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At least 1,441 records · Page 80Linked to original sources
USGS2021

Hydrographic and benthic mapping—St. Croix National Scenic Riverway—Osceola landing

High-resolution topographic and bathymetric mapping can assist in the analysis of river habitat. The National Park Service has been planning to relocate a boat ramp along the St. Croix River in Minnesota, across the river from the town of Osceola, Wisconsin, to improve visitor safety, improve operations for commercial use, enhance the overall visitor experience, and eliminate deferred maintenance at the landing. This landing grants access to the St. Croix River, which is a part of the National Park Service St. Croix National Scenic Riverway. Hydrographic and topographic surveys were needed to determine where the new location should be. The objective for these surveys was to provide baseline information in order to assess the direct effects of the landing relocation on physical habitat in areas adjacent to Osceola, Wisconsin. The study area for these surveys was about 18.5 hectares and located directly off the existing landing. Although the existing boat launch is referred to as the Osceola landing, it is located on the Minnesota side of the river and is the busiest National Park Service landing on the St. Croix River (National Park Service St. Croix National Scenic Riverway, 2020). This report documents methods and results of aquatic benthic mapping in a small area of the St. Croix River. The hydroacoustic and topographic surveys were collected from October 16–17, 2019. The hydrographic surveys consisted of multibeam and sidescan sound navigation and ranging (sonars). The topographic shoreline survey consisted of light detection and ranging (lidar) captured by boat adjacent to riverbanks. Additionally, an acoustic Doppler current profiler was used to measure flow velocities. The water level was higher than normal, and therefore had faster flow during the hydroacoustic surveys. Multibeam, lidar, and sidescan surveys occurred the first day, and the velocity mapping and ground truthing was conducted the second day. Multibeam and lidar provided derivative datasets that included bathymetry and a topobathy with a spatial resolution of 1 foot. From these data, additional data could be measured including slope and terrain ruggedness. Sidescan (acoustic reflectance measures) provided imagery that was used to help with interpretation of the river bottom. Outcomes from these combined datasets were substrate and bedform maps. Much of the area was covered in sand ripples or small dunes. A small area running adjacent to the deeper valley or cut down the river consisted of harder substrates, such as cobble and gravel. Large woody debris piles were found throughout the study area. Multiple stationary moving-bed tests were completed, and no corrections were recommended for the conditions occurring during survey. Mussel presence was noted in some of the underwater videos. The physical parameters of depth, flow, bedforms, and substrate derived from the datasets provided baseline measures for a benthic habitat map. Further analysis of benthic habitat might be possible with additional biological and chemical data.

Wisconsin↗
USGS2021

Renewing the National Cooperative Geologic Mapping Program as the Nation’s authoritative source for modern geologic knowledge

This document presents the renewed vision, mission, and goals for the National Cooperative Geologic Mapping Program (NCGMP). The NCGMP, as authorized by the National Cooperative Geologic Mapping Act of 1992 (Public Law 102-285, 106 Stat. 166 and its reauthorizations), is tasked with expediting the production of a geologic database for the Nation based on modern geologic maps and their supporting data. In addition to highlighting the benefits of geologic maps for economic prosperity, national security, and environmental quality, the report describes the NCGMP structure and components. A renewed vision and mission for the NCGMP are stated, and three goals for guiding the program toward that vision for the next ten years are established. The vision of creating an integrated, three-dimensional, digital geologic map of the United States and its territories to address the changing needs of the Nation by 2030 is thereby defined to drive the activities of all NCGMP components for the next ten years. The strategic actions required to realize the NCGMP vision are identified for each of its components.

