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At least 757 records · Page 42Linked to original sources
USGS2020

Stratigraphic units of shallow unconsolidated deposits in Deadwood, South Dakota, delineated by real-time kinematic surveys

The City of Deadwood, South Dakota, has been working on a new archeological investigation in preparation for economic growth and expansion within the city limits, through the Deadwood Historic Preservation Office. During the excavation process, buried artifacts and historical features from the late 1800s have been uncovered. The stratigraphy of shallow unconsolidated deposits in the city of Deadwood, S. Dak., was surveyed on January 29, 2020, using real-time kinematic survey methods and described to identify variations in geologic material, thickness, and depth from the land surface in support of archeological studies by the city. The findings of the study will provide city managers and the public with reliable and impartial information for their use by advancing field or analytical methodology and understanding of hydrologic processes in the study area. The primary excavation site was surveyed, and stratigraphic units were delineated from changes in material properties or depositional environment. The primary excavation site consisted of nine stratigraphic units; however, some units were not consistent along the length of the excavation and pinched out along the cross section. Survey data points also were collected for artifacts and other sites of interest. The shallow surficial geology in the study area was affected by human construction, fires, and flooding.

South Dakota↗
USGS2020

Potentiometric surfaces, 2011–12, and water-level differences between 1995 and 2011–12, in wells of the “200-foot,” “500-foot,” and “700-foot” sands of the Lake Charles area, southwestern Louisiana

Water levels were determined in 90 wells to prepare 2011–12 potentiometric surfaces focusing primarily on the “200-foot,” 500-foot,” and “700-foot” sands of the Lake Charles area, which are part of the Chicot aquifer system underlying Calcasieu and Cameron Parishes of southwestern Louisiana. These three aquifers provided 34 percent of the total water withdrawn and 93 percent of the groundwater withdrawn in Calcasieu and Cameron Parishes in 2012 (84.5 million gallons per day [Mgal/d]). This work was completed by the U.S. Geological Survey, in cooperation with the Louisiana Department of Transportation and Development, to assist in developing and evaluating groundwater-resource management strategies. The highest water levels determined in wells screened in the “200-foot,” “500-foot,” and “700-foot” sands were about 8 feet (ft) above the National Geodetic Vertical Datum of 1929 (NGVD 29), 2 ft below NGVD 29, and 14 ft below NGVD 29, respectively, and were located in northwestern Calcasieu Parish. The lowest water levels determined in wells screened in the “200-foot,” “500-foot,” and “700-foot” sands were approximately 50, 80, and 70 ft below NGVD 29, respectively, and were located in the southern Lake Charles metropolitan area, to the west of Prien Lake, and between the cities of Lake Charles and Sulphur, respectively. The primary groundwater flow direction in these three aquifers was radially towards pumping centers overlying the water-level lows. Comparisons of water-level differences in 42 wells measured in 1995 and 2011–12 indicated that the maximum increases in water levels for wells screened in the “200-foot,” “500-foot,” and “700-foot” sands were approximately 7, 31, and 19 ft, respectively. Water-level increases coincided with a decline in total groundwater withdrawals during the period (about 25 Mgal/d from 1995 to 2012) from these sands. More specifically, withdrawals from the “500-foot” sand affected water levels in wells screened in the “200-foot” and “700-foot” sands because the three are hydraulically connected and withdrawals from the “500-foot” sand were greater by volume than withdrawals from the “200-foot” and “700-foot” sands.

Louisiana↗
USGS2021

Machine-learning predictions of redox conditions in groundwater in the Mississippi River Valley alluvial and Claiborne aquifers, south-central United States

