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At least 397 records · Page 22Linked to original sources
USGS1987

Simulation of flow in the Edwards Aquifer, San Antonio region, Texas, and refinement of storage and flow concepts

The Edwards aquifer is a complexly faulted, carbonate aquifer lying within the Balcones fault zone of south-central Texas. The aquifer is recharged mainly by streamflow losses in the outcrop area of the Edwards aquifer and is discharged by major springs located at considerable distances, as much as 150 mi, from the areas of recharge, and by wells. Groundwater flow within the Edwards aquifer of the San Antonio region was simulated to investigate concepts relating to the storage and flow characteristics. A general purpose, finite difference model, modified to provide the capability of representing barrier faults, was used to simulate groundwater flow and storage in the aquifer. The simulations investigated the effects of complex geologic structures and significant changes in transmissivity, anisotropy, and storage coefficient, with initial values based on concepts developed in previous studies. Results of the simulations confirmed the original estimates of transmissivity values (> 100 sq ft/sec) in the confined zone of the aquifer between San Antonio and Comal Springs. A storage coefficient of 0.05 in the unconfined zone of the aquifer produced the best simulation of water levels and springflow. A major interpretation resulting from the simulations is that two essentially independent areas of regional flow were identified in the west and central part of the study area. Flow from the two areas converges at Comal Springs. The directions of computed flux vectors reflected the presence of major barrier faults which locally deflect patterns of groundwater movement. The most noticeable deflection is the convergence of flow through the geologic structural opening, the Knippa gap, in eastern Uvalde County. A second significant interpretation is that groundwater flow in northeastern Bexar, Comal, and Hays Counties is diverted by barrier faults toward San Marcos Springs, a regional discharge point. (Lantz-PTT)

Texas↗
USGS1954

Localization of uranium minerals in channel sediments at the base of the Shinarump conglomerate, Monument Valley, Arizona

During the summers of 1951 and 1952 the U.S. Geological Survey mapped the geology and uranium deposits in three 15-minute quadrangles on the Navajo Indian Reservation in Apache and Navajo Counties, northeastern Arizona. Exposed sedimentary rocks range in age from the Halgaito tongue of the Cutler formation (Permian) to the Salt Wash member of the Morrison formation (Jurassic), The dominant structural element of the area is the Monument upwarp, a arge asymmetrical anticline whose northern end is near the junction of the Green and Colorado Rivers in Utah, and whose southern end disappears near Kayenta, Ariz. Asymmetrical anticlines with steeply dipping east flanks and gently dipping west flanks are superimposed on the upwarp. These subsidiary structures trend north. The uranium ore bodies are localized in conglomeratic sandstone of the Upper Triassic Shinarump conglomerate that fills channels scoured in the underlying Lower and Middle (?) Triassic Moenkopi formation. These channels range from relatively narrow and shallow ones 15 feet wide and 10 feet deep to much broader and deeper ones 2,300 feet wide and 70 feet deep. Two types of channels can be distinguished-r-a short-type less than 2 miles Iong 5 and a long-type traceable for distances greater than 2 miles Plant matter in the form of trees, branches,'and twigs was deposited with Shinarump sediments in the channels. It is suggested that when the Shinarump conglomerate was invaded by mineralizing solutions the uranium ore was deposited primarily in localities formerly occupied by the plant material. Further, it is suggested that the short channels are more likely to have ore accumulations than long channels.

Arizona↗
USGS2024

Geophysical modeling of a possible blind geothermal system near Battle Mountain, NV