Open-File Report↗
USGS2021

Synthetic aperture radar and optical mapping used to monitor change and replacement of Phragmites australis marsh in the Lower Mississippi River Delta, Louisiana

Synthetic aperture radar (SAR) mapping of density as an enhancement of Phragmites australis optical live fractional cover (LFC) mapping was carried out in the lower Mississippi Delta during 2016 to 2019. Also, as part of the study, the replacement of P. australis with elephant-ear was analyzed. To that end, yearly maps from 2016 to 2019 of L-band SAR horizontal send, vertical receive (HV) data representing marsh density were produced for the lower Mississippi River Delta. The mapping indicated high local variability within broad yearly density change in P. australis marsh. LFC mapping indicated a similar pattern of broad yearly change. That overall density and LFC linear correspondence was confirmed with regressions of P. australis marsh HV-density data and optical-LFC data. Local differences reflected as high scatter in the plots. Based on those results, a combined LFC and HV-density assessment tracker of P. australis condition was developed. Major findings from the use of the trajectory tool were the high decrease in HV density from 2016 to 2017, the identification of severely degraded P. australis marsh and European P. australis marsh in some areas, and indications of linkage between the density decline from 2016 to 2017 and the elephant-ear replacement from 2018 to 2019. The trajectory tool application also indicated an inverse relationship between elephant-ear occurrence and HV-density changes from 2018 to 2019. A similar but weaker relationship was found between elephant-ear and LFC. These relationships may provide a means for early detection of replacement of P. australis marsh by elephant-ear and other unwanted plant species.

Louisiana↗
USGS2023

Monitoring Avian Productivity and Survivorship (MAPS) 6-year summary, Naval Outlying Landing Field, Imperial Beach, southwestern San Diego County, California, 2014–20

