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At least 1,243 records · Page 69Linked to original sources

USGS2019

Depth to bedrock based on modeling of gravity data of the eastern part of Edwards Air Force Base, California

We describe a gravity survey acquired to determine the thickness of basin-fill deposits (depth to bedrock) and to delineate geologic structures that might influence groundwater flow beneath the eastern part of Edwards Air Force Base, California. Inversion of these gravity data combined with geologic map and well information provides an estimate of the thickness of basin-fill deposits (defined here as Cenozoic sedimentary and volcanic rocks). After removing the gravitational effect of the basin-fill deposits, the inversion also results in a gravity map that reflects variations in the bedrock density. The depth to bedrock is generally less than 1 kilometer in the map area, except for localized depressions north and south of Kramer Hills, northwest-trending pockets about 4 kilometers northeast of Rogers Lake, and a large depression southwest of Rogers Lake. In the area near Leuhman Ridge, depth to bedrock is shallow. The Spring and Leuhman faults do not coincide with large variations in basin-fill thickness or with prominent gravity gradients, suggestive of minor vertical displacement and minor horizontal displacement at their southeastern mapped extents where they project across a large gravity low.

California↗

USGS1987

Geology and hydrology of the deep bedrock aquifers in eastern Colorado

Deep bedrock aquifers are present in rocks of Cretaceous through Pennsylvanian age in eastern Colorado. These aquifers are the Laramie-Fox Hills (the uppermost aquifer studied), Fort Hays-Codell, Dakota-Cheyenne, Entrada-Dockum, Lyons, and Fountain. Structural mapping indicates the aquifers are 2,000 to 9,000 ft below land surface in most of eastern Colorado but outcrop in local areas in a narrow band along the Front Range of the Rocky Mountains. Recharge primarily occurs in outcrops and produces a northerly or easterly groundwater flow to discharge areas along the South Platte or Arkansas Rivers. Deep aquifers also discharge by underflow to Kansas and Nebraska. Some water-yielding strata in the Dakota-Cheyenne aquifer are not in hydraulic connection with the aquifer, and abnormal fluid pressures, trapped hydrocarbons, and high dissolved-solids concentrations are found in these strata. Temperature and dissolved-solids mapping indicate water temperatures of 100 to 210 in northeastern Colorado and a zone of relatively fresh water extending through a 7,000 sq mi area of the Dakota-Cheyenne aquifer in southeastern Colorado. Water levels in the Laramie-Fox Hills aquifer continue to decline as much as 12 ft/yr in local areas near Denver.

Colorado↗

USGS2023

Hydrogeology, karst, and groundwater availability of Monroe County, West Virginia

Monroe County is in southeastern West Virginia, encompassing an area of 474 square miles. The area consists of karst and siliciclastic aquifers of Ordovician, Silurian, Devonian, and Mississippian age and is in parts of two physiographic provinces: the Valley and Ridge Province to the east of Peters Mountain, and the Appalachian Plateau Province to the west of Peters Mountain. This study was developed in response to inquiries from the Monroe County Commission requesting assessment of the water resources of the county to better understand the quantity of the county’s groundwater resources, for both current [2023] and future demand, and to provide information to support protection and management of the county’s valuable groundwater resources. Various products were developed for this study that provide knowledge with respect to water availability and contamination susceptibility of the karst aquifers within the county. U.S. Geological Survey (USGS) geologists conducted extensive geologic mapping in support of the project, producing (1) a countywide bedrock geologic map, (2) a countywide hydrogeologic map, and (3) a light detection and ranging (lidar)-derived countywide digital elevation model and associated sinkhole map. A significant part of this work was to map in detail the Greenbrier Group at the formation level, which prior to this study had only partially been completed. The report also includes (4) a description of the lithologic units identified as part of the geologic mapping process. U.S. Geological Survey hydrologists completed several additional products for the hydrology part of the effort, including development of (1) a countywide potentiometric surface (water-table) map, (2) a countywide base-flow stream assessment, (3) countywide water-budget estimates, (4) well log surveys for 15 wells to better understand subsurface controls on groundwater flow within the study area, (5) two groundwater tracer tests to better refine the groundwater divide from the northern and southern parts of the karst aquifer in Monroe County; and finally, based on all available data collected for the study including the potentiometric surface map, geologic map, current [2023] and legacy fluorometric groundwater tracer tests, and base-flow stream assessments, (6) groundwater-basin delineations were reassessed for principal groundwater basins within the Greenbrier aquifer. In Monroe County, four principal hydrogeologic settings produce large yields of water for residential, agricultural, and other uses. The most relied upon water-bearing zone with respect to current [2023] public water supply is from springs along Peters Mountain. These springs are derived from intervals of fractured sandstone and resultant alluvial deposits. Groundwater flows downslope through these permeable alluvial deposits and discharges at the contact with less permeable strata, such as the Reedsville Shale. The second most relied upon water-bearing zone in Monroe County is within the karstic Greenbrier Group aquifer, in which the basal Hillsdale Limestone overlies the less permeable Maccrady Shale. This geologic contact between the Hillsdale Limestone and Maccrady Shale is not only targeted as a source of water for agricultural supply but also is targeted as a source of water for residential supply. The third most relied upon water-bearing zone is composed of shallow perched aquifers within the Greenbrier Group. The discontinuous nature of these perched aquifers makes mapping their extent impossible, but they are related to permeable geologic strata, such as karstified limestones with solutionally enhanced permeability that overlies less permeable shale or chert bedrock. During geologic mapping of the county, several of these perched aquifers were documented in the Pickaway, Union, and Alderson Limestones. A fourth zone consists of springs from Ordovician carbonates at the base of Peters Mountain, which are influenced by sinking streams as well as upwelling along faults. In terms of water quantity, the most sustainable springs are those having deeper-sourced flows. Public supplies are a principal source of water used for residential and commercial supply in the region, accounting for 0.49 million gallons per day (Mgal/d) of fresh-water withdrawals (0.14 Mgal/d of groundwater and 0.35 Mgal/d of surface water) for residential and commercial use and serving 6,645 individuals (49.2 percent of the population). An estimated 6,861 people, (50.8 percent of the population) primarily rely on private wells or other unregulated sources, such as springs, and withdraw 0.55 Mgal/d of groundwater for their residential use. Public water supply in the region is primarily (71.4 percent) derived from springs and augmented by stream withdrawals (backup sources mainly during low-flow periods), with the remaining portion (28.6 percent) derived from groundwater withdrawals from wells. For rural residents, however, 100 percent of their withdrawals are derived from groundwater (wells or springs).

