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At least 865 records · Page 48Linked to original sources

USGS1995

Channel change on the Santa Cruz River, Pima County, Arizona, 1936-86

The Santa Cruz River in southeastern Arizona has a long history of channel instability. Since the late 19th century, lateral channel erosion has caused extensive property damage, particularly in Pima County. The dominant mechanism of channel change in a reach depends on channel morphology and flood magnitude. The timing and magnitude of channel change are controlled primarily by hydroclimatic factors. The location of change is controlled largely by topographic, geologic, hydraulic, and artificial factors.

Water Supply Paper↗

USGS1998

Geohistory and thermal maturation in the Cherokee Basin (Mid-Continent, U.S.A.): results from modeling

The Cherokee basin in southeastern Kansas contains a stratigraphic section consisting mostly of Permian-Pennsylvanian alternating clastics and thin carbonates overlying carbonates of Mississippian and Cambrian-Ordovician age on a Precambrian crytalline basement. Based on a conceptual model of events of deposition, nondeposition, and erosion, a burial history model for (1) noncompaction, and a series of models for (2) compaction are computed for a borehole location in the south-central part of the basin. The models are copled with the calculation of nonsteady-state geothermal conditions. Maximum temperatures during basin evolution of about 70??C at the base of the organic-rich Pennsylvanian are predicted by our models, assuming pure heat conduction and a heat flow from the basement of 60 m W/m2. The maturation of organic matter as indicated by three different vitrinite reflectance (Ro) models is on the order og 0.3-0.5% Ro for Pennsylvanian rocks and 0.6% Ro for the Devonian-Mississippian Cattanooga Shale. Vitrinite reflectance was measured on subsurface smaples from three wells. The measured values correlate in the upper part of the sequence with modeled data, but diverge slightly in the Lower Pennsylvanian and Cattanooga Shale. The differences in maturation may be a result of differing local geological conditions within the basin. The relatively high Ro-depth gradients observed in one borehole may be explained by conditions in the Teeter oil field, which is a typical plains-type anticline that has been affected by fluid flow through vertical faults. Higher Ro values correlate positively with the grade of sulfidfe mineralization in the sediment, which may be a hint of fluid impact. The high Ro values relative to the shallow depth of the Mississippian and the Chattanooga Shale in the Brown well are on the order of Ro values modeled for the same stratigraphic units at present-day greater depths and may reflect uplift of the Ozark dome, located further east, affecting the eastern side of the Cherokee Basin.Based on a concept model of deposition, nondeposition and erosion, a burial history model for noncompaction, and a series of models for compaction are developed for a borehole location in a south-central part of the Cherokee basin in southeastern Kansas. Coupled with the calculation of nonsteady state-state geothermal conditions, the models predict maximum temperatures during evolution of about 70 ??C at the base of the organic-rich Pennsylvanian. A difference in organic matter maturation in the Pennsylvanian and the Chattanooga shale exhibited by vitrinite reflectance models indicate probably differing local geological conditions within the basin.