Machine-learning models developed by the U.S. Geological Survey were used to predict iron concentrations and the probability of dissolved oxygen (DO) concentrations exceeding a threshold of 1 milligram per liter (mg/L) in groundwater in aquifers of the Mississippi embayment physiographic region. DO and iron concentrations are driven by and reflect the oxidation-reduction (redox) conditions in groundwater. Predictions from boosted regression trees, a type of machine-learning model, of iron concentration and DO threshold probability were used to categorize redox zones in the Mississippi River Valley alluvial aquifer (MRVA), middle Claiborne aquifer (MCAQ), and lower Claiborne aquifer (LCAQ). Model predictions indicated that DO concentrations greater than 1 mg/L are uncommon across the MRVA. DO events (where the predicted probability was greater than 0.5) tended to occur on the margins of the MRVA and in upland areas where MCAQ and LCAQ units crop out at the surface or are at shallow depth. Predicted iron concentrations were higher in the MRVA than in the MCAQ and LCAQ. Uncer­tainty in predicted iron concentrations tended to be high in areas where measured concentrations were also high, result­ing in small areas (encompassing less than 1.5 percent of the areal extent of the MRVA) of predicted iron concentrations that exceeded 100,000 micrograms per liter. Despite the large magnitude of overpredicted iron concentrations, the general proportion and spatial distribution of predicted iron concen­trations reflected observed concentrations in groundwater wells. Where the probability of exceeding a DO concentration of 1 mg/L was 0.8 or more and the iron concentration was less than 1,000 micrograms per liter, aquifers were catego­rized as oxic. Oxic conditions were mostly in the uplands where MCAQ and LCAQ units crop out at the margins of the modeled area. The MRVA was mostly anoxic, which was controlled by DO threshold probabilities less than 0.1. The predictions and redox zones support conceptual models of redox conditions in the Mississippi embayment. The MRVA is predominantly anoxic with high iron concentrations. In the Claiborne aquifers (including the MCAQ and LCAQ), groundwater flows along regional flow paths toward the axis of the Mississippi embayment (the approximate location of the Mississippi River), the residence time in the aquifer increases, DO is consumed, and iron concentrations generally increase. Elevated concentrations of trace elements, such as manganese and arsenic, are often associated with reducing conditions in anoxic and mixed anoxic zones, but other factors such as sediment mineralogy affect the occurrence and distribution of these constituents.

Alabama, Arkansas, Kentucky, Louisiana, Mississipp↗
USGS2021

Stratigraphic cross sections of the Mowry Shale and associated strata in the Wind River Basin, Wyoming

The Wind River Basin in Wyoming is one of many structural and sedimentary basins that formed in the Rocky Mountain foreland during the Laramide orogeny in the latest Cretaceous through the early Eocene. The basin (bounded by the Washakie, Owl Creek, and Bighorn uplifts on the north, the Casper arch on the east, the Granite Mountains uplift on the south, and Wind River uplift on the west) encompasses about 7,400 square miles in central Wyoming. The two stratigraphic cross sections presented in this report were constructed as part of a project carried out by the U.S. Geological Survey to characterize and evaluate the undiscovered continuous (unconventional) oil and gas resources of the Mowry Shale in the Wind River Basin in central Wyoming. The purpose of the cross sections is to show the stratigraphic relationship of the Mowry Shale and associated Lower and lowermost Upper Cretaceous strata in the Wind River Basin. These two cross sections were constructed using borehole geophysical logs from 41 wells drilled for oil and gas exploration and production, and one research well that was cored and logged by the U.S. Geological Survey. Both lines originate at Sheldon Dome in the northwestern part of the basin and end near Bates Creek in the extreme southeastern part of the basin. The stratigraphic interval extends from the uppermost part of the Upper Jurassic Morrison Formation to the basal part of the Upper Cretaceous Frontier Formation. The datum is the top of the Clay Spur Bentonite Bed, a distinctive bed at the top of the Upper Cretaceous Mowry Shale. A gamma ray and (or) spontaneous potential log was used in combination with a resistivity log to identify and correlate units.

Wyoming↗
USGS2022

Potentiometric surface, 2014–15, and water-level differences, 2009 to 2014–15, in the Chicot equivalent aquifer system in southeastern Louisiana

The U.S. Geological Survey constructed the potentiometric surface of the Upland terrace and upper Ponchatoula aquifers and the “400-foot” sand using the altitude of water levels from 121 wells measured January 2014 to March 2015. Differences in water levels in the Upland terrace and upper Ponchatoula aquifers and “400-foot” sand were measured at 55 wells in 2009 and again at the same wells in 2014–15. Long-term hydrographs for most wells screened in the Upland terrace aquifer and “400-foot” sand show seasonal fluctuations with little net change in water levels. The potentiometric surface of the “600-foot” sand was constructed by using the altitude of water levels from 14 wells measured from January 2014 to March 2015. Differences in water levels between 2009 and 2014–15 were determined in the “600-foot” sand by using measurements collected at seven wells. These differences do not necessarily indicate a trend but show water levels declined by more than 5 feet from 2009 to 2015. Long-term hydrographs for two wells screened in the “600-foot” sand show declines in water levels but vary in their drawdown and recovery based on location relative to areas of substantial groundwater withdrawal.