West Virginia↗

USGS1975

Hydrologic evaluation of the Haystack Butte area : with emphasis on possible discharge of class-I wastes, Edwards Air Force Base, California

The discharge of 3 acre-feet (4 x 10 -3 cubic hectometres) per year of Class-I wastes in the Haystack Butte area of Edwards Air Force Base, Calif., has been proposed by the Air Force. Evaporation in this arid basin exceeds the 4 inches (100 millimetres) of annual precipitation. Fifteen test holes, ranging in depth from 40 to 240 feet (12 to 73 metres) below land surface, indicate that ground water occurs mostly in Tertiary volcanic and sedimentary rocks overlying pre-Tertiary quartz monzonite. Depth to water averages about 100 feet (30 metres) below land surface. Hydraulic conductivity of cores of Tertiary rock taken from a test hole at depths of 9 to 88 feet (2.7 to 27 metres) below land surface suggests values of 6.9 x 10-5 to 4.9 x 10 -3 feet per day (2.1 x 10 -5 to 1.5 x 10 -3 metres per day). Petrographic analyses of these cores indicate a material consisting mostly of weathered volcanic rocks with a moderate concentration of montmorillonite clay. The water-level gradient averages about 4 feet per mile (0.76 metre per kilometre). Ground-water discharge through a narrow gap in the southeastern part of the basin is calculated to be 3.8 x 10 -4 acre-feet (4.7 x 10 -7 cubic hectometres) per year. After leaving the basin, the underflow becomes part of a regional flow system discharging into Harper Lake playa. An increase in the underflow from 3.8 x 10 -4 acre-feet (4.7 x 10 -7 cubic hectometres) per year to 3 acre-feet (4 x 10 -3 cubic hectometres) per year may result in an undesirable surface-water flow by increasing the saturated thickness of the aquifer near the narrow gap in the southeastern part of the basin. Also, the very low hydraulic-conductivity values suggest that some difficulties may exist in percolating 3 acre-feet (4 x 10 -3 cubic hectometres) per year of wastes resulting in possible saturation of the ground surface outside the boundaries of the potential Class-I site. Because the rate of evaporation is very high (116 inches or 294.6 millimetres per year) in the study area, many of the problems associated with the percolation of the waste water and the subsequent changes in ground-water movement could be minimized by evaporating the wastes to complete dryness. The quality of the ground water in the basin is generally unsuitable for domestic, industrial, and irrigation purposes. The concentration and type of chemical constituents in the ground water suggest slow circulation in a geologic environment with soluble minerals.

California↗

USGS1983

Preliminary appraisal of the hydrology of the Rock Island area, Le Flore County, Oklahoma

Bed rock in the Rock Island area of northeastern Le Flore County in southeastern Oklahoma consists of shale, siltstone, and sandstone of the McAlester, Hartshorne, and Atoka Formations of Pennsylvanian age. The area is on the south flank of the Backbone anticline; the rocks dip to the south at 5o-45o. Alluvium along James Fork consists of sandy and clayey silt and may be as much as 30 feet thick. Water in bedrock is under artesian conditions. The depth to water in most wells is less than 20 feet below the surface; a few wells flow. Yields of most wells probably are less than 5 gallons per minute. Water from nine wells was a sodium carbonate or sodium mixed anion type; dissolved-solids concentrations ranged from 294 to 1,250 milligrams per liter. No relationship between variations in chemistry of ground water and well depth, geographic distribution, or geologic formation is apparent. James Fork has flow most of the time and discharge exceeds 25 cubic feet per second about one-half the time. The mean dissolved-solids concentration in James Fork water ranged from 224 milligrams per liter near Williams, Oklahoma, to 332 milligrams per liter near Hackett, Arkansas. Water in James Fork is a calcium magnesium sulfate type about 75 percent of the time. Maximum suspended sediment discharge was 2,720 tons per day. Silt-clay particles (diameters less than 0.062 millimeter) are the dominant sediment size. Potential hydrologic effects of surface mining for coal include: (1) Creation of additional water storage in surface-mine ponds, (2) changes in rock permeability and ground-water storage, (3) changes in runoff and streamflow characteristics, (4) changes in drainage patterns, and (5) changes in the chemical quality and sediment load of James Fork. Although mining may increase the quantities of sediment and dissolved minerals added to James Fork, detection of these increases would be difficult because the potentially mineable area is very small in proportion to the total area of the basin.

