Search USGS⌕ Search

SEARCH · Search USGS

Results for “Map”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34Linked to original sources
USGS2016

Conflation and integration of archived geologic maps and associated uncertainties

Old, archived geologic maps are often available with little or no associated metadata. This creates special problems in terms of extracting their data to use with a modern database. This research focuses on some problems and uncertainties associated with conflating older geologic maps in regions where modern geologic maps are, as yet, non-existent as well as vertically integrating the conflated maps with layers of modern GIS data (in this case, The National Map of the U.S. Geological Survey). Ste. Genevieve County, Missouri was chosen as the test area. It is covered by six archived geologic maps constructed in the years between 1928 and 1994. Conflating these maps results in a map that is internally consistent with these six maps, is digitally integrated with hydrography, elevation and orthoimagery data, and has a 95% confidence interval useful for further data set integration.

Journal of Geography and Geology↗
USGS1978

Coastal mapping handbook

Passage of the Coastal Zone Management Act of 1972 focused attention on the Nation's coastal land and water areas. As plans for more effective management of the coastal zone evolved, it soon became apparent that improved maps and charts of these areas were needed. This handbook was prepared with the requirements of the entire coastal community in mind, giving greatest attention to the needs of coastal zone managers and planners at the State and local levels. Its principal objective is to provide general information and guidance; it is neither a textbook nor a technical manual, but rather a primer on coastal mapping. This handbook should help planners and managers of coastal programs to determine their mapping requirements, select the best maps and charts for their particular needs, and to deal effectively with personnel who gather data and prepare maps. The sections on "Sources of Assistance and Advice" and "Product and Data Sources" should be especially useful to all involved in mapping the coastal zone. Brief summaries of the mapping efforts of several State coastal zone management programs are included. "Future outlook" discusses anticipated progress and changes in mapping procedures and techniques. Illustrations are inserted, where appropriate, to illustrate the products and equipment discussed. Because of printing restrictions, the colors in map illustrations may vary from those in the original publication. The appendixes include substantial material which also should be of interest. In addition a glossary and an index are included to provide easy and quick access to the terms and concepts used in the text. For those interested in more technical detail than is provided in this handbook, the "Selected references" will be useful. Also, the publications of the professional societies listed in appendix 4 will provide technical information in detail.

Report↗
USGS1986

USGS NATIONAL MAPPING PROGRAM IN ALASKA--A STATUS REPORT.

The U. S. Geological Survey has been involved in mapping in Alaska since the late 1800's. The initial mapping projects were principally in support of geologic or hydrologic studies. In the late 1940's, responsibility for Alaska mapping was assigned to the Geological Survey's Rocky Mountain Mapping Center and a comprehensive and systematic mapping effort was undertaken. This effort was principally directed towards providing topographic map coverage of the State at 1:63,360 scale. In recent years, there has been a substantial increase in mapping activity in the State. Presently the National Mapping Program in Alaska includes 14 different production mapping activities and several information and cartographic assistance activities.

Conference Paper↗
USGS2009

Wildland-urban interface maps vary with purpose and context

Maps of the wildland-urban interface (WUI) are both policy tools and powerful visual images. Although the growing number of WUI maps serve similar purposes, this article indicates that WUI maps derived from the same data sets can differ in important ways related to their original intended application. We discuss the use of ancillary data in modifying census data to improve WUI maps and offer a cautionary note about this practice. A comparison of two WUI mapping approaches suggests that no single map is "best" because users' needs vary. The analysts who create maps are responsible for ensuring that users understand their purpose, data, and methods; map users are responsible for paying attention to these features and using each map accordingly. These considerations should apply to any analysis but are especially important to analyses of the WUI on which policy decisions will be made.