Louisiana↗
USGS2023

Stratigraphic cross sections of the Lewis Shale in the eastern part of the southwestern Wyoming Province, Wyoming and Colorado

Three stratigraphic cross sections A–A', B–B', and C–C' were created for the Lewis Shale and associated strata in the eastern part of the Southwestern Wyoming Province of Wyoming and Colorado. The cross sections highlight 15 clinothems within the Lewis Shale, Fox Hills Sandstone, and Lance Formation progradational system (also referred to as the Lewis Shale system). Additionally, the cross sections indicate that multiple source areas were active at the same time during deposition of the Lewis Shale. Specifically, the north-to-southeast cross section A–A' demonstrates that the northern, sand-rich source was being deposited and onlapping onto an older, southern, mud-rich source.

Colorado, Wyoming↗
USGS2024

Cross section N–N' through the Valley and Ridge province of the southern Appalachian basin, from Greene County, west-central Alabama, to Bibb County, central Alabama

Introduction Geologic cross section N–N′ is the sixth in a series of geologic cross sections constructed by the U.S. Geological Survey to document and improve understanding of the geologic framework and petroleum systems of the Appalachian basin. Cross section N–N′ provides a regional view of the structural and stratigraphic framework of the Appalachian basin in the Valley and Ridge province in western and central Alabama; it spans approximately 69 miles (mi) (111 kilometers [km]). This geologic cross section is a companion to geologic cross sections E–E′ , D–D′ , C–C′ , I–I′ , and A–A′ that are located approximately 350 to 550 mi (563 to 885 km) to the northeast. Cross section N–N' complements earlier geologic cross sections through the Alabama part of the Appalachian basin. Although some of the other cross sections show more structural and stratigraphic detail, they are of more limited extent geographically and stratigraphically. Cross section N–N′ contains information that is useful for evaluating energy resources in the Appalachian basin. Although the Appalachian basin petroleum systems are not shown on the cross section, many of their key elements (such as source rocks, reservoir rocks, seals, and traps) can be inferred from lithologic units, unconformities, and geologic structures shown on the cross section. Other aspects of petroleum systems (such as the timing of petroleum generation and petroleum migration pathways) may be evaluated by burial history, thermal history, and fluid flow models based on what is shown on the cross section. In addition, cross section N–N′ may be used as a reconnaissance tool to identify plausible geologic structures and strata for the subsurface storage of liquid waste or for the sequestration of carbon dioxide.

