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At least 559 records · Page 31Linked to original sources
USGS2003

Geologic framework and hydrogeologic characteristics of the Edwards aquifer, Uvalde County, Texas

The Edwards aquifer in Uvalde County is composed of Lower Cretaceous carbonate (mostly dolomitic limestone) strata of the Devils River Formation in the Devils River trend and of the West Nueces, McKnight, and Salmon Peak Formations in the Maverick basin. Rocks in the Devils River trend are divided at the bottom of the Devils River Formation into the (informal) basal nodular unit. Maverick basin rocks are divided (informally) into the basal nodular unit of the West Nueces Formation; into lower, middle, and upper units of the McKnight Formation; and into lower and upper units of the Salmon Peak Formation. The Edwards aquifer overlies the (Lower Cretaceous) Glen Rose Limestone, which composes the lower confining unit of the Edwards aquifer. The Edwards aquifer is overlain by the (Upper Cretaceous) Del Rio Clay, the basal formation of the upper confining unit. Upper Cretaceous and (or) Lower Tertiary igneous rocks intrude all stratigraphic units that compose the Edwards aquifer, particularly in the southern part of the study area. The Balcones fault zone and the Uvalde salient are the principal structural features in the study area. The fault zone comprises mostly en echelon, high-angle, and down-to-the-southeast normal faults that trend mostly from southwest to northeast. The Uvalde salient—resulting apparently from a combination of crustal uplift, diverse faulting, and igneous activity—elevates the Edwards aquifer to the surface across the central part of Uvalde County. Downfaulted blocks associated with six primary faults—Cooks, Black Mountain, Blue Mountain, Uvalde, Agape, and Connor—juxtapose the Salmon Peak Formation (Lower Cretaceous) in central parts of the study area against Upper Cretaceous strata in the southeastern part. The carbonate rocks of the Devils River trend and the Maverick basin are products of assorted tectonic and depositional conditions that affected the depth and circulation of the Cretaceous seas. The Devils River Formation formed in a fringing carbonate bank—the Devils River trend— in mostly open shallow marine environments of relatively high wave and current energy. The West Nueces, McKnight, and Salmon Peak Formations resulted mostly from partly restricted to open marine, tidal-flat, and restricted deep-basinal environments in the Maverick basin. The porosity of the Edwards aquifer results from depositional and diagenetic effects along specific lithostratigraphic horizons (fabric selective) and from structural and solutional features that can occur in any lithostratigraphic horizon (non-fabric selective). In addition to porosity depending upon the effects of fracturing and the dissolution of chemically unstable (soluble) minerals and fossils, the resultant permeability depends on the size, shape, and distribution of the porosity as well as the interconnection among the pores. Upper parts of the Devils River Formation and the upper unit of the Salmon Peak Formation compose some of the most porous and permeable rocks in Uvalde County.

Texas↗
USGS2013

The impact environment of the Hadean Earth

Impact bombardment in the first billion years of solar system history determined in large part the initial physical and chemical states of the inner planets and their potential to host biospheres. The range of physical states and thermal consequences of the impact epoch, however, are not well quantified. Here, we assess these effects on the young Earth's crust as well as the likelihood that a record of such effects could be preserved in the oldest terrestrial minerals and rocks. We place special emphasis on modeling the thermal effects of the late heavy bombardment (LHB) – a putative spike in the number of impacts at about 3.9 Gyr ago – using several different numerical modeling and analytical techniques. A comprehensive array of impact-produced heat sources was evaluated which includes shock heating, impact melt generation, uplift, and ejecta heating. Results indicate that ∼1.5–2.5 vol.% of the upper 20 km of Earth's crust was melted in the LHB, with only ∼0.3–1.5 vol.% in a molten state at any given time. The model predicts that approximately 5–10% of the planet's surface area was covered by >1 km deep impact melt sheets. A global average of ∼600–800 m of ejecta and ∼800–1000 m of condensed rock vapor is predicted to have been deposited in the LHB, with most of the condensed rock vapor produced by the largest (>100-km) projectiles. To explore for a record of such catastrophic events, we created two- and three-dimensional models of post-impact cooling of ejecta and craters, coupled to diffusion models of radiogenic Pb*-loss in zircons. We used this to estimate what the cumulative effects of putative LHB-induced age resetting would be of Hadean zircons on a global scale. Zircons entrained in ejecta are projected to have the following average global distribution after the end of the LHB: ∼59% with no impact-induced Pb*-loss, ∼26% with partial Pb*-loss and ∼15% with complete Pb*-loss or destruction of the grain. In addition to the relatively high erodibility of ejecta, our results show that if discordant ca. 3.9 Gyr old zones in the Jack Hills zircons are a signature of the LHB, they were most likely sourced from impact ejecta.