Journal of Forestry↗
USGS2014

Geopressure gradient maps of Southern Louisiana, state, and vicinity

This series of five maps characterizes the subsurface pressure system of southern Louisiana, including the associated State and Federal waters. These maps were generated using the U.S. Geological Survey’s (USGS) comprehensive geopressure-gradient model (Burke et al., 2012b, 2013) that delineates the regional pressure system spanning the onshore and offshore Gulf of Mexico basin, USA. Previously, the model was used to generate ten regional-scale maps (Burke et al., 2012a): five contour maps characterized the depth to the surface defined by the first occurrence of regional isopressure gradients ranging from 0.60 psi/ft to 1.00 psi/ft, in 0.10-psi/ft increments; and five supporting maps displayed the spatial density of the data used to construct the regional contour maps. Explanation of generalized geopressure gradients and pressure-regime nomenclature is given here. The five contour maps in this series characterize the depth to the surface defined by the first occurrence of isopressure gradients ranging from 0.60 psi/ft to 1.00 psi/ft, in 0.10-psi/ft increments. The geographical extent of this geopressure-gradient model is delineated on the maps, which encompass one of the most densely drilled regions of southern Louisiana and adjacent areas. The boundary of the model represents the area of greatest well density to maintain accurate contouring to the edge of the model. The pressure data were obtained from the IHS database (IHS Energy Group, 2011) and geologic folios (Dodge and Posey, 1981; Bebout and Gutiérrez, 1982; 1983; Eversull, 1984; Foote et al., 1990), which were compiled and digitally archived (Burke et al., 2011). Data quality analysis, linear-pressure interpolation calculations, and contouring algorithms defining the geopressure-gradient model are described by Burke et al. (2012b, 2013). The isopressure-gradient trends depicted on these maps are not intended for detailed interpretation at specific locations.

Louisiana↗
USGS2011

An open-water electrical geophysical tool for mapping sub-seafloor heavy placer minerals in 3D and migrating hydrocarbon plumes in 4D

A towed-streamer technology has been developed for mapping placer heavy minerals and dispersed hydrocarbon plumes in the open ocean. The approach uses induced polarization (IP), an electrical measurement that encompasses several different surface-reactive capacitive and electrochemical phenomena, and thus is ideally suited for mapping dispersed or disseminated targets. The application is operated at sea by towing active electrical geophysical streamers behind a ship; a wide area can be covered in three dimensions by folding tow-paths over each other in lawn-mower fashion. This technology has already been proven in laboratory and ocean settings to detect IP-reactive titanium- and rare-earth (REE) minerals such as ilmenite and monazite. By extension, minerals that weather and accumulate/concentrate by a similar mechanism, including gold, platinum, and diamonds, may be rapidly detected and mapped indirectly- even when dispersed and covered with thick, inert sediment. IP is also highly reactive to metal structures such as pipelines and cables. Currently, the only means for mapping an oil-spill plume is to park a large ship in the ocean and drop a sampling string over the side, requiring hours of time per sampling point. The samples must then be chemically analyzed, adding additional time and expense. We believe that an extension of the marine IP technology could also apply to rapidly mapping both seafloor- blanket and disseminated hydrocarbon plumes in the open ocean, as hydrocarbon droplets in conductive seawater are topologically equivalent to a metal-plates-and-dielectric capacitor. Because the effective capacitance would be frequency-dependent on droplet size, the approach we advocate holds the potential to not only map, but also to characterize the evolution and degradation of such a plume over time. In areas where offshore oil field development has been practiced for extended periods, making IP measurements from a towed streamer may be useful for locating buried - nd exposed pipelines, as well as pipeline leaks. We believe this technique will be a more cost-effective method than drop-sampling to map and monitor hydrocarbon plumes in open ocean settings. A marine induced polarization system was used successfully to map a 15 km × 45 km swath of the ocean floor off eastern South Africa with 3-meter sampling along 200-meter-separated profiles. The survey detected titanium-bearing sands up to 15 meters below the seafloor. From preliminary laboratory work it is apparent that we can extend this technology to monitor significant environmental problems including anthropogenic and industrial waste washed into sensitive estuaries and sounds during storm-water runoff episodes, and also to map and characterize dispersed oil plumes in the seawater column in three dimensions, as well as movement and dispersal of both over time.