Alabama↗
USGS2015

Southern Salish Sea Habitat Map Series: Admiralty Inlet

In 2010 the Environmental Protection Agency, Region 10 initiated the Puget Sound Scientific Studies and Technical Investigations Assistance Program, designed to support research in support of implementing the Puget Sound Action Agenda. The Action Agenda was created in response to Puget Sound having been designated as one of 28 estuaries of national significance under section 320 of the U.S. Clean Water Act, and its overall goal is to restore the Puget Sound Estuary's environment by 2020. The Southern Salish Sea Mapping Project was funded by the Assistance Program request for proposals process, which also supports a large number of coastal-zone- and ocean-management issues. The issues include the recommendations of the Marine Protected Areas Work Group to the Washington State Legislature (Van Cleve and others, 2009), which endorses a Puget Sound and coast-wide marine conservation needs assessment, gap analysis of existing Marine Protected Areas (MPA) and recommendations for action. This publication is the first of four U.S. Geological Survey Scientific Investigation Maps that make up the Southern Salish Sea Mapping Project. The remaining three map blocks to be published in the future, located south of Admiralty Inlet, are shown in figure 1. Puget Sound is a deep, fjord-type estuary covering an area of 2,330 km 2 in the Pacific Northwest region of the United States (fig. 1). It is connected to the ocean by the Strait of Juan de Fuca, a turbulent passage approximately 160 km in length and 22 km wide at its west end, expanding to over 40 km wide at its east end (Thomson, 1994). During the Pleistocene, the area was occupied several times by lobes of continental ice, resulting in a complex basin-fill of glacial and interglacial deposits that are locally as thick as 1100 m (Johnson and others, 2001). The last glaciation, called the Fraser glaciation, began after 28,800±740 14 C yr B.P. when ice started a slow expansion (Clague, 1981). At peak advance the westward Juan de Fuca lobe reached the edge of the continental shelf through the Juan de Fuca Strait shortly before 14,460±200 14 C yr B.P. (Herzer and Bornhold, 1982). The southward Puget lobe advanced to its terminal position in Puget Sound by around 14,150 14 C yr B.P. (Porter and Swanson, 1998). Ice retreated from its maximum to northern Whidbey Island by 13,650±350 14 C yr B.P. (Dethier and others, 1995). Retreating glaciers resulted in a thick sequence of ice-contact, glacial-marine sediment, and early post-glacial sediments (Linden and Schurrer, 1988). These deposits have experienced the effects of a marine transgression followed by regression, resulting in a sea-level several tens of meters lower than the present day (Linden and Schurrer, 1988). A second transgression brought sea level to about the present level by around 5,470±120 14 C yr B.P. (Clague and others, 1982) establishing the present oceanographic and geologic environment Puget Sound is separated into four interconnected basins; Whidbey, Central (Main), Hood Canal, and South (Thomson, 1994). The Whidbey, Central, and Hood Canal basins are the three main branches of the Puget Sound estuary and are separated from the Strait of Juan de Fuca by a double sill at Admiralty Inlet. The Admiralty Inlet map area includes the Inlet and a portion of the Whidbey Basin (fig. 1). The shallower South Basin is separated by a sill at Tacoma Narrows and is highly branched with numerous finger inlets. Flow within Puget Sound is dominated by tidal currents of as much as 1 m/s at Admiralty Inlet, reducing to approximately 0.5 m/s in the Central Basin (Lavelle and others, 1988). The lack of silt and clay-sized sediments in the Admiralty Inlet map area is likely a result of the strong currents (see Ground-Truth Studies for the Admiralty Inlet Map Area, sheet 3). The subtidal component of flow reaches approximately 0.1 m/s and is driven by density gradients arising from the contrast in salty ocean water at the entrance and freshwater inputs from stream flow (Lavelle and others, 1988). The total freshwater input to Puget Sound is approximately 3.4 x 10 6 m 3 /day, primarily from the Skagit River (Cannon, 1983). The subtidal circulation mostly consists of a two-layered flow in the basins with fresher water exiting at the surface and saltier water entering at depth (Ebbesmeyer and Cannon, 2001). In general, surface waters flow north and deeper waters flow south; variations arise from wind effects that can drive a surface current in the same direction as the wind, and a baroclinic response in the lower layer to about 100-m depth (Matsuura and Cannon, 1997). Oceanographic properties are influenced by temporal forcing parameters such as reduced stream flow during the 2000-01 drought that increased surface salinity and decreased differences between surface and bottom waters (Newton and others, 2003). On offshore seismic-reflection profiles, Pleistocene strata (excluding latest Pleistocene glacial and post-glacial deposits) form a distinct seismic unit, bounded below by pre-Tertiary or Tertiary basement and above by typically flat-lying latest Pleistocene to Holocene deposits that fill in erosional or depositional relief (Johnson and others, 2001). Cores from central Puget Sound have accumulation rates that range from 85 to 1200 mg/cm 2 /yr, or 0.12 to 2.4 cm/yr; the highest accumulation rates are near the southern end of central Puget Sound (Carpenter and others, 1985). Carpenter and others (1985) un-weighted arithmetic mean of accumulation rates for central Puget Sound deeper stations is 480±340 (± one standard deviation) mg/cm 2 /yr. Lavelle and others (1985) also found rates as high as 1200 mg/cm 2 /yr over the past approximately 70 years in cores in the Central Basin off of and north and south of Elliott Bay. Puget Sound basin rates are comparable to rates in midshelf silt deposits on the Washington coast north of the Columbia River (Nittrouer and others, 1979). The deep subtidal (in other words, below SCUBA depths) habitats of Puget Sound are relatively poorly known. A few subtidal surveys exist for several habitat types from the 1960s and 1970s (reviewed in Dethier, 1990), using grab and box core data. The Dethier (1990) review divides habitat up into Coast and Marine Ecological Classification Standard (CMECS) substrate, water column energy, and depth zones but does not attempt to map these habitats, rather it is an inventory of habitats found in the area and the flora and fauna associated with each habitat. The approach of the Southern Salish Sea Mapping project is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data (the undersea equivalent of satellite remote-sensing data in terrestrial mapping), acoustic backscatter, seafloor video, seafloor photography, and bottom-sediment sampling data. This approach is based in part on methods presented and data collection and product needs identified at the Washington State Seafloor Mapping Workshop (Washington State Seafloor Mapping Workshop Steering Committee, 2008), attended by coastal and marine managers and scientists. The map products display seafloor geomorphology and substrate, and identify potential marine benthic habitats. It is emphasized that the more interpretive habitat and geology maps rely on the integration of multiple, new high-resolution datasets and that mapping at small scales would not be possible without such data. Oceanographic current and wave data is not included in this analysis, however, the accompanying geographic information system (GIS) data set is designed and intended to be combined with oceanographic and biologic data sets assembled by others in the future and some of the GIS data has already been incorporated in the unpublished Nature Conservancy Benthic Habitats of Puget Sound database. This publication includes four map sheets, explanatory text, and a descriptive pamphlet. Each map sheet is published as a portable document format (PDF) file. ESRI ArcGIS compatible geotiffs (for example, bathymetry) and shapefiles (for example video observation points) will be available for download in the data catalog associated with this publication (Cochrane, 2015). An ArcGIS Project File with the symbology used to generate the map sheets is also provided. For those who do not own the full suite of ESRI GIS and mapping software, the data can be read using ESRI ArcReader, a free viewer that is available at http://www.esri.com/software/arcgis/arcreader/index.html .