Chemie der Erde↗
USGS1974

Geology and mineral resources of the Lehighton and Palmerton quadrangles, Carbon and Northampton Counties, Pennsylvania

The Lehighton and Palmerton 73 1/2-minute quadrangles cover an area of about 112 square miles of diversified terrain in the folded Appalachian Mountain and Great Valley sections of the Valley and Ridge physiographic province in Carbon, Lehigh, and Northampton Counties, Pennsylvania. The Lehigh River and Blue Mountain are the prominent features of the topography. Rock units defined and mapped in the area are the lithified sediments that were deposited in a variety of offshore marine, marine shelf, marginal marine, and fluvial environments associated with two phases of basin filling. The rocks are separated into four lithotectonic units, each deformed semi-independently of adjacent lithotectonic units. Decollements presumably separate the lithotectonic units. Lithotectonic unit 1 consists of about 12,000 feet of slate and graywacke of the Middle and Upper Ordovician Martinsburg Formation. This unit contains mainly asymmetric, similar, and nearly isoclinal folds, with wave lengths of 1,000 to 3,000 feet and amplitudes of 400 to 2,000 feet, formed mainly by passive flow and slip. Lithotectonic unit 2 includes about 3,100 feet of sandstone, siltstone, shale, and conglomerate of the Shawangunk Formation (Ordovician(?) and Silurian), Bloomsburg Red Beds (Silurian), and the lower part of the Poxono Island Formation (Silurian). This unit contains mainly asymmetric and concentric folds, with wavelengths of about one mile and amplitudes of 1,500 to 5,000 feet, formed by flexural slip with minor passive slip and flow. Lithotectonic unit 3 contains about 750 feet of limestone, shale, siltstone, sandstone, and dolomite of the upper part of the Poxono Island Formation, Bossardville Limestone, and Decker Formation (all Silurian), the Coeymans and New Scotland Formations, Shriver Chert, and Ridgeley Formation of the Oriskany Group and the Schoharie-Esopus Formation (all Lower Devonian), and the Palmerton Formation and Buttermilk Falls Limestone (both Middle Devonian). This unit has asymmetric, concentric, similar, and flap folds, with wavelengths of 1,000 to 1,500 feet and amplitudes of about 1,550 feet, formed by flexural slip and flow and passive slip and flow. Lithotectonic unit 4 consists of more than 13,000 feet of sandstone, conglomerate, siltstone, and shale of the Middle Devonian Marcellus and Mahantango Formations, the Upper Devonian Trimmers Rock and Catskill Formations, the Devonian-Mississippian Spechty Kopf Forma tion, the Mississippian Pocono and Mauch Chunk Formations, and the Pennsylvanian Pottsville Formation. This unit contains nearly symmetric, concentric flexural-slip folds with wavelengths of more than five miles and amplitudes of about one mile. Surficial deposits occur throughout the mapped area and include: Pleistocene pre-lllinoian(?) till and outwash(?), lllinoian(?) till and outwash, Wisconsinan outwash, shale-chip rubble, boulder fields, and colluvium; and Holocene alluvium, landslide deposits, and man-made dumps. The rocks of the mapped area, except for the deeply weathered lime stones, generally have good slope stability and foundation support strength, moderate to low primary infiltration capacity and aquifer potential but moderate to high secondary values for these properties, moderate resistance to weathering, and are moderately difficult to difficult to excavate. All of these properties are strongly influenced by the abundant bedding, cleavage, and joint partings of the rocks. Similar evaluations for the surficial deposits indicate less desirable values except for the ease of excavation of most of the unconsolidated materials. Currently active and potential mineral resources are numerous in the Lehighton and Palmerton quadrangles and include slate, sand, paint ore, building stone, crushed rock, lightweight aggregate, clinker residue, clay, hydraulic cement, and roofing granules.

