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At least 757 records · Page 42Linked to original sources

USGS1983

An interpretation of gravity and aeromagnetic surveys of the Greater Jiddah area, Kingdom of Saudi Arabia

A gravity survey of the Jiddah area between lat 21°23' and 21°48' N., long 39°03' and 39°20' E., carried out in early 1977, covers an area of 744 km 2 and includes 215 stations, at an average spacing of 1.9 km. The resulting simple Bouguer gravity anomaly map shows a series of four large (7-15 mgal) gravity anomaly highs along a north-trending gravity gradient located immediately west of outcrops of Precambrian rocks. The regional Bouguer gravity anomaly field of the map area decreases eastward at an approximately constant rate of about 1.1 mgal-km-1. Several anomalies suggest northeast-trending, right-lateral strike-slip faulting throughout the area. Interpretation of the Bouguer gravity anomaly map, combined with geologic, aeromagnetic, and paleomagnetic data, leads to an interpretive model in which the gravity gradient marks the boundary zone between Precambrian continental crust to the east and oceanic sea-floor crust overlain by marine sedimentary rocks to the west. The strike-slip faults in the area are probably the landward extension of offshore Red Sea transform faults, and, because they penetrate and offset continental crust, their study may yield useful information about the mechanism of transform faulting. The gravity anomaly highs are interpreted to result from shallow intrusive bodies, probably gabbroic in composition, that are buried a few hundred meters below the surface and that are approximately 2 km thick.

Report↗

USGS2006

Chapter 4: The GIS Project for the Geologic Assessment of Undiscovered Oil and Gas in the Upper Cretaceous Navarro and Taylor Groups, Western Gulf Province, Texas

A geographic information system (GIS) focusing on the Upper Cretaceous Navarro and Taylor Groups in the Gulf Coast region was developed as a visual-analysis tool for the U.S. Geological Survey's 2003 assessment of undiscovered, technically recoverable oil and natural gas resources in the Western Gulf Province. The Central Energy Resources Team of the U.S. Geological Survey has also developed an Internet Map Service to deliver the GIS data to the general public. This mapping tool utilizes information from a database about the oil and natural gas endowment of the United States - including physical locations of geologic and geographic data - and converts the data into visual layers. Portrayal and analysis of geologic features on an interactive map provide an excellent tool for understanding domestic oil and gas resources for strategic planning, formulating economic and energy policies, evaluating lands under the purview of the Federal Government, and developing sound environmental policies. Assessment results can be viewed and analyzed or downloaded from the internet web site.

Data Series↗

USGS1993

The Hatu gold anomaly, Xinjiang-Uygur Autonomous Region, China - testing the hypothesis of aeolian transport of gold

In 1987, a cooperative project between the U.S. Geological Survey and the Institute of Geophysical and Geochemical Exploration was initiated to evaluate the origin of the Hatu gold anomaly. The anomaly is located in the Hatu mining district in the northwest corner of Xinjiang-Uygur Autonomous Region in northwest China. The climate is semiarid to arid and wind erosion predominates. A regional soil survey of the Hatu district, based on samples collected on a 200 by 500 m grid and composited prior to chemical analysis to a density of one sample per square km, delineated a series of south-southeast-trending Au anomalies. Anomalous Au values range from 5 ppb to more than 700 ppb. The Hatu anomaly, the most prominent of these anomalies, is more than 30 km long and about 5 km wide. The mining town of Hatu and the economic gold deposits of Qiqu 1 and Qiqu 2 are at the northern end of this anomaly. The axis of the Hatu anomaly cuts across mapped structure and stratigraphy in the district, but is parallel to the prevailing wind direction. This observation led to the hypothesis that the Hatu anomaly is the result of acolian dispersion of gold from the vicinity of Qiqu 1 and Qiqu 2. The alternative interpretation, that the anomalies reflected additional primary gold occurrences, was not consistent with existing information on the known occurrences and the geology.