American Association of Petroleum Geologists Bulle↗

USGS2005

Surface-Water and Ground-Water Resources of Kendall County, Illinois

Water-supply needs in Kendall County, in northern Illinois, are met exclusively from ground water derived from glacial drift aquifers and bedrock aquifers open to Silurian, Ordovician, and Cambrian System units. As a result of population growth in Kendall County and the surrounding area, water use has increased from about 1.2 million gallons per day in 1957 to more than 5 million gallons per day in 2000. The purpose of this report is to characterize the surface-water and ground-water resources of Kendall County. The report presents a compilation of available information on geology, surface-water and ground-water hydrology, water quality, and water use. The Fox River is the primary surface-water body in Kendall County and is used for both wastewater disposal and as a drinking-water supply upstream of the county. Water from the Fox River requires pretreatment for use as drinking water, but the river is a potentially viable additional source of water for the county. Glacial drift aquifers capable of yielding sufficient water for municipal supply are expected to be present in northern Kendall County, along the Fox River, and in the Newark Valley and its tributaries. Glacial drift aquifers capable of yielding sufficient water for residential supply are present in most of the county, with the exception of the southeastern portion. Volatile organic compounds and select trace metals and pesticides have been detected at low concentrations in glacial drift aquifers near waste-disposal sites. Agricultural-related constituents have been detected infrequently in glacial drift aquifers near agricultural areas. However, on the basis of the available data, widespread, consistent problems with water quality are not apparent in these aquifers. These aquifers are a viable source for additional water supply, but would require further characterization prior to full development. The shallow bedrock aquifer is composed of the sandstone units of the Ancell Group, the Prairie du Chien Group, the Galena-Platteville dolomite, the Maquoketa Group, and the Silurian dolomite where these units are at the bedrock surface. The availability of water from the shallow bedrock aquifer depends primarily on the geologic unit utilized. The Silurian dolomite, Galena-Platteville dolomite, and Ancell Group can yield sufficient water for residential and municipal supply in at least some parts of the county. The Cambrian-Ordovician aquifer system is composed of the most widespread, productive aquifers in northern Illinois and is used for water supply by a number of municipalities and industrial facilities. Water levels in the aquifer system have declined by as much as 600 feet in Kendall County and the aquifer frequently contains concentrations of radium above established health guidelines.

Scientific Investigations Report↗

USGS1989

Late Cenozoic sea-level changes and the onset of glaciation: impact on continental slope progradation off eastern Canada

Late Cenozoic sedimentation from four varied sites on the continental slopes off southeastern Canada has been analysed using high-resolution airgun multichannel seismic profiles, supplemented with some single channel data. Biostratigraphic ties are available to exploratory wells at three of the sites. Uniform, slow accumulation of hemipelagic sediments was locally terminated by the late Miocene sea-level lowering, which is also reflected in changes in foraminiferan faunas on the continental shelf. Data are very limited for the early Pliocene but suggest a return to slow hemipelagic sedimentation. At the beginning of the late Pliocene, there was a change in sedimentation style marked by a several-fold increase in accumulation rates and cutting of slope valleys. This late Pliocene cutting of slope valleys corresponds to the onset of late Cenozoic growth of the Laurentian Fan and the initiation of turbidite sedimentation on the Sohm Abyssal Plain. Although it corresponds to a time of sea-level lowering, the contrast with the late Miocene lowstand indicates that there must also have been a change in sediment delivery to the coastline, perhaps as a result of increased rainfall or development of valley glaciers. High sedimentation rates continued into the early Pleistocene, but the extent of slope dissection by gullies increased. Gully-cutting episodes alternated with sediment-draping episodes. Throughout the southeastern Canadian continental margin, there was a change in sedimentation style in the middle Pleistocene that resulted from extensive ice sheets crossing the continental shelf and delivering coarse sediment directly to the continental slope. ?? 1989.

Marine and Petroleum Geology↗

USGS1973

Soda Creek springs - metamorphic waters in the eastern Alaska Range

The Soda Creek springs are a group of small, cold mineral springs on the southern flank of the eastern Alaska Range. The spring waters contain anomalous concentrations of carbon dioxide, sodium, chlorine, sulfate, boron, and ammonia and are actively precipitating deposits of calcite and aragonite. Sparingly present in these deposits are mixed-layer illite-montmorillonite clays and zeolite minerals. Low-temperature metamorphic reactions in subjacent marine sedimentary rocks of Jurassic and Cretaceous age may have produced the fluids and silicate minerals. With only a few exceptions, cool bicarbonate-rich springs in Alaska are concentrated south of the Denali fault system in south-central Alaska, southeastern Alaska, and along the Kaltag-Tintina fault system. These areas are characterized by active or recently active tectonism, major faults and folds, and an abundance of marine sedimentary rocks.

