deeper lithosphere, (2) the sparsity of strike-slip faults, and (3) other global or locally important stress fields. Stresses predicted by global models affect the entire thickness of the lithosphere, and they can be reconciled with narrow, closely spaced grabens that accommodate large amounts of extensional strain in the upper few kilometers of the lithosphere if the grabens are underlain and kinematically linked with dikes or other tension cracks, such as hydrofractures. Deeper levels of the lithosphere can accommodate this strain by elastic expansion if grabens are spaced far apart (many tens to hundreds of kilometers). Mechanical considerations suggest that deformation on faults beneath wrinkle ridges could extend through a significant thickness of the brittle crust. A number of factors, including stresses generated by the addition of overburden, intrusion of dikes, weakness of geologic materials under extension, and the laterally constrained nature of a single lithospheric plate, may have inhibited the formation of strike-slip faults on Mars. Stresses generated from the removal of overburden could have augmented planetwide wrinkle ridge formation during the Late Noachian/Early Hesperian and in Kasei Valles and western Chryse Planitia during the Early Amazonian. The nonuniform distribution of tectonic features around Tharsis can be understood in terms of the concentration of regional stresses and strain near weaker volcanotectonic centers.

Journal of Geophysical Research↗

USGS2014

Investigation of the high-frequency attenuation parameter, κ (kappa), from aftershocks of the 2010 M w 8.8 Maule, Chile earthquake

The Bío Bío region of Chile experienced a vigorous aftershock sequence following the 2010 February 27 M w 8.8 Maule earthquake. The immediate aftershock sequence was captured by two temporary seismic deployments: the Quake Catcher Network Rapid Aftershock Mobilization Program (QCN RAMP) and the Incorporated Research Institutions for Seismology CHile Aftershock Mobilization Program (IRIS CHAMP). Here, we use moderate to large aftershocks ( M L ≥ 4.0) occurring between 2010 March 1 and June 30 recorded by QCN RAMP and IRIS CHAMP stations to determine the spectral decay parameter, kappa ( κ ). First, we compare waveforms and κ estimates from the lower-resolution QCN stations to the IRIS CHAMP stations to ensure the QCN data are of sufficient quality. We find that QCN stations provide reasonable estimates of κ in comparison to traditional seismic sensors and provide valuable additional observations of local ground motion variation. Using data from both deployments, we investigate the variation in κ for the region to determine if κ is influenced primarily by local geological structure, path attenuation, or source properties (e.g. magnitude, mechanism and depth). Estimates of κ for the Bío Bío region range from 0.0022 to 0.0704 s with a mean of 0.0295 s and are in good agreement with κ values previously reported for similar tectonic environments. κ correlates with epicentral distance and, to a lesser degree, with source magnitude. We find little to no correlation between the site kappa, κ 0 , and mapped geology, although we were only able to compare the data to a low-resolution map of surficial geology. These results support an increasing number of studies that suggest κ observations can be attributed to a combination of source, path and site properties; additionally, measured κ are often highly scattered making it difficult to separate the contribution from each of these factors. Thus, our results suggest that contributions from the site, path and source should be carefully considered when interpreting κ values.

Bío Bío Region↗

USGS2003

Athena Mars rover science investigation

Each Mars Exploration Rover carries an integrated suite of scientific instruments and tools called the Athena science payload. The primary objective of the Athena science investigation is to explore two sites on the Martian surface where water may once have been present, and to assess past environmental conditions at those sites and their suitability for life. The remote sensing portion of the payload uses a mast called the Pancam Mast Assembly (PMA) that provides pointing for two instruments: the Panoramic Camera (Pancam), and the Miniature Thermal Emission Spectrometer (Mini-TES). Pancam provides high-resolution, color, stereo imaging, while Mini-TES provides spectral cubes at mid-infrared wavelengths. For in-situ study, a five degree-of-freedom arm called the Instrument Deployment Device (IDD) carries four more tools: a Microscopic Imager (MI) for close-up imaging, an Alpha Particle X-Ray Spectrometer (APXS) for elemental chemistry, a Mo??ssbauer Spectrometer (MB) for the mineralogy of Fe-bearing materials, and a Rock Abrasion Tool (RAT) for removing dusty and weathered surfaces and exposing fresh rock underneath. The payload also includes magnets that allow the instruments to study the composition of magnetic Martian materials. All of the Athena instruments have undergone extensive calibration, both individually and using a set of geologic reference materials that are being measured with all the instruments. Using a MER-like rover and payload in a number of field settings, we have devised operations processes that will enable us to use the MER rovers to formulate and test scientific hypotheses concerning past environmental conditions and habitability at the landing sites. Copyright 2003 by the American Geophysical Union.

Journal of Geophysical Research E: Planets↗