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Results for “Geological & Geophysical Surveys”

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At least 19 recordsLinked to original sources
USGS1973

A preliminary report on U.S. Geological Survey geophysical studies of the northeastern United States Outer Continental Shelf

Regional geological and geophysical studies are being conductedby the U.S. Geological Survey to determine the structural framework of the area from Cape Hatteras to the northeastern edge of Georges Bank in order to assess the petroleum potential of the Atlantic Outer Continental Shelf. Preliminary interpretations of geophysical data and integrating gravity and magnetic data from the U.S.Naval Oceanographic.Office with seismic surveys, suggest that the linear ridge reported by Drake and others in 1959 is deeper and is farther west than previously suspected. Although it is not observed under the seaward extension of the Norfolk arch, it can be traced trough from the south side of the Baltimore Canyon trough northeastward toward the eastern edge of Georges Bank trough. This ridge seems to form the eastward edge of a Mesozoic depocenter in the Baltimore Canyon area in which more than 10 km of relatively undisturbed post-Paleozoic sediments accumulated. The types of structures mapped are ingeneral agreement with the sedimentary structural models hypothesized for the Baltimore Canyon trough by Kraft and others in 1971. More than 8 km of sediments are present beneath the continental shelf on Georges Bank. On the basis of the preliminary regional geophysical studies, it appears that thick sedimentary sections and structural traps favorable for the accumulation of petroleum exist under the Atlantic Continental Shelf off the northeastern part of the United States.

Open-File Report↗
USGS2021

Chemical analysis of archived stream-sediment samples, Alaska

Geochemical data are presented for more than 1,500 archived stream-sediment samples and accompanying quality control samples. The archived sediments were reanalyzed to improve the stream geochemical dataset for Alaska and to support ongoing U.S. Geological Survey (USGS) studies. Sediment samples were primarily from the USGS Mineral Resources Program’s sample archive in Denver, Colorado, but a few were from the Alaska Geological & Geophysical Surveys’ Geologic Materials Center in Anchorage, Alaska. All samples were submitted to the USGS contract laboratory, AGAT Laboratories, for analysis. All samples were analyzed using a 60-element analytical method involving fusion of the sample by sodium peroxide, dissolution of the fusion cake by nitric acid, and elemental analysis by inductively coupled plasma-optical emission spectroscopy and inductively coupled plasma-mass spectroscopy. Additionally, 106 samples from the Nixon Fork area were analyzed by a second multi-element method involving decomposition by a mixture of hydrochloric, nitric, perchloric, and hydrofluoric acids and the elemental analysis of the resulting solution by inductively coupled plasma-optical emission spectroscopy and inductively coupled plasma-mass spectroscopy. The latter method was used because the detection limit is lower for several elements including As, Cd, Pb, and Sb. Mercury concentrations in 296 samples from southeast Alaska were determined using a cold-vapor atomic absorption spectrometry method. The concentration data from the archived samples are presented along with concentration data from the standard reference material that was submitted with the samples.

Alaska↗
USGS1976

Geological Survey and selected U.S. Bureau of Mines and Alaska Division of Geological and Geophysical Surveys reports and maps on Alaska released during 1975, indexed by quadrangle

All Geological Survey reports and maps on Alaska published or released to open files during 1975 are listed by the quadrangles (scale 1:250,000) into which Alaska has been divided for topographic mapping (p. 3). Also listed are U.S. Bureau of Mines reports on the geology and mineral resources of Alaska, but not those that deal exclusively with other subjects such as economics. Alaska Division of Geological and Geophysical Surveys published and open-filed reports and maps that were received by the Alaskan Geology Branch of the U.S. Geological Survey before March 1, 1976 are listed; the availability of several other reports and maps was publicly announced, but the documents were not available to me in time for them to be included here. Most of the reports and maps in this index bear a 1975 imprint date. Others bear earlier imprint dates, but were not released until 1975. All Alaska Division of Geological and Geophysical Surveys open-file reports and maps were withdrawn in 1974 for revision, consolidation, or assignment of new identification numbers. Those reissued reports and maps that I received before March 1, 1976 are listed in this index, no matter what imprint date they may bear. Also included are a few reports that were released before 1975, but hitherto had escaped my attention. Reports that deal with Alaska as a whole, with areas that can not be identified with a specific quadrangle, or that are mainly statistical presentations are listed under ALASKA - GENERAL, as are 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↗
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↗
USGS1977