Conference Paper↗
USGS2008

Seismic hazard mapping of California incorporating spatial variability of site conditions

The U.S. Geological Survey has recently released a 2008 version of the probabilistic National Seismic Hazard Maps. These maps plot the peak ground acceleration (PGA) and spectral acceleration (SA) ordinates at 0.2 and 1.0 sec with 2% and 10% probabilities of being exceeded in 50 years, corresponding to earthquake return periods of about 2,475 and 475 years, respectively. These acceleration levels were computed for uniform “firm rock” site conditions, i.e., 760 m/sec average shear-wave velocity in the upper 30 m, and therefore these maps do not show the potential spatial variability of ground motion associated with different site conditions, so we have combined the USGS National Seismic Hazard model with the California showing 17 generalized geologic units geologic units that can be defined by their shear-wave velocity (Wills and Clahan 2006), we regrouped these units into to 7 shear-wave velocities. At each shear-wave velocity value, a probabilistic seismic hazard map was generated for the entire state. By combining seismic hazard maps based on the 7 different shear-wave velocity values, a suite of seismic hazard maps was computed for California for 0.2 and 1.0 sec spectral ordinates at 2% probability of being exceeded in 50 years. The improved maps thus explicitly incorporate the site effects and their spatial variability on ground motion estimates. The SA at 1.0 sec map of seismic shaking potential for California has been now published as California Geological Survey Map Sheet 48, which is intended to be accessible and understandable to the general public.

California↗
USGS2017

Tools for mapping ecosystem services

Mapping tools have evolved impressively in recent decades. From early computerised mapping techniques to current cloud-based mapping approaches, we have witnessed a technological evolution that has facilitated the democratisation of Geographic Information Systems (GIS). These advances have impacted multiple disciplines including ecosystem service (ES) mapping. The information that feeds different mapping tools is also increasingly accessible and complex. In this chapter, we review the evolution of mapping tools that are shaping the field of ES mapping together with the different sources of information that exist at this point. We discuss briefly the suitability of these approaches for mapping different ES types and for different scientific and policy aims. Finally, we elaborate on the integration of multiple tools (from desktop applications to sensor, web-based, or mobile devices) and on the future developments of these methods and the possibilities they may open for ES mapping.

Book chapter↗
USGS1990

Coastal mapping programs at the U.S. Fish and Wildlife Service's National Wetlands Research Center

Over the past 10 years, the U.S. Fish and Wildlife Service's (FWS) National Wetlands Research Center (center; formerly the National Coastal Ecosystems Team) has been continuously involved in the production of maps for use by coastal decision makers. The types of maps produced by the center have been national, regional, or local in scope depending on user needs. Map scales have ranged from 1:24,000 to 1:250,000. Themes depicted have included biological resources, including wetlands and seagrasses; upland habitat or land use; water resources such as water quality, bathymetry, and salinity; cultural features such as ownership, archaeological sites, and dredge-spoil disposal areas; and soils and landforms. We present overviews on the various mapping programs of the center. We highlight efforts such as the ecological inventories of the Atlantic, Gulf, and Pacific coasts; the ecological characterization atlases of the Gulf of Mexico; and the large scale (1:24,000) habitat maps of various coastal regions of the United States. Center methods and techniques are discussed, including the collaborative efforts between the center and FWS's National Wetlands Inventory for updating wetland maps and adding upland and seagrass bed delineations to inventory maps. We also make recommendations for future coastal ecosystem mapping programs that use conventional and automated mapping methodologies, such as geographic information systems and image processing.

Biological Report↗
USGS2000

Geologic map of the Lima 30’ x 60’ quadrangle, southwest Montana

This geologic map represents a compilation of mostly previously unpublished maps by numerous authors. The map is divided into three areas of responsibility: 1) the Tendoy Mountains and western Centennial Mountains, mapped and compiled by Betty Skipp, Susanne Janecke, and Bill Perry (Part A); 2) the Snowcrest Range, mapped by Edward T. Ruppel (Part B), and 3) the remainder of the area, including the Sage Creek basin, the Red Rock Hills, the Blacktail Range, and the Upper Blacktail Deer Creek valley, compiled and mapped by Jeff Lonn and Jim Sears, with data also contributed by Bill Fritz, Hugh Hurlow, and Rob Thomas (Part C). Figure 1 shows mapping responsibilities. The geologic map (Plate 1) is accompanied by this text pamphlet describing map units for each of the three areas. The same lithologic distinctions among units and the same unit labels were used where possible, usually where formal stratigraphic nomenclature existed, but each area has its own informal Tertiary and Quaternary stratigraphy. References are also given separately in each section. However, correlation diagrams for each of the three areas are shown in a single Correlation Chart for the whole quadrangle (Figure 2). Plate 2, at the same scale, is provided in order to show more readily the names being applied to specific faults and folds, particularly in the Tendoy Mountains and western Centennial Mountains.