Water-Resources Investigations Report↗

USGS2012

Digital geologic map of the Redding 1° x 2° quadrangle, Shasta, Tehama, Humboldt, and Trinity Counties, California

The Redding 1° x 2° quadrangle in northwestern California transects the Franciscan Complex and southern Klamath Mountains province as well as parts of the Great Valley Complex, northern Great Valley, and southernmost Cascades volcanic province. The tectonostratigraphic terranes of the Klamath province represent slices of oceanic crust, island arcs, and overlying sediment that range largely from Paleozoic to Jurassic in age. The Eastern Klamath terrane forms the nucleus to which the other terranes were added westward, primarily during Jurassic time, and that package was probably accreted to North America during earliest Cretaceous time. The younger Franciscan Complex consists of a sequence of westward younging tectonostratigraphic terranes of late Jurassic to Miocene age that were accreted to North America from mid-Cretaceous through Miocene time, with the easternmost being the most strongly metamorphosed. The marine Great Valley sequence, of late Jurassic and Cretaceous age, was deposited unconformably across the southernmost Klamath rocks, but in turn was underthrust at its western margin by Eastern belt Franciscan rocks. Pliocene and Quaternary volcanic rocks and sediment of the Cascades province extend into the southeastern part of the quadrangle, abutting the northernmost part of the great central valley of California. This map and database represent a digital rendition of Open-File Report 87-257, 1987, by L.A. Fraticelli, J.P. Albers, W.P. Irwin, and M.C. Blake, Jr., with various improvements and additions.

California↗

USGS1979

Effects of karst and geologic structure on the circulation of water and permeability in carbonate aquifers

The results of the natural processes caused by solution and leaching of limestone, dolomite, gypsum, salt and other soluble rocks, is known as karst. Development of karst is commonly known as karstification, which may have a pronounced effect on the topography, hydrology and environment, especially where such karst features as sinkholes and vertical solution shafts extend below the land surface and intersect lateral solution passages, cavities, caverns and other karst features in carbonate rocks. Karst features may be divided into two groups: (1) surficial features that do not extend far below the surface; and (2) karst features such as sinkholes that extend below the surface and affect the circulation of water below. The permeability of the most productive carbonate aquifers is due chiefly to enlargement of fractures and other openings by circulation of water. Important controlling factors responsible for the development of karst and permeability in carbonate aquifers include: (1) climate, topography, and presence of soluble rocks; (2) geologic structure; (3) nature of underground circulation; and (4) base level. Another important factor is the condition of the surface of the carbonate rocks at the time they are exposed to meteoric water. A carbonate rock surface, with soil or relatively permeable, less soluble cover, is more favorable for initiation of karstification and solution than bare rocks. Water percolates downward through the cover to the underlying carbonate rocks instead of running off on the surface. Also, the water becomes more corrosive as it percolates through the permeable cover to the underlying carbonate rocks. Where there is no cover or the cover has been removed, the carbonate rocks become case hardened and resistant to erosion. However, in regions underlain not only by carbonate rocks but also by beds of anhydrite, gypsum and salt, such as the Hueco Plateau in southeastern New Mexico, subsurface solution may occur where water without natural acids moves down from bare rock surfaces through cracks to the beds that are more soluble than carbonate rocks. For example, in the area of Carlsbad Caverns in southeastern New Mexico, much of the water responsible for solution that formed the caverns apparently entered the groundwater system through large open fractures and did not form sinkhole topography. East of the Carlsbad Caverns, however, in the Pecos River Valley where the carbonate rocks are overlain by the less soluble Ogallala Formation of Late Tertiary age, solution began along escarpments as the Pecos River and its tributaries cut through the less soluble cover. As these escarpments retreated, sinkholes and other karst features developed. Joints or fractures are essential for initiation of downward percolation of water in compact carbonate rocks such as some Paleozoic limestone in which there is no intergranular permeability. Also joints or fractures and bedding planes may be essential in the initiation of lateral movement of water in the zone of saturation. Where conditions of recharge and discharge are favorable, groundwater may move parallel to the dip. However, the direction of movement of water in most carbonate rocks is not necessarily down dip or parallel to the dip. The general direction of movement of both surface and groundwater may be parallel to the strike in a breached anticline. Faults may restrict the lateral movement of water, especially if water-bearing beds are faulted against relatively impervious beds. Conversely, some fault may serve as avenues through which water may move as, for example, in the Cretaceous Edwards aquifer in the San Antonio area, Texas. Karst aquifers, chiefly carbonate rocks, may be placed in three groups according to water-bearing capacity. Water in aquifers of group 1 occurs chiefly in joints, fractures, and other openings that have not been enlarged by solution. The yield of wells is small. Aquifers in group 2 , with low to intermediate yields, are those in which water occurs in joints and fractures with some cavities and channels enlarged by solution. Aquifers in group 3 are those in which the yield of wells and springs range from intermediate to very large. This group includes five of the most productive aquifers in the U.S.A. The water-bearing beds of all of these productive aquifers, except the Biscayne aquifer in southeastern Florida, contain buried paleokarst in which the permeability has been reactivated and enlarged by the present circulation system.

Journal of Hydrology↗

USGS2016

Status and trends of land change in selected U.S. ecoregions - 2000 to 2011

U.S. Geological Survey scientists developed a dataset of 2006 and 2011 land-use and land-cover ( LULC ) information for selected 100-km 2 sample blocks within 29 U.S. Environmental Protection Agency ( EPA ) Level III ecoregions across the conterminous United States. The data can be used with the previously published Land Cover Trends Dataset: 1973 to 2000 to assess landuse/land-cover change across a 37-year study period. Results from analysis of these data include ecoregion-based statistical estimates of the amount of LULC change per time period, ranking of the most common types of conversions, rates of change, and percent composition. Overall estimated amount of change per ecoregion from 2001 to 2011 ranged from a low of 370 km 2 in the Northern Basin and Range Ecoregion to a high of 78,782 km 2 in the Southeastern Plains Ecoregion. The Southeastern Plains continues to encompass one of the most intense forest harvesting and regrowth regions in the country, with 16.6 percent of the ecoregion changing between 2001 and 2011. These LULC change statistics provide a new, valuable resource that complements other reference data and field-verified LULC data. Researchers can use this resource to independently validate other land change products or to conduct regional land change assessments.