Pennsylvania↗
USGS2020

An overview of bioaerosol load and health impacts associated with dust storms: A focus on the Middle East

Dust storms are an important environmental problem worldwide. The main sources of dust storms include the Sahara, the Middle East, and central and northeastern Asia. Dust storms originating from these regions can be dispersed across oceans and in some cases globally. They occur throughout the year and vary in frequency and intensity. The biological agents (e.g., fungi, bacteria and viruses) and the mineral and chemical compositions of dust may have adverse effects on human health and quality of life. Desert dusts may cause respiratory diseases, cardiovascular diseases, cardiopulmonary diseases, mental health issues, injuries and death from transport accidents caused by poor visibility. This paper presents dust storm human health research conducted in the Middle East in both indoor and outdoor environments. Results illustrate that particle concentration and bioaerosol types in the atmosphere are affected by climate change and meteorological factors. Recent data trends indicate that annual dust aerosol concentrations have increased worldwide. According to studies conducted in the Middle East, the incidence of respiratory and cardiovascular mortality and hospital visits have increased dramatically following dust storm exposures but very few have demonstrated a regional causation. National and international collaborative efforts are needed to advance our understanding of the global implications of dust storms and what may be the most effective means of mitigation.

Middle East↗
USGS1984

The Balmat-Edwards zinc-lead deposits; synsedimentary ore from Mississippi Valley-type fluids

Reconstruction of some aspects of the initial environment of ore deposition through detailed S, C, and O isotope studies of the Fowler orebody, and through reconnaissance trace element and S isotope studies of sphalerite concentrates and composite samples of ore from 22 orebodies; and (2) evaluation of the effects of high-grade metamorphism on the stable isotope geochemistry of both the ore and gangue minerals of a massive sulfide orebody. The delta 34 S values of pyrite, sphalerite, and galena in the Fowler orebody range from 11.5 to 17.5 per mil; anhydrite associated with ore ranges from 25.6 to 27.0 per mil. Average equilibration temperatures calculated from the delta 34 S differences between coexisting sulfur-bearing phases are 388 degrees C for pyrite-sphalerite, 338 degrees C for sphalerite-galena, 329 degrees C for pyrite-galena, and 602 degrees C for anhydrite-pyrite; all pairs display narrow temperature distributions. The delta 13 C and delta 18 O values of carbonates from the Fowler orebody range from -1.6 to 1.4 per mil and from 24.8 to 27.0 per mil, respectively; quartz delta 18 O values range from 23.0 to 27.0 per mil. The delta 34 S values of sphalerite concentrated from composite samples of the orebodies range from 12.7 to 14.7 per mil. This narrow range contrasts sharply with the wide variability of associated evaporitic anhydrite lenses, which range from 8 to 28 per mil. A stratigraphic increase in the delta 34 S value of the evaporitic anhydrite at Balmat, and large sulfide iron-formation occurrences near Balmat, imply that bacterial sulfate reduction occurred on an unusually large scale during Balmat sedimentation. The presence of such an increase in a sedimentary section may constitute a valuable exploration guide.

Economic Geology↗
USGS1985

Review of the use of magnetic concentrates in geochemical exploration

Magnetic concentrates recovered readily by hand magnet from alluvial sediments or panned concentrates have been used successfully in exploration as a geochemical sample medium for Cu, Zn, Co, Cr, Mo, Ni, V, Sn, and Be, particularly in arid environments where alluvial sediments may be contaminated by aeolian debris. Opportunity for this use arose recently as chemical and spectrographic techniques were developed to determine the abundances of a variety of trace elements in Fe-rich media. The use of analytical data from magnetic concentrates was introduced as one of several anomaly-enhancement techniques based on heavy minerals and intended to identify blind ore deposits. An extensive literature, reviewed here, on the relation of the chemical composition of the mineral magnetite, a main component of magnetic concentrates, to geologic conditions of origin, facilitates the interpretation of trace-element data in the context of association with ore deposits.

