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At least 1,081 records · Page 60Linked to original sources
USGS2026

Top-down targeted network analysis of critical mineral commodities applied to international geochemistry database

The global demand for critical mineral commodities is rapidly increasing, making domestic production an important factor in supporting the economy and national security. Large scale, publicly available geochemical databases allow for the application of data informatics methods to interrogate critical mineral commodities data for correlations in deposit formation and distribution, particularly for identifying enrichment of multiple critical mineral commodities at the same deposit. In this study, we applied network analysis to the Critical Minerals Mapping Initiative (CMMI) ore geochemistry (Critical Minerals in Ores, CMiO) database to identify the high concentration (defined as 10× bulk crustal abundance) co-occurrence of different critical mineral commodities across a mineral system hierarchy from deposit environments to individual deposits. Identifying patterns or unique outliers in enrichment in network communities will allow for the location of secondary critical mineral commodity resources from under-utilized deposits. We find trends in the enrichment of critical mineral commodities in network-communities between the elements praseodymium (Pr), neodymium (Nd), terbium (Tb), and dysprosium (Dy) across multiple CMiO database deposit environments and groups down to specific deposit types and sites. A separate trend in network community deposition is observed as well between iridium (Ir) and platinum (Pt) in deposit environments, groups, types, and sites. Network analysis focused on critical minerals in magmatic-hydrothermal deposits identified multiple deposit sites from different deposit types within the CMiO database with concentrations of Dy, Nd, Tb, Pr, Ir, and Pt that are at least ten times greater than the crustal average. This approach can be applied to any target element(s) or deposit(s) of interest, allowing broad investigation of co-enriched critical mineral commodities.

Journal of Geochemical Exploration↗
USGS2024

Global potential distribution of mangroves: Taking into account salt marsh interactions along latitudinal gradients

Mangrove is one of the most productive and sensitive ecosystems in the world. Due to the complexity and specificity of mangrove habitat, the development of mangrove is regulated by several factors. Species distribution models (SDMs) are effective tools to identify the potential habitats for establishing and regenerating the ecosystem. Such models usually include exclusively environmental factors. Nevertheless, recent studies have challenged this notion and highlight the importance of including biotic interactions. Both factors are necessary for a mechanistic understanding of the mangrove distribution in order to promote the protection and restoration of mangroves. Thus, we present a novel approach of combining environmental factors and interactions with salt marsh for projecting mangrove distributions at the global level and within latitudinal zones. To test the salt marsh interaction, we fit the MaxEnt model with two predicting sets: (1) environments only and (2) environments + salt marsh interaction index (SII). We found that both sets of models had good predictive ability, although the SII improved model performance slightly. Potential distribution areas of mangrove decrease with latitudes, and are controlled by biotic and abiotic factors. Temperature, precipitation and wind speed are generally critical at both global scale and ecotones along latitudes. SII is important on global scale, with a contribution of 5.9%, ranking 6th, and is particularly critical in the 10–30°S and 20–30°N zone. Interactions with salt marsh, including facilitation and competition, are shown to affect the distribution of mangroves at the zone of coastal ecotone, especially in the latitudinal range from 10° - 30°. The contribution of SII to mangrove distribution increases with latitudes due to the difference in the adaptive capacity of salt marsh plants and mangroves to environments. Totally, this study identified and quantified the effects of salt marsh on mangrove distribution by establishing the SII. The results not only facilitate to establish a more accurate mangrove distribution map, but also improve the efficiency of mangrove restoration by considering the salt marsh interaction in the mangrove management projects. In addition, the method of incorporating biotic interaction into SDMs through establish the biotic interaction index has contributed to the development of SDMs.

Journal of Environmental Management↗
USGS2017

Millennial-scale variability in the local radiocarbon reservoir age of south Florida during the Holocene