The northeastern portion of the Reese River basin in north-central Nevada is the focus of detailed geophysical and geological studies as part of the INGENIOUS project, which aims to identify new, commercially viable hidden geothermal systems in the Great Basin region of the western U.S. This location, herein referred to as Argenta Rise, occupies a broad (~15km wide) left-step between major range-front fault systems along the northwestern edge of the Shoshone Range and Argenta Rim, with numerous ENE-striking intra-basin faults presumably accommodating sinistral-normal oblique slip across the step-over. Four discrete regions have been identified within the study area that have favorable structural settings for hosting a blind hydrothermal system. However, with no definitive or extensive surface manifestations of an active hydrothermal system (e.g., geysers, steam vents, sinter, etc.), detailed geophysical studies are necessary to resolve subsurface geology and structure, and identify zones of enhanced structural complexity that may promote hydrothermal fluid flow. Hence, we collected high-resolution gravity, MT, and rock property data (density, magnetic susceptibility), and analyzed the recently acquired GeoDAWN aeromagnetic data to characterize potential geothermal resources in this region. Using the new geophysical datasets, we jointly modeled gravity and magnetic data along a series of intersecting 2D profiles that integrated information from recent, local-scale fault mapping. Rock property measurements performed on outcrops and hand samples throughout the study area constrained the models. The MT data were used to construct a 3D resistivity model that highlights the location of inferred alteration and fluids in the subsurface. Combined MT and potential field results reveal which structures may be most important for controlling hydrothermal fluid migration, as well as which geologic units may host hydrothermal fluids. Our gravity derived depth to basement surface coincides well with the base of shallow conductive anomalies, suggesting hydrothermal fluids may be confined to basin fill sediments and volcanics. This work supports our development of 3D geophysical and geologic models that are focused along the western flank of the northern Shoshone Range and aids the process of selecting sites for temperature gradient drilling.

Nevada↗
USGS2016

Documentation of a groundwater flow model developed to assess groundwater availability in the Northern Atlantic Coastal Plain aquifer system from Long Island, New York, to North Carolina

The U.S. Geological Survey developed a groundwater flow model for the Northern Atlantic Coastal Plain aquifer system from Long Island, New York, to northeastern North Carolina as part of a detailed assessment of the groundwater availability of the area and included an evaluation of how these resources have changed over time from stresses related to human uses and climate trends. The assessment was necessary because of the substantial dependency on groundwater for agricultural, industrial, and municipal needs in this area. The three-dimensional, groundwater flow model developed for this investigation used the numerical code MODFLOW–NWT to represent changes in groundwater pumping and aquifer recharge from predevelopment (before 1900) to future conditions, from 1900 to 2058. The model was constructed using existing hydrogeologic and geospatial information to represent the aquifer system geometry, boundaries, and hydraulic properties of the 19 separate regional aquifers and confining units within the Northern Atlantic Coastal Plain aquifer system and was calibrated using an inverse modeling parameter-estimation (PEST) technique. The parameter estimation process was achieved through history matching, using observations of heads and flows for both steady-state and transient conditions. A total of 8,868 annual water-level observations from 644 wells from 1986 to 2008 were combined into 29 water-level observation groups that were chosen to focus the history matching on specific hydrogeologic units in geographic areas in which distinct geologic and hydrologic conditions were observed. In addition to absolute water-level elevations, the water-level differences between individual measurements were also included in the parameter estimation process to remove the systematic bias caused by missing hydrologic stresses prior to 1986. The total average residual of –1.7 feet was normally distributed for all head groups, indicating minimal bias. The average absolute residual value of 12.3 feet is about 3 percent of the total observed water-level range throughout the aquifer system. Streamflow observation data of base flow conditions were derived for 153 sites from the U.S. Geological Survey National Hydrography Dataset Plus and National Water Information System. An average residual of about –8 cubic feet per second and an average absolute residual of about 21 cubic feet per second for a range of computed base flows of about 417 cubic feet per second were calculated for the 122 sites from the National Hydrography Dataset Plus. An average residual of about 10 cubic feet per second and an average absolute residual of about 34 cubic feet per second were calculated for the 568 flow measurements in the 31 sites obtained from the National Water Information System for a range in computed base flows of about 1,141 cubic feet per second. The numerical representation of the hydrogeologic information used in the development of this regional flow model was dependent upon how the aquifer system and simulated hydrologic stresses were discretized in space and time. Lumping hydraulic parameters in space and hydrologic stresses and time-varying observational data in time can limit the capabilities of this tool to simulate how the groundwater flow system responds to changes in hydrologic stresses, particularly at the local scale.