Selected Geological Survey, U.S. Bureau of Mines, and Alaska Division of Geological and Geophysical Surveys reports and maps on Alaska released during 1976, 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 1976. 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 1976 imprint date; a few with a 1975 imprint date actually were not delivered until 1976. Also included are a few that I overlooked when I prepared a similar index of reports and maps issued in 1975. 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↗
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↗
USGS1975

Geological Survey and selected U.S. Bureau of Mines and Alaska Division of Geological and Geophysical Surveys reports and maps on Alaska released during 1974, indexed by quadrangle

All Geological Survey reports and maps on Alaska published or released to open files during 1974 are listed by the quadrangle (scale 1:250,000) into which Alaska has been divided for topographic mapping (p. 2). Also listed are U.S. Bureau of Mines reports on the geology and mineral resources of Alaska, but not those dealing exclusively with other subjects such as economics. Alaska Division of Geological and Geophysical Surveys published reports on geology and mineral resources are listed, but those released to open files are not. This is because all open-file reports and maps were withdrawn in 1974 for revision, consolidation, or assignment of new identification numbers before possible reissue. At the time of preparation of this index I had received so few newly released open-file reports that I felt that including any of them might cause confusion to potential users because of possible duplication of titles or numbers.

Alaska↗
USGS1993

U.S.-Soviet Collaborative Geological and Geophysical Survey of the Mid-Atlantic Ridge near 31 degrees N, the Petrov Fracture Zone

Introduction In February 1989, the first formal U.S.-Soviet joint marine geologic-geophysical study in 10 years was undertaken along the Mid-Atlantic Ridge near 31°N on the 12th Cruise of the RN Akademik Boris Petrov of the Vernadsky Institute of Geochemistry (USSR Academy of Sciences, Moscow). This survey was initiated as part of the U.S.S.R.-U.S. cooperative research project "Mid-Atlantic Ridge Crest Processes" within the framework of the Soviet-U.S. bilateral Ocean Studies Agreement (Ostenso, 1989). U.S. scientists from the U.S. Geological Survey, University of Houston, and Woods Hole Oceanographic Institution participated in this program with Soviet scientists from the Vernadsky Institute of Geochemistry, Institute of Geology, and Schmidt Institute of Physics of the Earth, all institutes of the USSR Academy of Sciences in Moscow (Appendix 1 ). The ship departed from Rotterdam, Nederlands on February 2, 1989 and docked in Bridgetown, Barbados on February 28, 1989. A log of the ship's schedule during this cruise is given in Appendix 2. This study involved a limited multibeam-bathymetric, gravity, magnetic, and seismic- reflection survey. and dredging program of a short-offset transform fault named the Petrov Fracture Zone near 31 °N, located just north of the Atlantis Fracture Zone on the Mid Atlantic Ridge. A site survey at King's Trough in the northeast Atlantic for a MIR submersible program in June 1989 was originally planned as part of this program, but bad weather and the resultant poor quality geophysical data forced this work to be terminated after only one day. Nearly 6000 km of geophysical profile data and 13 dredge stations were completed during this cruise. A description of the geophysical systems aboard the RN Petrov is given in Appendices 3 and 4. All geophysical data were recorded on magnetic tape in data formats described in Appendix 5. Dredge locales and description summaries only are presented in Appendix 6. Detailed descriptions of dredge samples will be presented elsewhere. Operational plan for the studies on this cruise was developed as a cooperative effort between U.S. and Soviet scientists, who established jointly the basic objectives of the study. The U.S. scientists were given the responsibility for developing the detailed survey and dredge sampling plans. Dredge operations and basic geophysical systems operations were the responsibility of the Soviet personnel.

Open-File Report↗
USGS2015

Reconnaissance stratigraphic studies in the Susitna basin, Alaska, during the 2014 field season

The Susitna basin is a poorly-understood Cenozoic successor basin immediately north of Cook Inlet in south-central Alaska (Kirschner, 1994). The basin is bounded by the Castle Mountain fault and Cook Inlet basin on the south, the Talkeetna Mountains on the east, the Alaska Range on the north, and the Alaska–Aleutian Range on the west (fig. 2-1). The Cenozoic fill of the basin includes coal-bearing nonmarine rocks that are partly correlative with Paleogene strata in the Matanuska Valley and Paleogene and Neogene formations in Cook Inlet (Stanley and others, 2013, 2014). Mesozoic sedimentary rocks are present in widely-scattered uplifts in and around the margins of the basin; these rocks differ significantly from Mesozoic rocks in the forearc basin to the south. Mesozoic strata in the Susitna region were likely part of a remnant ocean basin that preceded the nonmarine Cenozoic basin (Trop and Ridgway, 2007). The presence of coal-bearing strata similar to units that are proven source rocks for microbial gas in Cook Inlet (Claypool and others, 1980) suggests the possibility of a similar system in the Susitna basin (Decker and others, 2012). In 2011 the Alaska Division of Geological & Geophysical Surveys (DGGS) and Alaska Division of Oil and Gas, in collaboration with the U.S. Geological Survey, initiated a study of the gas potential of the Susitna basin (Gillis and others, 2013). This report presents a preliminary summary of the results from 14 days of helicopter-supported field work completed in the basin in August 2014. The goals of this work were to continue the reconnaissance stratigraphic work begun in 2011 aimed at understanding reservoir and seal potential of Tertiary strata, characterize the gas source potential of coals, and examine Mesozoic strata for source and reservoir potential