Montana↗
USGS2023

UAS mapping of surface roughness and digital grain size to assess pre-dam removal baseline conditions along the mainstem Klamath River corridor below Iron Gate Dam, California

Surface roughness and grain size in river corridors are fundamental indicators of river hydraulics. In hydraulic models for coarse-grained rivers, the roughness parameter is often assumed to be related to a representative grain diameter. This paper documents a workflow for using aerial imagery and Structure-from-Motion (SfM) photogrammetry to map surface roughness and digital grain size (DGS) on gravel bars. In June 2022, an Uncrewed Aerial System (UAS) was used to collect aerial imagery at 7 study sites distributed longitudinally downstream from Iron Gate Dam along the mainstem Klamath River. The study sites were selected for repeat monitoring as part of a larger effort to monitor post-dam removal response of the Klamath River to a temporary increase in fine-sediment flux. Advantages of SfM, in comparison to other methods used to acquire high-resolution topography data, is the ability to generate topographic data and orthophotos for DGS analysis from imagery easily collected at multiple spatial scales. UAS imagery was collected at three altitudes (62-m, 15-m, and 4-m), and a workflow for creating georeferenced surface roughness and grain size maps at the patch (100 m2) to site-scale (100,000 m2) was developed. The multi-scale UAS imagery was post-processed, and Digital Surface Models (DSMs) and orthophotos were exported, using AgiSoft Metashape Professional and standardized SfM methods. The DSMs were detrended using an automated tools implemented in ArcGIS to remove bedform gradients and the reach slope. Surface roughness maps were created using the standard deviation of detrended elevations. Plots for DGS analysis were randomly selected from the orthophotos, and DGS was estimated using a wavelet-based method, which minimizes surface disturbance and does not require calibration. For the 62-m survey, the grid-cell resolutions for the DSMs and surface roughness maps was 4 cm, and the orthophotos have a resolution of 2 cm. For the 15-m survey, the resolution of the DSMs and surface roughness maps was 8 mm, and the orthophotos have a resolution of 4 mm. For the 4-m survey, the resolution of the DSMs and surface roughness maps was 3 mm, and the orthophotos have a resolution of 2 mm. The surface roughness maps for the 62-m, 15-m, 4-m surveys provided surface roughness maps suitable for assessing variations in roughness heights across the study sites. The 15-m survey also provided orthophotos suitable for heads-up digitizing of coarse- and fine-grained facies. The 4-m survey provided orthophotos with the grains clearly resolved and suitable for DGS. The wavelet-based DGS analysis used in this study is most appropriate for assessing relative differences in the grain size distributions across a single site or among multiple sites, instead of absolute estimates. This workflow produced a series of digital products to support multi-scale investigations at resolutions appropriate for detecting textural changes in grain size on gravel bars and for producing roughness maps to define roughness parameters for hydraulic modeling.

California↗
USGS2026

Statewide surficial geologic map of Nebraska underscores Quaternary landscape evolution from the High Plains to the Central Lowland

Surficial geologic mapping in Nebraska has been conducted primarily at the 1:24,000 scale since the mid-1990s, although there have also been limited efforts to map generalized Quaternary and surficial geology within the state and the region. We compiled and evaluated disparate maps (1:24,000–1:1,000,000) and datasets—including geologic, soil and soil parent material, and geomorphic maps as well as LiDAR derivatives—to produce a single 1:500,000 scale surficial geologic map of Nebraska that is the first of its kind. This new map provides a coarse-scale surficial geologic map that will be incorporated into a nationwide U.S. Geological Survey Quaternary geologic map. It also reflects the variation and uniqueness of physical landscapes in the state, where the Great Plains and Central Lowland physiographic provinces meet, further developing a richer interdisciplinary understanding of regional geomorphology in the heart of North America.