Delaware, Maryland, New Jersey, New York, North Ca↗
USGS1972

Report of the field trip, February 24 to April 2, 1965 in part of the northeastern Hijaz quadrangle, Saudi Arabia

In 1963, in response to a request from the Ministry of Petroleum and Mineral Resources, the Saudi Arabian Government and the U. S. Geological Survey, U. S. Department of the Interior, with the approval of the U. S. Department of State undertook a joint and cooperative effort to map and evaluate the mineral potential of central and Saudi Arabia. The results of this program are being released in USGS open files in the United States and are also available in the Library of the Ministry of Petroleum and Mineral Resources. Also on open file in that office is a large amount of material, in the form of unpublished manuscripts, maps, field notes, drill logs, annotated aerial photographs, etc., that has resulted from other previous geologic work by Saudi Arabian government agencies. The Government of Saudi Arabia makes this information available to interested persons, and has set up a liberal mining coda which is included in "Mineral Resources of Saudi Arabia, a Guide for Investment and Development," published in 1965 as Bulletin 1 of the Ministry of Petroleum and Mineral Resources, Directorate General of Mineral Resources, Jiddah, Saudi Arabia.

Hijaz quadrangle↗
USGS1997

Revised preliminary geologic map of the Rifle Quadrangle, Garfield County, Colorado

The Rifle quadrangle extends from the Grand Hogback monocline into the southeastern part of the Piceance basin. In the northeastern part of the map area, the Wasatch Formation is nearly vertical, and over a distance of about 1 km, the dip decreases sharply from about 70-85o to about 15-30o toward the southwest. No evidence of a fault in this zone of sharp change in dip is observed but exposures in the Shire Member of the Wasatch Formation are poor, and few marker horizons that might demonstrate offset are distinct. In the central part of the map area, the Shire Member is essentially flat lying. In the south and southwest part of the map area, the dominant dip is slightly to the north, forming an open syncline that plunges gently to the northwest. Evidence for this fold also exists in the subsurface from drill-hole data. According to Tweto (1975), folding of the early Eocene to Paleocene Wasatch Formation along the Grand Hogback reqired an early Eocene age for the last phase of Laramide compression. We find the attitude of the Wasatch Formation to be nearly horizontal, essentially parallel to the overlying Anvil Points Member of the Eocene Green River Formation; therefore, we have no information that either confirms or disputes that early Eocene was the time of the last Laramide event. Near Rifle Gap in the northeast part of the map area, the Mesaverde Group locally dips about 10o less steeply than the overlying Wasatch Formation, indicating that not only had the formation of the Hogback monocline not begun by the time the Wasatch was deposited at this locality, but the underlying Mesaverde Group was locally tilted slightly toward the present White River uplift. Also the basal part of the Atwell Gulch Member of the Wasatch Formation consists of fine-grained mudstones and siltstones containing sparse sandstone and rare conglomerates, indicating that the source of sediment was not from erosion of the adjacent Upper Cretaceous Mesaverde Group. The most likely source of andesitic conglomerate clasts abundant in the upper part of the Atwell Gulch Member was Late Cretaceous-Early Tertiary andesitic igneous rocks, remnants of which are present southeast of the Piceance Basin (Tweto, 1979). Thinning of the Atwell Gulch and Molina Members to the northwest also suggests a southeastern source of sediments, ruling out a northeastern source related to earlier deformation of the Upper Cretaceous Mesa Verde Group.

Colorado↗
USGS1962

Geology of the Powder River Basin, Wyoming and Montana, with reference to subsurface disposal of radioactive wastes

The Powder River Basin is a structural and topographic basin occupying an area of about 20,000 square miles in northeastern Wyoming arid southeastern Montana. The Basin is about 230 miles long in a northwest-southeast direction and is about 100 miles wide. It is bounded on three sides by mountains in which rocks of Precambrian age are exposed. The Basin is asymmetrical with a steep west limb adjacent to the Bighorn Mountains and a gentle east limb adjacent to the Black Hills. Sedimentary rocks within the Basin have a maximum thickness of about 18,000 feet and rocks of every geologic period are represented. Paleozoic rocks are about 2,500 feet thick and consist of marine bonate rocks and sandstone; Mesozoic rocks are about 9,500 feet thick and consist of both marine and nonmarine siltstone and sandstone; and Cenozoic rocks are from 4,000 to 6,000 feet thick and consist of coal-bearing sandstone and shale. Radioactive waste could be stored in the pore space of permeable sandstone or in shale where space could be developed. Many such rock units that could be used for storing radioactive wastes are present within the Powder River Basin. Permeable sandstone beds that may be possible reservoirs for storage of radioactive waste are present throughout the Powder River Basin. These include sandstone beds in the Flathead Sandstone and equivalent strata in the Deadwood Formation, the Tensleep Sandstone and equivalent strata in the Minnelusa Formation and the Sundance Formation in rocks of pre-Cretaceous age. However, most of the possible sandstone reservoirs are in rocks of Cretaceous age and include sandstone beds in the Fall River, Lakota, Newcastle, Frontier, Cody, and Mesaverde Formations. Problems of containment of waste such as clogging of pore space and chemical incompatibility would have to be solved before a particular sandstone unit could be selected for waste disposal. Several thick sequences of impermeable shale such as those in the Skull Creek, Mowry, Frontier, Belle Fourche, Cody, Lewis, and Pierre Formations, occur in rocks of Cretaceous age in the Basin. Limited storage space for liquid waste might be developed in impermeable shale by fracturing the shale and space for calcined or fused waste could be developed by mining cavities.