Open-File Report↗
USGS1996

Hydraulic characteristics and nutrient transport and transformation beneath a rapid infiltration basin, Reedy Creek Improvement District, Orange County, Florida

The Reedy Creek Improvement District disposes of about 7.5 million gallons per day (1992) of reclaimed water through 85 1-acre rapid infiltration basins within a 1,000-acre area of sandy soils in Orange County, Florida. The U.S. Geological Survey conducted field experiments in 1992 at an individual basin to examine and better understand the hydraulic characteristics and nutrient transport and transformation of reclaimed water beneath a rapid infiltration basin. At the time, concentrations of total nitrogen and total phosphorus in reclaimed water were about 3 and 0.25 milligrams per liter, respectively. A two-dimensional, radial, unsaturated/saturated numerical flow model was applied to describe the flow system beneath a rapid infiltration basin under current and hypothetical basin loading scenarios and to estimate the hydraulic properties of the soil and sediment beneath a basin. The thicknesses of the unsaturated and saturated parts of the surficial aquifer system at the basin investigated were about 37 and 52 feet, respectively. The model successfully replicated the field-monitored infiltration rate (about 5.5 feet per day during the daily flooding periods of about 17 hours) and ground-water mounding response during basin operation. Horizontal and vertical hydraulic conductivity of the saturated part of the surficial aquifer system were estimated to be 150 and 45 feet per day, respectively. The field-saturated vertical hydraulic conductivity of the shallow soil, estimated to be about 5.1 feet per day, was considered to have been less than the full-saturation value because of the effects of air entrapment. Specific yield of the surficial aquifer was estimated to be 0.41. The upper 20 feet of the basin subsurface profile probably served as a system control on infiltration because of the relatively low field-saturated, vertical hydraulic conductivity of the sediments within this layer. The flow model indicates that, in the vicinity of the basin, flow in the deeper, saturated zone was relatively slow compared to the more vigorous flow in the shallow saturated zone. The large radial component of flow below the water table in the vicinity of the basin implies that reclaimed water moves preferentially in the shallow part of the saturated zone upon reaching the water table. Therefore, there may be some vertical stratification in the saturated zone, with recently infiltrated water overlying ambient water. The infiltration capacity at the basin would be unaffected by a small (less than 10 feet) increase in background water-table altitude, because the water table would remain below the system control on infiltration. However, water-table rises of 15 and 20 feet were estimated to reduce the infiltration capacity of the basin by 8 and 25 percent, respectively. Model simulations indicate that increasing ponded depth within the basin from 4 to 12 inches and from 4 to 24 inches would increase basin infiltration capacity by less than 6 and 11 percent, respectively. A loading strategy at the basin that relies on long, uninterrupted flooding was shown to offer the possibility of inducing a more anaerobic environment conducive to denitrification while maintaining reclaimed-water disposal capacity. Field measurements indicated that transient, elevated concentrations or "spikes" of nitrate (as high as 33 milligrams per liter as nitrogen) occurred at the leading edge of the infiltrating water and in the shallow saturated zone following a prolonged basin rest period. This phenomenon probably is the result of mineralization and nitrification of organic nitrogen retained within the subsurface during earlier basin loading events. The organic nitrogen was retained in the shallow soil (due to adsorption/straining) and the shallow saturated zone (due to deposition under slacking pore-water velocity). The magnitude of the nitrate spikes appears to be influenced by the scheduling of basin loading, with short flooding and resting periods being most favorable to minimization of nitrate spikes. Removal of nitrogen by denitrification from the percolating reclaimed water is minimal in the vicinity of the basin, probably because of the lack of reducing conditions and a relative paucity of organic carbon substrates. It is speculated that longer flooding periods could induce reducing conditions that would be favorable for nitrogen removal from the system, but probably would lead to more pronounced nitrate spiking. Phosphorus concentrations were decreased by about 90 percent from concentrations in reclaimed water after moving through the upper 15 feet of the soil profile. This most likely was a result of adsorption onto abundant iron and aluminum hydrous oxyhydroxide coatings on sand grains. However, some phosphorus (coarse fraction, organic) passes through the shallow soil and accumulates below the water table under slacking pore-water velocity. This phosphorus is immobilized by adsorption, fixation, or precipitation reactions during basin rest periods.