Alaska↗

USGS2017

Water resources of the Southern Hills regional aquifer system, southeastern Louisiana

Information concerning the availability, use, and quality of groundwater in the 10 parishes overlying the Southern Hills regional aquifer system of Louisiana (fig. 1) is critical for water-supply management. The purpose of this fact sheet is to present information that can be used by water managers, residents, and others for stewardship of this vital resource. Information on the availability, past and current use, use trends, and water quality from groundwater sources in these parishes is presented. Previously published reports (see References Cited section) and data stored in the U.S. Geological Survey’s National Water Information System (U.S. Geological Survey, 2017) are the primary sources of the information presented here.

Louisiana↗

USGS2011

Chronology, sedimentology, and microfauna of groundwater discharge deposits in the central Mojave Desert, Valley Wells, California

During the late Pleistocene, emergent groundwater supported persistent and long-lived desert wetlands in many broad valleys and basins in the American Southwest. When active, these systems provided important food and water sources for local fauna, supported hydrophilic and phreatophytic vegetation, and acted as catchments for eolian and alluvial sediments. Desert wetlands are represented in the geologic record by groundwater discharge deposits, which are also called spring or wetland deposits. Groundwater discharge deposits contain information on the timing and magnitude of past changes in water-table levels and, thus, are a source of paleohydrologic and paleoclimatic information. Here, we present the results of an investigation of extensive groundwater discharge deposits in the central Mojave Desert at Valley Wells, California. We used geologic mapping and stratigraphic relations to identify two distinct wetland sequences at Valley Wells, which we dated using radiocarbon, luminescence, and uranium-series techniques. We also analyzed the sediments and microfauna (ostracodes and gastropods) to reconstruct the specific environments in which they formed. Our results suggest that the earliest episode of high water-table conditions at Valley Wells began ca. 60 ka (thousands of calendar yr B.P.), and culminated in peak discharge between ca. 40 and 35 ka. During this time, cold (4–12 °C) emergent groundwater supported extensive wetlands that likely were composed of a wet, sedge-rush-tussock meadow mixed with mesic riparian forest. After ca. 35 ka, the water table dropped below the ground surface but was still shallow enough to support dense stands of phreatophytes through the Last Glacial Maximum (LGM). The water table dropped further after the LGM, and xeric conditions prevailed until modest wetlands returned briefly during the Younger Dryas cold event (13.0–11.6 ka). We did not observe any evidence of wet conditions during the Holocene at Valley Wells. The timing of these fluctuations is consistent with changes in other paleowetland systems in the Mojave Desert, the nearby Great Basin Desert, and in southeastern Arizona, near the border of the Sonoran and Chihuahuan Deserts. The similarities in hydrologic conditions between these disparate locations suggest that changes in groundwater levels during the late Pleistocene in desert wetlands scattered throughout the American Southwest were likely driven by synoptic-scale climate processes.

California↗

USGS1903

Tishomingo folio, Indian Territory

The Tishomingo quadrangle is bounded by meridians 96° 30' and 97° and parallels 34° and 34° 30', and occupies one-quarter of a square degree of the earth's surface. It is 34.5 miles long north and south and 28.58 miles wide, and contains about 986 square miles. It lies in the southeastern part of the Chickasaw Nation, Indian Territory, the eastern edge being nearly 3 miles west of the Choctaw-Chickasaw boudary line, and the southern side about 3 miles north of the nearest approach of Red River.