Open-File Report↗
USGS1987

Interpretation of the regional geochemistry of the Tonopah 1 degree by 2 degrees Quadrangle, Nevada, based on analytical results from stream-sediment and nonmagnetic heavy-mineral-concentrate samples

Results of more than 2,400 analyses of <0.25-mm fraction of stream sediments and nonmagnetic heavy-mineral concentrates from stream sediments from 1,217 sites in the Tonopah quadrangle demonstrate the existence of anomalous concentrations of many metals of economic interest in many areas. Single-element anomalies of As, Pb, or Sb in stream sediment provide general guides to possible mineralization, but multi-element suites are more reliable to characterize types of mineralization. Various combinations of Ag, As, Bi, Cu, Mo, Pb, Sb, and W in stream sediments and concentrates provide guides to five general types of deposits and their geologic environments. Multi-element suites that recur in stream-sediment media resemble those observed in mineralized rock samples, and the distribution of the suites corresponds to the distribution of known types of deposits and to the general geology of the region. Multi-element geochemical anomalies are prominent in the Pilot Mountains, Monte Cristo Range, Paradise Range, Lone Mountain, northeastern Toiyabe Range, Cedar Mountains, and Toquima Range. Strongest multi-element anomalies are associated with plutonic rocks in the western part of the quadrangle. Two base-metal suites are enriched in and around plutons: (1) Bi + W + Pb + Mo ± As, Cu, Sb, a suite that resembles metals enriched in rocks samples from skarn deposits; and (2) Pb + Mo ± As,Cu,Sb, which resembles base-metal enrichments in sulfide vein and replacement deposits, generally associated with intrusions. A third variety of base-metal enrichment that contains Ag is distinguished for its possible economic importance. This Ag-Pb-rich suite occurs both near plutons and in volcanic terrane and generally is near areas of known Ag-rich polymetallic deposits. Many sites are characterized by modest enrichments of two to five elements in the suite As-Mo-Sb-Zn-Ag that resemble enrichments in epithermal ore deposits. Many anomalies of this type are from drainages underlain by Tertiary welded tuff, commonly lacking alteration and mineral prospects. Some of these anomalous sites correlate with areas of known epithermal deposits or siliceous alteration of calcareous rocks, thus this suite may be a guide to precious-metal deposits if there is supporting geologic evidence. The results from regional sampling of stream sediments, utilizing the <0.25-mm fraction and nonmagnetic heavy-mineral-concentrate media, effectively outline most areas of known deposits or alteration in the Tonopah quadrangle. Some clusters of anomalies are larger than the area of known mineral prospects, suggesting that other deposits remain to be discovered. This regional geochemical information is most effective for exploration and resource analysis when integrated with other geologic information, especially rock alteration.