Photogrammetric Engineering and Remote Sensing↗

USGS2013

National assessment of shoreline change: historical shoreline change along the Pacific Northwest coast

Beach erosion is a chronic problem along most open ocean shores of the United States. As coastal populations continue to increase and infrastructure is threatened by erosion, there is increased demand for accurate information regarding past and present trends and rates of shoreline movement. There is also a need for a comprehensive analysis of shoreline movement that is consistent from one coastal region to another. To meet these national needs, the U.S. Geological Survey (USGS) is conducting an analysis of historical shoreline changes along the open-ocean sandy shores of the conterminous United States and parts of Hawaii, Alaska, and the Great Lakes. One purpose of this work is to develop standard, repeatable methods for mapping and analyzing shoreline movement so that periodic, systematic, and internally consistent updates regarding coastal erosion and land loss can be made nationally. In the case of the analysis of shoreline change in the Pacific Northwest (PNW), the shoreline is the interpreted boundary between the ocean water surface and the sandy beach. This report on the PNW coasts of Oregon and Washington is the seventh in a series of regionally focused reports on historical shoreline change. Previous investigations include analyses and descriptive reports of the U.S. Gulf of Mexico (Morton and others, 2004), the southeastern Atlantic (Morton and Miller, 2005), the sandy shorelines (Hapke and others, 2006) and coastal cliffs (Hapke and Reid, 2007) of California, the New England and mid-Atlantic coasts (Hapke and others, 2011), and parts of the Hawaii coast (Fletcher and others, 2012). Like the earlier reports in this series, this report summarizes the methods of analysis, interprets the results of the analysis, provides explanations regarding long- and short-term trends and rates of shoreline change, and describes how different coastal communities are responding to coastal erosion. This report differs from the early USGS reports in the series in that those shoreline change analyses incorporated only four total shorelines to represent specific time periods. This assessment of the PNW incorporates all available shorelines that meet minimum quality standards for resolution and positional accuracy. Shoreline change evaluations are based on a comparison of historical shoreline positions digitized from maps or aerial photographic data sources with recent shorelines, at least one of which is derived from lidar surveys. The historical shorelines cover a variety of time periods ranging from the 1800s through the 1980s, whereas the lidar shoreline is from 2002. Long-term rates of change are calculated using all available shoreline data and short-term rates of change are calculated using the lidar shoreline and the historical shoreline that will produce an assessment for a 15- to 35-year period. The rates of change presented in this report represent conditions up to the date of only the most recent shoreline data and therefore are not intended for predicting future shoreline positions or rates of change. The PNW coast was subdivided into eight analysis regions for the purpose of graphically reporting regional trends in shoreline change rates. The average rate of long-term shoreline change for the entire PNW coast was 0.9 meter per year (m/yr) of progradation with an uncertainty of 0.07 m/yr. This rate is based on 8,823 individual transects, of which 36 percent was determined to be eroding. Long-term shoreline change was generally more progradational in Washington than in Oregon. This is primarily due to the influence of the Columbia River and human perturbations to the natural system, particularly the construction of jetties at both the mouth of the Columbia River and at Grays Harbor, Washington. The majority of the beaches in southwestern Washington have responded to these large-scale engineered structures by experiencing dramatic beach progradation during the past century. Although these beaches are still responding to the human effects, in several locations beaches that had been rapidly prograding are now either prograding at a slower rate or eroding. The average rate of short-term shoreline change in the PNW was also progradational at a rate of 0.9 m/yr with an uncertainty of 0.03 m/yr. This rate is based on 9,087 individual transects, of which 44 percent was determined to be eroding. Similar to the results of the long-term shoreline change analysis, the shorelines in Washington were typically more progradational than those in Oregon in the short term. However, many stretches of coast in Oregon are either less accretional, changed from accretional to erosional, or more erosional when comparing the long- and short-term rate calculations. In the long and short term, there are significantly different historical shoreline change trends for beaches deriving their modern sediments from the Columbia River in southwestern Washington and northwestern Oregon, and beaches elsewhere in the PNW. The majority of shorelines in Oregon and in Washington’s Olympic Peninsula are not influenced by the human effects to the Columbia River littoral cell and typically have not experienced the human-induced century-scale trends apparent in southwestern Washington and northwestern Oregon. An increase in erosion hazards in much of Oregon may be related to the effects of sea-level rise and increasing storm wave heights. Of importance, particularly in the short term, is the alongshore variability in land uplift rates due to tectonics, which results in an alongshore varying rate of relative sea level rise that appears to at least partially control the regional variability in short-term shoreline change rates. Other climate related processes, such as the occurrence of major El Niño events, also significantly affect the shoreline changes in the region. Major El Niño events elevate monthly mean sea levels by tens of centimeters throughout the winter and produce a shift in the storm tracks, resulting in alongshore redistributions in sand volumes on the beaches, leading to hotspot beach erosion and property losses north of headlands and tidal inlets to bays and estuaries. There are limited modern-day sources of sand to Oregon’s beaches, with much of the sand being relict in having arrived thousands of years ago at a time of lowered sea levels when headlands did not prevent the alongshore movement of the beach sediments, the result being that many beaches today are deficient in sand volumes and therefore do not provide sufficient buffer protection to backshore properties during winter storms.