Tishomingo Quadrangle↗

USGS1972

Water resources of part of Canyonlands National Park, southeastern Utah

Canyonlands National Park is in about the center of the Canyon Lands section of the Colorado Plateaus physiographic province in southeastern Utah. The part of the park discussed embraces an area of about 400 square miles comprising isolated mesas, precipitous canyons, and dissected broad benches near the confluence of the Green and Colorado Rivers, the only perennial streams in the area. The climate is arid to semiarid; normal annual precipitation ranges from less than 8 to about 10 inches. Potential evapotranspiration is about 41 inches annually. Geology of the park is characterized by nearly horizontal strata that dip gently northward. Exposed rock formations and deposits range in age from Middle Pennsylvanian to Holocene. Owing to the elevated and deeply dissected topography, only parts of the Cedar Mesa and White Rim Sandstone Members of the Cutler Formation of Permian age have potential for development of wells. Strata above and below them support only small springs, are dry, or contain brine. In the northwest part of the park, the Green River at Taylor Canyon is a potential source of surface water for public supplies for the Island In The Sky area and a small part of the northwest White Rim area. It will require filtration and treatment before use. In the same area, two unused wells in Taylor Canyon will supply enough water for present requirements from the White Rim Sandstone Member of the Cutler Formation, about 140 gallons per minute combined, but yield mineralized water that will require treatment before use. Springs yielding good water at the Island In The Sky and White Rim are mostly intermittent and too small for public-water supply. Most of the White Rim area is dry, having no usable ground water. In The Needles area, wells provide water of good quality from the Cedar Mesa Sandstone Member of the Cutler Formation. Springs yielding good water in the same area are available for supplementary supplies. West of The Needles, The Grabens area is without springs or potential aquifers bearing usable water. During 1970 about 510,000 gallons of water was used in Canyonlands National Park. Of this amount, 110,000 gallons was supplied to Island In The Sky by tank truck from a source outside the park, and about 400,000 gallons was withdrawn from the well in use at The Needles. Estimated total annual requirements in 10 years (1980) may be as much as 6 million gallons. Sources of water supplies within the park now in use and potential sources of surface water or ground water outlined by this investigation will meet the estimated requirements. Development of rainfall-collection and cistern-storage systems could furnish small emergency sources of water for waterless areas on the White Rim and in The Grabens.

Utah↗

USGS2000

Physical characteristics of stream subbasins in the Cannon River Basin, southeastern Minnesota

Data that describe the physical characteristics of stream subbasins upstream from selected sites on streams in the Cannon River Basin, located in southeastern Minnesota, are presented in this report. The physical characteristics are the drainage area of the subbasin, the percentage area of the subbasin covered only by lakes, the percentage area of the subbasin covered by both lakes and marsh, the main-channel length, and the main-channel slope. Stream sites include outlets of subbasins of at least 5 square miles, and locations of U.S. Geological Survey high-flow, and continuous-record gaging stations.

Minnesota↗

USGS1996

Water Budget and the Effects of Land-Use Changes on Ground-Water Recharge, Oahu, Hawaii

Detailed water budgets calculated for southern and southeastern Oahu are used with a geographic information system to develop simplified methods for estimating areal water budgets for predevelopment and mid-1980's land use. The methods were applied to estimate water budgets for the Waianae area of western Oahu, and for north-central, southern, and southeastern Oahu. A water budget was calculated for windward Oahu by developing a separate geographic information system model of the area. The water budgets for these areas were combined into a single water budget for the entire island. The geographic information system model was used to calculate mid-1980's ground-water recharge to small areas of specific interest and the distribution of recharge by geologic formation. The most significant changes in the water budget and ground-water recharge have occurred in north-central and southern Oahu as a result of large-scale agricultural development and urbanization by the mid-1980's. Runoff increased by 23 million gallons per day in southern Oahu where extensive urban areas have been developed. Evapotranspiration increased by 8 million gallons per day in southern Oahu and 28 million gallons per day in north-central Oahu as result of the 146 million gallons per day of agricultural irrigation. Ground-water recharge increased in both areas: by about 56 million gallons per day in southern Oahu and by about 32 million gallons per day in north-central Oahu. Predevelopment ground-water recharge to Oahu was an estimated 792 million gallons per day. Changes in land-use practices in the mid-1980's resulted in an estimated island-wide recharge of 880 million gallons per day.