Florida↗
USGS2003

Geochemical processes controlling transport of arsenic in groundwater: A review of adsorption

Adsorption is the predominate mechanism controlling transport of arsenic in many ground water systems. Hydrous oxides of iron, aluminum, and manganese, and clay minerals are commonly associated with aquifer solids and have been shown to be significant adsorbents of arsenic. The extent of arsenic adsorption is influenced by the chemistry of the aqueous phase including pH, arsenic speciation, and the presence and concentration of competing ions. Under moderately reducing conditions, trivalent arsenite is stable and adsorption increases with increasing pH. In an oxidizing environment, arsenate is stable and adsorption decreases with increasing pH. The presence of phosphate, sulfate, carbonate, silica, and other anions have been shown to decrease adsorption of arsenic to varying degrees. The effects of complex aqueous and solid phase chemistry on arsenic adsorption are best simulated using surface complexation models. Coupling of such models with hydrologic solute transport codes provide a powerful method for predicting the spatial and temporal distribution of arsenic in ground water.

Book chapter↗
USGS2013

Characterizing regional soil mineral composition using spectroscopyand geostatistics

This work aims at improving the mapping of major mineral variability at regional scale using scale-dependent spatial variability observed in remote sensing data. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and statistical methods were combined with laboratory-based mineral characterization of field samples to create maps of the distributions of clay, mica and carbonate minerals and their abundances. The Material Identification and Characterization Algorithm (MICA) was used to identify the spectrally-dominant minerals in field samples; these results were combined with ASTER data using multinomial logistic regression to map mineral distributions. X-ray diffraction (XRD)was used to quantify mineral composition in field samples. XRD results were combined with ASTER data using multiple linear regression to map mineral abundances. We testedwhether smoothing of the ASTER data to match the scale of variability of the target sample would improve model correlations. Smoothing was donewith Fixed Rank Kriging (FRK) to represent the mediumand long-range spatial variability in the ASTER data. Stronger correlations resulted using the smoothed data compared to results obtained with the original data. Highest model accuracies came from using both medium and long-range scaled ASTER data as input to the statistical models. High correlation coefficients were obtained for the abundances of calcite and mica (R2 = 0.71 and 0.70, respectively). Moderately-high correlation coefficients were found for smectite and kaolinite (R2 = 0.57 and 0.45, respectively). Maps of mineral distributions, obtained by relating ASTER data to MICA analysis of field samples, were found to characterize major soil mineral variability (overall accuracies for mica, smectite and kaolinite were 76%, 89% and 86% respectively). The results of this study suggest that the distributions of minerals and their abundances derived using FRK-smoothed ASTER data more closely match the spatial variability of soil and environmental properties at regional scale.

Remote Sensing of Environment↗
USGS1972

Interim results of geological investigations in the vicinity of the Ergani-Maden massive copper deposits near Maden, Elazig, Turkey

As a result of geologic studies and geochemical reconnaissance by Griffitts, Albers, and brier in 1969 in the Ergani-Maden district of eastern Turkey, seven areas were recommended for more detailed investigation. Two of these, here termed Areas 1 and 2, were mapped geologically and sampled geochemically in June and July 1970 by .4. E. Weissenborn, U. S. Geological Survey, and Omer Oner and Metin Sengun, Mineral Research and Exploration Institute (MTA), an agency of the Turkish Government. This study was part of a mineral exploration and training project conducted by the U. S. Geological Survey in cooperation with MTA under the auspices of the Agency for International Development, U. S. Department of State. Mapping and sampling of four of the other areas was completed in August and September by Oner and Sengun, but this report concerns only Areas 1 and 2. The geological environment in Areas 1 and 2 appears favorable for additional ore bodies of the Ergani-Maden type, which have been Turkey's most important producer of copper. Weak but distinct anomalies developed by the geochemical sampling in Area 1 adjacent to the Mihrap Dagi deposit suggest that other ore bodies maybe found along the northwesterly trend defined by the Mihrap Dagi, Arpa Meydan, Ana Yatak mines, and the Mizir Tepe prospect. Recommendations are made for 8 drill holes in Area 1 to test this possibility. Two additional holes are also recommended in Arc.: 1. Two less pronounced anomalies were developed in Area 2. Two drill holes are suggested to test them.