Oregon;Washington↗

USGS1990

Geohydrology and water quality of Kalamazoo County, Michigan, 1986-88

Thick, glacial sand and gravel deposits provide most ground-water supplies in Kalamazoo County. These deposits range in thickness from 50 to about 600 feet in areas that overlie buried bedrock valleys. Most domestic wells completed at depths of less than 75 feet in the sands and gravels yield adequate water supplies. Most industry, public supply, and irrigation wells completed at depths of 100 to 200 feet yield 1,000 gallons per minute or more. The outwash plains include the most productive of the glacial aquifers in the county. The Coldwater Shale of Mississippian age, which underlies the glacial deposits in most of the county, usually yields only small amounts of largely mineralized water. Ground-water levels in Kalamazoo County reflect short- and long-term changes in precipitation and local pumpage. Ground-water levels increase in the spring and decline in the fall. Ground-water recharge rates, for different geologic settings, were estimated from ground-water runoff to the streams. Recharge rates ranged from 10.86 to 5.87 inches per year. A countywide-average ground-water recharge rate is estimated to be 9.32 inches per year. Chemical quality of precipitation and dry fallout at two locations in Kalamazoo County were similar to that of other areas in the State. Total deposition of dissolved sulfate is 30.7 pounds per acre per year, of total nitrogen is 13.2 pounds per acre per year, and of total phosphorus is 0.3 pounds per acre per year. Rainfall and snow data indicated that the pH of precipitation is inversely proportional to its specific conductance. Water of streams and rivers of Kalamazoo County is predominately of the calcium bicarbonate type, although dissolved sulfate concentrations are slightly larger in streams in the southeastern and northwestern parts of the county. The water in most streams is hard to very hard. Concentrations of dissolved chloride in streams draining urban-industrial areas are slightly larger than at other locations. Concentrations of total nitrogen and total phosphorus in streams are directly proportional to streamflow. Except for elevated concentrations of iron, none of the trace elements in streams exceeded maximum contaminant levels for drinking water established by the U.S. Environmental Protection Agency. Pesticides were detected in some streams. Ground water in the surficial aquifers is of the calcium bicarbonate type, although sodium, sulfate, and chloride ions predominate at some locations. Specific conductance and hardness and concentrations of total dissolved-solids slightly exceed statewide averages. Concentrations of dissolved sodium and dissolved chloride in 6 wells were greater than most natural ground waters in the State, indicating possible contamination from road salts. Water samples from 6 of the 46 wells sampled contained concentrations of total nitrate as nitrogen greater than 10.0 milligrams per liter. Elevated concentrations of total nitrate as nitrogen in water from wells in rural-agricultural areas probably are related to fertilizer applications. Results of partial chemical analyses by the Michigan Department of Public Health indicates specific conductance, and concentrations of hardness, dissolved fluoride, and total iron are fairly uniform throughout the county. Concentrations of dissolved sodium, dissolved chloride, and total nitrate as nitrogen differed among townships. Pesticides were detected in water from only one well. Water from five wells contained volatile organics. A map of susceptibility of ground water to contamination in Kalamazoo County was developed using a system created by the U.S. Environmental Protection Agency. Seven geohydrologic factors that affect and control ground-water movement are mapped and composited onto a countywide map. All seven factors have some effect on countywide susceptibility, but the most important factors are depth to water and composition of the materials above the aquifer.

Michigan↗

USGS1985

Geochemical map of the Guadalupe Escarpment Wilderness Study Area, Eddy County, New Mexico

During 1982, the U.S. Geological Survey and the U.S. Bureau of Mines conducted field investigations to evaluate the mineral resource potential of the Guadalupe Escarpment Wilderness Study Area. Field studies included geologic mapping, geochemical sampling, and a survey of known mines, prospects, and mineralized zones. This map presents the results of a geochemical survey of the area by the Geological Survey and complements the mineral resource assessment of the area by Hayes and others (1983). The Guadalupe Escarpment Wilderness Study Area encompasses approximately 21,300 acres along Guadalupe Ridge in the southern end of the Guadalupe Mountains about 35 miles southwest of Carlsbad, N. Mex. (fig. 1). The area trends northeasterly, is bounded on the south by the Texas State line and the northern boundary of Guadalupe Mountains National Park. The study area is bounded on the northeast by Carlsbad Caverns National Park. The area comprises several narrow, gently sloping mesas bounded by deeply incised canyons. Elevations range from 7,413 feet on Camp Wilderness Ridge to approximately 4,875 feet at Franks Spring. A rough jeep road along the northwest boundary of the study area can be reached by U.S. Forest Service roads from the northwest. The southeastern part of the study area can be approached via unimproved ranch roads leading off U.S. Highway 62-180.

New Mexico↗

USGS1985

Mesozoic ash-flow caldera fragments in southeastern Arizona and their relation to porphyry copper deposits

Jurassic and Upper Cretaceous volcanic and associated granitic rocks in southeast Arizona are remnants of large composite silicic volcanic fields, characterized by voluminous ash-flow tuffs and associated calderas. Presence of 10–15 large caldera fragments is inferred primarily from (1) ash-flow deposits more than 1 km thick, having features of intracaldera ponding; (2) “exotic-block” breccias within a tuff matrix, interpreted as caldera-collapse megabreccias; and (3) local granitic intrusions along arcuate structural boundaries of the thick volcanic sequences. Several porphyry copper deposits are associated with late granitic intrusions within the calderas or along their margins.

Geology↗

USGS2015

Geochemical, modal, and geochronologic data for 1.4 Ga A-type granitoid intrusions of the conterminous United States