Nevada↗
USGS1978

Ground-water records for eastern Oklahoma, Part 2; water-quality records for wells, test-holes, and springs

The U. S. Geological Survey has collected data on Oklahoma's ground-water resources since 1934. Most of these data were collected as part of specific ground-water studies conducted in cooperation with various Federal, State, and local agencies. Data on construction, yield, water levels, and other physical well parameters are given in 'Ground-Water Records for Northeastern Oklahoma, Part 1 - Records of Wells, Test Holes, and Springs' and in 'Ground-Water Records for Southeastern Oklahoma, Part 1 - Records of Wells, Test Holes, and Springs.' These reports are available from the U.S. Department of the Interior, Geological Survey, Rm. 621, 201 N.W. Third, Oklahoma City, OK 73102. Although some water-quality data for wells, test-holes, and springs have been published, they are scattered through a variety of reports and are not readily available on a regional basis. Furthermore, a considerable amount of data have never been published and can be obtained only from the files of the Geological Survey. The purpose of this report is to make available both published and unpublished water-quality records for approximately 1,740 wells, test-holes, and springs in 23 counties in northeastern Oklahoma and 16 counties in southeastern Oklahoma. Acknowledgment is extended to the many hundreds of individuals who have provided the data compiled in this report.

Oklahoma↗
USGS2016

Pesticide concentrations in wetlands on the Lake Traverse Indian Reservation, South and North Dakota, July 2015

During July 2015, water samples were collected from 18 wetlands on the Lake Traverse Indian Reservation in northeastern South Dakota and southeastern North Dakota and analyzed for physical properties and 54 pesticides. This study by the U.S. Geological Survey in cooperation with the Sisseton-Wahpeton Oyate was designed to provide an update on pesticide concentrations of the same 18 wetlands that were sampled for a reconnaissance-level assessment during July 2006. The purpose of this report is to present the results of the assessment of pesticide concentrations in selected Lake Traverse Indian Reservation wetlands during July 2015 and provide a comparison of pesticide concentrations between 2006 and 2015. Of the 54 pesticides that were analyzed for in the samples collected during July 2015, 47 pesticides were not detected in any samples. Seven pesticides—2-chloro-4-isopropylamino-6-amino-s-triazine (CIAT); 2,4–D; acetachlor; atrazine; glyphosate; metolachlor; and prometon—were detected in the 2015 samples with estimated concentrations or concentrations greater than the laboratory reporting level, and most pesticides were detected at low concentrations in only a few samples. Samples from all wetlands contained at least one detected pesticide. The maximum number of pesticides detected in a wetland sample was six, and the median number of pesticides detected was three. The most commonly detected pesticides in the 2015 samples were atrazine and the atrazine degradate CIAT (also known as deethylatrazine), which were detected in 14 and 13 of the wetlands sampled, respectively. Glyphosate was detected in samples from 11 wetlands, and metolachlor was detected in samples from 10 wetlands. The other detected pesticides were 2,4–D (4 wetlands), acetochlor (3 wetlands), and prometon (1 wetland). The same pesticides that were detected in the 2006 samples were detected in the 2015 samples, with the exception of simazine, which was detected only in one sample in 2006. Atrazine and CIAT were the most commonly detected pesticides in both sampling years; however, atrazine and CIAT were detected in fewer wetlands in 2015 (14 and 13 wetlands, respectively) than in 2006 (17 wetlands for both pesticides). The pesticides 2,4–D and prometon also were detected in fewer wetlands in 2015 than 2006, and simazine was only detected in 2006. In contrast, acetochlor, glyphosate, and metolachlor were detected in samples from more wetlands in 2015 than in 2006. In samples from individual wetlands, the number of pesticides detected was similar between 2006 and 2015. At least one pesticide was detected in all wetlands in 2015, and all but one wetland had pesticide detections in 2006. Concentrations of pesticides detected in samples from wetlands were compared to selected water-quality (human-health and aquatic-life) benchmarks. None of the concentrations in either 2006 or 2015 were greater than water-quality benchmarks, with the exception of atrazine. All detections of atrazine in the 2006 and 2015 samples were greater than the acute benchmark of 0.001 microgram per liter (μg/L) for vascular plants. In addition, some concentrations of 2,4–D and atrazine were within an order of magnitude of a water-quality benchmark. The 2,4–D concentrations in the 2015 samples from three wetlands were within an order of magnitude of the U.S. Environmental Protection Agency’s Maximum Contaminant Level of 70 μg/L (that is, sample concentrations were greater than 7.0 μg/L). The maximum dissolved atrazine concentration of 0.185 μg/L in the 2015 samples along with the concentrations in 2006 samples from two wetlands were within an order of magnitude of the acute benchmark of less than 1 μg/L for nonvascular plants (that is, concentrations were greater than 0.1 μg/L).