Elazig↗
USGS2017

Documenting mudstone heterogeneity by use of principal component analysis of X-ray diffraction and portable X-ray fluorescence data: A case study in the Triassic Shublik Formation, Alaska North Slope

Determining the chemical and mineralogical variability within fine-grained mudrocks poses analytical challenges but is potentially useful for documenting subtle stratigraphic differences in physicochemical environments that may influence petroleum reservoir properties and behavior. In this study, we investigate the utility of combining principal component analysis (PCA) of X-ray diffraction (XRD) data and portable X-ray fluorescence (pXRF) data to identify simplifying relationships within a large number of samples and subsequently evaluate a subset that encompasses the full spectrum or range of mineral and chemical variability within a vertical section. Samples were collected and analyzed from a vertical core of the Shublik Formation, a heterogeneous, phosphate-rich, calcareous mudstone-to-marl unit deposited in the Arctic Alaska Basin (AAB) during the Middle and Late Triassic. The Shublik is a major petroleum source rock in the Alaskan North Slope, and is considered a prime target for continuous self-sourced resource plays.

Conference Paper↗
USGS1994

Airborne remote sensing for geology and the environment; present and future

In 1988, a group of leading experts from government, academia, and industry attended a workshop on airborne remote sensing sponsored by the U.S. Geological Survey (USGS) and hosted by the Branch of Geophysics. The purpose of the workshop was to examine the scientific rationale for airborne remote sensing in support of government earth science in the next decade. This report has arranged the six resulting working-group reports under two main headings: (1) Geologic Remote Sensing, for the reports on geologic mapping, mineral resources, and fossil fuels and geothermal resources; and (2) Environmental Remote Sensing, for the reports on environmental geology, geologic hazards, and water resources. The intent of the workshop was to provide an evaluation of demonstrated capabilities, their direct extensions, and possible future applications, and this was the organizational format used for the geologic remote sensing reports. The working groups in environmental remote sensing chose to present their reports in a somewhat modified version of this format. A final section examines future advances and limitations in the field. There is a large, complex, and often bewildering array of remote sensing data available. Early remote sensing studies were based on data collected from airborne platforms. Much of that technology was later extended to satellites. The original 80-m-resolution Landsat Multispectral Scanner System (MSS) has now been largely superseded by the 30-m-resolution Thematic Mapper (TM) system that has additional spectral channels. The French satellite SPOT provides higher spatial resolution for channels equivalent to MSS. Low-resolution (1 km) data are available from the National Oceanographic and Atmospheric Administration's AVHRR system, which acquires reflectance and day and night thermal data daily. Several experimental satellites have acquired limited data, and there are extensive plans for future satellites including those of Japan (JERS), Europe (ESA), Canada (Radarsat), and the United States (EOS). There are currently two national airborne remote sensing programs (photography, radar) with data archived at the USGS' EROS Data Center. Airborne broadband multispectral data (comparable to Landsat MSS and TM but involving several more channels) for limited geographic areas also are available for digital processing and analysis. Narrow-band imaging spectrometer data are available for some NASA experiment sites and can be acquired for other locations commercially. Remote sensing data and derivative images, because of the uniform spatial coverage, availability at different resolutions, and digital format, are becoming important data sets for geographic information system (GIS) analyses. Examples range from overlaying digitized geologic maps on remote sensing images and draping these over topography, to maps of mineral distribution and inferred abundance. A large variety of remote sensing data sets are available, with costs ranging from a few dollars per square mile for satellite digital data to a few hundred dollars per square mile for airborne imaging spectrometry. Computer processing and analysis costs routinely surpass these expenses because of the equipment and expertise necessary for information extraction and interpretation. Effective use requires both an understanding of the current methodology and an appreciation of the most cost-effective solution.