Executive Summary From 2014 to 2020, a Monitoring Avian Productivity and Survivorship (MAPS) banding station (station) was operated at the Naval Outlying Landing Field (NOLF), Imperial Beach, in southwestern San Diego County, California. The station was established as part of a long-term monitoring program of Neotropical migratory bird populations on NOLF and helps Naval Base Coronado (NOLF is a component) meet the goals and objectives of the Department of Defense Partners in Flight program and the Birds and Migratory Birds Management Strategies of the Naval Base Coronado Integrated Natural Resources Management Plan. The station was established in 2009 and has been in operation during the spring and summer since 2009 except for 2016 when it was not funded. The station was operated by AMEC Earth and Environmental, Inc., from 2009 to 2011, by the U.S. Geological Survey from 2012 to 2015, the San Diego Natural History Museum in 2017, and the U.S. Geological Survey again from 2018 to 2023. This report synthesizes results from 2014 to 2020. A prior report presents summaries and analyses from 2009 to 2013. The banding station at NOLF was operated according to the standard MAPS protocol with some exceptions. Ten mist nets used to capture birds were erected in fixed locations that remained consistent between and within years, with few minor relocations. Nets were open for 6 hours per day, once every 10 days (a netting period) for 13 netting periods starting April 1 each year. Occasionally, poor weather conditions (for example, rain, wind, or excessive heat) prevented net operation or forced nets to be closed early (or, rarely, late). Nets were checked periodically throughout the day and birds were removed, processed (leg bands affixed, measurements recorded), and released. From 2014 to 2020, we had 3,543 captures (including initial captures and recaptures) of a maximum of 3,264 year-unique captures (543±143 year-unique captures [the total number of individual birds captured for the first time each year]). The count of year-unique captures included 2,702 newly banded birds, 258 individuals that were recaptured from previous years, and 304 birds that were released unbanded (218 hummingbirds and 86 other birds that were intentionally released unbanded [game birds, and so forth] or escaped before banding). Individuals of 68 species were captured, 39 of which breed at or in the immediate vicinity of the MAPS banding station. Bird capture rate averaged 43±30 captures per day (corrected to account for variation in effort) for all years (range 7–163 effort-corrected captures per day) and species richness per year averaged 43±4. Bushtit ( Psaltriparus minimus ) was the most abundant species captured, followed by Orange-crowned Warbler ( Leiothlypis celata ), Wilson’s Warbler ( Cardellina pusilla ), House Finch ( Haemorhous mexicanus ), Song Sparrow ( Melospiza melodia ), and Common Yellowthroat ( Geothlypis trichas ). The mean adult sex ratio of all species combined across all years was 54:46 male:female. Adults averaged 73±12 percent of known age captures per year (range 59–94 percent), and juveniles averaged 27±12 percent (range 6–41 percent). Nineteen sensitive species were detected at NOLF (12 captured and 7 observed only). During 2014–20, we captured one State and federally endangered species, Least Bell’s Vireo ( Vireo bellii pusillus ); one federally threatened species, California Gnatcatcher ( Polioptila californica ); one State endangered species, Willow Flycatcher ( Empidonax traillii ); and two State species of concern, Yellow-breasted Chat ( Icteria virens ) and Yellow Warbler ( Setophaga petechia ). One additional State species of concern, Northern Harrier ( Circus hudsonius ), was observed at the MAPS banding station but not captured. Peregrine Falcon ( Falco peregrinus ) and White-tailed Kite ( Elanus leucurus ), California State fully protected species, also were observed at the MAPS banding station. Seven federal bird species of conservation concern—Calliope Hummingbird ( Selasphorus calliope ), Rufous Hummingbird ( Selasphorus rufus ), Allen’s Hummingbird ( Selasphorus sasin ), Nuttall’s Woodpecker ( Dryobates nuttallii ), Wrentit ( Chamaea fasciata ), California Thrasher ( Toxostoma redivivum ), and Lawrence’s Goldfinch ( Spinus lawrencei )—also were captured, and four additional federal bird species of conservation concern—Willet ( Tringa semipalmata ), Western Gull ( Larus occidentalis ), California Gull ( Larus californicus ), and Bullock’s Oriole ( Icterus bullockii )—were observed but not captured. Local population trends varied among species and years. From 2012 to 2019, year-round residents Bushtit, Song Sparrow, and Common Yellowthroat significantly decreased, whereas the migrant Least Bell’s Vireo increased. The total number of captures for all species except Least Bell’s Vireo was lowest in 2017, corresponding to the habitat damage caused by Kuroshio shot hole borer beetle ( Euwallacea kuroshio ) in the Tijuana River Valley. Annual productivity and annual adult survival were calculated for seven breeding species based on criteria used by the Institute for Bird Populations (Least Bell’s Vireo, Bushtit, Wrentit, House Wren [ Troglodytes aedon ], Song Sparrow, Orange-crowned Warbler, and Common Yellowthroat). Productivity was highest for most species in 2010 and 2019, years with high precipitation, and lowest in 2014 and 2018, years with low precipitation. Song Sparrow demonstrated the highest productivity among species and Least Bell’s Vireo had the lowest productivity. Annual adult survival was generally high from 2011 to 2012 and from 2018 to 2019. Bushtit had higher annual survival with lower late winter precipitation. Either temperature or precipitation was associated with productivity for all species except Wrentit, and with survival for all species except Least Bell’s Vireo and Common Yellowthroat. For most species, productivity was positively associated with precipitation, and both productivity and survival were negatively associated with temperature. Other studies have found that higher temperatures led to increased predation by snakes and birds and also increased vector-borne disease transmission, such as West Nile virus. Predicted regional increases in temperature over the next 30 years will likely affect the demographics of these species. The Song Sparrow population increased with higher breeding productivity during the previous year, and the Bushtit population increased with higher annual survival and higher productivity during the previous year. Aside from a possible positive association between survivorship and Common Yellowthroat population growth, productivity and survival rates did not appear to influence population change for other focal species.

California↗
USGS2025

Mapping eelgrass (Zostera marina) cover and biomass at Izembek Lagoon, Alaska, using in-situ field data and Sentinel-2 satellite imagery