Nebraska↗
USGS1986

Map showing slope movements in the Oak Forest Quadrangle, Greene County, southwestern Pennsylvania

This map is the first example in the eastern United States of a 1:24,000-scale 7.5– minute quadrangle map that identifies areas with slope—stability problems in detail. Such a map enables the user to make a rapid evaluation of the potential for mass movement. Furthermore, detailed slope movement inventory of this type can serve as a framework for statistical analyses of several factors that cause slope failures, such as the effects of bedrock lithology, soil and slope characteristics, and precipitation. Planners, engineers, soil scientists, geologists, and elected officials should find the map useful in the assessment of slope hazards and planning for future land use. Final evaluation of any site within the quadrangle should be based on an examination by a soils engineer or an engineering geologist. Field investigations in the springs of 1981 and 1982 and the fall of 1981 involved nearly 60 days of traverses. The foot traverses were supplemented by the interpretation of the land surface on vertical black-and-white aerial photography flown in January and February of 1973 at a scale of nearly 1:24,000. Earlier aerial photography flown in June and July 1939 at a scale of 1:20,000 and more recent but significantly smaller scale photography (1:80,000) flown in June 1977 supplied additional documentation. More than 1,200 active or recently active and 900 older slope movements were identified. The geologic map of the Oak Forest quadrangle (Roen, 1972) is one of several geologic maps at a scale of 1:24,000 in eastern and central Greene County. Stone (1932) wrote an earlier report of the geology and mineral resources of Greene County. A series of reconnaissance landslide maps at 1:24,000 scale based mainly on aerial photographic interpretation included Greene and adjacent counties (Hackman and Thomas, 1978). Selection of the Oak Forest quadrangle for a more comprehensive study of the slope movements was based on the existence of a recent geologic map (Roen, 1972), sizeable tracts of both forested and non-forested land, nearby precipitation record stations, a large number of pipelines which could offer pertinent data, and good accessibility of terrain from secondary roads. Finally, Hackman and Thomas (1978) showed that the area was representative of any quadrangle in the northern part of the Dunkard basin in its distribution and density of slope movements. The quadrangle is located about 65 km southwest of Pittsburgh, Penn. (fig. 1). Three distinct drainage systems (north, east, and south trending) are represented within the quadrangle (fig. 2).

Pennsylvania↗
USGS1988

Map showing locations of mines, prospects, and patented mining claims, and classification of mineral deposits in the Silver City 7 1/2-minute Quadrangle, Black Hills, South Dakota

This map is one in a set of 26 maps (see index map) at 1:24,000 scale of the Black Hills region of South Dakota and Wyoming om which are shown a geologic classification of mines, a bibliography of mineral deposits, and locations of active and inactive mines, prospects, and patented mining claims. Some of these maps are published as U. S. Geological Survey Miscellaneous Field Studies Maps (MF series) and some as U.S. Geological Survey Open-File Reports (QF series); see index map. An earlier unpublished version of this set of maps was the data base from which plate 4 (scale 1:250,000) of DeWitt and others (1986) was compiled. Subsequent to that publication, the set has been revised and updated, and prospects and patented claims have been added. These revised and more detailed 1:24,000-scale maps should be used for the equivalent areas of plate 4 of DeWitt and others (1986).

South Dakota↗
USGS1994

Map showing seismicity and sandblows in the vicinity of New Madrid, Missouri

This is one of a series of five seismotectic maps of the seismically active New Madrid, Missouri, area (table 1; Wheeler and others, 1992). The map area centers near the sites of three great earthquakes that struck during the winter of 1811-12 (Fuller, 1912; Nuttli, 1973). These earthquakes and continuing subsequent seismicity rank the New Madrid area with Cherlevoix, Quebec, as the two most seismically active areas in North America east of the Rocky Mountains. The threat posed by New Madrid seismicity to the central United States makes the area the focus of many investigations (for examples, Heyl and McKeown, 1978; McKeown and Pakiser, 1982; Algemissen and Hopper, 1984; Hamilton and Johnston, 1990; Applied Technology Council, 1991; Johnston and others, 1992). The map area includes the most intense seismic activity in the New Madrid region. A seismotectic map shows some of the geologic and geophysical information needed to assess seismic hazard (Hadley and Devine, 1974; Pavoni, 1985). A previous seismotectonic map of the central Mississippi River valley (Heyl and McKeown, 1978) has had wide use for planning field surveys, as a base map for plotting data collected during single investigations, and for compiling a range of information. Since 1978 numcrous researchers have greatly advanced our knowledge of the geology and geophysics of the central Mississippi Valley. The New Madrid seismotectonic map folio updates approximately the south-central sixth of the central Mississippi Valley seismotectonic map of Heyl and McKeown (1978).