Professional Paper↗

USGS1976

Hard rock uranium potential in Alaska

Discussing the potential of "hardrock" (i.e., non-sedimentary type) uranium deposits in a 586,000 mi 2 portion of the North America Cordillera is a difficult task compounded by the fact that the remoteness of much of the region and the logistical difficulties have resulted in only reconnaissance geologic information being available for large parts of the state. Cobb (1970) has listed known occurrences of uranium and thorium minerals in the state and a somewhat modified version of his compilation showing chiefly hardrock occurrences is given in figure 1; it should be emphasized that these are occurrences only and not necessarily deposits of possible economic significance. The distribution pattern shows a concentration of occurrences in southeastern Alaska and particularly in the interior. The only production of uranium in Alaska from any type of deposit has been from a hardrock deposit, that being the roughly 120,000 tons of ore averaging about one percent U 3 0 8 from the Ross-Adams mine near Bokan Mountain on Prince of Wales Island close to the southern tip of southeastern Alaska. The Bokan Mountain uranium-thorium area includes about 71 mi 2 and is largely underlain by plutonic rocks (MacKevett, 1963). The plutonic rocks range from pyroxenite to peralkaline granite and syenite, but they consist chiefly of diorite, quartz diorite, granodiorite, and quartz monzonite. The peralkaline granite, a small pluton about 3 mi2 in area, is Late Triassic or Early Jurassic in age while the other plutonic rocks are early Paleozoic.

Alaska↗

USGS2009

Iodine-129 in the Snake River Plain Aquifer at and Near the Idaho National Laboratory, Idaho, 2003 and 2007

From 1953 to 1988, wastewater containing approximately 0.94 curies of iodine-129 (129I) was generated at the Idaho National Laboratory (INL) in southeastern Idaho. Almost all of this wastewater was discharged at or near the Idaho Nuclear Technology and Engineering Center (INTEC) on the INL site. Most of the wastewater was discharged directly into the eastern Snake River Plain aquifer through a deep disposal well until 1984; however, some wastewater also was discharged into unlined infiltration ponds or leaked from distribution systems below the INTEC. In 2003, the U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, collected samples for 129I from 36 wells used to monitor the Snake River Plain aquifer, and from one well used to monitor a perched zone at the INTEC. Concentrations of 129I in the aquifer ranged from 0.0000066 +- 0.0000002 to 0.72 +- 0.051 picocuries per liter (pCi/L). Many wells within a 3-mile radius of the INTEC showed decreases of as much as one order of magnitude in concentration from samples collected during 1990-91, and all of the samples had concentrations less than the Environmental Protection Agency's Maximum Contaminant Level (MCL) of 1 pCi/L. The average concentration of 129I in 19 wells sampled during both collection periods decreased from 0.975 pCi/L in 1990-91 to 0.249 pCi/L in 2003. These decreases are attributed to the discontinuation of disposal of 129I in wastewater after 1988 and to dilution and dispersion in the aquifer. Although water from wells sampled in 2003 near the INTEC showed decreases in concentrations of 129I compared with data collected in 1990-91, some wells south and east of the Central Facilities Area, near the site boundary, and south of the INL showed slight increases. These slight increases may be related to variable discharge rates of wastewater that eventually moved to these well locations as a mass of water from a particular disposal period. In 2007, the USGS collected samples for 129I from 36 wells that are used to monitor the aquifer south of INTEC and from 2 wells that are used to monitor perched zones at INTEC. Concentrations of 129I in the eastern Snake River Plain aquifer ranged from 0.000026 +- 0.000002 to 1.16 +- 0.04 pCi/L, and the concentration at one well exceeded the maximum contaminant level (1 pCi/L) for public drinking water supplies. The average concentration of 19 wells sampled in 2003 and 2007 did not differ; however, slight increases and decreases of concentrations in several areas around the INTEC were evident in the aquifer. The decreases are attributed to the discontinued disposal and to dilution and dispersion in the aquifer. The increases may be due to the movement into the aquifer of remnant perched water below the INTEC. In 2007, the USGS also collected samples from 31 zones in 6 wells equipped with multi-level WestbayTM packer sampling systems to help define the vertical distribution of 129I in the aquifer. Concentrations ranged from 0.000011 +- 0.0000005 to 0.0167 +- 0.0007 pCi/L. For three wells, concentrations of 129I between zones varied one to two orders of magnitude. For two wells, concentrations varied for one zone by more than an order of magnitude from the wells' other zones. Similar concentrations were measured from all five zones sampled in one well. All of the 31 zones had concentrations two or more magnitudes below the maximum contaminant level.