Washington↗
USGS2011

Mapping perennial vegetation cover in the Mojave Desert

Scientists with the U.S. Geological Survey's Western Geographic Science Center have recently created a regional map of perennial vegetation cover for the Mojave Desert. The scientists used existing field data collected for a variety of previous studies and satellite data available for free through USGS archives to create a calibrated model of percent vegetation cover, an important attribute of desert ecosystems. This map is being used to inform ongoing scientific investigations and land-management efforts, including endangered species habitat mapping and vulnerability and recoverability studies of desert landscapes in the arid Southwest.

California;Nevada;Utah;Arizona↗
USGS2018

Unmanned aerial systems capabilities of the U.S. Geological Survey Woods Hole Coastal and Marine Science Center

Unmanned aerial system (UAS) technology provides a rapid and low-cost solution for mapping coastal environments and assessing short- and long-term changes. The interdisciplinary nature of the data collected and the breadth of applications make UAS technology applicable to multiple scientific investigations. The Aerial Imaging and Mapping (AIM) group at the U.S. Geological Survey (USGS) Woods Hole Coastal and Marine Science Center provides UAS services to scientists to advance the science mission of the Coastal-Marine Hazards and Resources Program. Scientists at the Woods Hole Coastal and Marine Science Center use UASs to acquire imagery of coastal and wetland environments, which is then used to produce detailed topographic and visual reflectance datasets. UAS technology supports the work of geologists, engineers, physical scientists, geographers, and geochemists who study coastal erosion, sediment transport, storm impacts, habitats, biomass, and marsh stability.

Fact Sheet↗
USGS1993

Geologic map of science study area 8, Apollinaris Patera region of Mars

Volcanoes are among the most imposing and geologically interesting features on Mars. Nearly 60 percent of the planet’s surface is covered by volcanic rocks dating from the Early Noachian to Late Amazonian Epochs (Tanaka and others, 1988). This map of the volcano Apollinaris Patera and surrounding area is one of a series of large-scale (1:500,000) geologic maps initiated by the National Aeronautics and Space Administration to investigate areas of particular scientific interest. The areas selected for mapping contain candidate landing sites for future sample-return missions to Mars (fig. 1). The map area is considered to be of special scientific interest for several reason: (1) it includes the prominent volcano Apollinaris Patera, a type of volcanic edifice unusual on Mars in that it is not associated with significant faulting and is partly surrounded by a basal scarp similar to that of its much larger counterpart at the base of Olympus Mons; (2) it is located in a major transition zone between ancient highlands to the south and much of the younger lowland plains to the north; (3) rocks have different origins and a ide range of ages occurring in the area; and (4) erosional processes associated with fluvial, volcanic, and eolian activity have shaped the terrain. The map area’s potential as a landing site is increased by its extensive, relatively smooth areas at low elevation (0 to 1 km), which would permit access by an automated vehicle and atmospheric breaking by a landing craft.