The U.S. Geological Survey and the U.S. Fish and Wildlife Service have developed a three-tiered strategy for monitoring eelgrass ( Zostera marina ) beds at Izembek Lagoon, Alaska, that targets different spatial and temporal scales. The broadest-scale monitoring (tier-1) uses satellite imagery about every 5 years to delineate the spatial extent of eelgrass beds throughout the lagoon. This report describes the most recent (mid-2020s) tier-1 eelgrass monitoring at Izembek Lagoon. The monitoring effort began by canvasing all satellite imagery collected during summer, under clear daytime skies and at low-tide, since the last tier-1 effort in 2006. Two eelgrass maps of Izembek Lagoon were generated by first creating maps of spectrally unique classes from two Sentinel-2 satellite images collected on July 1, 2016, and August 14, 2020, then attributing those spectral classes with information about eelgrass conditions based on field data. Specifically, maps depicting various eelgrass metrics, such as percentage of cover and modeled biomass, were generated using summaries of the ground data that spatially intersected each spectral class. Comparisons of the 2016 and 2020 Sentinel-2 maps showing eelgrass distributional extent, as well as a 2006 Landsat map, indicated that areas where eelgrass presence may have declined during 2006–20 were most prevalent in the central part of Izembek Lagoon. More recently, during 2016-20, areas of possible biomass decline were more prevalent in the southern part of the lagoon. Monitoring eelgrass conditions at Izembek Lagoon with satellite imagery and concurrent ground data allows conditions to be compared over time, but the influences of tide levels, growing season phenology, and spatiotemporal co-registration accuracy should be considered when designing and interpreting change detection analyses.

Alaska↗
USGS1945

Topographic and geologic maps of manganese deposits in California

Geologic and topographic maps of several manganese properties in California were released today by the Geological Survey according to an announcement made by Survey Director W. E. Wrather to Secretary of the Interior Harold L. Ickes. The maps have been placed on open file at the offices of the Geological Survey in Washington, D. C., and at the offices of the Geologic Branch, California Division of Mines, Ferry Building, San Francisco, where they may be consulted by persons directly interested in the properties. The recently increased demand for information regarding deposits of manganese silicates for new uses in connection with the war effort has indicated the desirability of releasing unpublished detailed maps of the California deposits, many of which carry manganese silicates. The maps were made as part of the strategic minerals investigations of the Geological Survey from 1941 to 1943. The deposits covered by the maps are in the following counties of California: Amador, Calaveras, Eldorado, Glenn, Humboldt, Los Angeles, Madera, Mariposa, Mendocino, Mono, Placer, Plumas, San Bernardino, San Benito, San Luis Obispo, San Joaquin, Sonoma, Stanislaus, Trinity, and Tuolumne.

California↗
USGS1962

Portrayal of drainage and vegetation on topographic maps

Accurate measurements of drainage networks are necessary for studies in many scientific disciplines, especially hydrology. To this end, topographic maps must show accurate classification as well as a consistent pattern of the stream network. A recent study in Georgia has developed two photo-interpretive keys which permit accurate drainage classification during the normal stereo-compilation procedures in map-making. The study was made in the Tired Creek basin in the Coastal Plain, and in the Yellow River basin in the Piedmont Province. In the Tired Creek basin, the perennial stream channels were associated with blackgum swamps which showed as a characteristic pattern on the aerial photographs of the area. Although the areas were classed as evergreen forest on specially-compiled vegetation maps without field checking, the classification was relatively consistent, indicating that the perennial channels could be identified accurately within the basin. In the Yellow River basin origins of perennial flow were found in valleys having concave-upward profiles. Valleys with convex-upward profiles remained ephemeral up to their juncture with a larger stream. Field checks indicated better than 80 percent accuracy in delineating these points of origin of perennial flow through stereoscopic viewing of the aerial photographs of the area. Vegetative difference above and below the origins of perennial flow were to subtle to be readily discerned on the photographs. Errors in classifying vegetation on special maps were attributed mainly to inexperience and to faulty criteria for for classification. Proposals are presented to improve portrayal of both drainage and vegetation on topographic maps. The proposed drainage criteria suggest portrayal of all perennial streams as well as ephemeral drainage below the first branching. The proposed vegetation criteria suggest classification of forest and shrubs, with further sub-division of distinctive patterns of vegetation easily recognized on the aerial photographs.