North Dakota, South Dakota↗
USGS2006

Aqueous geochemical data from the analysis of stream water samples collected in August 2004: Taylor Mountains 1:250,000 scale quadrangle, Alaska

We report on the chemical analysis of water samples collected from the Taylor Mountains 1:250,000 quadrangle. Samples were collected as part of the multi-year U.S. Geological Survey's project -- Geologic and Mineral Deposit Data for Alaskan Economic Development. Data presented here are from water samples collected primarily in the northeastern part of the Taylor Mountains quadrangle. The data include samples taken from the Taylor Mountains C1, C2, D1, D2, and D4 1:63,360 scale quadrangles. The data are being released at this time with minimal interpretation. Site selection was based on a regional sampling strategy that focused on first and second order drainages. Water sampling site selection was based on landscape parameters that included physiography, wetland extent, lithological changes, and the cursory field review of the mineralogy from the pan concentrates. Stream water in the Taylor Mountians quadrangle is dominated by bicarbonate (HCO3-), though in a few samples more than 50% of the anionic charge can be attibuted to sulfate ( SO42-). The major-cation chemistry range from Ca/Mg dominated to a mix of Ca/Mg/Na+K. Good agreement was found between the major cation and anions in the duplicate samples. Many trace elements were at or near the method detection limit in these samples but good agreement was found between duplicate samples for elements with detectable concentrations. Major ion concentrations were below detection in all field blanks and the trace elements concentrations generally were below detection. However, Ta (range 0.9 -.1 ug/L) and Zn (1 to 3.5 ug/L) were detected in all blanks and Ba ( 0.24 ug/L) and Th (0.2 ug/L) were detected in one blank. There was good agreement between dupilicate total- and methyl- mercury and DOC samples; however, total mercury, methyl-mercury and dissolve organic carbon (DOC) were detected in the blank at 2.35 ng/L, 0.07 ng/L and 0.57 mg/L, respectively.

Alaska↗
USGS1995

Tectonic setting of the Portland-Vancouver area, Oregon and Washington: Constraints from low-altitude aeromagnetic data

Seismic activity in the Portland-Vancouver metropolitan area may be associated with various mapped faults that locally offset volcanic basement of Eocene age and younger. This volcanic basement is concealed in most places by young deposits, vegetation, and urban development. The U.S. Geological Survey conducted an aeromagnetic survey in September 1992 to investigate the extent of these mapped faults and possibly to help identify other seismic and volcanic hazards in the area. The survey was flown approximately 240 m above terrain, along flight lines spaced 460 m apart, and over an area about 50 × 50 km. These magnetic data indicate a pronounced northwest-striking magnetic lineation east of the Willamette River in downtown Portland associated with a fault concealed beneath Quaternary sedimentary deposits and previously inferred from shallow well data. The magnetic lineation confirms the existence of the fault and suggests that it has had a prolonged history: (1) Although well data indicate <200 m of vertical offset of underlying volcanic basement, models based on the aeromagnetic data from downtown Portland suggest reverse faulting with up to 1 km of offset deeper in the section. (2) The magnetic lineation associated with this fault extends southeast to the Clackamas River drainage, a distance of 50 km and considerably beyond the mapped extent of the fault. A northwest-striking magnetic anomaly located southwest of the Tualatin Mountains corresponds closely with another mapped fault and with mixed reverse and strike-slip faulting during a seismic swarm (M ≤ 3) in 1991. We believe these and other anomalies in the aeromagnetic data reflect the Portland Hills fault zone, believed to be the southwestern boundary of a structural basin now occupied by Portland and Vancouver. The postulated northeastern boundary of the basin, the Frontal fault zone, is also evident, although less well represented in the aeromagnetic data. Aeromagnetic anomalies, geologic mapping, and earthquake focal-plane solutions demonstrate a complex deformational history in the Portland-Vancouver area since middle Miocene time that includes elements of compression, extension, and dextral slip. These complexities reflect Portland-Vancouver's unique position within a north-south transition in tectonic styles along the Cascadia margin, from compressional in the north to extensional in the south.