IMAP↗
USGS2013

Optimization of water-level monitoring networks in the eastern Snake River Plain aquifer using a kriging-based genetic algorithm method

Long-term groundwater monitoring networks can provide essential information for the planning and management of water resources. Budget constraints in water resource management agencies often mean a reduction in the number of observation wells included in a monitoring network. A network design tool, distributed as an R package, was developed to determine which wells to exclude from a monitoring network because they add little or no beneficial information. A kriging-based genetic algorithm method was used to optimize the monitoring network. The algorithm was used to find the set of wells whose removal leads to the smallest increase in the weighted sum of the (1) mean standard error at all nodes in the kriging grid where the water table is estimated, (2) root-mean-squared-error between the measured and estimated water-level elevation at the removed sites, (3) mean standard deviation of measurements across time at the removed sites, and (4) mean measurement error of wells in the reduced network. The solution to the optimization problem (the best wells to retain in the monitoring network) depends on the total number of wells removed; this number is a management decision. The network design tool was applied to optimize two observation well networks monitoring the water table of the eastern Snake River Plain aquifer, Idaho; these networks include the 2008 Federal-State Cooperative water-level monitoring network (Co-op network) with 166 observation wells, and the 2008 U.S. Geological Survey-Idaho National Laboratory water-level monitoring network (USGS-INL network) with 171 wells. Each water-level monitoring network was optimized five times: by removing (1) 10, (2) 20, (3) 40, (4) 60, and (5) 80 observation wells from the original network. An examination of the trade-offs associated with changes in the number of wells to remove indicates that 20 wells can be removed from the Co-op network with a relatively small degradation of the estimated water table map, and 40 wells can be removed from the USGS-INL network before the water table map degradation accelerates. The optimal network designs indicate the robustness of the network design tool. Observation wells were removed from high well-density areas of the network while retaining the spatial pattern of the existing water-table map.

Idaho↗
USGS2007

Integration of seafloor point data in usSEABED

Sediments of the beach, nearshore, and continental shelves record a complex interplay of processes including wave energy and direction , currents, beach erosion or accretion, bluff or cliff retreat, fluvial input, sediment longshore and cross-shelf transport processes, contaminant content and transport, sediment sources and sinks, and others. In turn, sediments and rocks modify wave patterns, affect recreation and tourism, and provide habitat for fish, epifauna, and infauna. Character of the surficial seafloor also influences navigation, commercial and recreational fishing and gathering of other food sources, communication, piplines, national defense, and provides geologic resources including sand and gravel aggregates, minerals, and real or potential energy sources. The beaches, nearshore, and continental margins fall under overlapping levels of managerial responsibility between Federal, State, regional, and local government agencies and consortia. In addition, universities and other academic institutions investigate these places for pure or applied scientific reasons. Mapping is usually the first step in understanding any issue and is often comprised of remotely gathered geophysical data such as bathymetry and backscatter imagery, and groundtruthing; that is, the collection of physical and virtual samples to tie the remotely gathered data to reality. The physical samples are described and (or) carefully analyzed for grain-size information -- which records both the site's physical conditions and geologic past -- and commonly, for constituent components such as mineral and rock types (to determine onland sources and in situ chemical processes), carbonate and organic content and microfossils (for biological and oceanographic influences), and structure such as layering and bioturbation (for physical influences). The samples may also be subjected to physical tests such as comp[action analyses, liquefaction or plasticity limits, ans other parameters important when considering construction of offshore structures. In recent years, virtual sampling of the seafloor has become popular, through the use of towed video or photographic equipment and the addition of camera to oceanographic equipment such as corers and tripods. Before about ten years ago, most maps were made by hand. Recently, with the advent of desktop GIS packages, map making and resource analysis can be done nearly "on-the-fly" if geographically located data exist. While the problems of projection, scale, and resolution of digitized paper maps are commonly known amongst GIS-users, access to the original underlying point data allows for maps to be regenerated for digital use using statistically proven methods, provides increasing data density by including multiple studies, as well as allows the point data to be used in other ways than just mapping. These point data may be available in raw or refined or in worded descriptions. Raw data such as granulometric analyses can be manipulated through the use of known equations or empirical relationships to provide information about other parameters of the sediment, such as mean grainsize, sorting, erodability, or rugosity. If refined data are presented such as gravel, sand, and mud percentages, the parameter noted earlier may be estimated. In the case of worded descriptions, values for geologic terms can be assigned, for example, "fine sand" equate to 0.2 mm sized particles, to provide numeric terms for GIS or modeling purposes.