A growing body of research suggests that the marine environments of south Florida provide a critical link between the tropical and high-latitude Atlantic. Changes in the characteristics of water masses off south Florida may therefore have important implications for our understanding of climatic and oceanographic variability over a broad spatial scale; however, the sources of variability within this oceanic corridor remain poorly understood. Measurements of ΔR, the local offset of the radiocarbon reservoir age, from shallow-water marine environments can serve as a powerful tracer of water-mass sources that can be used to reconstruct variability in local-to regional-scale oceanography and hydrology. We combined radiocarbon and U-series measurements of Holocene-aged corals from the shallow-water environments of the Florida Keys reef tract (FKRT) with robust statistical modeling to quantify the millennial-scale variability in ΔR at locations with (“nearshore”) and without (“open ocean”) substantial terrestrial influence. Our reconstructions demonstrate that there was significant spatial and temporal variability in ΔR on the FKRT during the Holocene. Whereas ΔR was similar throughout the region after ∼4000 years ago, nearshore ΔR was significantly higher than in the open ocean during the middle Holocene. We suggest that the elevated nearshore ΔR from ∼8000 to 5000 years ago was most likely the result of greater groundwater influence associated with lower sea level at this time. In the open ocean, which would have been isolated from the influence of groundwater, ΔR was lowest ∼7000 years ago, and was highest ∼3000 years ago. We evaluated our open-ocean model of ΔR variability against records of local-to regional-scale oceanography and conclude that local upwelling was not a significant driver of open-ocean radiocarbon variability in this region. Instead, the millennial-scale trends in open-ocean ΔR were more likely a result of broader-scale changes in western Atlantic circulation associated with an increase in the supply of equatorial South Atlantic water to the Caribbean and shifts in the character of South Atlantic waters resulting from variation in the intensity of upwelling off the southwest coast of Africa. Because accurate estimates of ΔR are critical to precise calibrations of radiocarbon dates from marine samples, we also developed models of nearshore and open-ocean ΔR versus conventional 14 C ages that can be used for regional radiocarbon calibrations for the Holocene. Our study provides new insights into the patterns and drivers of oceanographic and hydrologic variability in the Straits of Florida and highlights the value of the paleoceanographic records from south Florida to our understanding of Holocene changes in climate and ocean circulation throughout the Atlantic.

Florida↗
USGS2023

Investigating spatio-temporal variability of initial 230Th/232Th in intertidal corals

One of the key factors in obtaining precise and accurate 230 Th ages of corals, especially for corals with ages less than a few thousand years, is the correction for non-radiogenic 230 Th based on an initial 230 Th/ 232 Th value ( 230 Th/ 232 Th 0 ). Studies that consider coral 230 Th/ 232 Th 0 values in intertidal environments are limited, and it is in these environments that corals have Th concentrations 100–1000 times greater than open-ocean corals. Here we present 66 reconstructed U–Th isochrons of modern and Holocene Porites lutea and lobata corals from throughout the Sumatran forearc islands (SFI). Mean square of weighted deviates ( MSWD ) is used to evaluate the variabilities of 28 location-specific 230 Th/ 232 Th0 values before the regional mean. Results show no significant spatial difference between the means of 3.1 ± 3.2 × 10 −6 for the northern SFI and 4.7 ± 1.3 × 10 −6 for the southern SFI. Using the weighted mean of 4.3 ± 2.5 × 10 −6 for all islands has the advantage that no data need be subjectively excluded in the calculation of reliable 230 Th ages, where a local initial value is unknown. There were no clear centennial to millennial time-scale changes in 230 Th/ 232 Th 0 in the past 2500 years. This study, therefore, suggests a reliable value of initial 230 Th/ 232 Th ratio in intertidal environments.

Sumatran forearc islands↗
USGS2023

Latency and geofence testing of wireless emergency alerts intended for the ShakeAlert® earthquake early warning system for the West Coast of the United States of America

ShakeAlert, the earthquake early warning (EEW) system for the West Coast of the United States, attempts to provides crucial warnings before strong shaking occurs. However, because the alerts are triggered only when an earthquake is already in progress, and the alert latencies and delivery times are platform dependent, the time between these warnings and the arrival of shaking is variable. The ShakeAlert system uses, among other public alerting platforms like a mobile phone operating system, smartphone apps, and the Federal Emergency Management Agency Integrated Public Alert & Warning System (IPAWS). IPAWS sends Wireless Emergency Alerts (WEAs) informing people via their smartphones and other mobile devices about various events, such as natural hazards, child abductions, or public health information about COVID-19. However, little is known about the IPAWS delivery latencies. Given that people may have only a few seconds of notice after they receive an alert to take a protective action before they feel earthquake shaking, quantifying latencies is critical to understanding whether the IPAWS system is useful for EEW. In this study, we developed new methods to test the IPAWS distribution system's performance, both with devices in a controlled environment and as well as with a 2019 community-based feedback form, in Oakland and San Diego County, California, respectively. The controlled environment test used mobile phones (including smart and non-smart phones) and associated devices to determine alert receipt times; the community research form had participants self-report their receipt times. By triangulating the data between the controlled test environment and the community research, we determined the latency statistics as well as whether the geofence (the geographic area where the alert was intended to be sent) held broadly. We found that the latencies were similar between the two tests despite the large differences in population sizes. WEA messages were received within a median time frame of 6–12 s, and the geofence held with only a few exceptions. We use this latency to assess how the system would have performed in two large earthquakes, the 1989 M6.9 Loma Prieta and 2019 M7.1 Ridgecrest earthquakes, which both occurred near our WEA test locations. Our analysis revealed that had IPAWS been available during those earthquakes, particularly Loma Prieta, it would have provided crucial seconds of notice that damaging shaking was imminent in some locations relatively far from the epicenter. Further, we find affordable non-smart phones can receive WEAs as fast as smartphones. Finally, our new method can be used for latency and geospatial testing going forward for IPAWS and other similar alerting systems.