Scientific Investigations Report↗

USGS2011

Hydrogeologic framework of the Johns Creek subbasin and vicinity, Mason County, Washington

This report describes the hydrogeologic framework of the groundwater-flow system in the Johns Creek subbasin and vicinity. The study area covers 97 square miles in southeastern Mason County, Washington, and includes the Johns Creek subbasin, which drains an area of about 11 square miles. The study area extends beyond the Johns Creek subbasin to include major hydrologic features that could be used as regional groundwater-flow model boundaries. The subbasin is underlain by a thick sequence of unconsolidated Quaternary glacial and interglacial deposits, which overlie Tertiary igneous and sedimentary bedrock units. Geologic units were grouped into eight hydrogeologic units consisting of aquifers, confining units, undifferentiated deposits, and an underlying bedrock unit. A surficial hydrogeologic map was developed and used with lithologic information from 200 drillers' logs to construct 4 hydrogeologic sections, and unit extent and thickness maps.

Scientific Investigations Report↗

USGS2015

Geochemical conditions and the occurrence of selected trace elements in groundwater basins used for public drinking-water supply, Desert and Basin and Range hydrogeologic provinces, 2006-11: California GAMA Priority Basin Project

The geochemical conditions, occurrence of selected trace elements, and processes controlling the occurrence of selected trace elements in groundwater were investigated in groundwater basins of the Desert and Basin and Range (DBR) hydrogeologic provinces in southeastern California as part of the Priority Basin Project (PBP) of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA PBP is designed to provide an assessment of the quality of untreated (raw) groundwater in the aquifer systems that are used for public drinking-water supply. The GAMA PBP is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey and the Lawrence Livermore National Laboratory. The DBR hydrogeologic provinces consist of 141 defined groundwater basins separated by mountain ranges, faults, and other features. This report presents analyses of data collected from nine study areas within the DBR hydrogeologic provinces: Antelope Valley, Borrego Valley, the Central Desert area, Coachella Valley, Colorado River, Indian Wells Valley, Low-Use Basins of the Mojave and Sonoran Deserts, the Mojave, and Owens Valley. Collectively, these nine study areas are referred to as the DBR study unit. The study unit covers approximately 7,000 square miles and includes the 63 groundwater basins in the DBR hydrogeologic provinces in which groundwater is used for public drinking-water supply. The vast majority of the 223 wells sampled for this study were long-screened production wells used primarily for public supply. Uncorrected carbon-14 ( 14 C) groundwater ages for samples collected in the DBR study unit ranged from less than (<) 100 to 33,700 years before present (BP). Sixty-six percent of sample ages were greater than (>) 100 years BP, and 40 percent were >3,800 years BP. Samples collected from wells located adjacent to mountain-front recharge areas or major surface-water features generally had younger groundwater ages than did samples collected from wells located away from mountain fronts or towards the distal ends of basin groundwater flow paths. Most groundwater sampled in the DBR study unit had alkaline pH: 89 percent of sample pH values ranged from 7.1 to 9.8, with 37 percent greater than or equal to (≥) 7.9. Groundwater age was significantly correlated (positively) with pH, likely because silicate weathering is a primary control on groundwater pH and is a slow process. The oxidation-reduction (redox) condition of the groundwater sampled in the DBR study unit was predominantly oxic (71 percent), except in the Colorado River study area where organic-rich fluvial aquifers provide the electron donors necessary to support iron-reducing (anoxic-Fe) redox processes. The cation type of 78 percent of the samples was either sodium- or mixed-type, and the anion type of 83 percent of the samples was either bicarbonate- or mixed-type. Sodium-type groundwaters