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Results for “The Alaska Miner”
Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.
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Distribution and abundance of gold and silver in non-magnetic and moderately magnetic heavy-mineral-concentrate and minus-80-mesh stream-sediment samples and silver in ash of aquatic-bryophyte samples, Medfra quadrangle, Alaska
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Analytical results of non-magnetic heavy-mineral-concentrate sample data from the Bethel and southern part of the Russian Mission 1 degree x 3 degrees quadrangles, Southwest Alaska
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Analytical results of non-magnetic heavy-mineral-concentrate sample data from the Bethel and southern part of the Russian Mission 1 degree x 3 degrees quadrangles, southwest Alaska
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U.S. Geological Survey activities related to American Indians and Alaska Natives: Fiscal year 2004
The USGS works in cooperation with American Indian and Alaska Native governments to conduct research on (1) water, energy, and mineral resources, (2) animals and plants that are important for traditional lifeways or have environmental or economic significance, and (3) natural hazards. This report describes most of the activities that the USGS conducted with American Indian and Alaska Native governments, educational institutions, and individuals during Federal fiscal year (FY) 2004. Most of these USGS activities were collaborations with Tribes, Tribal organizations, or professional societies. Other activities were conducted cooperatively with the U.S. Bureau of Indian Affairs (BIA) or other Federal entities.
Geochronology of the western and central Brooks Range, Alaska: Implications for the geologic evolution of the Anarraaq and Red Dog Zn-Pb-Ag deposits
A compilation of published geochronology of rocks and minerals from the western and central Brooks Range provides a framework for understanding the complex history of the Brooks Range and northern Alaska. A simplified timeline of events comprises (1) Devonian extension, (2) Mississippian extension and Zn-Pb-Ag mineralization, (3) a passive interval, (4) pre-Brooks Range orogeny rock-formation and thermal event, (5) inception of Brooks Range orogeny, (6) exhumation and the end of main-stage deformation, and (7) subsequent episodic deformation. This compilation is supplemented by new 40Ar/39Ar dates of white mica from the Anarraaq and Red Dog Zn-Pb-Ag (+ barite) deposits from the western Brooks Range. The deposits are hosted in black shale and carbonate rocks of the Late Mississippian-Early Pennsylvanian Kuna Formation. Quartz-pyrite-white mica grains in sedimentary rocks above the Anarraaq deposit yield an age of 195.0 ?? 2.0 Ma, and paragenetically late quartz-pyrite-white mica from the Main orebody at the Red Dog deposit has an age of 126.1 ?? 0.7 Ma. These white micas are much younger than the age of Zn-Pb-Ag mineralization at Red Dog (338 ?? 5.8 Ma Re-Os age of pyrite). The date for white mica from Anarraaq (???195 Ma) appears to be related to a large-scale thermal event in the region immediately before the inception of the Brooks Range orogeny. The white mica from the Red Dog deposit (???126 Ma) correlates with the later stages of the orogeny, a period of blueschist metamorphism, extension, and rapid exhumation, which varied with geographic location. These dates suggest that the Red Dog deposits underwent significant hydrothermal overprinting during multiple episodes of the Brooks Range orogeny. ?? 2004 by Economic Geology.
Geochemical maps showing the distribution and concentration of selected elements in nonmagnetic heavy-mineral-concentrate samples from stream sediment from the Craig, Dixon Entrance, and western edges of the Ketchikan and Prince Rupert quadrangles, southeast Alaska
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A workshop model simulating fate and effect of drilling muds and cuttings on benthic communities
Oil and gas exploration and production at marine sites has generated concern over potential environmental impacts resulting from the discharge of spent drilling muds and cuttings. This concern has led to a broad array of publicly and privately sponsored research. This report described a cooperative modeling effort designed to focus information resulting from this research through construction of explicit equations that simulate the potential impacts of discharge drilling fluids (muds) and cuttings on marine communities. The model is the result of collaboration among more than 30 scientists. The principal cooperating organizations were the E.S. Environmental Protection Agency, the U.S. Minerals Management Service, the Offshore Operators Committee, and the Alaska Oil and Gas Association. The overall simulation model can be conceptualized as three connected submodels: Discharge and Plume Fate, Sediment Redistribution, and Benthic Community Effects. On each day of simulation, these submodels are executed in sequence, with flows of information between submodels. The Benthic Community Effects submodel can be further divided into sections that calculate mortality due to burial, mortality due to toxicity, mortality due to resuspension disturbance, and growth of the community. The model represents a series of seven discrete 1-m 2 plots at specified distances along a transect in one direction away from a discharge point. It consists of coupled difference equations for which parameter values can easily be set to evaluate different conditions or to examine the sensitivity of output to various assumptions. Sets of parameter values were developed to represent four general cases or scenarios: (1) a shallow (5 m), cold environment with ice cover during a substantial fraction of the year, such as might be encountered in the Beaufort Sea, Alaska; (2) a shallow (20 m), temperate environment, such as might be encountered in the Gulf of Mexico; (3) a deeper (80 m), temperate environment, such as might be encountered in the Gulf of Mexico; and (4) a very deep (1,000 m) environment, such as might be encountered on the Atlantic slope. The focus of the modeling effort was on the connection of a reasonable representation of physical fate to the biological responses of populations, rather than on highly detailed representations of individual processes. For example, the calculations of physical fate are not as detailed as those in the recently published model of Brandsma et al. (1983). The value of the model described herein is in the broad scope of processes that are explicitly represented and linked