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1,657 records · Page 36Linked to original sources
USGS2025

Chemostratigraphy of the Cretaceous Hue Shale in Arctic Alaska: Exploring paleoceanographic controls on trace element enrichment, organic matter accumulation, and source-rock evolution

We document chemostratigraphy in an outcrop of late Albian to early Campanian (∼103–82 Ma) marine source rocks to better understand paleoenvironmental controls on trace element (TE) enrichment and organic matter accumulation in the distal Colville foreland basin of Arctic Alaska and how those drivers are linked to arc volcanism and successions of Cretaceous oceanographic and climatic biogeochemical events. This unique, 113-m-thick section of Cretaceous Hue Shale deposited during a series of previously undocumented Arctic Cretaceous oceanic anoxic events (Lease et al., 2024) is the only known exposure of thermally immature (0.48–0.52% R o , random vitrinite reflectance) Hue Shale in Arctic Alaska. Strata comprise mainly clay-rich mudstone with elevated total organic carbon (TOC) and hydrogen index values reaching 26.3 wt% (mean = 7.5 wt%) and 689 mg hydrocarbon (HC)/g TOC (mean = 385 mg HC/g TOC), respectively. Maceral composition consists predominantly of fluorescent amorphous organic matter, with abundant brightly fluorescent alginite, including Tasmanites , acritarchs, and Leiosphaeridia . Discrete layers of volcanic ash (preserved as bentonite) are present throughout the section and provide quantitative age control based on U–Pb dates. Chemostratigraphic trends are investigated to advance our understanding of local oceanographic conditions and controls on stratigraphic and temporal heterogeneity of Brookian source rocks. Concurrent sedimentary enrichment in Mo, U, V, Pb, and Cu across the Albian–Cenomanian boundary of the exposed basal gamma-ray zone, may reflect anoxic to euxinic benthic redox conditions favoring organic matter accumulation and preservation. Fluctuating degrees of anoxia-euxinia are inferred throughout the overlying Hue Shale succession, reflected by varying patterns of TE enrichment and TE–TOC covariation. Elevated C org /P molar ratios (>250) across most of the section, with several values exceeding 690, signify that enhanced biological productivity is sustained throughout deposition. Enhanced productivity, recorded by both C org /P and excess Ba, also parallels increases in source rock richness (elevated TOC and S 2 values) during the late Albian–early Cenomanian and late Cenomanian – Turonian. Enhanced productivity and variations in oceanic circulation/stratification likely both drove changes in benthic redox conditions that favored organic carbon accumulation and preservation. Increased continental arc volcanism (e.g., Okhotsk–Chukotka volcanic belt) and High Arctic Large Igneous Province magmatic eruptions throughout the Cretaceous, inferred to have influenced nutrient cycling and local aqueous nutrient availability, also have been invoked as potential drivers of organic carbon burial and source-rock development across the sedimentary sequence. Results presented here document the organic-rich and oil-prone source-rock quality of the Hue Shale in the distal part of the Colville foreland basin and bolster the potential for a Cretaceous petroleum system beneath the eastern North Slope.

Alaska↗
USGS2024

Trends and environmental impacts of virtual water trade

Virtual water describes water embedded in the production of goods and offers meaningful insights about the complex interplay between water, trade and sustainability. In this Review, we examine the trends, major players, traded products and key drivers of virtual water trade (VWT). Roughly 20% of water used in global food production is traded virtually rather than domestically consumed. As such, agriculture dominates VWT, with livestock products, wheat, maize, soybean, oil palm, coffee and cocoa contributing over 70% of total VWT. These products are also driving VWT growth, the volume of which has increased 2.9 times from 1986 to 2022. However, the countries leading VWT contributions (with China, the United States, the Netherlands, Germany and India accounting for 34% of the global VWT in 2022) have remained relatively stable over time, albeit with China becoming an increasingly important importer. VWT can mitigate the effects of water scarcity and food insecurity, although there are concerns about the disconnect between consumers and the environmental impacts of their choices, and unsustainable resource exploitation. Indeed, approximately 16% of unsustainable water use and 11% of global groundwater depletion are virtually traded. Future VWT analyses must consider factors such as water renewability, water quality, climate change impacts and socioeconomic implications.