Journal of Geochemical Exploration↗

USGS1986

Aeromagnetic map of the Holy Cross Wilderness Area, Eagle, Lake, and Pitkin counties, Colorado

The Holy Cross Wilderness (02–170), called simply "the wilderness area" in this report, lies in the northern Sawatch Range of Colorado. Regionally, the wilderness area lies on a strong gravity gradient that marks the northwest side of the deepest gravity low in the central United States (Behrendt and Bajwa, 1974). This low (fig. 1) reflects a series of Laramide and younger granitic intrusive bodies which are probably related genetically to the Colorado mineral belt (Tweto and Sims, 1963; Behrendt and others, 1968). The wilderness area lies on a structural dome, on which Proterozoic basement rocks have been uplifted, exhumed, and sculpted by glacial and fluvial erosional processes into spectacular alpine ridges. Steep faults bound the western edge of the dome; west of these domal border faults lies a sequence of Paleozoic sedimentary strata, which dip gently and thicken to the west. The dome is marked by an oval regional gravity high (Webring, written commun., 1985) whose shape suggests that maximum domal uplift may have occurred along or just to the east of the domal border fault complex. For more extensive descriptions of the regional geologic setting and mineral deposits of central Colorado, see Tweto (1968). Map B is a generalized bedrock geologic map of the wilderness area, showing locations of faults, shear zones, and geologic units referred to in this report. Many smaller outcrops are not shown on Map B, however. For precise locations, descriptions of geologic units, and a more complete discussion of the geology of the wilderness area, see the companion map by Wallace and others (1986).

Colorado↗

USGS2009

Mapping the mineral resource base for mineral carbon-dioxide sequestration in the conterminous United States

This database provides information on the occurrence of ultramafic rocks in the conterminous United States that are suitable for sequestering captured carbon dioxide in mineral form, also known as mineral carbon-dioxide sequestration. Mineral carbon-dioxide sequestration is a proposed greenhouse gas mitigation technology whereby carbon dioxide (CO 2 ) is disposed of by reacting it with calcium or magnesium silicate minerals to form a solid magnesium or calcium carbonate product. The technology offers a large capacity to permanently store CO 2 in an environmentally benign form via a process that takes little effort to verify or monitor after disposal. These characteristics are unique among its peers in greenhouse gas disposal technologies. The 2005 Intergovernmental Panel on Climate Change report on Carbon Dioxide Capture and Storage suggested that a major gap in mineral CO 2 sequestration is locating the magnesium-silicate bedrock available to sequester the carbon dioxide. It is generally known that silicate minerals with high concentrations of magnesium are suitable for mineral carbonation. However, no assessment has been made in the United States that details their geographical distribution and extent, nor has anyone evaluated their potential for use in mineral carbonation. Researchers at Columbia University and the U.S. Geological Survey have developed a digital geologic database of ultramafic rocks in the conterminous United States. Data were compiled from varied-scale geologic maps of magnesium-silicate ultramafic rocks. The focus of our national-scale map is entirely on ultramafic rock types, which typically consist primarily of olivine- and serpentine-rich rocks. These rock types are potentially suitable as source material for mineral CO 2 sequestration.

Conterminous United States↗

USGS2013

Water-level altitudes 2013 and water-level changes in the Chicot, Evangeline, and Jasper aquifers and compaction 1973--2012 in the Chicot and Evangeline aquifers, Houston-Galveston region, Texas