Oregon, Washington↗
USGS1962

Exploration for uranium-vanadium deposits by U.S. Geological Survey 1948-56 in western Disappointment Valley area, Slick Rock district, San Miguel County, Colorado

The western Disappointment Valley area is in San Miguel County, Colo., in the northeastern part of the Slick Rock district, (see location map). It covers an area of approximately 50 square miles in Tps. 43 and 44 N., Rs. 17, 18, and 19 W., New Mexico principal meridian. The mining camp of Slick Rock is in the western part of the area. On the northeast the area is bounded by Gypsum Valley; the other boundaries are arbitrarily drawn to delimit the area in which drilling was done.

Colorado↗
USGS2018

Geology and assessment of undiscovered oil and gas resources of the Mezen’ Basin Province, 2008

The Mezen’ Basin Province is situated along the White and Barents Seas in the northeastern part of the Russian Federation. Only a small area of the province, part of one graben, extends slightly north of the Arctic Circle onto the Kanin-Kola monocline, where it converges with the Timan-Varanger deformed belt and the Fennoscandian shield. The main petroleum potential in the Mezen’ Basin Province is associated with grabens in which clastic Proterozoic source and reservoir rocks are present. One Proterozoic-Paleozoic Composite Total Petroleum System was defined, although Paleozoic and younger strata are too thin (<1–2 km) for significant petroleum accumulation. The total thickness of the sedimentary interval is <6 km. The Northwest Mezen’ Basin Assessment Unit was delineated north of the Arctic Circle. Proterozoic (Riphean) mudstone is organic rich and thermally mature, providing a source for petroleum; younger Proterozoic (Vendian) rocks are also organic rich but thermally immature (Kuz’min, 2005). Because of its limited extent, the potential for an oil or gas field exceeding the minimum size of 50 million barrels of oil equivalent (MMBOE) within the small graben north of the Arctic Circle is remote (assessment-unit probability, 0.005). Therefore, the Mezen’ Basin Province was not quantitatively assessed.

Mezen’ Basin Province↗
USGS2004

Geologic framework and hydrogeologic characteristics of the Glen Rose limestone, Camp Stanley Storage Activity, Bexar County, Texas

The Trinity aquifer is a regional water source in the Hill Country of south-central Texas that supplies water for agriculture, commercial, domestic, and stock purposes. Rocks of the Glen Rose Limestone, which compose the upper zone and upper part of the middle zone of the Trinity aquifer, crop out at the Camp Stanley Storage Activity (CSSA), a U.S. Army weapons and munitions supply, maintenance, and storage facility in northern Bexar County (San Antonio area) (fig. 1). On its northeastern, eastern, and southern boundaries, the CSSA abuts the Camp Bullis Training Site, a U.S. Army field training site for military and Federal government agencies. During 2003, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army, studied the outcropping Glen Rose Limestone at the CSSA and immediately adjacent area (Camp Stanley study area, fig. 1) to identify and map the hydrogeologic subdivisions and faults of the Glen Rose Limestone at the facility. The results of the study are intended to help resource managers improve their understanding of the distribution of porosity and permeability of the outcropping rocks, and thus the conditions for recharge and the potential for contaminants to enter the Glen Rose Limestone. This study followed a similar study done by the USGS at Camp Bullis (Clark, 2003). The purpose of this report is to present the geologic framework and hydrogeologic characteristics of the Glen Rose Limestone in the study area. The hydrogeologic nomenclature follows that introduced by Clark (2003) for the outcropping Glen Rose Limestone at Camp Bullis in which the upper member of the Glen Rose Limestone (hereinafter, upper Glen Rose Limestone), which is coincident with the upper zone of the Trinity aquifer, is divided into five intervals on the basis of observed lithologic and hydrogeologic properties. An outcrop map, two generalized sections, related illustrations, and a table summarize the description of the framework and distribution of characteristics.