Bulletin↗
USGS2019

Element cycling in the Middle-Late Triassic Shublik Formation: Mineralization vs. recycling of biolimiting nutrients in an unconventional resource play

The Triassic Shublik Formation in northern Alaska is one of the major source rocks in North America, having generated much of the petroleum in Prudhoe Bay and associated fields. The middle Shublik Formation, the focus of this study, is a highly phosphatic, organic-rich carbonate mudstone interval. Apatite cements can occur as phosphatic peloids, steinkerns, elongate or angular nodules, and shells or shell fragments. We propose a model whereby phosphatization is favored in early diagenetic environments that have low concentrations of dissolved iron relative to reactive organic matter in the pore water sulfate reduction zone.

Alaska↗
USGS2021

The Mars Orbiter for Resources, Ices, and Environments (MORIE) science goals and instrument trades in radar, imaging, and spectroscopy

The Mars Orbiter for Resources, Ices, and Environments (MORIE) was selected as one of NASA's 2019 Planetary Mission Concept Studies. The mission builds upon recent discoveries and current knowledge gaps linked to two primary scientific questions: (1) when did elements of the cryosphere form and how are ice deposits linked to current, recent, and ancient climate, and (2) how does the crust record the evolution of surface environments and their transition through time? Addressing these questions has emerged in numerous recent reports as a high priority in investigating the evolution of Mars as a habitable world. A subsidiary goal of the mission concept is to provide information relevant to the eventual human exploration of Mars, specifically helping to locate and quantify near-surface water ice and hydrated mineral resources. The proposed instrument suite includes polarimetric synthetic aperture radar imaging, radar sounding, high-resolution visible and infrared imaging, both short-wave and thermal-infrared spectroscopy, and multichannel wide-angle imaging. MORIE would provide novel measurements of Mars expected to lead to significant new discoveries by the first radar imaging from orbit, radar sounding directly over the poles, and mineral mapping at spatial scales that will unravel geologic sequence stratigraphy through time. The final report of the mission concept provides details on the spacecraft, orbital design, technological maturity, results from systems-level integration studies, and costs. This article is intended to expand upon the science motivation for the mission, the measurement goals and objectives, and the instrument trade space that was examined in detail during the concept study.

The Planetary Science Journal↗
USGS2016

News from the seabed: Geological characteristics and resource potential of deep-sea mineral resources

Marine minerals such as manganese nodules, Co-rich ferromanganese crusts, and seafloor massive sulfides are commonly seen as possible future resources that could potentially add to the global raw materials supply. At present, a proper assessment of these resources is not possible due to a severe lack of information regarding their size, distribution, and composition. It is clear, however, that manganese nodules and Co-rich ferromanganese crusts are a vast resource and mining them could have a profound impact on global metal markets, whereas the global resource potential of seafloor massive sulfides appears to be small. These deep-sea mineral commodities are formed by very different geological processes resulting in deposits with distinctly different characteristics. The geological boundary conditions also determine the size of any future mining operations and the area that will be affected by mining. Similarly, the sizes of the most favorable areas that need to be explored for a global resource assessment are also dependent on the geological environment. Size reaches 38 million km 2 for manganese nodules, while those for Co-rich crusts (1.7 million km 2 ) and massive sulfides (3.2 million km 2 ) are much smaller. Moreover, different commodities are more abundant in some jurisdictions than in others. While only 19% of the favorable area for manganese nodules lies within the Exclusive Economic Zone of coastal states or is covered by proposals for the extension of the continental shelf, 42% of the favorable areas for massive sulfides and 54% for Co-rich crusts are located in EEZs