Most of the subsidence in the Houston-Galveston region, Texas, has occurred as a direct result of groundwater withdrawals for municipal supply, commercial and industrial use, and irrigation that depressured and dewatered the Chicot and Evangeline aquifers, thereby causing compaction mostly in the clay and silt layers of the aquifer sediments. This report, prepared by the U.S. Geological Survey in cooperation with the Harris-Galveston Subsidence District, City of Houston, Fort Bend Subsidence District, Lone Star Groundwater Conservation District, and Brazoria County Groundwater Conservation District, is one in an annual series of reports depicting water-level altitudes and water-level changes in the Chicot, Evangeline, and Jasper aquifers and measured compaction of subsurface sediments in the Chicot and Evangeline aquifers in the Houston-Galveston region. The report contains maps depicting approximate water-level altitudes for 2013 (represented by measurements made during December 2012-February 2013) for the Chicot, Evangeline, and Jasper aquifers; maps depicting 1-year (2012-13) water-level changes for each aquifer; maps depicting 5-year (2008--13) water-level changes for each aquifer; maps depicting long-term (1990-2013 and 1977-2013) water-level changes for the Chicot and Evangeline aquifers; a map depicting long-term (2000-13) water-level changes for the Jasper aquifer; a map depicting locations of borehole-extensometer sites; and graphs depicting measured compaction of subsurface sediments at the extensometers during 1973-2012. Tables listing the data used to construct each water-level map for each aquifer and the compaction graphs are included. In 2013, water-level-altitude contours for the Chicot aquifer ranged from 200 feet (ft) below North American Vertical Datum of 1988 (hereinafter, datum) in a small area in southwestern Harris County to 200 ft above datum in central to west-central Montgomery County. Water-level changes during 2012-13 in the Chicot aquifer ranged from a 58-ft decline to a 37-ft rise. Contoured 5-year and long-term changes in water levels in the Chicot aquifer ranged from a 30-ft decline to an 80-ft rise (2008-13), from a 120-ft decline to a 100-ft rise (1990-2013), and from an 80-ft decline to a 200-ft rise (1977-2013). In 2013, water-level-altitude contours for the Evangeline aquifer ranged from 300 ft below datum in south-central Montgomery County to 200 ft above datum in southeastern Grimes and northwestern Montgomery Counties. Water-level changes for 2012-13 in the Evangeline aquifer ranged from a 37-ft decline to a 68-ft rise. Contoured 5-year and long-term changes in water levels in the Evangeline aquifer ranged from an 80-ft decline to an 80-ft rise (2008-13), from a 220-ft decline to a 220-ft rise (1990-2013), and from a 360-ft decline to a 260-ft rise (1977-2013). In 2013, water-level-altitude contours for the Jasper aquifer ranged from 200 ft below datum in south-central Montgomery and north-central Harris Counties to 250 ft above datum in northwestern Montgomery County and extending into northeastern Grimes and south-central Walker Counties. Water-level changes for 2012-13 in the Jasper aquifer ranged from a 36-ft decline to an 87-ft rise. Contoured changes in water levels in the Jasper aquifer ranged from a 100-ft decline to 20-ft rise (2008-13) and from a 220-ft decline to no change (2000-13). Compaction of subsurface sediments (mostly in the clay and silt layers) of the Chicot and Evangeline aquifers was recorded continuously by 13 borehole extensometers at 11 sites that were either activated or installed between 1973 and 1980. For the period of record beginning in 1973 (or later depending on activation or installation date) and ending in December 2012, cumulative measured compaction by 12 of the 13 extensometers ranged from 0.100 ft at the Texas City-Moses Lake extensometer to 3.632 ft at the Addicks extensometer (data were used from only one of two extensometers at one site). The rate of compaction varies from site to site because of differences in groundwater withdrawals near each site and differences among sites in the clay-to-sand ratio in the subsurface sediments. Therefore, it is not possible to extrapolate or infer a rate of compaction for adjacent areas based on the rate of compaction measured at a nearby extensometer.

Texas↗

USGS2014

Water-level altitudes 2014 and water-level changes in the Chicot, Evangeline, and Jasper aquifers and compaction 1973-2013 in the Chicot and Evangeline aquifers, Houston-Galveston region, Texas