Open-File Report↗
USGS1970

Geologic map of the Arvada quadrangle, Colorado

Many of the engineering-geologic problems in the Arvada quadrangle are related to the unconsolidated surficial deposits, which mantle the bedrock to depths of as much as 40 or 50 feet. In this report most of the emphasis is placed on the map distribution of these materials and on a description of their physical properties. Much of the information presented on the geologic map in the form of abbreviated columnar sections is from water-well and exploration drill holes; the remainder is from foundation excavations and natural rock outcrops. A brief description of the composition and thickness of each map unit is given in the Explanation. The generalized statements that follow, regarding the engineering properties of the map units, are based on field observations and on general performance information obtained from local engineers, contractors, builders, and property owners. It is hoped that this information, used in conjunction with the geologic map and cross sections, will be helpful to land-use planners and developers, engineers, public officials, and others in making preliminary plans and designs. It is obvious that such information cannot and should not take the place of detailed field and laboratory investigations that are required in the design of specific engineering structures.

Colorado↗
USGS1970

Map showing recently active breaks along the San Andreas Fault between Pt. Delgada and Bolinas Bay, California

This strip map is one of a series of maps showing recently active fault breaks along the San Andreas and other active faults in California. It is designed to inform persons who are concerned with land use near the fault of the location of those fault breaks that have moved recently. The lines on the map are lines of rupture and creep that can be identified by field evidence and that clearly affect the present surface of the land. Map users should keep in mind that these lines are intended primarily as guides to help locate the fault; the mapped lines are not necessarily shown with the precision demanded by some engineering or land utilization needs.

California↗
USGS1974

Geologic map of the Monrovia Quadrangle, Liberia

As part of a program undertaken cooperatively by the Liberian Geological Survey and the U. S. Geological Survey, under the sponsorship of the Government of Liberia and the Agency for International Development, U. S. Department of State, Liberia was mapped by geologic and geophysical methods during the period 1965 to 1972.- The resulting geologic and geophysical maps are published in ten folios, each covering one quadrangle (see index map). The Monrovia quadrangle was systematically mapped by the author from June 1971 to July 1972. Field data provided by private companies and other members of the LGS-USGS project were used in map compilation, and are hereby acknowledged. Interpretation of gravity data (Behrendt and Wotorson, 1974, c), and total-intensity aeromagnetic and total count gamma radiation surveys (Behrendt and Wotorson, 1974, a, and b) were also used in the compilation, as were other unpublished geophysical data furnished by Behrendt and Wotorson (near-surface, regional magnetic component, and geologic correlations based on aeromagnetic and radiometric characteristics).

Monrovia Quadrangle↗
USGS1976

Bouguer gravity map of Alaska

The Bouguer gravity map of Alaska has been compiled from about 30,000 Alaska land gravity measurements plus approximately 40,000 km of surface-ship gravimeter traverses over the bordering continental shelves. The compilation thus represents nearly three times as much land data and ten times as much marine data as were available for one previous Alaskan gravity map (Barnes, 1969b) and fiftyfold increase since the original compilation of Alaskan land gravity data (Wollard and others, 1960). However, data from many parts of the state are still too scattered (inset 1) for accurate contouring; such deficiencies are most serious in the southwestern part of the state and in the Bering Sea. The map shows the variation of the simple Bouguer anomaly field and is thus comparable to the existing Bouguer gravity map of the conterminous 48 states (Wollard and Joesting, 1964). On land the Bouguer anomaly contours reflect the regional variations of gravity better than free-air anomaly contours, which are not adequately corrected for topography. However, in oceanic areas the free-air anomaly is less sensitive to bottom topography than the Bouguer anomaly. Accordingly, the map coverage includes available data from the continental shelves where the bottom relief is small, but it has not been extended to cover the continental slope, the deep ocean, or the islands of the Aleutian arc, where the free-air anomaly would be a better indicator of the regional variation of gravity, and where Bouguer gravity are only available for a few small areas (Miller and Bath, 1969; Healy and Kibler, 1976a and 1976b).