Texas↗
USGS1959

Geology of the State of Morelos and contiguous areas in south-central Mexico

The area described lies in south-central Mexico and embraces all but the southeastern corner and easternmost border of the State of Moreles, the second smallest State in the Mexican Republic. It includes small contiguous parts of the State of Mexico, in the northeastern corner, and of the State of Guerrero in the southwestern corner. Limiting geographic coordinates are 98 45 to 99 39 west longitude and 18 18 to 19 08 north latitude, the northern boundary being only 35 km south of Mexico City, capital of the Republic. The geological map does not cover the entire rectangle outlined, but is irregular in form and measures roughly 4150 sq. km, three-quarters of it representing two0thirds of the State of Moreles and the rest lying outside the State. The region ranges in altitude from 730 m above sea level at Iguala near the south edge of the map, to a general level of about 3000 m at the north edge, although individual peaks rise to 3900 m and Popocatepetl Volcano, a few kilometers east of the northeastern border of the map, rises to 5452 m above sea level. Annual rainfall ranges from a minimum of about 640 mm in the low country, to 1200 mm and more at altitudes above 2000 m. Most of it falls in summer between June and September. Winter frosts are rare below 1800 m. The climate is of savanna to steppe type; soils are thin and may be classified as belonging to the tachernoses group, with strong development of calcareous evaporates (caliche) at altitudes below 1800 m. The northern border of the area forms the southern half of the late Pliocene to Recent Neo-volcanic Belt of basic volcanism that crosses Mexico in the direction N. 80 W., and thus has constructional topography. The rest of the area belongs to the Balsas Basin physiographic province, which is characterized by maturely dissected terrain tributary to the large Balsas River. All but the southwestern corner of the area drains southward via the Amacuzac River into the Mexcala-Balsas River, and thence westward into the Pacific Ocean. The southwestern corner drains directly into the Balsas River via the Iguala River. Local relief is of the order of 300 to 600 m. The mature topography was partly buried by late Pliocene alluvium in the central part of the area, owing largely to local volcanism. Dissolution of limestone, dolomite, and anhydrite of the Cretaceous formations has produced sinks and poljes, some of which contain small lakes. Other karst features are also common, such as caves, caverns, underground rivers, and surficial lapies or karren. Drainage blocking by lava and polje development in late Pleistocene and Recent time produced new alluvial flats in this otherwise dissected region. The oldest rock unit in the region is the Texco schist series of late Paleozoic (?) age. It was folded, metamorphosed, foliated, intruded by dikes, and strongly eroded before the next unit, the Texco Viejo green volcanic series of Late Triassic (?) age, was deposited. Another period of metamorphism and erosion followed before the calcareous clastic sediments of the Upper Jurassic (?) Acahuizotla formation were laid down. The next unit consists of the partly phyllitic calcareous shale of the Acuitlapan formation, which is of Neocenian (?) age and rests with at least disconformity on the Acahuizotla formation. The overlying Aptian-Barresian Kochicalco formation of thin-bedded limestone appears to grade upward from the Acuitlapan formation, locally, but it seems to be unconformable elsewhere. All these units have small outcrops in the area mapped and were not studied in detail. Warping and erosion occurred before the overlying Morelos formation began to accumulate in early Albian time. The basal member is anhydrite in the eastern part of the area mapped, but limestone and dolomite were deposited elsewhere. The formation consists largely of shallow-water calcareous bank deposits, with a maximum thickness of about 900 m. Deposition ceased in early Cenomanian time and further warpi

Open-File Report↗
USGS2019

Drought forecasting for streams and groundwaters in northeastern United States

Background When rainfall is lower than normal over an extended period, streamflows decline, groundwater levels fall, and hydrological drought can occur. Droughts can reduce the water available for societal needs, such as public and private drinking-water supplies, farming, and industry, and for ecological health, such as maintenance of water quality and natural ecosystems. Recent droughts in the northeastern United States have highlighted the need for new scientific tools to forecast the probability of future droughts so water managers and the public can be better prepared for these events when they happen. Two recent U.S. Geological Survey (USGS) studies provide tools that can forecast the probabilities of summer droughts for streams and the probabilities of groundwater-level declines below specified targets or thresholds. These tools provide promising methods for identifying and anticipating probable streamflow and groundwater droughts specific to the northeastern United States. USGS Water Science Centers in the northeastern United States have acted together to use these methods for numerous streamflow gages and groundwater-level monitoring wells, and to make the results of the analyses available on the world wide web. This fact sheet describes the drought forecasting techniques used in a study to predict droughts for streamflow and groundwater in the northeastern United States.

Connecticut, Delaware, Maine, Massachusetts, New H↗