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At least 1,189 records · Page 66Linked to original sources
USGS1972

Placer deposits of Alaska

Placer deposits, in addition to their intrinsic value, serve as indicators of areas of potential development of lode deposits. Any possibility that Alaska may again become an important source of metallic mineral commodities depends in part on an inventory of placer deposits and a knowledge of the geology of their source areas. Information on Alaska's placer deposits is far from complete. Many mining camps have been at best the subject of only cursory examination by geologists or mining engineers at liberty to publish the results of their studies. Many placers are vaguely known from unconfirmed reports that someone was working on a creek, in many instances a creek bearing a name that cannot now be identified with any particular stream. Such data are, of course, practically valueless and were generally ignored in preparing the report. Other major gaps in our knowledge result from the lack of bedrock exposures in many areas where valuable placer deposits were mined, a circumstance that made impossible the determination of lode sources and their mode of occurrence during reconnaissance studies of mining districts. And the reluctance of many prospectors to divulge data on their claims has undoubtedly caused some deposits to be "lost" or overlooked.

Alaska↗
USGS1973

Lithologic characteristics and palynology of Upper Cretaceous and Tertiary rocks in the Deep Creek Unit well, Kenai Peninsula, Alaska

This report describes a reference section for Tertiary rocks drilled in the Standard Oil Co. of Cal. 1 Deep Creek Unit well located about 25 miles north of Homer, Kenai Peninsula, southern Alaska (pl. 1) The work is part of a study of the petroleum geology of the Cock Inlet basin and is intended to aid in the continuing search for oil and gas in the basin. A previous report (Carter and Adkison, 1972) presented preliminary electrical-log correlations of Tertiary rocks along two intersecting cross sections in the basin, and one of the cross sections included the Deep Creek well. The work was done under a cooperative agreement between the U.S. Geological Survey and the Division of Geological and Geophysical Surveys, Department of Natural Resources,' State of Alaska. The writers gratefully acknowledge the assistance of W.'C. Fackler, State Geologist and T. R. Marshall, Jr., Chief Petroleum Geologist, Division of Oil and Gas. The Standard Oil Co. of Cal. gave the conventional cores from the Deep Creek well to the State, and T. R. Marshall, Jr. made the cores available for study.

Alaska↗
USGS1973

Geologic setting and chemical characteristics of hot springs in central and western Alaska

Numerous hot springs occur in a variety of geologic provinces in central and western Alaska. Granitic plutons are common to all the provinces and the hot springs are spatially associated with the contacts of these plutons. Of 23 hot springs whose bedrock geology is known, all occur within 3 miles of a granitic pluton. The occurrence of hot springs, however, appears to be independent of the age, composition, or magmatic history of the pluton. Preliminary chemical and isotopic analyses suggest the hot springs waters belong to two groups. Most of the analyzed hot springs appear to have chemical and Isotopic compositions indicating they were derived from deeply circulating meteoric water. About 25 percent of the analyzed hot springs show a distinct saline character with high concentrations of chloride, sodium, potassium, and calcium indicating either much more complex water rock reactions than occurred in the other hot springs or the addition of another type of water. The present chemical and isotopic data are insufficient to determine the source of the constituents of the saline hot springs. Chemical geothermometers suggest subsurface temperatures in the general range of 100°C to 160°C. If the hot spring waters have derived their heat solely from deep circulation, the waters must have reached depths of 9,000 to 15,000 feet, assuming geothermal gradients of 30°C to 50°C/km. If hot magmatic water has been added to the geothermal systems or if dilution or mixing has occurred, temperatures of 100°C to 160°C may be reached at shallower depths. The geologic and chemical data are too preliminary to make an estimate of the potential of the hot springs as a geothermal resource. The data suggest, however, that most of the hot springs of central and western Alaska have relatively low subsurface temperatures and limited reservoir capacities in comparison with geothermal areas presently being utilized for electrical power generation.

Alaska↗
USGS1975

Interim report on petroleum resource potential and geologic hazards in the outer continental shelf of the Gulf of Alaska Tertiary province

The potential for discovering large accumulations of petroleum on the Outer Continental Shelf of the Gulf of Alaska Tertiary Province cannot be evaluated with much confidence at present because of the inadequacies of the available offshore geological and geophysical data. The 22 deep test wells that have been drilled since 1954 have been unsuccessful because structure is complex and because suitable reservoir rocks have not been found in favorable structural positions. Although it is possible that the factors controlling accumulation of petroleum may improve offshore, regional stratigraphic and structural considerations together with the limited geophysical data suggest that this is not necessarily the case. Extrapolation of onshore geology together with the limited amount of marine geophysical data, indicate that the eastern Gulf of Alaska Outer Continental Shelf is geologically complex and consists of several areas with markedly differing structural styles and petroleum potential.