Nature Reviews Earth & Environment↗
USGS2026

Seabed maps showing topography, ruggedness, backscatter intensity, sediment mobility, and the distribution of geologic substrates in quadrangle 3 of the Stellwagen Bank National Marine Sanctuary region offshore of Boston, Massachusetts

The U.S. Geological Survey, in cooperation with the National Marine Sanctuary Program of the National Oceanic and Atmospheric Administration, has conducted seabed mapping and related research in the Stellwagen Bank National Marine Sanctuary (SBNMS) region since 1993. The area being mapped using geophysical and geological data includes the SBNMS and the surrounding region, which totals approximately 3,700 square kilometers (km 2 ) and is subdivided into 18 quadrangles. The seabed is a glaciated terrain that is topographically and texturally diverse. Quadrangle 3, the subject of this scientific investigations map, has a mapped area of 185 km 2 and has water depths that range from about 30 meters (m) on the Stellwagen Bank crest to about 135 m in a basin east of South Ninety Bank, which lies off the eastern margin of Stellwagen Bank. Seven map types, each at a scale of 1:25,000, depict seabed topography, ruggedness, backscatter intensity, distribution of geologic substrates, sediment mobility, distribution of fine- and coarse-grained sand, and substrate mud content. These maps show the distribution of geologic substrates on the southeastern part of Stellwagen Bank, on adjacent banks and basins in deeper water to the east, in the eastern part of Race Point Channel to the south of the bank, and on the northern slope of Cape Cod. Interpretations of multibeam sonar bathymetric and seabed backscatter imagery, photographs, video imagery, and grain-size analyses were used to create the geology-based maps. Data from 309 stations were analyzed, including 279 sediment samples. The geologic substrate maps of quadrangle 3 show the distribution of 21 geologic substrates that represent a wide range of textures, such as rippled sand, immobile sand, immobile muddy sand, sand that partially veneers gravel, and boulder ridges. Mapped substrates are characterized by sediment grain-size composition, surface morphology, substrate layering, the mobility or immobility of substrate surfaces, and water depth range. This scientific investigations map portrays the major geological elements (substrates, topographic features, and processes) of environments in quadrangle 3. It is intended to provide a foundation for research into present and past sediment transport processes in a complex terrain, provide insights into the ecological requirements of invertebrate and vertebrate species that use the various substrates, and support seabed management in the region.

Quadrangle 3 of the Stellwagen Bank National Marin↗
USGS2025

Observing northern high-latitude river systems to understand changes in a warming Arctic

Purpose of Review Streams and rivers are undergoing rapid change as the Arctic warms and thaws. We review recent observations in Arctic stream systems to identify ubiquitous changes and the most useful tools for observing change and exploring the underlying processes. Recent Findings Recent literature indicates increasingly significant trends in river hydrology and chemistry due to persistent warming in the Arctic and longer observational records for analysis. However, regional differences in the magnitude and direction of these trends persist. We also observe thresholds in ground thaw and surface–groundwater interactions that can impact river hydrology and chemistry. Summary Warming and thaw are occurring rapidly at high latitudes, resulting in increasing, yet variable responses in stream systems across regions and scales. These differences highlight the need for long-term records and an interdisciplinary approach to explain trends and predict future states. Stream systems respond to multiple landscape changes related to hydrology (changing precipitation and subsurface flow), geology (ground thaw dynamics), and ecology (vegetation change).

Current Climate Change Reports↗
USGS1995

Evaluation of ground-water flow and hydrologic budget for Lake Five-O, a seepage lake in northwestern Florida

Temporal and spatial distributions of ground-water inflow to, and leakage from Lake Five-O, a softwater, seepage lake in northwestern Florida, were evaluated using hydrologic data and simulation models of the shallow ground-water system adjacent to the lake. The simulation models indicate that ground-water inflow to the lake and leakage from the lake to the ground-water system are the dominant components in the total inflow (precipitation plus ground-water inflow) and total outflow (evaporation plus leakage) budgets of Lake Five-O. Simlulated ground-water inflow and leakage were approximately 4 and 5 times larger than precipitation inputs and evaporative losses, respectively, during calendar years 1989-90. Exchanges of water between Lake Five-O and the ground-water system were consistently larger than atmospheric-lake exchanges. A consistent pattern of shallow ground-water inflow and deep leakage was also evident throughout the study period. The mean time of travel from ground-water that discharges at Lake Five-O (time from recharge at the water table to discharge at the lake) was estimated to be within a range of 3 to 6 years. Flow-path evaluations indicated that the intermediate confining unit probably has a negligible influence on the geochemistry of ground-water inflow to Lake Five-O. The hydrologic budgets and flow-path evaluations provide critical information for developing geochemical budgets for Lake Five-O and for improving the understanding of the relative importance of various processes that regulate the acid-neutralizing capacity of softwater seepage lakes in Florida.