Most of the land-surface subsidence in the Houston-Galveston region, Texas, has occurred as a direct result of groundwater withdrawals for municipal supply, commercial and industrial use, and irrigation that depressured and dewatered the Chicot and Evangeline aquifers, thereby causing compaction of the aquifer sediments, mostly in the fine-grained clay and silt layers. This report, prepared by the U.S. Geological Survey in cooperation with the Harris-Galveston Subsidence District, City of Houston, Fort Bend Subsidence District, Lone Star Groundwater Conservation District, and Brazoria County Groundwater Conservation District, is one in an annual series of reports depicting water-level altitudes and water-level changes in the Chicot, Evangeline, and Jasper aquifers and measured compaction of subsurface sediments in the Chicot and Evangeline aquifers in the Houston-Galveston region. The report contains maps depicting approximate 2014 water-level altitudes (represented by measurements made during December 2013–March 2014) for the Chicot, Evangeline, and Jasper aquifers; maps depicting 1-year (2013–14) water-level changes for each aquifer; maps depicting contoured 5-year (2009–14) water-level changes for each aquifer; maps depicting contoured long-term (1990–2014 and 1977–2014) water-level changes for the Chicot and Evangeline aquifers; a map depicting contoured long-term (2000–14) water-level changes for the Jasper aquifer; a map depicting locations of borehole-extensometer sites; and graphs depicting measured cumulative compaction of subsurface sediments at the borehole extensometers during 1973–2013. Tables listing the data used to construct each water-level map for each aquifer and the compaction graphs are included. In 2014, water-level-altitude contours for the Chicot aquifer ranged from 200 ft below the vertical datum (National Geodetic Vertical Datum of 1929 or the North American Vertical Datum of 1988; hereinafter, datum) in a small, localized area in southwestern Harris County to 200 ft above datum in western Montgomery County. Water-level changes for 2013–14 in the Chicot aquifer ranged from a 19-foot (ft) decline to a 31-ft rise. Contoured 5-year and long-term water-level changes in the Chicot aquifer ranged from an 80-ft decline to a 70-ft rise (2009–14), from a 120-ft decline to a 100-ft rise (1990–2014), and from a 120-ft decline to a 200-ft rise (1977–2014). In 2014, water-level-altitude contours for the Evangeline aquifer ranged from 300 ft below datum in two small, localized areas in south-central Montgomery County to 200 ft above datum in southeastern Grimes and northwestern Montgomery Counties. Water-level changes for 2013–14 in the Evangeline aquifer ranged from a 57-ft decline to a 47-ft rise. Contoured 5-year and long-term water-level changes in the Evangeline aquifer ranged from a 60-ft decline to a 100-ft rise (2009–14), from a 220-ft decline to a 240-ft rise (1990–2014), and from a 340-ft decline to a 260-ft rise (1977–2014). In 2014, water-level-altitude contours for the Jasper aquifer ranged from 250 ft below datum in south-central Montgomery County to 250 ft above datum in northwestern Montgomery County and extending into east-central Grimes and southwestern Walker Counties. Water-level changes for 2013–14 in the Jasper aquifer ranged from a 51-ft decline to a 40-ft rise. Contoured 5-year and long-term water-level changes in the Jasper aquifer ranged from a 100-ft decline to 40-ft rise (2009–14) and from a 220-ft decline to no change (2000–14). Compaction of subsurface sediments (mostly in the fine-grained clay and silt layers) composing the Chicot and Evangeline aquifers was recorded continuously by using analog technology at the 13 borehole extensometers at 11 sites that were either activated or installed between 1973 and 1980. For the period of record beginning in 1973 (or later depending on activation or installation date) and ending in December 2013, measured cumulative compaction at the 13 extensometers ranged from 0.100 ft at the Texas City-Moses Lake extensometer to 3.654 ft at the Addicks extensometer. The rate of compaction varies from site to site because of differences in rates of groundwater withdrawal in the areas adjacent to each extensometer site and differences among sites in the ratios of clay, silt, and sand and compressibility of the subsurface sediments. Therefore, it is not appropriate to extrapolate or infer a rate of compaction for an adjacent area on the basis of the rate of compaction measured at nearby extensometers.