generally were older and more alkaline than calcium-type groundwaters, consistent with the change in water chemistry expected from cation exchange between groundwater and aquifer sediments over long periods of time. Because of the correlation with young groundwater, calcium-type groundwater was predominantly from wells located adjacent to mountain-front recharge areas. Arsenic (As), boron (B), fluoride (F), molybdenum (Mo), strontium (Sr), uranium (U), and vanadium (V) were selected for assessment in this study because they occurred at concentrations greater than California Department of Public Health or U.S. Environmental Protection Agency regulatory or non-regulatory drinking-water-quality benchmarks in more than 2 percent of the 223 samples collected in the DBR study unit. As and F were detected most commonly (18 and 13 percent, respectively) at concentrations above associated water-quality benchmarks and Sr and V least frequently (both at 3 percent). Given that 14 C groundwater ages are predominantly >100 years BP, land use in the study unit is primarily undeveloped, and chemicals derived from anthropogenic sources, such as volatile organic compounds, were infrequently detected, high concentrations of these trace elements in groundwater were most likely the result of natural factors and not anthropogenic factors. As, F, Mo, and V concentrations showed significant positive correlations to groundwater age and to pH. This relation is partly due to the sources of trace elements likely being the weathering of primary minerals, such as silicate minerals, which is a slow process that takes place over hundreds to thousands of years. This relation also reflects the positive correlation between groundwater age and pH. Geochemical modeling predicted that the dominant species of As, Mo, and V in solution were oxyanions (HAsO 4 2– , MoO 4 2– , and H 2 VO 4– ), which are likely to be mobile in alkaline groundwater because mineral surfaces composing aquifer matrices have a predominantly negative surface charge under alkaline conditions. F also exists predominantly as a negatively charged ion (F – ). At pH values >7.5, saturation indices generated by the geochemical modeling program PHREEQC indicated that F solubility may be somewhat limited by the precipitation of the mineral fluorapatite [Ca 5 (PO 4 ) 3 F]. Speciation modeling of As in anoxic-Fe groundwater (iron-reducing conditions) showed that samples were supersaturated with orpiment (As 2 S 3 ), indicating that mineral precipitation may be responsible for low As concentrations observed in reducing groundwater. In contrast, U concentrations showed significant negative correlations to groundwater age and to pH. Higher U concentrations generally occurred in samples for which geochemical modeling indicated that the uncharged ternary complex Ca 2 UO 2 (CO 3 ) 3 was the dominant aqueous U species. This uncharged complex is not attracted to the charged surfaces of minerals and thus increases U solubility. Formation of Ca 2 UO 2 (CO 3 ) 3 was greater in younger groundwaters because calcium and uranium concentrations generally were lower in older groundwaters, likely due to cation-exchange processes and precipitation of the mineral calcite as groundwater pH increased. Co-precipitation of U with the calcite (CaCO 3 ) may remove U from the aqueous phase. Saturation indices indicated that the anoxic-Fe groundwaters from the Colorado River study area were supersaturated with the mineral uraninite (UO 2 ), suggesting that UO 2 precipitation may be responsible for the low concentrations of U observed in these samples. Concentrations of strontium, which exists primarily in a cationic form (Sr 2+ ), were not significantly correlated with either groundwater age or pH. Strontium concentrations showed a strong positive correlation with total dissolved solids (TDS). Dissolved constituents, such as Sr, that interact with mineral surfaces through outer-sphere complexation become increasingly soluble with increasing TDS concentrations of groundwater. Boron concentrations also showed a significant positive correlation with TDS, indicating the B may interact to a large degree with mineral surfaces through outer-sphere complexation.