Florida↗
USGS2025

High frequency and region-scale simulations of large (Mw7+) earthquakes on the southern Whidbey Island fault, Washington, USA

We simulate ground shaking in western Washington State from hypothetical M w 7.0–7.5 earthquakes on the southern Whidbey Island fault (SWIF). Ground motions are modeled considering kinematic source distributions on a complex fault plane, a 3D seismic velocity model, and region‐specific soil velocity models. We run simulations with varying model resolutions, including regional‐scale simulations with a maximum‐modeled frequency of ∼1 Hz and local‐scale simulations with a maximum‐modeled frequency of ∼2.5 Hz. Additional local‐scale simulations are run considering high‐resolution surface topography. We explore how source parameters (i.e., magnitude, hypocenter location, and dip direction) and 3D velocity structure impact peak shaking intensity and its variability. In particular, we find that earthquakes on the SWIF would likely produce strong shaking throughout the populated Puget Lowland, including in the cities of Everett, Seattle, Bellevue, and Tacoma, Washington. Simulated short‐period ( T ≤ 2 s) spectral accelerations are strong throughout the Puget Lowland, and long‐period shaking ( T ≥ 5 s) is strong in the deep regional sedimentary basins, especially the Everett and Seattle basins. Source parameters strongly influence intra‐ and interevent variability in response, primarily through changes in source and site geometry, as well as rupture directivity. We also note a potential coupling between rupture directivity and basin effects, wherein directivity pulses are seemingly guided through the region’s deep, interconnected sedimentary basins. Overall, this work highlights the impacts of 3D source, path, and site effects on seismic hazard in the U.S. Pacific Northwest and substantially expands the catalog of simulated ground motions for Puget Sound area crustal faults.

Washington↗
USGS2025

Summary of results from monitoring the Geysers with continuous passive seismic and repeat magnetotelluric measurements (2021-2023)

Understanding temporal variations in a geothermal field can support operators in decision making that pertains to optimizing production and mitigating hazards. Between 2021 and 2023, The Geysers geothermal field in northern California was monitored with an array of continuous passive seismic sensors and annual repeat magnetotelluric (MT) measurements. Each of these data sets were analyzed and modelled separately to understand the data, sensitivity, and any observable changes. Then, the data were inverted jointly using a crossgradient method to further constrain temporal changes in geophysical properties within the geothermal field. Multiple permutations of annual datasets were used as inputs to the joint inversion. Results demonstrate seismic data constrain smooth inversion of the MT data, and the MT data provide supplementary information about the location of temporal fluid changes. Estimating relative changes in steam saturation for various time intervals of the joint models shows compartmentalized changes in the field, and good spatial correlation with the location of injection wells. These results demonstrate that collecting both passive seismic and MT measurements then modeling them jointly provide complementary information and a relatively inexpensive method for monitoring temporal changes in an active geothermal field that provides results to support operators.

California↗
USGS2025

The impact of burial diagenesis on soil-formed minerals in paleosols using stable isotopes of phyllosilicates and carbonate clumped isotopes