Texas↗

USGS2014

USGS Field Activities 12BHM01, 12BHM02, 12BHM03, 12BHM04, and 12BHM05 on the West Florida Shelf, in February, April, May, June, and August 2012

Atmospheric carbon dioxide (CO 2 ) is absorbed by the ocean’s surface where it combines with seawater to form a weak, naturally occurring acid called carbonic acid (H 2 CO 3 ). Increasing carbon dioxide in the atmosphere results in the absorption of more CO 2 by the ocean and, therefore, increases in the acidity of seawater. This process, known as ocean acidification, has the potential to elicit change in ecosystems and organisms by disrupting biological processes. For example, ocean acidification is a problem for marine organisms such as corals, foraminifera, and algae that precipitate calcium carbonate to form their skeletons and shells (Kleypas and others, 2006). The effects are related to corresponding changes in the carbonate saturation state (Ω), where Ω is the ratio of the ion concentration product (Ca 2+ x CO 3 2- ) to the stoichiometric aragonite solubility product (K*sp) (Langdon and Atkinson, 2005). Because pH and CO 3 2- are strongly interdependent through the inorganic carbon system, the decrease in pH will cause a proportionally greater decrease in CO 3 2- . Globally, ocean acidification is occurring faster than at any time in the last 300 million years (Broeker and others, 1979). Recent evidence indicates that individual oceans are responding at different rates, depending on physical and biological processes. For example in the Arctic Ocean, the rate of saturation state decrease was 2.1 percent per year between 1997 and 2010 (Robbins and others., 2013) in an area as large as Montana, largely because of increases in melt of ice, versus the average rate observed for the Pacific Ocean (0.36 percent per year) (Feely and others, 2012). Unfortunately, comparative data sets over multiyear time frames are often not available because time series baseline carbon information has not been collected in many oceans. Data are needed in subtropical latitudes where carbonate saturation states are already naturally low and fluctuate seasonally. These data will help construct a baseline for the assessment of future changes. As part of the U.S. Geological Survey (USGS) Coastal and Marine Geology Program project "R esponse of Florida Shelf Ecosystems to Climate Change " and in partnership with Kendra Daly, University of South Florida ( USF ), data on surface ocean carbonate chemistry were collected on five cruises along transects on the shallow inner west Florida shelf and northern Gulf of Mexico in 2012. Data from the 2011 cruises were also published (Robbins and others., 2013). The data collected allows the USGS, National Oceanic and Atmospheric Administration ( NOAA ), and USF scientists to map variations in ocean chemistry including carbonate saturation states along designated tracks. The USGS also partners with NOAA and the National Aeronautics and Space Administration ( NASA ) to model air-sea flux as part of a Gulf of Mexico Carbon Synthesis project led by NASA.

Florida↗

USGS2004

Topographic Map of the Northwest Ascraeus Mons Region of Mars - MTM 500k 15/252E OMKT

This map is part of a series of topographic maps of areas of special scientific interest on Mars. The topography was compiled photogrammetically using Viking Orbiter stereo image pairs. The contour interval is 250 meters. Horizontal and vertical control was established using the USGS Mars Digital Image Model 2.0 (MDIM 2.0) and data from the Mars Orbiter Laser Altimeter (MOLA).

IMAP↗

USGS2004

Topographic Map of the Northeast Ascraeus Mons Region of Mars - MTM 500k 15/257E OMKT

IMAP↗

USGS2004

Topographic Map of the Southeast Ascraeus Mons Region of Mars - MTM 500k 10/257E OMKT

IMAP↗

USGS2004

Topographic Map of the Southwest Ascraeus Mons Region of Mars - MTM 500k 10/252E OMKT

IMAP↗

USGS1970

Water Resources Data for California, 1966, 1967, 1968; Part 3: Ground Water Records

Ground-water records for wells in California in which periodic measurements of water level have been made during the years 1966-68 are given in this report. The records were collected and processed by the U.S. Geological Survey, Water Resources Division, under the overall supervision of R. Stanley Lord, district chief in charge of water-resources investigations in California. Beginning with this report, water-level data will be released in the annual Geological Survey series "Water Resources Data for California." Prior records of water level and many additional well data are contained in the reports listed in the References section of this report. The observation-well program in California is carried on principally in cooperation with the several agencies listed on page III. In addition, several other agencies, also listed on page III, have provided data and their cooperation is gratefully acknowledged. Figure I shows, insofar as the map scale permits, the location of observation wells for which data are included in this report. The water-level records are arranged alphabetically by county, and for each county by valley or ground-water basin. Thus, each group of data pertains to a distinct ground-water area, as indicated by subheadings in the report. Under each subhead, the records are arranged numerically by well number.