Conference Paper↗
USGS2009

Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971-2007

To address questions concerning ongoing geomorphic processes in the St. Clair River, selected bathymetric datasets spanning 36 years were analyzed. Comparisons of recent high-resolution datasets covering the upper river indicate a highly variable, active environment. Although statistical and spatial comparisons of the datasets show that some changes to the channel size and shape have taken place during the study period, uncertainty associated with various survey methods and interpolation processes limit the statistically certain results. The methods used to spatially compare the datasets are sensitive to small variations in position and depth that are within the range of uncertainty associated with the datasets. Characteristics of the data, such as the density of measured points and the range of values surveyed, can also influence the results of spatial comparison. With due consideration of these limitations, apparently active and ongoing areas of elevation change in the river are mapped and discussed.

Michigan;Ontario↗
USGS2023

Preliminary machine learning models of manganese and 1,4-dioxane in groundwater on Long Island, New York

Manganese and 1,4-dioxane in groundwater underlying Long Island, New York, were modeled with machine learning methods to demonstrate the use of these methods for mapping contaminants in groundwater in the Long Island aquifer system. XGBoost, a gradient boosted, ensemble tree method, was applied to data from 910 wells for manganese and 553 wells for 1,4-dioxane. Explanatory variables included soil properties, groundwater flow, land use, and other features that describe the hydrogeology and geochemistry of the aquifer system. Four models were developed to predict the probability of manganese concentrations greater than a detection level of 10 micrograms per liter (μg/L) and greater than three threshold concentrations (50, 150, and 300 μg/L) relevant to drinking-water quality. One model was developed to predict the probability of 1,4-dioxane concentrations greater than a detection level of 0.07 μg/L. The 1,4-dioxane model was limited geographically to Suffolk County because of data availability. Predictions were made for two layers in the upper glacial aquifer and three layers in the Magothy aquifer, which are the upper two of the three major aquifers of the Long Island aquifer system. The objective of the study described in this report was to demonstrate the application of the methods rather than to develop precise estimates of manganese or 1,4-dioxane concentrations at any given location. The predictive models developed in the study are considered preliminary in the sense that they are an initial effort at developing these kinds of models specifically for Long Island. The models could be improved by the inclusion of additional data, by the use of methods to improve the modeling of infrequent high concentrations of manganese and 1,4-dioxane (above threshold concentrations), and by including more explanatory variables that specifically describe conditions and contaminant sources on Long Island. Nonetheless, the distribution of model predictions and the influence of explanatory variables in the models were consistent with the expected relations between contaminant concentrations and groundwater-flow-system characteristics and the distribution of manmade sources. Mapped predictions indicated that manganese detections were more probable in the upper glacial aquifer and along the southern shore of Long Island, consistent with the distribution of anoxic conditions in groundwater in the Long Island aquifer system. Manganese was infrequently predicted at concentrations greater than thresholds of concern for drinking-water quality in any of the aquifer layers. Detections of 1,4-dioxane were predicted in the western, more highly developed parts of Suffolk County, in the upper glacial aquifer and the top and middle layers of the Magothy aquifer, and in northwestern Suffolk County in the bottom layer of the Magothy aquifer. Although preliminary in nature and based on limited data, these mapped predictions can be used to generally identify areas where manganese and 1,4-dioxane may be present at concentrations of concern to prioritize areas for future monitoring and to guide future modeling and mapping efforts.