California↗
USGS1998

Chemical weathering in a tropical watershed, Luquillo Mountains, Puerto Rico: I. Long-term versus short-term weathering fluxes

The pristine Rio Icacos watershed in the Luquillo Mountains in eastern Puerto Rico has the fastest documented weathering rate of silicate rocks on the Earth's surface. A regolith propagation rate of 58 m Ma-1 calculated from iso-volumetric saprolite formation from quartz diorite, is comparable to the estimated denudation rate (25-50 Ma-1) but is an order of magnitude faster than the global average weathering rate (6 Ma-1). Weathering occurs in two distinct environments; plagioclase and hornblende react at the saprock interface and biotite and quartz weather in the overlying thick saprolitic regolith. These environments produce distinctly different water chemistries, with K, Mg, and Si increasing linearly with depth in saprolite porewaters and with stream waters dominated by Ca, Na, and Si. Such differences are atypical of less intense weathering in temperate watersheds. Porewater chemistry in the shallow regolith is controlled by closed-system recycling of inorganic nutrients such as K. Long-term elemental fluxes through the regolith (e.g., Si = 1.7 ?? 10-8 moles m-2 s-1) are calculated from mass losses based on changes in porosity and chemistry between the regolith and bedrock and from the age of the regolith surface (200 Ma). Mass losses attributed to solute fluxes are determined using a step-wise infiltration model which calculates mineral inputs to the shallow and deep saprolite porewaters and to stream water. Pressure heads decrease with depth in the shallow regolith (-2.03 m H2O m-1), indicating that both increasing capillary tension and graviometric potential control porewater infiltration. Interpolation of experimental hydraulic conductivities produces an infiltration rate of 1 m yr-1 at average field moisture saturation which is comparable with LiBr tracer tests and with base discharge from the watershed. Short term weathering fluxes calculated from solute chemistries and infiltration rates (e.g., Si = 1.4 ?? 10-8 moles m-2 s-1) are compared to watershed flux rates (e.g., Si = 2.7 ?? 10-8 moles m-2 s-1). Consistency between three independently determined sets of weathering fluxes imply that possible changes in precipitation, temperature, and vegetation over the last several hundred thousand years have not significantly impacted weathering rates in the Luquillo Mountains of Puerto Rico. This has important ramifications for tropical environments and global climate change. Copyright ?? 1998 Elsevier Science Ltd.

Geochimica et Cosmochimica Acta↗
USGS2002

Coal quality controls of the Danville coal in Indiana (Illinois Basin, Central USA)

The Danville Coal Member (Dugger Formation, upper Desmoinesian, Pennsylvanian) is a significant economic coal resource in the Illinois Basin, central USA. Deposition of the Danville Coal (peat) was in coastal environments, varying distances from the coastline and, in turn, variable influences from saline waters. The purpose of this study is to examine the coal quality and petrography of the Danville Coal; and to discuss their relationship with depositional environment as it relates to the final coal product. A medium sulfur (1.0-1.5 wt.%) Danville Coal reserve area (northern Indiana coalfield) was compared to a low sulfur (<1.0 wt.%) Danville Coal (central Indiana coalfield) reserve area, the two being approximately 70 km apart. The medium sulfur coal resulted from the peat being deposited in a near-marine environment less protected from the influence of saline waters, whereas the low sulfur coal resulted from fine-grained, clay-dominated sediment protecting the peat from the direct influence of saline waters. Within both areas, the coal quality, coal composition, and trace element concentrations vary as a function of the proximity of the coal to the overlying Busseron Sandstone Member (Pennsylvanian). Where the Busseron Sandstone rests near or directly on the coal, the sulfur content is significantly higher in the top third of the seam. Conversely, where there is a thick section (>3 m) of finer-grained clastic sediments atop the Danville, the sulfur and trace elements contents are significantly lower. ?? 2002 Elsevier Science B.V. All rights reserved.