Alaska↗
USGS1976

A summary of petroleum potential, environmental geology, and the technology, time frame, and infrastructure for exploration and development of the western Gulf of Alaska

This summary of the regional geology, petroleum potential, geologic hazards and time frame for exploration of the western Gulf of Alaska has been written to aid the Bureau of Land Management in preparing the Draft Environmental Impact Statement. A preliminary version was written in Sept., 1975.(von Huene and others, 1975) in support of the Call for Nominations, Proposed OCS Oil and Gas Lease Sale #46. Since that time, there has been a substantial increase in information as the result of a two-month examination of recent studies of the adjacent Gulf of Alaska Tertiary Province and a preliminary interpretation of some publicly available common depth point (CDP) seismic reflection data recently acquired by the U.S. Geological Survey. The main source of geologic and geophysical data used in the preparation of this summary is published and unpublished information of the U.S. Geological Survey (Plafker and others, 1975,Bruns and Plafker, 1975; Carlson, Bruns and Molnia, 1975; Carlson and Molnia, 1975; Core, Mattick, and Bayer, 1975; Molnia and Carlson, 1975 a & b; von Huene and others, 1975). Prior to 1975, data were gathered mainly for purposes other than for assessment of oil and gas resources and of the environmental consequences of exploration and development. A systematic survey for such an assessment is planned for the summer of 1976 and, therefore, this summary is tentative. Although the major problems and regional setting are discussed in this paper, a great deal more specific data and interpretations will begin to become available in about one year. In this summary we consider the geology of a broad region on the continental shelf off the Kodiak group of islands and the Kenai Peninsula. We will concentrate on the area proposed for leasing in Sale #46. The area lies between about 56°N latitude and 60°N latitude (Fig. 1), and it measures approximately 660 km x 100 km. Water depths are generally less than 200 m.

Alaska↗
USGS1976

Preliminary report on uranium-, thorium-, and rare-earth-bearing rocks near Golovin, Alaska

Uranium-, thorium-, and rare-earth bearing rocks were found by a U.S. Geological Survey field party 15 miles northeast of Golovin, Alaska, in the southeastern Seward Peninsula (fig. 1) in June 1976. The mineralized areas occur in syenite and appear to be concentrated along the margins of alkaline dikes, with allanite tentatively identified as the principal mineral containing the uranium-, thorium-, and rare-earths. Samples contain as much as 0.15 percent U 3 0 8 and 1.05 percent Th0 2 , and over 2 percent rare-earth elements. These mineralized rocks are closely associated with alkaline dikes which are part of a dike swarm that crops out over at least 250 km 2 (100 mi 2 ). This large dike swarm is thus of considerable economic interest. These uranium-, thorium-, and rare-earth-rich rocks occur near the west end of the western Alaska uranium-thorium province (West, 1953; Clark and others, 1975; Miller, 3976) and were found during a regional investigation of this province by the Geological Survey. The alkaline dikes were known from previous mapping by the two senior authors (Miller and others, 1972) to be anomalously radioactive. The mineralized areas described in this report were found while making a brief study of (1) alteration and/or mineralization associated with these dikes and (2) their relation to similar dikes and rocks which occur elsewhere in the province (Miller, 1972).

Alaska↗
USGS1976

Interpretation of Landsat imagery of the Tanacross quadrangle, Alaska

In this study of Landsat imagery for the Tanacross quadrangle, Alaska, two fundamentally different types of images were used: (1) a black and white, single band, Landsat mosaic of Alaska, constructed with images that are not computer-enhanced; and (2) various types of computer-enhanced Landsat images.