New York↗
USGS2004

Thrust-induced collapse of mountains-an example from the "Big Bend" region of the San Andreas Fault, western Transverse Ranges, California

Mount Pinos and Frazier Mountain are two prominent mountains just south of the San Andreas fault in the western Transverse Ranges of southern California, a region that has undergone rapid Quaternary contraction and uplift. Both mountains are underlain, at least in part, by thrusts that place granitic and gneissic rocks over sedimentary rocks as young as Pliocene. Broad profiles and nearly flat summits of each mountain have previously been interpreted as relicts of a raised erosion surface. However, several features bring this interpretation into question. First, lag or stream gravels do not mantle the summit surfaces. Second, extensive landslide deposits, mostly pre?Holocene and deeply incised, mantle the flanks of both mountains. Third, a pervasive fracture and crushed?rock network pervades the crystalline rocks underlying both mountains. The orientation of the fractures, prominent in roadcuts on Mount Pinos, is essentially random. 'Hill?and?saddle' morphology characterizes ridges radiating from the summits, especially on Mount Pinos; outcrops are sparse on the hills and are nonexistent in the saddles, suggesting fractures are concentrated in the saddles. Latest movement on the thrusts underlying the two mountain massifs is probably early Quaternary, during which the mountains were uplifted to considerably higher (although unknown) elevations than at present. A model proposes that during thrusting, ground accelerations in the hanging wall, particularly near thrust tips, were high enough to pervasively fracture the hanging?wall rocks, thereby weakening them and producing essentially an assemblage of loose blocks. Movement over flexures in the fault surface accentuated fracturing. The lowered shear stresses necessary for failure, coupled with deep dissection and ongoing seismic activity, reduced gravitational potential by spreading the mountain massifs, triggering flanking landslides and producing broad, flat?topped mountains. This study developed from mapping in the western Transverse Ranges as part of the U.S. Geological Survey's Southern California Areal Mapping Project (SCAMP).

California↗
USGS2005

Potentiometric surface of the Ozark aquifer in northern Arkansas, 2004

The Ozark aquifer in northern Arkansas comprises dolomites, limestones, sandstones, and shales of Late Cambrian to Middle Devonian age, and ranges in thickness from approximately 1,100 feet to more than 4,000 feet. Hydrologically, the aquifer is complex, characterized by discrete and discontinuous flow components with large variations in permeability. The potentiometric-surface map, based on 59 well and 5 spring water-level measurements collected in 2004 in Arkansas and Missouri, indicates maximum water-level altitudes of about 1,188 feet in Benton County and minimum water-level altitudes of about 116 feet in Randolph County. Regionally, the flow within the aquifer is to the south and southeast in the eastern and central part of the study area and to the northwest and north in the western part of the study area. Comparing the 2004 potentiometric- surface map with a predevelopment potentiometricsurface map indicates general agreement between the two surfaces. Potentiometric-surface differences could be attributed to differences in pumping related to changing population from 1990 to 2000, change in source for public supplies, processes or water use outside the study area, or differences in data-collection or map-construction methods.

Scientific Investigations Report↗
USGS2008

Cartography for lunar exploration: 2008 status and mission plans

The initial spacecraft exploration of the Moon in the 1960s-70s yielded extensive data, primarily in the form of film and television images, which were used to produce a large number of hardcopy maps by conventional techniques. A second era of exploration, beginning in the early 1990s, has produced digital data including global multispectral imagery and altimetry, from which a new generation of digital map products tied to a rapidly evolving global control network has been made. Efforts are also underway to scan the earlier hardcopy maps for online distribution and to digitize the film images so that modern processing techniques can be used to make high-resolution digital terrain models (DTMs) and image mosaics consistent with the current global control. The pace of lunar exploration is accelerating dramatically, with as many as eight new missions already launched or planned for the current decade. These missions, of which the most important for cartography are SMART-1 (Europe), Kaguya/SELENE (Japan), Chang'e-1 (China), Chandrayaan-1 (India), and Lunar Reconnaissance Orbiter (USA), will return a volume of data exceeding that of all previous lunar and planetary missions combined. Framing and scanner camera images, including multispectral and stereo data, hyperspectral images, synthetic aperture radar (SAR) images, and laser altimetry will all be collected, including, in most cases, multiple data sets of each type. Substantial advances in international standardization and cooperation, development of new and more efficient data processing methods, and availability of resources for processing and archiving will all be needed if the next generation of missions are to fulfill their potential for high-precision mapping of the Moon in support of subsequent exploration and scientific investigation.

The International Archives of the Photogrammetry, ↗