International Journal of Coal Geology↗
USGS1985

Effects of contaminants on toxicity of the lampricides TFM and Bayer 73 to three species of fish

Waters in the Great Lakes basin contain more than 400 contaminant chemicals that potentially affect fishery resources, commerce, and human inhabitants. We determined in the laboratory the effects of selected contaminants on the toxicity of the widely used lampricides TFM (3-trifluoromethyl-4-nitrophenol) and Bayer 73 (2′,5-dichloro-4′-nitrosalicylanilide) to three species of fish—rainbow trout ( Salmo gairdneri ), white sucker ( Catostomus commersoni ), and fathead minnow ( Pimephales promelas ). The fish were exposed to paired mixtures of lampricides and selected contaminants in standardized, acute static toxicity tests to determine the resulting type of response—less than additive, additive, or greater than additive (synergistic). As expected, the toxicities of combinations of lampricides with organic pesticides, metal, industrial or municipal pollutants, and tannic acid were mostly additive. However, the toxicity of a combination of TFM, Delnav, and malathion was synergistic, and extremely small quantities of each chemical became lethal when mixed. The concentration that produced 50% mortality was 1.64 mg/L for TFM alone but only 0.041 mg/L for TFM with the pesticides. Toxicities of the pesticides in the combination also increased commensurately. The triple combination of chemicals produced extraordinary synergism and effectively demonstrated the hazards that may result if certain chemical combinations occur in the aquatic environment. However, synergism is not the only kind of toxic action that produces hazards to aquatic organisms. All three types of toxic action are of concern because toxic units produced by contaminant chemicals add to the toxic units of applied management chemicals. Since the toxicity of the majority of chemical combinations is simply additive, this cumulative toxic action contributes more total units to aquatic environments than the extreme actions of less than additive and synergism. The toxicity of the lampricide TFM, as well as other management chemicals, is reinforced by the presence of any contaminant that contributes additional units of toxicity. Therefore, all types of cumulative toxic action should be of concern to people and agencies involved with protecting the environment.

Journal of Great Lakes Research↗
USGS2015

Global volcanic hazards and risk

An estimated 800 million people live within 100 km of an active volcano in 86 countries and additional overseas territories worldwide [see Chapter 4 and Appendix B]1. Volcanoes are compelling evidence that the Earth is a dynamic planet characterised by endless change and renewal. Humans have always found volcanic activity fascinating and have often chosen to live close to volcanoes, which commonly provide favourable environments for life. Volcanoes bring many benefits to society: eruptions fertilise soils; elevated topography provides good sites for infrastructure (e.g. telecommunications on elevated ground); water resources are commonly plentiful; volcano tourism can be lucrative; and volcanoes can acquire spiritual, aesthetic or religious significance. Some volcanoes are also associated with geothermal resources, making them a target for exploration and a potential energy resource. Much of the time volcanoes are not a threat because they erupt very infrequently or because communities have become resilient to frequently erupting volcanoes. However, there is an everpresent danger of a long-dormant volcano re-awakening or of volcanoes producing anomalously large or unexpected eruptions. Volcanic eruptions can cause loss of life and livelihoods in exposed communities, damage or disrupt critical infrastructure and add stress to already fragile environments. Their impacts can be both short-term, e.g. physical damage, and long-term, e.g. sustained or permanent displacement of populations. The risk from volcanic eruptions and their attendant hazards is often underestimated beyond areas within the immediate proximity of a volcano. For example, volcanic ash hazards can have effects hundreds of kilometres away from the vent and have an adverse impact on human and animal health, infrastructure, transport, agriculture and horticulture, the environment and economies. The products of volcanism and their impacts can extend beyond country borders, to be regional and even global in scale. Although known historical loss of life from volcanic eruptions (since 1600 AD about 280,000 fatalities are recorded, Auker et al. (2013)) is modest compared to other major natural hazards, volcanic eruptions can be catastrophic for exposed communities. In 1985 the town of Armero in Colombia was buried by lahars (volcanic mudflows) with more than 21,000 fatalities due to relatively small explosive eruptions at the summit of Nevado del Ruiz volcano that partially melted a glacier (Voight, 1990).