Missouri↗
USGS1972

Preliminary photointerpretation map of landslide and other surficial deposits of the Mount Hamilton quadrangle and parts of the Mount Boardman and San Jose quadrangles, Alameda and Santa Clara Counties, California

The nine San Francisco Bay region counties lie within a geologically active, young, and dynamic part of the central and northern Coast Ranges of California. Significant movements of the earth's crust are occurring here at the present time, posing numerous problems to urbanization, including some of special concern. Geological processes such as fault movements, earthquakes, land subsidence, landsliding, slow downslope movement of bedrock and surficial materials, coastal and stream erosion, flooding, and sedimentation are all potentially hazardous. Because of these factors, an understanding of the operation of physical processes in the bay region is desirable for harmonious, efficient, and safe land-use planning, particularly now, with greatly expanded pressures for urban growth. This map presents preliminary information about one aspect of the physical environment necessary to sound land-use planning--the nature and distribution of surficial deposits. Because surficial deposits are common and well developed in much of the bay region, it is useful to know how and why they have formed, as well as what properties they possess. When maps like this are used in combination with other types of environmental information, such as data on soils, bedrock geology, slopes, vegetation, climatic variation, seismic response, and hydrology, it should be easier to arrive at sound decisions regarding the physical aspects of land use. The U.S. Geological Survey is studying many of these factors in the bay region and hopes to provide the community with much of the required information as part of its San Francisco Bay Region Study in cooperation with the Department of Housing and Urban Development. The representation of surficial deposits on this map reflects the way in which a geologist, working exclusively with aerial photographs, interpreted the origin of various elements of the present landscape. The deposits shown here have not been examined in the field. However, by viewing overlapping vertical aerial photographs through a stereoscope, the geologist sees a three-dimensional relief model of the ground surface and can study and interpret the origins of landforms with considerable ease. In fact, for mapping surficial deposits, particularly in reconnaissance-type studies, photointerpretation has advantages over both ground observations and laboratory studies of surficial materials. Of course, better information can be provided when all aspects of the study are integrated. These preliminary photointerpretation maps are only the first stage in a detailed study of surficial deposits in the bay region, but they should provide land-use planners with immediately useful information about the regional distribution of landslide and other surficial deposits. This map indicates the dominant surficial processes that have probably been operative by showing the distribution of different types of surficial deposits. Processes such as weathering, erosion, sedimentation, and the slow as well as rapid downslope movement of earth materials have constantly reshaped the land surface in the past and will continue to in the future, although at varying rates. The processes are interrelated to varying degrees. For example, crustal uplift of the Coast Ranges will lead to increased erosion and downcutting by streams that in turn generally results in increased deposition of sediments in river valleys, lakes, and shoreline areas. Older flood planes and river deposits may be eroded, leaving elevated terrace deposits. In addition, downcutting by streams may cause adjacent slopes to become unstable, thereby increasing the possibility of slope failures. Man's activities can alter natural physical processes in many ways. Simple acts such as overwatering a lawn or placing a septic tank drainfield in ground that is marginally stable may weaken the bedrock and surficial materials enough to induce landsliding. Relatively stable areas may be made unstable as a result of construction activities that involve cutting or oversteepening of natural slopes. Engineers, builders, conservationists, and others concerned with land use must evaluate the potential effects of all types of development, and maps that show the nature and distribution of surficial deposits should provide much of the basic information they need. This map, then, shows the cumulative effects of various processes that have yielded surficial deposits up to the time the photographs used for photointerpretation were taken. It does not indicate directly areas where processes will be most active, nor does it show the rate at which they will operate. However, knowledge of the history of geologic events is a key to understanding and predicting the evolution of an area, even where man's activities significantly change the character of the land. Almost all new landslides, for example, occur in areas with a history of landslide activity.