Alaska↗
USGS2015

Stratigraphic reconnaissance of the Middle Jurassic Red Glacier Formation, Tuxedni Group, at Red Glacier, Cook Inlet, Alaska

The Alaska Division of Geological & Geophysical Surveys (DGGS) and U.S. Geological Survey (USGS) are implementing ongoing programs to characterize the petroleum potential of Cook Inlet basin. Since 2009 this program has included work on the Mesozoic stratigraphy of lower Cook Inlet, including the Middle Jurassic Tuxedni Group between Tuxedni and Iniskin bays (LePain and others, 2013; Stanley and others, 2013; fig. 5-1). The basal unit in the group, the Red Glacier Formation (fig. 5-2), is thought to be the principal source rock for oil produced in upper Cook Inlet, and available geochemical data support this contention (Magoon and Anders, 1992; Magoon, 1994). Despite its economic significance very little has been published on the formation since Detterman and Hartsock’s (1966) seminal contribution on the geology of the Iniskin–Tuxedni area nearly 50 years ago. Consequently its stratigraphy, contact relations with bounding formations, and source rock characteristics are poorly known. During the 2014 field season, a nearly continuous stratigraphic section through the Red Glacier Formation in its type area at Red Glacier was located and measured to characterize sedimentary facies and to collect a suite of samples for analyses of biostratigraphy, Rock-Eval pyrolysis, vitrinite reflectance, and sandstone composition (fig. 5-3). The poorly known nature of the Red Glacier Formation is likely due to its remote location, steep terrain, and the fact that the type section is split into two segments that are more than 3 km apart. The lower 375 m segment of the formation is on the ridge between Red Glacier and Lateral Glacier and the upper 1,009 m segment is on the ridge between Red Glacier and Boulder Creek (fig. 5-3). Structural complications in the area add to the difficulty in understanding how these two segments fit together.

Alaska↗
USGS1972

Tectonic map of Liberia based on geophysical and geological surveys

Interpretation of the results of aeromagnetic, total-gamma radioactivity, and gravity surveys combined with geologic data for Western Liberia from White and Leo (1969) and other geologic information allows the construction of a tectonic map of Liberia. The map approximately delineates the boundaries between the Liberian (ca. 2700 m.y.) province in the northwestern two-thirds of the country, the Eburnean (ca. 2000 m.y.) province in the south-eastern one-third, and the Pan-African (ca. 550 m.y.) province in the coastal area of the northwestern two-thirds of the country. Rock follation and tectonic structural features trend northeastward in the Liberian province, east-northeastward to north-northeastward in the Eburnean province, and northwestward in the Pan-African age province. Linear residual magnetic anomailes 20-80 km wide and 200-600 gammas in amplitude and following the northeast structural trend typical of the Liberian age province cross the entire country and extend into Sierra Leone and Ivory Coast.

Open-File Report↗
USGS2017

Geospatial analysis identifies critical mineral-resource potential in Alaska

Alaska consists of more than 663,000 square miles (1,717,000 square kilometers) of land—more than a sixth of the total area of the United States—and large tracts of it have not been system atically studied or sampled for mineral- resource potential. Many regions of the State are known to have significant mineral-resource potential, and there are currently six operating mines in the State along with numerous active mineral exploration projects. The U.S. Geologi cal Survey and the Alaska Division of Geological & Geophysical Surveys have developed a new geospatial tool that integrates and analyzes publicly available databases of geologic information and estimates the mineral-resource potential for criti cal minerals, which was recently used to evaluate Alaska. The results of the analyses highlight areas that have known mineral deposits and also reveal areas that were not previously considered to be prospective for these deposit types. These results will inform land manage ment decisions by Federal, State, and private landholders, and will also help guide future exploration activities and scientific investigations in Alaska.

Alaska↗