Introduction The purpose of this report is to present available geochemical, modal, and geochronologic data for approximately 1.4 billion year (Ga) A-type granitoid intrusions of the United States and to make those data available to ongoing petrogenetic investigations of these rocks. A-type granites, as originally defined by Loiselle and Wones (1979), are iron-enriched granitoids (synonymous with the ferroan granitoids of Frost and Frost, 2011) that occur in an anorogenic, within-continent setting. Relative to other granitic rocks, A-type granites have high FeO*/(FeO*+MgO), high K 2 O and K 2 O/Na 2 O, are metaluminous to weakly peraluminous, and are enriched in incompatible trace elements. Loiselle and Wones (1979) further suggested that A-type granites are relatively anhydrous. Anderson (1983) provides an early compilation of data for the products of 1.4 Ga magmatism in North America and notes the spatial and temporal association of a trio of rock types, which includes gabbro to anorthosite, intermediate composition mangerite, and granitic rapakivi rocks. In North America, the majority of known A-type intrusions were emplaced between 1.5 and 1.3 Ga and are predominantly of the granitic variety (Anderson, 1983). This report addresses the broadly Mesoproterozoic-age granitic rocks of the conterminous United States. Constituents of this group of intrusive rocks were defined using a variety of spatial, compositional, and geochronologic metrics. Thomas and others (2012) provided an updated synthesis, largely based on new isotopic and geochronologic data (for example, Fisher and others, 2010), for the large-scale geologic and tectonic evolution of the eastern United States. Their findings suggest that the basement rocks of the central and southern Appalachian region are allochthonous relative to the remainder of Laurentia and were accreted along the Grenville front between 1.25 and 1.0 Ga. Accordingly, Mesoproterozoic rocks east of the Grenville front and south of the approximate latitude of New York City do not represent North American magmatism. Consequently, geochemical, modal, and geochronologic data for these rocks are not included in the compilation described herein. Further, the structural styles and compositions of granitoid rocks east of the Grenville front, mostly highly deformed gneissic rocks, are dissimilar to those characteristic of the A-type granitoid rocks described herein. A variety of compositional and age information further characterizes the 1.4 Ga A-type granitoid rocks in the conterminous United States. Most samples included in this compilation have felsic compositions, although some extend to intermediate compositions. SiO2 contents range from 56 to almost 78 weight percent, and median and mean SiO2 contents are 72.0 and 71.1 weight percent, respectively. The majority of these rocks for which modal data are available are composed of monzogranite (Streckeisen, 1976), although the dataset also contains many samples composed of granodiorite and syenogranite. A smaller group of the granitoid rocks in this dataset are composed of quartz monzodiorite and quartz monzonite, and a very small subset of samples is composed of alkali-feldspar granite, tonalite, alkali-feldspar quartz syenite, and quartz syenite (fig. 1). Many of the 1.4 Ga granitoid rocks are further characterized by medium- to coarse-grain size and are also conspicuously porphyritic; alkali feldspar phenocrysts or megacrysts (2–10 cm), often with rapakivi overgrowths, are a common feature of many of these rocks (Anderson, 1983; Anderson and Bender, 1989; Anderson and Cullers, 1978; Condie and Budding, 1979). The age of A-type magmatism in North America ranges from about 1.8 to 1.0 Ga, although Anderson (1983) suggests that more than 70 percent (by volume) of A-type magmatism in this region occurred between 1.49 and 1.41 Ga. In the conterminous United States, ages of A-type granitoid rocks are restricted to the period between about 1.49 and 1.33 Ga (Anderson, 1983; Bauer and Pollock, 1993; Bickford and Mose, 1975; Bickford, Harrower, and others, 1981; Bickford and others, 1989; Dewane and Van Schmus, 2007; Hoppe and others, 1983; Peterman and Hedge, 1968; Van Schmus and Bickford, 1981; Van Schmus and others, 1975). Using these recognition criteria, we identified A-type granitoid intrusions of the conterminous United States; for those intrusions, we compiled available geochemical, modal, isotopic (Sr and Nd) and geochronologic data for inclusion in the databases described herein. The significance of 1.4 Ga granitoid rocks relative to the geologic evolution of the conterminous United States remains unclear, despite Anderson’s (1983) compilation and synthesis of compositional data pertinent to these rocks. The large-volume magmatic events indicated by these rocks, as well as their broad geographic distribution, tectonic significance, and association with mineral deposits, underscore their importance. The broad distribution of these rocks, from the northern mid-continent to the southwestern United States (in New Mexico, Arizona, California, and southernmost Nevada), throughout the Rocky Mountains in New Mexico and Colorado (and sporadically in southern Wyoming and central Idaho), and beneath much of the Plains region (as indicated by drilling), has led to the large-scale tectonic and magmatic processes responsible for genesis of the associated magmas being actively studied. In addition, Kisvarsanyi (1972) suggests that iron-copper deposits in the St. Francois Mountains of southeastern Missouri are petrogenetically associated with 1.4 Ga A-type granitoids that occur in that region. Similarly, Dall’Agnol and others (2012) summarize important global associations between A-type granitoid rocks and a variety of important ore deposit types, particularly tin, high-field-strength elements (Zr, Hf, Nb, Ta), rare-earth elements, and iron oxide-copper-gold deposits. Consequently, the need to better understand relations between A-type granitoid rocks, tectonic setting, and magma petrogenesis, as well as their genetic associations with important types of ore deposits, suggests that developing a definitive geochemical, modal, and geochronologic database for these rocks in the conterminous United States is of considerable value.

Data Series↗

USGS1993

Delineation of recharge areas for selected wells in the St. Peter-Prairie du Chien-Jordan aquifer, Rochester, Minnesota

Accurate delineation of recharge areas for wells is an important requisite to protecting ground-water quality. Zones of transport and zones of contribution are two types of recharge areas that can be delineated. Analytical-calculation, numerical-modeling, and hydrogeologic-mapping methods were used to delineate recharge areas for two high-capacity wells (greater than about 200 gallons per minute discharge) completed in a karstic aquifer in the city of Rochester, in southeastern Minnesota. One well is less than 1,000 feet from a river in an area where the aquifer is unconfined, whereas the other well is more than 2,000 feet from a stream in an area where a bedrock confining unit is present. Ground-water travel times from points along the top of the aquifer to a pumped well are identified by use of a constructed map showing lines of equal advective travel time. A zone of transport, therefore, is defined by the area bounded by lines of equal travel time. Zones of transport are delineated by analytical models (calculations) and by numerical models that account for hydrologic factors. Analytical models that were used include fixed-radius (Theis drawdown, Theis time-of-travel, and volumetric equation) and variable shape. Numerical modeling was done with the U.S. Geological Survey three-dimensional ground-water-flow model MODFLOW and particle-tracking code MODPATH. The zone-of-transport areas for each of the two wells calculated by the various analytical models were very similar. The Theis-drawdown method yielded results that compared least favorably with results from the other analytical methods. The zone-of-transport areas computed by use of the numerical model were generally larger than areas computed by use of analytical models. Hydrogeologic mapping and numerical modeling were used to delineate zones of contribution to wells, defined as all parts of a ground-water-flow system that could supply water to a well. The zones of contribution delineated by use of numerical modeling have similar orientation (parallel to regional flow directions) but significantly different areas than the zones of contribution delineated by use of hydrogeologic mapping. Differences in computed areas of recharge are attributed to the capability of the numerical model to more accurately represent (1) the three-dimensional flow system, (2) hydrologic boundaries such as streams, (3) variable recharge, and (4) the influence of nearby pumped wells, compared to the analytical models.