To understand the effects of burial diagenesis on the stable isotope geochemistry of soil-formed clay and carbonate minerals in paleosols, samples were collected from seven cores, spanning middle- to upper-Pennsylvanian strata of the Illinois Basin, with varied maximum burial depths of 1–3 km. Mixed-layer illite-smectite and kaolinite mixtures give δ 2 H and δ 18 O values of −83 ‰ to −36 ‰ and 11.9 ‰ to 21.1 ‰ (VSMOW), respectively. After carbonates were screened petrographically for diagenetic textures using transmitted light and cathodoluminescence, measured clumped isotope Δ 47 values range from 0.504 to 0.563 ‰ (I-CDES). Resulting mineral formation temperatures for phyllosilicate mineral mixtures are 28 to 66 °C (mean = 47 °C), whereas T(Δ 47 ) estimates for calcites are 36 to 61 °C (mean = 45 °C). Calculated δ 18 O water values from which phyllosilicate minerals and calcites precipitated under isotopic equilibrium ranges from −7.1 to −1.2 ‰ and − 1.4 to +4.9 ‰, respectively. Closed and open-system phyllosilicate-fluid exchange modeling indicates that phyllosilicate alteration occurred in the presence of a low temperature brine or meteoric water and is interpreted to occur in a layer-by-layer illitization transformation. Due to the lack of diagenetic textures and positively correlated T(Δ 47 ) and δ 18 O water , calcites are interpreted to have undergone solid-state bond reordering. Despite low to moderate temperatures (<125 °C) and varying depths of shallow burial (1–3 km), solid-state transformation of phyllosilicates and calcites indicates paleosols had prolonged exposure to burial conditions which has implications for the use of paleosol minerals for paleoenvironmental reconstructions.

Illinois, Indiana, Kentucky↗
USGS1998

Design, revisions, and considerations for continued use of a ground-water-flow model of the coastal plain aquifer system in Virginia

A digital numerical model of the ground-water-flow system in the Virginia Coastal Plain was constructed as part of the Regional Aquifer System Analysis program of the U.S. Geological Survey and subsequently revised based on reinterpretations of the hydrogeologic framework. The revised model has been incorporated by the Virginia Department of Environmental Quality as a means to evaluate the effects of existing and proposed ground-water withdrawals. The revised model, which is documented here, includes many design features of the original model. Principal modifications are (1) reassignment of some model layers to represent different aquifers, (2) replacement of applied recharge and the uppermost surface-water layer by constant-head cells to represent the unconfined aquifer, and (3) revision of the lateral extents and transmissivity and vertical leakance values assigned to model layers. Ground-water levels simulated by the revised model under steady-state conditions, using withdrawal rates representing the period 1978-80, generally are similar to the water levels simulated by the original model under transient conditions using the same withdrawal rates. Differences probably result largely from changes in transmissivity and vertical leakance values. T he revised model enables the continued evaluation of development of the large and complex aquifer system. Improved information on parts of some aquifers has been incorporated. Only large, regional-scale trends in ground-water water levels, flow directions, and flow rates are simulated, however, and not local trends and (or) short-term changes in water level and flow. Changing hydraulic stresses, knowledge of hydrogeologic conditions, and resource-management needs require periodic revision of the model to maintain its usefulness for the management of ground-water resources in the Virginia Coastal Plain.

Virginia↗
USGS2026

Development of a hydrologic flow model of the Zuñi Salt Lake and surrounding areas, west-central New Mexico

The terminal Zuñi Salt Lake is in a maar in west-​central New Mexico and contains hypersaline water that has long been used by Native Americans for religious purposes and the collection of salt. The U.S. Geological Survey (USGS), in cooperation with the Zuni Tribe of the Zuni Reservation, New Mexico, and Bureau of Reclamation, developed the Zuñi Salt Lake hydrologic flow model to simulate the steady-state conditions of the lake and surrounding groundwater-flow system. The model is a tool that can be used to analyze the potential hydrologic responses to resource development in the region under different water-use scenarios, which can support negotiations that could help protect future use of the lake. The USGS modular hydrologic model, MODFLOW 6, was used to simulate the hydrologic system of the lake and surrounding areas. To define the layering of the model, a three-dimensional hydrogeologic framework was constructed, which included seven informal hydrogeologic units and the locations of faults that truncate and offset the units. Calibration of the model was performed using the iterative ensemble smoother included in a parameter estimation software suite (PEST++). The iterative ensemble smoother approach resulted in a posterior parameter ensemble of model realizations with parameter and simulated values that show similar success in matching observations. Groundwater flux to the Zuñi Salt Lake simulated by using the posterior parameter distribution ranged from 26 to 730 acre-feet per year with a mean, median, and standard deviation of 530, 570, and 170 acre-feet per year, respectively. The relative contribution of groundwater discharge to the lake was simulated using a particle-tracking model for MODFLOW (MODPATH) to be from, in order of decreasing contribution, the Mesaverde, Cenozoic, Mancos, and Dakota hydrogeologic units. Simulations of future conditions using the ensemble of models can provide an empirical estimate of forecast uncertainty without substantial additional analysis.