California↗

USGS2018

A practical primer on geostatistics

Introduction The Challenge —Most geological phenomena are extraordinarily complex in their interrelationships and vast in their geographical extension. Ordinarily, engineers and geoscientists are faced with corporate or scientific requirements to properly prepare geological models with measurements involving a small fraction of the entire area or volume of interest. Exact description of a system such as an oil reservoir is neither feasible nor economically possible. The results are necessarily uncertain. Note that the uncertainty is not an intrinsic property of the systems; it is the result of incomplete knowledge by the observer. The Aim of Geostatistics —The main objective of geostatistics is the characterization of spatial systems that are incompletely known, systems that are common in geology. A key difference from classical statistics is that geostatistics uses the sampling location of every measurement. Unless the measurements show spatial correlation, the application of geostatistics is pointless. Ordinarily the need for additional knowledge goes beyond a few points, which explains the display of results graphically as fishnet plots, block diagrams, and maps. Geostatistical Methods —Geostatistics is a collection of numerical techniques for the characterization of spatial attributes using primarily two tools: probabilistic models, which are used for spatial data in a manner similar to the way in which time-series analysis characterizes temporal data, or pattern recognition techniques. The probabilistic models are used as a way to handle uncertainty in results away from sampling locations, making a radical departure from alternative approaches like inverse distance estimation methods. Differences with Time Series —On dealing with time-series analysis, users frequently concentrate their attention on extrapolations for making forecasts. Although users of geostatistics may be interested in extrapolation, the methods work at their best interpolating. This simple difference has significant methodological implications. Historical Remarks —As a discipline, geostatistics was firmly established in the 1960s by the French engineer Georges Matheron, who was interested in the appraisal of ore reserves in mining. Geostatistics did not develop overnight. Like other disciplines, it has built on previous results, many of which were formulated with different objectives in various fields. Pioneers —Seminal ideas conceptually related to what today we call geostatistics or spatial statistics are found in the work of several pioneers, including: 1940s: A.N. Kolmogorov in turbulent flow and N. Wiener in stochastic processing; 1950s: D. Krige in mining; 1960s: B. Mathern in forestry and L.S. Gandin in meteorology Calculations —Serious applications of geostatistics require the use of digital computers. Although for most geostatistical techniques rudimentary implementation from scratch is fairly straightforward, coding programs from scratch is recommended only as part of a practice that may help users to gain a better grasp of the formulations. Software —For professional work, the reader should employ software packages that have been thoroughly tested to handle any sampling scheme, that run as efficiently as possible, and that offer graphic capabilities for the analysis and display of results. This primer employs primarily the package Stanford Geomodeling Software (SGeMS) - recently developed at the Energy Resources Engineering Department at Stanford University - as a way to show how to obtain results practically. This applied side of the primer should not be interpreted as the notes being a manual for the use of SGeMS. The main objective of the primer is to help the reader gain an understanding of the fundamental concepts and tools in geostatistics. Organization of the Primer —The chapters of greatest importance are those covering kriging and simulation. All other materials are peripheral and are included for better comprehension of these main geostatistical modeling tools. The choice of kriging versus simulation is often a big puzzle to the uninitiated, let alone the different variants of both of them. Chapters 14, 18, and 19 are intended to shed light on those subjects. The critical aspect of assessing and modeling spatial correlation is covered in chapter 7. Chapters 2 and 3 review relevant concepts in classical statistics. Course Objectives —This course offers stochastic solutions to common problems in the characterization of complex geological systems. At the end of the course, participants should have: an understanding of the theoretical foundations of geostatistics; a good grasp of its possibilities and limitations; and reasonable familiarity with the SGeMS software, thus opening the possibility of practically applying geostatistics.