Minnesota↗

USGS2020

Hydrogeologic characterization, groundwater chemistry, and vulnerability assessment, Ute Mountain Ute Reservation, Colorado and Utah

The U.S. Geological Survey, in cooperation with the Ute Mountain Ute Tribe (UMUT), initiated a study in 2016 to increase understanding of the hydrogeology and chemistry of groundwater within select areas of the Ute Mountain Ute Reservation (UMUR) in Colorado and Utah, identify vulnerabilities to the system and other natural resources, and outline information needs to aid in the understanding and protection of groundwater resources. The results presented for this study can be used to support the UMUT’s goal of protecting their vital groundwater resources on the UMUR. Hydrogeologic conditions were characterized for the surficial aquifer contained in Quaternary-age unconsolidated surficial deposits and the Dakota aquifer contained in the Cretaceous-age Dakota Sandstone. In the surficial aquifer, median depth to water ranges from about 5.4 to 17.2 feet below land surface in the Farm and Ranch Enterprise area and 11 to 34 feet below land surface in the Towaoc area, and the water table slopes generally southwest or south. A map of depth to the top of the Dakota Sandstone was constructed from existing well data. Depths range from zero in outcrop areas to more than 3,000 feet below land surface on mesas in the southeastern part of the UMUR. Groundwater-chemistry data were collected by the UMUT from 13 springs and 31 wells from 1996 through 2017. Specific conductance was much lower for samples from springs than from wells; median values were 512 and 6,024 microsiemens per centimeter at 25 degrees Celsius, respectively. Spring samples were well oxygenated. A few well samples were anoxic (dissolved oxygen concentrations less than 0.5 milligrams per liter [mg/L]), indicating reducing conditions in the aquifer. About 75 percent of spring samples had fresh water (total dissolved solids concentrations less than 1,000 mg/L), and about 85 percent of well samples had brackish or highly saline water (total dissolved solids concentrations greater than 1,000 mg/L). Water type for springs on the Ute Mountains was calcium bicarbonate. Lower-altitude springs had a calcium-sulfate water type. Most well samples had sodium as the dominant cation, and sulfate, bicarbonate, and chloride as the dominant anions. Fluoride concentrations in about 45 percent of well samples were greater than an agricultural-use standard of 2 mg/L. Nitrate plus nitrite concentrations in most spring and well samples were less than about 1.6 mg/L per liter. Concentrations in samples from wells in the irrigated agricultural area were elevated; the maximum concentration was 78.5 mg/L. About one-half of the trace-element samples had concentrations that were less than laboratory reporting limits. Only aluminum, arsenic, and selenium in spring samples, and boron and selenium in well samples, were detected at concentrations greater than surface-water standards or water-quality standards for agricultural use of groundwater. Only three organic compounds, the pesticides alachlor and atrazine and the volatile organic compound di(2-ethylhexyl) phthalate, were detected in well samples. The Escherichia coli bacteria was detected in 47 and 23 percent of samples from wells and springs, respectively. The E. coli detections included samples from three culturally significant springs, which did not meet the UMUT cultural-use standard of total absence of E. coli. Tritium and carbon-14 were the primary environmental tracers used for interpreting groundwater ages for Lopez 2 Spring and five wells (AP–1, 5000 Block, Cottonwood Spring, Goodknight, and SE Toe). Water from the AP–1 well contained a mixture of pre- and post-1950s recharge. Tritium and carbon-14 recharge ages for Lopez 2 Spring (post-1950s in age), Goodknight and SE Toe wells (pre-1950s in age), and Cottonwood Spring well (primarily pre-1950s in age) are supported by helium-4 data. The helium-4 data for the 5000 Block well are inconsistent with the tritium and carbon-14 age of pre-1950s recharge because of interference caused by high methane concentrations in the water. Springs and surficial deposits are more vulnerable to contamination from anthropogenic chemicals than deeper bedrock wells. Bedrock aquifers are vulnerable in areas where the geologic formations containing the aquifers are exposed at the land surface. Groundwater in deep bedrock aquifers is likely thousands of years old and is not currently affected by present-day land uses. Both shallow and deep groundwater are vulnerable to naturally occurring salts and minerals, such as of total dissolved solids, major ions, nitrate, and trace elements. Effects of a changing climate on water resources and other ecological characteristics of the UMUR could include changes in evapotranspiration, a decrease in snowpack, decreased aquifer recharge and flow of springs, a decrease in soil moisture, and increased occurrence of wildfires and forest mortality. Of particular interest for the UMUT are possible effects of a changing climate on medicinal and culturally important plants and springs Several information needs were identified during this study that would aid in the understanding and protection of groundwater resources on the UMUR. These include well-completion information for bedrock wells, the collection of environmental tracer data at additional wells, the addition of methane and hydrocarbon analysis to well sampling plans, and the resampling of springs and wells that were last sampled in 2002 or earlier.