New Mexico↗
USGS1995

Water quality of the Boca Raton canal system and effects of the Hillsboro Canal inflow, southeastern Florida, 1990-91

The City of Boca Raton in southeastern Palm Beach County, Florida, is an urban residential area that has sustained a constant population growth with subsequent increase in water use. The Boca Raton network of canals is controlled to provide for drainage of excess water, to maintain proper coastal ground-water levels to prevent saltwater intrusion, and to recharge the surficial aquifer system from which the city withdraws potable water. Most of the water supplied to the Boca Raton canal system and the surficial aquifer system, other than rainfall and runoff, is pumped from the Hillsboro Canal. The Biscayne aquifer, principal hydrogeologic unit of the surficial aquifer system, is highly permeable and there is a close relation between water levels in the canals and the aquifer. The amount of water supplied by seepage from the conservation areas is unknown. Because the Hillsboro Canal flows from Lake Okeechobee and Water Conservation Areas 1 and 2, which are places of more highly mineralized ground water and surface water, the canal is a possible source of contamination. Water samples were collected at 10 canal sites during wet and dry seasons and analyzed for major inorganic ions and related characteristics, nutrients, and trace elements. All concentrations were generally within or less than the drinking-water standards established by the Florida Department of Environmental Protection. The high concentrations of sodium and chloride that were detected in samples from the Boca Raton canal system are probably from the more mineralized water of the Hillsboro Canal. Other water-quality data, gathered from various sources from 1982 through 1991, did not indicate any significant changes nor trends. The data include pesticide and metal analyses of water samples and bottom sediments collected at four canal sites in the Boca Raton study area by the U.S. Geological Survey during 1982-84. The effects of the Hillsboro Canal on the water quality of the Boca Raton canal system are indicated by increased concentrations of sodium, chloride, dissolved solids, and total organic carbon. Concentrations of the constituents in the canal water generally decrease with distance from the Hillsboro Canal pumping station and are the result of dilution by receiving canal waters.

Florida↗
USGS2025

Tracing mercury from land to river: Global sources, retention, and implications for sustainability

Mercury (Hg) pollution in river systems is a global sustainability challenge. Yet the transport, transformation, and retention of Hg within global rivers remain poorly quantified, particularly in regions with sparse observations such as Southeast Asia and Africa, hindering effective pollution mitigation and reinforcing geographic inequities in scientific knowledge and environmental governance. Here, we present the first global, high-resolution simulation of riverine Hg dynamics using a process-based model that traces Hg from land-based sources through river networks to the ocean. Under a realistic scenario, we estimate that ~1,900 megagrams per year (Mg/yr) of Hg enters global rivers, including 1,500 Mg/yr from human-induced sources and 400 Mg/yr from soil erosion. Nearly half of this flux (~1,000 Mg/yr) is retained in reservoirs and dams, which act as major sinks. While such retention limits downstream delivery to the oceans, it also heightens in-reservoir Hg methylation risks. By bridging the gap between Hg releases and observed riverine exports, our framework offers a scalable tool for data-limited regions, promotes data access, and supports global freshwater and pollution-management strategies.

EarthArXiv↗
USGS2026

Understanding the resource potential of natural hydrogen on Earth: Scientific gaps, uncertainties and recommendations