Book chapter↗
USGS2008

Mesozoic non-marine petroleum source rocks determined by palynomorphs in the Tarim Basin, Xinjiang, northwestern China

The Tarim Basin in Northwest China hosts petroleum reservoirs of Cambrian, Ordovician, Carboniferous, Triassic, Jurassic, Cretaceous and Tertiary ages. The sedimentary thickness in the basin reaches about 15 km and with an area of 560000 km2, the basin is expected to contain giant oil and gas fields. It is therefore important to determine the ages and depositional environments of the petroleum source rocks. For prospective evaluation and exploration of petroleum, palynological investigations were carried out on 38 crude oil samples collected from 22 petroleum reservoirs in the Tarim Basin and on additionally 56 potential source rock samples from the same basin. In total, 173 species of spores and pollen referred to 80 genera, and 27 species of algae and fungi referred to 16 genera were identified from the non-marine Mesozoic sources. By correlating the palynormorph assemblages in the crude oil samples with those in the potential source rocks, the Triassic and Jurassic petroleum source rocks were identified. Furthermore, the palynofloras in the petroleum provide evidence for interpretation of the depositional environments of the petroleum source rocks. The affinity of the miospores indicates that the petroleum source rocks were formed in swamps in brackish to lacustrine depositional environments under warm and humid climatic conditions. The palynomorphs in the crude oils provide further information about passage and route of petroleum migration, which is significant for interpreting petroleum migration mechanisms. Additionally, the thermal alternation index (TAI) based on miospores indicates that the Triassic and Jurassic deposits in the Tarim Basin are mature petroleum source rocks. ?? Cambridge University Press 2008.

Geological Magazine↗
USGS2024

Methane clumped isotopologue variability from ebullition in a mid-latitude lake

Methane is a greenhouse gas and is an important component of carbon cycling in freshwater environments. Isotope ratios of methane ( 13 C/ 12 C and D/H) are used extensively as tracers to identify methane sources. Recent advances in the measurement of clumped methane isotopologues ( 13 CH 3 D, 12 CH 2 D 2 ) offer new opportunities to constrain sources and sinks of atmospheric methane. Previous measurements of clumped methane isotopologues from freshwater environments have been spatially and temporally limited. The abundance of 13 CH 3 D and methane flux from ebullition in the deep basin of Upper Mystic Lake were measured from May to November 2021 to characterize the source isotopologue signatures and methane fluxes for mid-latitude lakes. The trends in δ 13 C and δD values support decreased methane oxidation in the early summer compared to fall. The Δ 13 CH 3 D values from this study range from 2.0 to 4.2‰, reflecting methane oxidation occurring anaerobically in lake sediments and euxinic bottom waters at sample sites. The relatively large variation in the Δ 13 CH 3 D values observed within this lake basin aligns with previous observations of bubbles from arctic lakes. The values of Δ 13 CH 3 D do not correlate with methane flux, suggesting that Δ 13 CH 3 D measurements from background ebullition are not sensitive as a proxy for ebullition rates. This study presents a uniquely large ( n = 40) set of freshwater Δ 13 CH 3 D values from a single lake basin, which we use to recommend a sampling strategy of ≥9 samples to constrain the Δ 13 CH 3 D source signal within ∼0.5‰ from similar environments. This data demonstrates the utility of clumped methane isotopologues to gain insights into local biogeochemical processes from field studies and points to the challenge of using clumped isotopologue measurements to constrain global freshwater–methane sources to the atmosphere.