together. The model cannot be considered to produce reliable predictions of the quantitative impacts of discharged drilling fluids and cuttings on biological populations at a particular site. Limitations of the model in predicting integrated fate and effects can be traced to three general areas: level of refinement of the algorithms used in the model; lack of understanding of the processes determining fate and effects; and parameter and data values. Despite the limitations, several qualitative conclusions concerning both potential impacts and the importance of various remaining data gaps can be drawn from the modeling effort. These include: (1) Simple, unequivocal conclusions about fate and effects across geographical regions and drilling operations are difficult, if not misleading, due to the large amount of variability in characteristics of discharged materials (e.g., oil content and toxicity), discharge conditions (e.g., duration of drilling operations), physical environments (e.g., water depth, current direction, and sediment disturbance regimes), and biological communities (e.g., intrinsic growth rates). Different combinations of these characteristics can result in substantial differences in simulated environmental fate and biological effects. For examples, simulated recovery in some high-energy environments occurs within months after the cessation of discharge operations, even at heavily impacted sites, whereas simulated recover in some low-energy environments takes years at heavily impacted sites. <2) Considerable difficulties remain in the reliable extrapolation of results from laboratory toxicity experiments to predictions of population effects in the field. (3) The volume of material discharged and duration of operations in the production drilling operations simulated by the model are sufficient to produce substantial simulated biological impacts at some plots, both in terms of differences from a control plot during the period of discharge operations, and in terms of the recovery period following the perturbations. Evaluation of the significance of potential effects involves the following factors: • Definition of a specific spatial and temporal reference frame (e.g., What is the natural variation? Is 1 year to be considered a "long" or "short" time? Is 50 m to be considered a "large" or "trivial" distance? • Consideration of rare or unique resources and particularly sensitive biotic assemblages. • Consideration of the potential for long term, cumulative effects. Some of these aspects are clearly beyond the scope of this modeling efforts (e.g., the model does not simulate the long term fate of resuspended material). The model does, however, contain an internal "reference frame" by comparison to simulated behavior at a control plot. The model, in general, simulates substantial "natural" variation at the reference or control plots, both over time, due to sediment disturbance events in medium to high energy environments, and over space, due to geographically varying conditions, such as water depth and current regime.
Geologic studies in Alaska by the U.S. Geological Survey, 1990
This collection of papers continues the annual series of U.S. Geological Survey (USGS) reports on geologic investigations in Alaska. From 1975 through 1988, the series was published as USGS circulars. The first of these appeared under the title "The United States Geological Survey in Alaska: Accomplishments during 1975," and the series continued to the last annual circular entitled "Geologic studies in Alaska by the U.S. Geological Survey during 1987," which reflects a title change made in 1986. This 1990 volume continues the bulletin format started in 1988. As in 1989, this volume separates shorter contributions as Geologic Notes from more extensive Articles. This 1990 volume of 18 Articles and 4 Geologic Notes represents the broad range of USGS research activities carried out in Alaska over the past few years. These studies include topics on mineral and other resources such as gold (Y eend), platinum-group elements (Cathrall and Antweiler), coal (Roberts, Stricker, and Affolter), and petroleum (Howell, Bird, and others). Many other investigations provide background geochemical (Kilburn, Box, and others) and geologic data needed for resource evaluation as well as for determining the general geologic framework of Alaska, as in stratigraphic, sedimentologic, and paleontologic and radiometric age studies (Blodgett, Clough, and others; Box and Elder; Dickinson and Skipp; Marincovich and Moriya; McLean and Stanley; Stanley, Flores, and Wiley; Roeske, Pavlis, and others); geophysics (Sampson, Labson, and Long); structure and tectonic evaluations (Bradley and Kosky; Clendenen, Sliter, and Byrne; Karl; Csejtey; Howell, Johnsson, and others); and geomorphic and late Quaternary studies (Carter and Hillhouse; Galloway, Huebner, and others; McGimsey, Richter, and others; Nelson and Carter). These studies span nearly the entire State from the North Slope and Brooks Range to interior, southwestern, and south-central Alaska (fig. 1). Two bibliographies (White) at the end of the volume list (1) reports about Alaska in USGS publications released in 1990 and (2) reports about Alaska by USGS authors in publications outside the USGS in 1990. A bibliography and index of papers in past USGS circulars that are devoted to geologic research and accomplishments in Alaska (1975 to 1986) is published as USGS Open-File Report 87-420.
U.S. Geological Survey—Department of the Interior, Region 11, Alaska—2023–24 biennial science report
Introduction U.S. Geological Survey (USGS) Mission—The USGS national mission is to monitor, analyze, and predict the current and evolving dynamics of complex human and natural Earth-system interactions and to deliver actionable information at scales and timeframes relevant to decision makers. Consistent with the national mission, the USGS in Alaska provides timely and objective scientific information to help address issues and inform management decisions across five interconnected focus areas: Energy and Minerals; Geospatial Mapping; Natural Hazards; Water Quality, Streamflow, and Ice Dynamics; and Ecosystems. The USGS in Alaska consists of approximately 350 scientists and support staff working in 3 Alaska-based science centers. USGS science activities are also initiated by the Cooperative Research Unit and USGS centers outside Alaska. In the last 5 years, USGS research in Alaska has produced many scientific benefits resulting from more than 900 publications. Publications relevant to Alaska can be conveniently searched by keyword through the USGS Publications Warehouse at https://pubs.usgs.gov/.