California↗
USGS2004

NADM Conceptual Model 1.0 -- A Conceptual Model for Geologic Map Information

Executive Summary -- The NADM Data Model Design Team was established in 1999 by the North American Geologic Map Data Model Steering Committee (NADMSC) with the purpose of drafting a geologic map data model for consideration as a standard for developing interoperable geologic map-centered databases by state, provincial, and federal geological surveys. The model is designed to be a technology-neutral conceptual model that can form the basis for a web-based interchange format using evolving information technology (e.g., XML, RDF, OWL), and guide implementation of geoscience databases in a common conceptual framework. The intended purpose is to allow geologic information sharing between geologic map data providers and users, independent of local information system implementation. The model emphasizes geoscience concepts and relationships related to information presented on geologic maps. Design has been guided by an informal requirements analysis, documentation of existing databases, technology developments, and other standardization efforts in the geoscience and computer-science communities. A key aspect of the model is the notion that representation of the conceptual framework (ontology) that underlies geologic map data must be part of the model, because this framework changes with time and understanding, and varies between information providers. The top level of the model distinguishes geologic concepts, geologic representation concepts, and metadata. The geologic representation part of the model provides a framework for representing the ontology that underlies geologic map data through a controlled vocabulary, and for establishing the relationships between this vocabulary and a geologic map visualization or portrayal. Top-level geologic classes in the model are Earth material (substance), geologic unit (parts of the Earth), geologic age, geologic structure, fossil, geologic process, geologic relation, and geologic event.

Open-File Report↗
USGS2005

Geologic and geophysical maps of the Las Vegas 30' x 60' quadrangle, Clark and Nye counties, Nevada, and Inyo County, California

Las Vegas and Pahrump are two of the fastest growing cities in the US, and the shortage of water looms as among the greatest future problems for these cities. These new maps of the Las Vegas 30 x 60-minute quadrangle provide a geologic and geophysical framework and fundamental earth science database needed to address societal issues such as ground water supply and contamination, surface flood, landslide, and seismic hazards, and soil properties and their changing impact by and on urbanization. The mountain ranges surrounding Las Vegas and Pahrump consist of Mesozoic, Paleozoic and Proterozoic rocks. A majority of these rocks are Paleozoic carbonate rocks that are part of Nevada's carbonate rock aquifer province. The Spring Mountains represent a major recharge site in the province, where maximum altitude is 3,632 m (Charleston Peak) above sea level. Rocks in the Sheep and Las Vegas Ranges and Spring Mountains contain correlative, northeast-striking, southeast-verging thrust faults that are part of the Cretaceous, Sevier orogenic belt. These thrusts were offset during the Miocene by the Las Vegas Valley shear system (LVVSZ). We conducted new mapping in the Blue Diamond area, highlighting refined work on the Bird Spring thrust, newly studied ancient landslides, and gravity-slide blocks. We conducted new mapping in the Las Vegas Range and mapped previously unrecognized structures such as the Valley thrust and fold belt; recognition of these structures has led to a refined correlation of Mesozoic thrust faults across the LVVSZ. New contributions in the quadrangle also include a greatly refined stratigraphy of Paleozoic bedrock units based on conodont biostragraphy. We collected over 200 conodont samples in the quadrangle and established stratigraphic reference sections used to correlate units across the major Mesozoic thrust faults. Quaternary deposits cover about half of the map area and underlie most of the present urbanized area. Deposits consist of large coalescing alluvial fans that grade downslope to extensive areas of fine-grained sediment indicative of groundwater-discharge during the Pleistocene. In the central areas of Las Vegas and Pahrump valleys, Quaternary fault scarps associated with past ground-water discharge deposits suggest a genetic relationship. In collaboration with NBMG and University of Nevada, a variety of ages of gravelly alluvium are newly mapped using surficial characteristics and soil development, along with reassessment of previously published mapping during compilation. Reconnaissance geochronology (thermoluminescence and U-series) of eolian and authigenic components of surficial and buried soils and spring deposits is applied to test hypotheses of geomorphic and hydrologic response to climate change over the past 100 k.y.). The major structure in the Las Vegas quadrangle is the LVVSZ. Because the LVVSZ is concealed by thick basin-fill deposits of Quaternary and Tertiary age, it was characterized primarily based on geophysics. Likewise, the newly described State line fault system in Pahrump Valley has also been characterized by geophysics, where geophysically inferred structures correlate remarkably with surface structures defined by our new geologic mapping in the Mound Spring and Hidden Hills Ranch 7.5-minute quadrangles.

Scientific Investigations Map↗