Colorado↗

USGS2011

20 cool facts about the New Madrid Seismic Zone-Commemorating the bicentennial of the New Madrid earthquake sequence, December 1811-February 1812 [poster]

This poster summarizes a few of the more significant facts about the series of large earthquakes that struck the New Madrid seismic zone of southeastern Missouri, northeastern Arkansas, and adjacent parts of Tennessee and Kentucky from December 1811 to February 1812. Three earthquakes in this sequence had a magnitude (M) of 7.0 or greater. The first earthquake occurred on December 16, 1811, at 2:15 a.m.; the second on January 23, 1812, at 9 a.m.; and the third on February 7, 1812, at 3:45 a.m. These three earthquakes were among the largest to strike North America since European settlement. The mainshocks were followed by many hundreds of aftershocks that occurred over the next decade. Many of the aftershocks were major earthquakes themselves. The area that was strongly shaken by the three main shocks was 2-3 times as large as the strongly shaken area of the 1964 M9.2 Alaskan earthquake and 10 times as large as that of the 1906 M7.8 San Francisco earthquake. Geologic studies show that the 1811-1812 sequence was not an isolated event in the New Madrid region. The 1811-1812 New Madrid earthquake sequence was preceded by at least two other similar sequences in about A.D. 1450 and A.D. 900. Research also indicates that other large earthquakes have occurred in the region surrounding the main New Madrid seismicity trends in the past 5,000 years or so.

General Information Product↗

USGS2015

Effects of groundwater pumping on agricultural drains in the Tule Lake subbasin, Oregon and California

Since 2001, irrigators in the upper Klamath Basin have increasingly turned to groundwater to compensate for reductions in surface-water allocation caused by shifts from irrigation use to instream flows for Endangered Species Act listed fishes. The largest increase in groundwater pumping has been in and around the Bureau of Reclamation’s Klamath Irrigation Project, which includes the Tule Lake subbasin in the southern part of the upper Klamath Basin. Agricultural drains on the Klamath Project are an important source of water for downstream irrigators and for the Tule Lake and Lower Klamath Lake National Wildlife Refuges. U.S. Geological Survey regional groundwater-flow model simulations and records of irrigation-return flow pumped from the Tule Lake subbasin into the adjacent Lower Klamath Lake subbasin have indicated that water-level declines from pumping may be causing decreased flow of shallow groundwater to agricultural drains. To better define the effect of increased pumping on drain flow and on the water balance of the groundwater system, the annual water volume pumped from drains in three subareas of the Tule Lake subbasin was estimated and a fine-grid, local groundwater model of the Tule Lake subbasin was constructed. Results of the agricultural-drain flow analysis indicate that groundwater discharge to drains has decreased such that flows in 2012 were approximately 32,400 acre-ft less than the 1997–2000 average flow. This decrease was concentrated in the northern and southeastern parts of the subbasin, which corresponds with the areas of greatest groundwater pumping. Model simulation results of the Tule Lake subbasin groundwater model indicate that increased supplemental pumping is the dominant stress to the groundwater system in the subbasin. Simulated supplemental pumping and decreased recharge from irrigation between 2000 and 2010 totaled 323,573 acre-ft, 234,800 acre-ft (73 percent) of which was from supplemental pumping. The response of the groundwater system to this change in stress included about 180,500 acre-ft (56 percent) of decreased groundwater discharge to drains and a 126,000 acre-ft (39 percent) reduction in aquifer storage. The remaining 5 percent came from reduced groundwater flow to other model boundaries, including the Lost River, the Tule Lake sumps, and interbasin flow.

California, Oregon↗

USGS1967

Ground water in the vicinity of American Falls Reservoir, Idaho

Analysis of ground- and surface-water relationships suggests that increasing the capacity of the American Falls Reservoir by raising the height of the dam 15 feet would increase leakage from the reservoir by less than 0.2 percent of the average inflow to the reservoir, or less than 10,000 acre feet per year. This amount is less than one-tenth of the evaporation rate from the reservoir. The American Falls Reservoir lies near the south margin of the Snake River Plain in southeastern Idaho. The Snake River Plain is about 200 miles long and averages nearly 60 miles in width. It is underlain by a thick sequence of basaltic lava flows, interbedded pyroclasties, and sedimentary deposits. The uppermost few thousand feet of this sequence is the Snake Plain aquifer, one of the great aquifers of the United States. Recharge to the aquifer is chiefly by water percolating from the Snake River, its tributaries, and irrigated tracts, and by underflow from surrounding areas. Ground water moves generally southwestward and discharges to the Snake River through springs in the American Falls Reservoir reach and in the Hagerman Valley reach (between Twin Falls and Bliss). Total discharge from the aquifer is about 9,000 cfs (cubic feet per second). The occurrence and movement of ground water in the viscinity of American Falls Reservoir are controlled by the local geology. Silt and tuff in the Neeley Formation and the Walcott Tuff and silt and fine sand in the FT ft Formation and American Falls Lake Beds have a low permeability. These rocks transmit little ground water compared with the basalt and intercalated pyroclasties and gravels of the Snake Plain aquifer. The less permeable deposits underlie the reservoir area and act as a barrier to the movement of ground water. Under present conditions the water table on the periphery of the reservoir slopes toward the reservoir, except within 3 or 4 miles of the dam, where the water table slopes away from the reservoir. Most of the springs discharge at altitudes above 4,370 feet, some 15 feet above the maximum reservoir stage. Thus, reservoir stage has little effect on ground-water inflow to the reservoir. A fairly close relationship exists between the annual amount of surface water diverted for irrigation of lands up the Snake River from the reservoir and the annual ground-water discharge through springs for the period 1911-60. After about 1952, greatly increased ground-water withdrawals from wells, which increased consumptive use, virtually balanced increased diversions from the surface- water system for irrigation, so that ground-water inflow to the reservoir remained about constant.

Idaho↗