Marine Policy↗
USGS1987

Mineral Resources of the Antelope Wilderness Study Area, Nye County, Nevada

At the request of the U.S. Bureau of land Management, 83,100 acres of the Antelope Wilderness Study Area (NV-4)60-231/241) was studied. In this report the studied area is called the 'wilderness study area', or simply the 'study area.' No identified mineral or energy resources occur within the study area. The southern part of the area has moderate mineral resource potential for undiscovered gold and silver, and the Woodruff Formation in the southern part of the area has high resource potential for undiscovered vanadium, zinc, selenium, molybdenum, and silver (fig. 1). This assessment is based on field geochemical studies in 1984 and 1985 by the U.S. Bureau of Mines and field geochemical studies and geologic mapping by the U.S. Geological Survey in 1984 and 1985. The remainder of the study area has low resource potential for undiscovered gold, silver, lead, zinc, manganese, tin, and molybdenum. The study area also has low resource potential for undiscovered oil and gas resources. The Antelope Wilderness Study Area is about midway between Tonopah and Eureka, Nev., in the northern Hot Creek Range and southern Antelope Range of central Nevada. It is accessible by unimproved dirt roads extending 20 mi (miles) north from U.S. Highway 6 and 40 mi south from U.S. Highway 50 (fig. 2). Most of the study area consists of rugged mountainous terrain having approximately 2,600 ft (feet) of relief. The mountain range is a block tilted gently to the east and bounded on both sides by normal faults that dip steeply to moderately west and have major displacements. Most of the study area is underlain by a thick sequence of Tertiary volcanic rocks that predominantly consist of silicic ash-flow tuff, the Windous Butte Formation. Paleozoic and lower Mesozoic (see geologic time chart in appendix) marine sediments occur along the southern margin of the study area, and lower Paleozoic rocks are exposed in the northeast corner. The areas of exposed Paleozoic-Mesozoic rocks along the southern margin of the study area have moderate mineral resource potential for gold and silver in sediment-hosted, disseminated, epithermal (low-temperature) gold-silver deposits (fig. 1). These rocks consist of folded and thrust-faulted, fine-grained clastic sediments and limestone and dolomite that locally have been brecciated and hydrothermally altered. The alteration (locally, strong silicification) and geochemical associations of these rocks indicate a favorable environment for such deposits. Exploration for disseminated gold deposits in the same geologic environment is currently being conducted just south of the study area. The remainder of the study area has low resource potential for epithermal gold and silver vein deposits in the Tertiary volcanic rocks. The Cenozoic sedimentary basins adjacent to the fault-bounded mountain block have moderate potential for petroleum resources; the study area itself has low potential for petroleum resources.

Bulletin↗
USGS1994

Black Hills hydrology study

The Black Hills area of western South Dakota is a valuable resource center. The area has attracted numerous residents and industries because of the availability of mineral, timber, agricultural, recreational, and water resources. The water resources of the area have been stressed locally by increasing population, periodic drought, and development of other resources. In response to residents' concerns about these stresses on the water resources, the Black Hills Hydrology Study was initiated in 1990 as a cooperative effort among the U.S. Geological Survey, the South Dakota Department of Environment and Natural Resources, and the West Dakota Water Development District. West Dakota represents the various local and county cooperators. This report describes the purpose, scope, approach, and status of the study and presents highlights from the first project data report produced for the study.

Open-File Report↗
USGS2010

Linking microbial and ecosystem ecology using ecological stoichiometry: a synthesis of conceptual and empirical approaches

Currently, one of the biggest challenges in microbial and ecosystem ecology is to develop conceptual models that organize the growing body of information on environmental microbiology into a clear mechanistic framework with a direct link to ecosystem processes. Doing so will enable development of testable hypotheses to better direct future research and increase understanding of key constraints on biogeochemical networks. Although the understanding of phenotypic and genotypic diversity of microorganisms in the environment is rapidly accumulating, how controls on microbial physiology ultimately affect biogeochemical fluxes remains poorly understood. We propose that insight into constraints on biogeochemical cycles can be achieved by a more rigorous evaluation of microbial community biomass composition within the context of ecological stoichiometry. Multiple recent studies have pointed to microbial biomass stoichiometry as an important determinant of when microorganisms retain or recycle mineral nutrients. We identify the relevant cellular components that most likely drive changes in microbial biomass stoichiometry by defining a conceptual model rooted in ecological stoichiometry. More importantly, we show how X-ray microanalysis (XRMA), nanoscale secondary ion mass spectroscopy (NanoSIMS), Raman microspectroscopy, and in situ hybridization techniques (for example, FISH) can be applied in concert to allow for direct empirical evaluation of the proposed conceptual framework. This approach links an important piece of the ecological literature, ecological stoichiometry, with the molecular front of the microbial revolution, in an attempt to provide new insight into how microbial physiology could constrain ecosystem processes.

Ecosystems↗