ACS Earth and Space Chemistry↗
USGS2006

Anaerobic biotransformation of organoarsenical pesticides monomethylarsonic acid and dimethylarsinic acid

Monomethylarsonic acid (MMAV) and dimethylarsinic acid (DMAV) are extensively utilized as pesticides, introducing large quantities of arsenic into the environment. Once released into the environment, these organoarsenicals are subject to microbial reactions. Aerobic biodegradation of MMAV and DMAV has been evaluated, but little is known about their fate in anaerobic environments. The objective of this study was to evaluate the biotransformation of MMAV and DMAV in anaerobic sludge. Biologically mediated conversion occurred under methanogenic or sulfate-reducing conditions but not in the presence of nitrate. Monomethylarsonous acid (MMAIII) was consistently observed as an important metabolite of MMAV degradation, and it was recovered in molar yields ranging from 5 to 47%. The main biotransformation product identified from DMAV metabolism was MMAV, which was recovered in molar yields ranging from 8 to 65%. The metabolites indicate that reduction and demethylation are important steps in the anaerobic bioconversion of MMAV and DMAV, respectively. ?? 2006 American Chemical Society.

Journal of Agricultural and Food Chemistry↗
USGS2001

Nomad Rover field experiment, Atacama Desert, Chile 1. Science results overview

Nomad was deployed for a 45 day traverse in the Atacama Desert, Chile, during the summer of 1997. During this traverse, 1 week was devoted to science experiments. The goal of the science experiments was to test different planetary surface exploration strategies that included (1) a Mars mission simulation, (2) a science on the fly experiment, where the rover was kept moving 75% of the operation time. (The goal of this operation was to determine whether or not successful interpretation of the environment is related to the time spent on a target. The role of mobility in helping the interpretation was also assessed.) (3) a meteorite search using visual and instrumental methods to remotely identify meteorites in extreme environments, and (4) a time-delay experiment with and without using the panospheric camera. The results were as follow: the remote science team positively identified the main characteristics of the test site geological environment. The science on the fly experiment showed that the selection of appropriate targets might be even more critical than the time spent on a study area to reconstruct the history of a site. During the same operation the science team members identified and sampled a rock from a Jurassic outcrop that they proposed to be a fossil. The presence of paleolife indicators in this rock was confirmed later by laboratory analysis. Both visual and instrumental modes demonstrated the feasibility, in at least some conditions, of carrying out a field search for meteorites by using remote-controlled vehicles. Finally, metrics collected from the observation of the science team operations, and the use team members made of mission data, provided critical information on what operation sequences could be automated on board rovers in future planetary surface explorations.

Atacama Desert↗
USGS2009

Implications of anthropogenic river stage fluctuations on mass transport in a valley fill aquifer

In humid regions a strong coupling between surface water features and groundwater systems may exist. In these environments the exchange of water and solute depends primarily on the hydraulic gradient between the reservoirs. We hypothesize that daily changes in river stage associated with anthropogenic water releases (such as those from a hydroelectric dam) cause anomalous mixing in the near‐stream environment by creating large hydraulic head gradients between the stream and adjacent aquifer. We present field observations of hydraulic gradient reversals in a shallow aquifer. Important physical processes observed in the field are explicitly reproduced in a physically based two‐dimensional numerical model of groundwater flow coupled to a simplistic surface water boundary condition. Mass transport simulations of a conservative solute introduced into the surface water are performed and examined relative to a stream condition without stage fluctuations. Simulations of 20 d for both fluctuating river stage and fixed high river stage show that more mass is introduced into the aquifer from the stream in the oscillating case even though the net water flux is zero. Enhanced transport by mechanical dispersion leads to mass being driven away from the hydraulic zone of influence of the river. The modification of local hydraulic gradients is likely to be important for understanding dissolved mass transport in near‐stream aquifer environments and can influence exchange zone processes under conditions of high‐frequency stream stage changes.

Water Resources Research↗
USGS2009

Contemporaneous deposition of phyllosilicates and sulfates: Using Australian acidic saline lake deposits to describe geochemical variability on Mars

Studies of the origin of the Martian sulfate and phyllosilicate deposits have led to the hypothesis that there was a marked, global-scale change in the Mars environment from circum-neutral pH aqueous alteration in the Noachian to an acidic evaporitic system in the late Noachian to Hesperian. However, terrestrial studies suggest that two different geochemical systems need not be invoked to explain such geochemical variation.Western Australian acidic playa lakes have large pH differences separated vertically and laterally by only a few tens of meters, demonstrating how highly variable chemistries can coexist over short distances in natural environments. We suggest diverse and variable Martian aqueous environments where the coetaneous formation of phyllosilicates and sulfates at the Australian sites are analogs for regions where phyllosilicates and sulfates coexist on Mars. In these systems, Fe and alkali earth phyllosilicates represent deep facies associated with upwelling neutral to alkaline groundwater, whereas aluminous phyllosilicates and sulfates represent near-surface evaporitic facies formed from more acidic brines. Copyright 2009 by the American Geophysical Union.