Alaska↗
USGS1978

Selected Geological Survey, U.S. Bureau of Mines, and Alaska Division of Geological and Geophysical Surveys reports and maps on Alaska released during 1977, indexed by quadrangle

This open-file report lists all Geological Survey, U.S. Bureau of Mines, and State of Alaska Division of Geological and Geophysical Surveys reports and maps on the geology, geophysics, and mineral and water resources of Alaska published or released to open files in 1977. They are listed by the quadrangles (scale 1:250,000) into which Alaska has been subdivided for topographic mapping (p. 3). As these three agencies also issued reports and maps on other subjects, the following lists are selected in the sense that such documents are not included. Most of the listed reports and maps bear a 1977 imprint date; a few with earlier imprint dates actually were not delivered until 1977. Reports that deal with regional tectonic hypotheses, regional syntheses, Alaska as a whole, or with areas that can not be identified with a specific quadrangle are listed under Alaska - General, as are statistical presentations, indexes, and the like. Reports and maps that deal with offshore areas not within quadrangle boundaries are listed under Offshore Areas. The Alaska - General and Offshore Areas lists appear before the alphabetically arranged quadrangle listings. This index is intended to bring up to date the other indexes of this series, which are listed on p. 2.

Alaska↗
USGS1979

Selected Geological Survey, U.S. Bureau of Mines, and Alaska Division of Geological and Geophysical surveys reports and maps on Alaska released during 1978, indexed by quadrangle

This open—file report lists all Geological Survey, U.S. Bureau of Mines, and State of Alaska Division of Geological and Geophysical Surveys reports and maps on the geology, geophysics, and mineral and water resources of Alaska published or released to open files in 1978. They are listed by the quadrangles (scale 1:250,000) into which Alaska has been subdivided for topographic mapping (p. 4). As these three agencies also issued reports and maps on other subjects, the following lists are selected in the sense that such documents are not included. Most of the listed reports and maps bear a 1978 imprint date; a few with earlier imprint dates actually were not delivered until 1978. Reports that deal with regional tectonic hypotheses, regional syntheses, Alaska as a whole, or with areas that can not be identified with a specific quadrangle are listed under Alaska — General, as are statistical presentations, indexes, and the like. Reports and maps that deal with offshore areas not within quadrangle boundaries are listed under Offshore Areas. The Alaska — General and Offshore Areas lists appear before the alphabetically arranged quadrangle listings.

Alaska↗
USGS1980

Potentiometric surface maps of the Sparta Sand, northern Louisiana and southern Arkansas, 1900, 1965, 1975, and 1980

The potentiometric surface of the Sparta Sand in northern Louisiana is shown by contours on four maps. Maps for 1900, 1965 , and spring 1975 are generalized, small-scale maps from previously published reports. The spring 1980 map (1:500,000) is based on measurements in 144 wells and includes the southern tier of counties in southern Arkansas. The map shows regional effects of pumping from the Sparta Sand and effects of local pumping centers at Magnolia and El Dorado, Ark., and at Minden, Ruston, Jonesboro-Hodge, Winnfield, Bastrop, and in the Monroe area of Louisiana.

Arkansas, Louisiana↗
USGS1982

Digital colored residual and regional Bouguer gravity maps of the conterminous United States: Comments on significant features

The gravity maps were prepared from data obtained primarily from data files maintained by the Defense Mapping Agency of the Department of Defense and the Canadian Gravity Data Centre of the Earth Physics Branch of the Department of Energy, Mines, and Resources (Canada). The maps have been used in studies relating to earthquake/reactor hazards, geothermal energy, and nuclear repository site programs of the U.S. Geological Survey. Those shown here (250 km and 1000 km wavelength cut-off regional and residual gravity maps) are part of a series of digital gravity and terrain maps of the United States currently being developed by the authors.