A comprehensive scientific research roadmap is essential to bridge knowledge gaps and deepen the understanding of key geological, geochemical, and geophysical aspects of natural hydrogen (H 2 ) as a potential new energy resource. This paper reviews major scientific uncertainties on natural H 2 , suggesting research priorities, as a guide for defining exploration strategies, techniques, and data interpretation. The uncertainties concern all phases of the natural H 2 cycle, from generation (source rocks) through migration (advection and diffusion) and accumulation (reservoir and cap rocks) to the application and interpretation of subsurface and surface geochemical and geophysical exploration techniques. Understanding H 2 sources and generation rates (the amount of H 2 generated by a given volume of rock over time) is crucial for determining whether a geological H 2 system operates as a short-term dynamic system with rapid H 2 production and release, or as a conventional gas system with long-term accumulations, analogous to petroleum reservoirs. Preliminary estimates for serpentinisation, radiolysis, and organic matter degradation suggest that H 2 generation is not inherently fast, especially for non-hydrothermal continental systems (crystalline basement of shields, ophiolites, peridotite massifs, sedimentary basins), and long-term accumulations, like those of fossil natural gas systems, represent the most likely scenario. The mechanisms of H 2 migration through geological formations require application of fundamental principles of fluid-flow physics, distinguishing advection and diffusion, as well as their forms (from gas-phase, bubble flows to aqueous solutions). Additional studies of H 2 accumulation and retention in subsurface reservoirs could improve understanding of mechanisms of H 2 migration by focusing on the rock fluid-bearing properties and the factors affecting H 2 preservation, such as the presence of cap rocks impermeable to H 2 , pressure conditions, residence times, and microbial or abiotic consumption. Advanced techniques, including reservoir modelling, flow simulations, 3D imaging (micro-CT) of H 2 -bearing rocks, and extraction and analysis of gas occluded in rocks, can provide insights into the stability and potential recoverability of H 2 accumulations. The interpretation of surface exploration techniques, including gas geochemistry, geophysics, and remote sensing, long employed in mineral and energy resource exploration, is now being adapted for natural H 2 studies, but challenges remain in the data interpretation. Distinguishing H 2 seepage due to geological degassing from H 2 produced near the surface by modern microbial processes or artificial sources, such as hammering or drilling for soil-gas sampling, drilling into aquifers, and corrosion in boreholes, is an essential step in exploration. The simple detection of H 2 in soils, even in morphological structures like sub-circular depressions or “fairy circles”, cannot be cursorily interpreted as a signal of natural H 2 seepage from a deep source. A holistic geochemical approach, including isotopic analyses of gases associated with H 2 , is recommended to distinguish among the variety of possible H 2 origins. Observations of H 2 in wells should be interrogated to rule out possible artifacts such as corrosion and drill bit metamorphism. The integration of multiple geophysical methods, including seismic, gravimetric, magnetic, and electro-magnetic surveys, is recommended to mitigate interpretation ambiguities regarding the structure of a subsurface H 2 system (source and reservoir rocks, including fluid and gas storage), due to the non-uniqueness of rock-specific physical properties.

Earth-Science Reviews↗
USGS2024

Simulation of groundwater flow in the Long Island, New York regional aquifer system for pumping and recharge conditions from 1900 to 2019