Geophysical Research Letters↗
USGS2024

Manganese-rich sandstones as an indicator of ancient oxic lake water conditions in Gale crater, Mars

Manganese has been observed on Mars by the NASA Curiosity rover in a variety of contexts and is an important indicator of redox processes in hydrologic systems on Earth. Within the Murray formation, an ancient primarily fine-grained lacustrine sedimentary deposit in Gale crater, Mars, have observed up to 45× enrichment in manganese and up to 1.5× enrichment in iron within coarser grained bedrock targets compared to the mean Murray sediment composition. This enrichment in manganese coincides with the transition between two stratigraphic units within the Murray: Sutton Island, interpreted as a lake margin environment, and Blunts Point, interpreted as a lake environment. On Earth, lacustrine environments are common locations of manganese precipitation due to highly oxidizing conditions in the lakes. Here, we explore three mechanisms for ferromanganese oxide precipitation at this location: authigenic precipitation from lake water along a lake shore, authigenic precipitation from reduced groundwater discharging through porous sands along a lake shore, and early diagenetic precipitation from groundwater through porous sands. All three scenarios require highly oxidizing conditions and we discuss oxidants that may be responsible for the oxidation and precipitation of manganese oxides. This work has important implications for the habitability of Mars to microbes that could have used Mn redox reactions, owing to its multiple redox states, as an energy source for metabolism.

JGR Planets↗
USGS2024

An orbital comparison of a late mantling unit on Aeolis Mons with other erosion-resistant strata explored by MSL in Gale crater, Mars

Previous investigations along Curiosity 's traverse in Gale crater have explored the relationship between orbital and in situ observations. This work aims to better understand the geologic environment of units only observable from orbit and compare them to the properties of units examined by Curiosity . Here, we map an erosion-resistant dark-toned mantling unit that overlies the modern topography of Aeolis Mons (informally known as Mt. Sharp) and compare this unit to two other previously mapped dark-toned resistant units, the marker band and the mound skirting unit (MSU), that have been inferred to represent different geologic environments (lacustrine and aeolian, respectively). Visible to short wave infrared spectra from the Compact Reconnaissance Imaging Spectrometer for Mars and visual images from the High Resolution Imaging Science Experiment and Context Cameras aboard the Mars Reconnaissance Orbiter are used for this comparison. Spectral data suggest a mafic composition with minor alteration, although the composition varies more with location around Mt. Sharp rather than between units. Morphologically, the mantling unit has strong similarities to the marker band based on their consistent low-albedo, erosion-resistance, and smooth appearance, contrasting with the highly variable surface texture of the MSU. We hypothesize that all three units had a similar sediment source but experienced aqueous alteration at different times: early ubiquitous cementation in a surface aqueous environment in the mantling unit and marker band versus patchy late diagenesis in the MSU. If true, these results suggest that water activity continued within the Gale crater long after the erosion of Mt. Sharp.

JGR Planets↗
USGS2025

Pathways for potential exposure to onshore oil and gas wastewater: What we need to know to protect human health

Produced water is a chemically complex waste stream generated during oil and gas development. Roughly four trillion liters were generated onshore in the United States in 2021 (ALL Consulting, 2022, https://www.gwpc.org/wp-content/uploads/2021/09/2021_Produced_Water_Volumes.pdf ). Efforts are underway to expand historic uses of produced water to offset freshwater needs in water-stressed regions, avoid induced seismic activity associated with its disposal, and extract commodities. Understanding the potential exposures from current and proposed produced water uses and management practices can help to inform health-protective practices. This review summarizes what is known about potential human exposure to produced water from onshore oil and gas development in the United States. We synthesize 236 publications to create a conceptual model of potential human exposure that illustrates the current state of scientific inquiry and knowledge. Exposure to produced water can occur following its release to the environment through spills or leaks during its handling and management. Exposure can also arise from authorized releases, including permitted discharges to surface water, crop irrigation, and road treatment. Knowledge gaps include understanding the variable composition and toxicity of produced water released to the environment, the performance of treatment methods, migration pathways through the environment that can result in human exposure, and the significance of the exposures for human and ecosystem health. Reducing these uncertainties may help in realizing the benefits of produced water use while simultaneously protecting human health.

Environmental Health Perspectives↗