Open-File Report↗

USGS1999

Geologic map of the Barrymore Quadrangle (V-59), Venus

The Barrymore quadrangle (V–59) is a predominantly ridged plains region south of Imdr Regio, incorporating portions of Helen, Nuptadi, and Nsomeka Planitiae. The map area extends from lat 50°–75° S. and long 180°–240°, with nearly 70% coverage by cycle 1 synthetic aperture radar (SAR) images (left-look, incidence angles 16°–23°) and complete coverage by cycle 2 images (right-look, incidence angles 20°–25°) (fig. 1). The majority of the map area is covered by regional plains material that may either be smooth or deformed by wrinkle ridges or ridge belts of variable spacing. The difference in elevation between highest and lowest points in the map area is about 2.3 km. A north-south-oriented, 1,375-km linear ridge belt named “Saule Dorsa” is in the center of the region. The southern tip of this belt is intersected by a stratigraphically complicated, east-west-trending intermittent series of disrupted material, arcuate depressions and rises, regional plains, and volcanic centers. This region (hereafter referred to as the “east-west disrupted zone”) lies within a belt between 63°–67° S. extending from Kadlu Dorsa to Moombi Corona. A high concentration of canali-type channels (long sinuous lava channels that may contain subsidiary channels that branch off from the main channel [Baker and others, 1992; Komatsu and others, 1992]) occurs in Nsomeka Planitia. This includes Xulab Vallis and Citlalpul Valles, which form the eastern extent of a 3,000-km-long canali system (Komatsu and others, 1993). Three instances of canali bifurcation from north-south to east-west orientations occur in this region (fig. 2). Several large impact craters with fluidized ejecta blanket (FEB) outflows occur in the map area, along with some impact crater extended deposits (parabolas). The latter are mapped as surficial material using stipple patterns over the plains materials. These surficial deposits show variations in radar backscatter properties between cycle 1 and cycle 2 images related to orientation of aeolian dune or ripple faces (for example, Weitz and others, 1994; table 1). This region provides an interesting geologic setting for interpreting the history of regional and local plains formation and evolution, mainly due to development and subsequent deformation of the areally extensive plains units and accompanying canali (Komatsu and Baker, 1994).

IMAP↗

USGS2009

Hydrographs Showing Ground-Water Level Changes for Selected Wells in the Lower Skagit River Basin, Washington

Hydrographs for selected wells in the Lower Skagit River basin, Washington, are presented in an interactive web-based map to illustrate monthly and seasonal changes in ground-water levels in the study area. Ground-water level data and well information were collected by the U.S. Geological Survey using standard techniques and were stored in the USGS National Water Information System (NWIS), Ground-Water Site-Inventory (GWSI) System.

Data Series↗

USGS2010

Groundwater Levels for Selected Wells in the Chehalis River Basin, Washington

Groundwater levels for selected wells in the Chehalis River basin, Washington, are presented on an interactive web-based map to document the spatial distribution of groundwater levels in the study area during late summer 2009. Groundwater level data and well information were collected by the U.S. Geological Survey using standard techniques. The data are stored in the USGS National Water Information System (NWIS), Ground-Water Site-Inventory (GWSI) System.

Data Series↗

USGS2013

Geophysical logging and geologic mapping data in the vicinity of the GMH Electronics Superfund site near Roxboro, North Carolina

Geologic mapping, the collection of borehole geophysical logs and images, and passive diffusion bag sampling were conducted by the U.S. Geological Survey North Carolina Water Science Center in the vicinity of the GMH Electronics Superfund site near Roxboro, North Carolina, during March through October 2011. The study purpose was to assist the U.S. Environmental Protection Agency in the development of a conceptual groundwater model for the assessment of current contaminant distribution and future migration of contaminants. Data compilation efforts included geologic mapping of more than 250 features, including rock type and secondary joints, delineation of more than 1,300 subsurface features (primarily fracture orientations) in 15 open borehole wells, and the collection of passive diffusion-bag samples from 42 fracture zones at various depths in the 15 wells.

North Carolina↗