The U.S. Geological Survey has developed a transient, groundwater-flow model that simulates hydrologic conditions in the Long Island aquifer system as part of an ongoing (since 2016) multiyear, cooperative investigation with the New York State Department of Environmental Conservation. The goals of this investigation are to assist stakeholders and resource managers to evaluate the response of the hydrologic system to changes in future hydraulic stresses. Responses in the hydrologic system include changes in water levels in the hydrogeologic units; discharge to streams, coastal waters, and subsurface infrastructure; and the extent of saline groundwater in the aquifers. Hydraulic stresses include future water-supply management and changes in land use and infrastructure. The numerical model synthesizes a diverse set of physiographic, geologic, climatic, land-use, and historical population, water use, and infrastructure data to physically represent the Long Island aquifer system from land surface to bedrock and to simulate annual hydrologic conditions between 1900 and 2019. A three-dimensional hydrogeologic framework was developed from existing and recently collected borehole geologic and geophysical data collected as part of a companion drilling program. Water-transmitting properties of the principal aquifer sediments were defined in three dimensions from new and existing lithologic logs. The distribution of recharge from precipitation was estimated from landscape characteristics and climate data. Anthropogenic recharge from wastewater, leaky infrastructure, and storm runoff were estimated from population, infrastructure, and pumping data. Water-use data, including well locations, depths, and pumping rates, were obtained from historical sources and records and used to estimate pumping stresses continuously in time and space, at an annual average time scale. The data were incorporated into a three-dimensional numerical model using the U.S. Geological Survey finite difference modeling code MODFLOW 6; the model encompassed all of Long Island and surrounding surface waters and simulated historical hydrologic conditions from 1900 to 2019. The calibration process involved trial and error adjustments using prior knowledge to improve general fit to observations followed by an inverse calibration to update and optimize input parameters, using an iterative ensemble smoother algorithm implemented in PEST++ version 5.0. This resulted in a model that generally was in good agreement with observed, dynamically varying hydrologic conditions from 1900 to 2019. The calibrated model was used to develop two base-case models for scenario testing of future, hypothetical conditions where one represented average-annual conditions, and one represented average-seasonal conditions from 2010 to 2019. The model representing average-annual conditions was modified further to represent an alternate sea-level position of 6 feet above the North American Vertical Datum of 1988, and the model representing average-seasonal conditions was modified to represent the average seasonal effects of a 5-year drought imposed upon current hydrologic conditions. Recharge is the sole source of water to the aquifer system; groundwater discharges to coastal water and streams and is withdrawn by pumped wells. Model-estimated annual recharge ranged from about 11 inches in 1965 to 41 inches in 1983. On average, from 2010 to 2019, about 23 percent of water was pumped from wells, and about 47 and 27 percent discharged to coastal waters and streams, respectively; the remaining 4 percent was water that moved into storage in the aquifer matrix. Water levels on Long Island vary naturally during time in response to changes in recharge; the amount of variation is largest in the interior of the island, in areas with highest water table altitudes near groundwater divides and lowest near streams and the coastal waters. The total range of water table altitudes on Long Island between 1900 and 2019 ranged from near 0 to more than 70 feet in western parts of Long Island. The largest range in altitudes is in New York City and is associated with areas of large historical withdrawals between the 1920s and the late 1980s. Water table altitudes generally varied by less than 10 feet in eastern Suffolk County, where the aquifer is under more natural conditions. Saltwater intrusion is of great concern on Long Island, particularly in western Long Island where both the unconfined and confined parts of the aquifer system have been intruded in response to large-scale groundwater withdrawals; however, the volume of freshwater in the islandwide aquifer system only has changed by about 5 percent between 1900 and 2019. The decadal change in the freshwater volume was largest during the early and mid-20th century, corresponding to the largest historical pumping, but that volume change did not exceed 1 percent. The negligible change in freshwater volume suggests that saltwater intrusion as of 2019 was limited at an islandwide scale but continues to occur in local areas of Queens and Nassau Counties, adversely affecting current water supplies and limiting future water supplies for affected communities. The regional groundwater model developed for this investigation is a tool that can be used to help determine the viability of current and future water supplies at a regional scale and can be used to support development of additional models at finer scale to support more focused assessments of groundwater sustainability.

New York↗
USGS2026

Tracing mercury from land to river: Global sources, retention, and implications for sustainability

Mercury (Hg) pollution in river systems is a global sustainability challenge. Yet the transport, transformation, and retention of Hg within global rivers remain poorly quantified, particularly in regions with sparse observations such as Southeast Asia and Africa, hindering effective pollution mitigation and reinforcing geographic inequities in scientific knowledge and environmental governance. Here, we present the first global, high-resolution simulation of riverine Hg dynamics using a process-based model that traces Hg from land-based sources through river networks to the ocean. Under a realistic scenario, we estimate that ∼1900 megagrams per year (Mg/yr) of Hg enters global rivers, including 1500 Mg/yr from human-induced sources and 400 Mg/yr from soil erosion. Nearly half of this flux (∼1000 Mg/yr) is retained in reservoirs and dams, which act as major sinks. While such retention limits downstream delivery to the oceans, it also heightens in-reservoir Hg methylation risks. By bridging the gap between Hg releases and observed riverine exports, our framework offers a scalable tool for data-limited regions, promotes data access, and supports global freshwater and pollution-management strategies.