Open-File Report↗
USGS1982

Lineaments derived from analysis of linear features mapped from Landsat images of the Four Corners region of the Southwestern United States

Linear features are relatively short, distinct, non-cultural linear elements mappable on Landsat multispectral scanner images (MSS). Most linear features are related to local topographic features, such as cliffs, slope breaks, narrow ridges, and stream valley segments that are interpreted as reflecting directed aspects of local geologic structure including faults, zones of fracturing (joints), and the strike of tilted beds. 6,050 linear features were mapped on computer-enhanced Landsat MSS images of 11 Landsat scenes covering an area from the Rio Grande rift zone on the east to the Grand Canyon on the west and from the San Juan Mountains, Colorado, on the north to the Mogollon Rim on the south. Computer-aided statistical analysis of the linear feature data revealed 5 statistically important trend intervals: 1.) N. 10W.-N.16E., 2.) N.35-72E., 3.) N.33-59W., 4.) N. 74-83W., and 5.) N.89-9-W. and N. 89-90E. Subsequent analysis of the distribution of the linear features indicated that only the first three trend intervals are of regional geologic significance. Computer-generated maps of the linear features in each important trend interval were prepared, as well as contour maps showing the relative concentrations of linear features in each trend interval. These maps were then analyzed for patterns suggestive of possible regional tectonic lines. 20 possible tectonic lines, or lineaments, were interpreted from the maps. One lineament is defined by an obvious change in overall linear feature concentrations along a northwest-trending line cutting across northeastern Arizona. Linear features are abundant northeast of the line and relatively scarce to the southwest. The remaining 19 lineaments represent the axes of clusters of parallel linear features elongated in the direction of the linear feature trends. Most of these lineaments mark previously known structural zones controlled by linear features in the Precambrian basement or show newly recognized relationships to geological and/or geophysical patterns that suggest probable influence by buried basement features. The remaining few lineaments are not strongly correlative with geological or geophysical patterns, but on the basis of existing data they cannot be dismissed as being possible expressions of basement features.

Open-File Report↗
USGS1983

A search for stratiform massive-sulfide exploration targets in Appalachian Devonian rocks; a case study using computer-assisted attribute-coincidence mapping

The empirical model for sediment-associated, stratiform, exhalative, massive-sulfide deposits presented by D. Large in 1979 and 1980 has been redesigned to permit its use in a computer-assisted search for exploration-target areas in Devonian rocks of the Appalachian region using attribute-coincidence mapping (ACM). Some 36 gridded-data maps and selected maps derived therefrom were developed to show the orthogonal patterns, using the 7-1/2 minute quadrangle as an information cell, of geologic data patterns relevant to the empirical model. From these map and data files, six attribute-coincidence maps were prepared to illustrate both variation in the application of ACM techniques and the extent of possible significant exploration-target areas. As a result of this preliminary work in ACM, four major (and some lesser) exploration-target areas needing further study and analysis have been defined as follows: 1) in western and central New York in the outcrop area of lowermost Upper Devonian rocks straddling the Clarendon-Linden fault; 2) in western Virginia and eastern West Virginia in an area largely coincident with the well-known 'Oriskany' Mn-Fe ores; 3) an area in West Virginia, Maryland, and Virginia along and nearby the trend of the Alabama-New York lineament of King and Zietz approximately between 38- and 40-degrees N. latitude; and 4) an area in northeastern Ohio overlying an area coincident with a significant thickness of Silurian salt and high modern seismic activity. Some lesser, smaller areas suggested by relatively high coincidence may also be worthy of further study.

Open-File Report↗
USGS1984

Geologic map of southeastern Alaska

Southeastern Alaska is underlain by sedimentary, volcanic, intrusive, and metamorphic rocks of Quaternary to Cambrian, and probable Proterozoic age. These rocks have been classified on the geologic map and in this pamphlet into units that emphasize the regional distribution of lithically similar and generally coeval geologic units. The distribution, age, stratigraphic or intrusive relations, and metamorphic and structural characteristics of the map units are described below in the Description of Map Units, and the temporal relations between units are shown on the Correlation of Map Units (Plate). Figure I shows the primary sources of information used in compiling the geologic map.

Alaska↗