California↗

USGS1953

Thorium investigations, 1950-52, Wet Mountains, Colorado

The Wet Mountain thorium district was discovered in 1950 by members of the U.S. Geological Survey during reconnaissance investigations for uranium made on the behalf of the Atomic Energy Commission The size of this new district is incompletely known, but the deposits found to date are in an area 20 miles long and about 10 miles wide, the southwest boundary of which extends northwest from Querida and Rosita Custer County, into Fremont County. Most of the deposits, however, are in the southeastern half of this area The thorium minerals occur in barite-sulfide veins along northwest-trending shear zones that cut a pre-Cambrian complex or amphibolite, biotite-granite gneiss, metagabbro, migmatite, microcline granites, pegmatite and white granite, and syenite (?) o Along the shear zones are premineralization basic (lamprophyre (?)) dikes. Thorite has been tentatively identified as the principal radio- active mineral It is associated with barite: quartz, galena, fluorite, limonite, and pyrite Some of the shear zones perhaps can be traced for as much as 2 miles, but the largest known thorium-bearing ore body is as much as 300 feet long, 26 feet wide, and 400 feet deep. Samples from the veins contain as much as 1.6 percent equivalent Th0 2 Eleven diamond drill holes, totaling 3,292.4 feet have explored five shear zones on the Haputa Ranch. Three ore bodies of possible economic interest are indicated in two interconnecting shear zones. No other deposits in the wet Mountains have been explored, or even sampled adequately to hazard an estimate as to grade and tonnage of reserves.

Colorado↗

USGS1988

The Blake Plateau Basin and Carolina Trough

Presently, the continental margin of the southeastern United States (Fig. 1) forms a zone of transition between the actively building, steep-fronted carbonate platform of the Bahamas and the typical eastern North American terrigenous clastic-dominated, drowned, shelf-slope-rise configuration. This region of the continental margin is underlain by two major sedimentary basins—the Blake Plateau Basin and the Carolina Trough (Fig. 2)—which are different in shape, basement structure, and history. Indeed, the two southern basins show some of the greatest contrasts of any basins of eastern North America, especially in their early response to rifting and in the change from rifting to drifting. The region has experienced abrupt major changes in geological conditions, most notably the onset of Gulf Stream flow in the early Tertiary. Morphologically, the area is dominated by the broad, flat Blake Plateau at about 800-1,000 m water depth (Fig. 1). The plateau is bounded to the east by the extremely steep Blake Escarpment, descending to 5,000 m water depths. To the west, a short continental slope rises to a continental shelf. This Blake Plateau morphology characterizes the margin east of Florida and north of the Bahamas. North of Florida the margin merges into the typical shelf-slope-rise morphology. Just north of the Blake Escarpment and its northern projection, the Blake Spur, the Blake Ridge extends away from the continental slope at water depths exceeding 2,000 m (Fig. 1). This broad ridge is a Cenozoic, sedimentary drift deposit controlled by bottom currents. (For the reader who is beginning to wonder why half of the features of this region seem to be named "Blake", the Blake was a Coast Survey steamer from which investigations off the southeastern U.S. were carried out in 1877 to 1880. Ferromanganese nodules were discovered on the Blake Plateau at that time [Murray, 1885].)

Blake Plateau basin; Carolina Trough↗

USGS1972

Geologic map of the Aristoteles Quadrangle of the Moon

The Aristoteles quadrangle, located on the northeastern periphery of the Imbrium basin on the near side of the Moon, consist of four physiographic provinces : a northern mountainous belt, chiefly of lineated crater rims and other lineated terra; a middle-northern belt covered by mare material of Mare Frigoris ; and a southern belt composed of mountainous material of diverse characteristics. The crater Aristoteles and its ejecta blanket dominate the southwestern part of the quadrangle, and ejecta from the crater Hercules (outside the quadrangle) covers a small part of the southeastern corner. Other promin ent craters are Democritus, C. Mayer, Gartner, and Kane. Two probable centers of tectonism and volcanism are present in the southern mount ainous belt.

IMAP↗