Environmental Science & Technology↗
USGS2025

Hydrogeology and groundwater quality in the Snake River alluvial aquifer at Jackson Hole Airport, Wyoming, 2011–20

The Snake River alluvial aquifer underlying the Jackson Hole Airport (JHA) in northwest Wyoming is an important source of water used for domestic, commercial, and irrigation purposes by the airport and nearby residents. The U.S. Geological Survey, in response to previously identified water-quality concerns in the area, monitored and evaluated changes in hydrogeologic characteristics and groundwater-quality conditions of the alluvial aquifer during 2011–20. During that period, the Jackson Hole Airport made several changes that potentially improved water quality at and downgradient from the airport. Well, water level, and hydrogeologic data were collected from the alluvial aquifer to identify hydrogeologic characteristic and groundwater quality changes. Additionally, results of statistical tests were applied to water-quality results to evaluate trends in selected physical properties and constituent concentrations with time. The trends of those data show that water quality did improve overall during the study period compared to previously collected data. Presumably, these trends are in response to the changes in the aircraft deicing/anti-icing fluid (ADAF) formulation used by the JHA, the many JHA infrastructure improvements made during 2011–20, the degradation of existing ADAFs in subsurface soils and groundwater, or some combination of these possibilities.

Wyoming↗
USGS2025

Depth of magma crystallization and fluid exsolution beneath the porphyry-skarn Cu deposits at Santa Rita and Hanover-Fierro, New Mexico, USA

The depth level at which porphyry Cu–forming magmas fractionated and exsolved mineralizing fluids is actively debated. In the classic model, extensive magma fractionation occurs in large, upper crustal magma chambers, and concomitant fluid exsolution leads to forceful expulsion of residual magmas in the form of porphyry dikes, stocks, and breccia pipes, which subsequently serve as pathways for the mineralizing fluids. In contrast, some recent studies highlighting the role of deep crustal magma fractionation in the production of fertile magmas essentially deny the existence of upper crustal magma chambers at the time of mineralization. To address this, we conducted a detailed thermobarometric investigation of 13 intermediate to felsic, porphyritic intrusive rocks related to porphyry-skarn Cu mineralization at Santa Rita and Hanover-Fierro, New Mexico, United States, representing two premineralization magmas (61–60 Ma), seven synmineralization magmas (60–58 Ma), and four late- to postmineralization magmas (58–57 Ma). For each sample, the pressure of last magma crystallization before final magma ascent to the current exposure level was reconstructed based on Al-in-hornblende barometry of small hornblende inclusions trapped within quartz phenocrysts and through titanium-in-quartz (TitaniQ) thermobarometry of the host quartz phenocrysts themselves. Since quartz is one of the last crystallizing magmatic minerals, and no significant phenocryst growth could have occurred in small dikes and stocks after final magma emplacement, quartz phenocrysts and their contained hornblende inclusions record the depth of last magma crystallization before final magma ascent. When present, hornblende phenocrysts and hornblende inclusions within other major phenocrysts were also analyzed. Both quartz and hornblende barometers return consistent average pressures of 3.2 ± 0.4 kbar for the entire suite of pre- to postmineralization magmas, corresponding to depths of 11 to 14 km. The synmineralization magmas return even more consistent average pressures of 3.1 ± 0.2 kbar, corresponding to a depth of 12 ± 1 km. The volume of the mineralizing porphyry dikes and stocks at the emplacement level is far too small to have provided all the fluids and metals required to form the observed ore deposits. Therefore, the majority of the ore-forming fluids must have originated from the magmas that crystallized at 12 ± 1 km depth. The ore deposits, conversely, formed at ~5-km paleodepth. This implies that most of the mineralizing fluids traveled an average vertical distance of ~7 km from their magmatic source to the eventual site of ore precipitation. The relatively unaltered nature and low veining degree of deeper parts of mineralized porphyry dikes and stocks suggest that the fluid transport through these intrusive bodies occurred mostly at near-solidus conditions by means of fluid percolation along grain boundaries. In summary, our results suggest that (1) a large, upper crustal pluton exists ~7 km beneath the Santa Rita and Hanover-Fierro deposits; (2) abundant phenocryst crystallization occurred at this depth level; and (3) this pluton was the main source for the exsolution of ore-forming fluids. However, the investigated rocks have elevated whole-rock Sr/Y ratios, indicating magma fractionation at deep crustal levels. As a result, our preferred model is a combination of the two end-member models introduced above, with most magma fractionation having occurred in the deep crust and with residual, intermediate to felsic melts having ascended and accumulated at 11 to 14 km paleodepth, where they continued to crystallize with comparatively little crystal-liquid separation, before some of these magmas ascended further to shallow levels and quenched to porphyries.

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