Alaska↗
USGS1977

Sub-sea temperatures and a simple tentative model for offshore permafrost at Prudhoe Bay, Alaska

In this report, we present temperatures measured in three holes drilled into the sea bed in the Prudhoe Bay region and a tentative interpretation of them in terms of the gross thermal regime and shoreline history of the area. The new holes (PB-1, PB-2, and PB-3, Figure 1) were drilled in spring, 1976 (see Sellmann, 1976) as part of a cooperative study of off-shore permafrost by the USGS, CRREL, and the University of Alaska. Results from two of the holes (#190 and #3370, Figure 1) drilled earlier by the University of Alaska (Osterkamp and Harrison, 1976) have been included in our interpretation. The reader not interested in analytical details may wish to examine Figures 1, 2, and 3, and then skip to the concluding section "Summary and Discussion," page 32.

Alaska↗
USGS1974

Some aspects of remote sensing for consideration in planning for environmental monitoring of the Alyeska Pipeline, Alaska

Remote sensing data were taken along a line surveyed for the building of the Alyeska Pipeline, Alaska, in the winter of 1973-74. The portion considered in this report is the area from the Yukon River south to Isabel Pass in the Alaska Range. The occurrences of aufeis gave the appearance of four rather distinct modes of formation. In the area south of Big Delta, the icings occurred as seepage at the toes of the terraces and along the bottoms of the stream channels cutting into the terraces. In the Yukon-Tanana uplands, the icings occurred generally as seepage at the lowest points in the U-shaped valleys and along the surfaces of the streams in the tributary valleys incised into the rolling hills. The icings formed in the stream channels in both regions have similar hydraulic considerations as do the icings formed in the lower part of the valleys at the toes of the terraces. Aerial techniques of collecting data by photography and thermal imagery were tested in this setting as a basis for consideration in planning for potential environmental monitoring of the pipeline.

Open-File Report↗
USGS1977

Organic geochemistry, lithology, and paleontology of Tertiary and Mesozoic rocks from wells on the Alaska Peninsula

Core chips and drill cuttings from eight of the nine wells drilled along the Bering Sea lowlands of the Alaska Peninsula were subjected to lithologic and paleontologic analyses. Results suggest that at least locally, sedimentary rocks of Tertiary age contain oil and gas source and reservoir rocks capable of generating and accumulating liquid and gas hydrocarbons. Paleogene strata rich in organic carbon are immature. However, strata in offshore basins to the north and south may have been subjected to a more productive thermal environment. Total organic carbon content of fine grained Neogene strata appears to be significantly lower than in Paleogene rocks, possibly reflecting nonmarine or brackish water environments of deposition. Neogene sandstone beds locally yield high values of porosity and permeability to depths of about 8,000 feet (2,439 m). Below this depth, reservoir potential rapidly declines. The General Petroleum, Great Basins No. 1 well drilled along the shore of Bristol Bay reached granitic rocks. Other wells drilled closer to the axis of the present volcanic arc indicate that both Tertiary and Mesozoic sedimentary rocks have been intruded by dikes and sills of andesite and basalt. Although the Alaska Peninsula has been the locus of igneous activity throughout much of Mesozoic and Tertiary time, thermal maturity indicators such as vitrinite reflectance and coal rank suggest, that on a regional scale, sedimentary rocks have not been subjected to abnormally high geothermal gradients.

Open-File Report↗
USGS1978

Geotechnical properties of sediments from the Continental Shelf south of Icy Bay, northeastern Gulf of Alaska

Studies of geotechnical properties of marine sediments have recently intensified as the search for natural resources has expanded on the continental shelf. The U. S. Geological Survey has begun a detailed evaluation of geologic environmental conditions in continental shelf regions in order to facilitate safe development of continental shelf resources. Investigations of geohazards in the northeastern Gulf of Alaska (Fig. 1) began in 1974 when 6500 km of high and medium resolution seismic reflection data were collected from the eastern gulf between Yakutat and Montague Island (Carlson, Bruns and Molnia, 1975; Von Huene and others, 1975). The first extensive sediment sampling program was begun in 1975 when approximately 400 samples of continental shelf sediments were collected from the same area of the gulf (Carlson and others, 1977b). A limited number of geotechnical measurements were made from these samples and samples collected by subsequent programs, however, systematic measurement of geotechnical properties was not started until the 1977 cruise of the NOAA ship DISCOVERER. Once unstable environments or "geohazards", such as slumps and slides, are delineated, geotechnical testing is an important means of quantifying such geologic processes and consequently furthering our understanding of them. The purposes of this report are two-fold: (1) to report variations of physical properties in 1-2 meter gravity cores and (2) to recognize any variations in the areal distribution of these properties within and adjacent to an area of mass movement in the northeastern Gulf of Alaska.

Alaska↗
USGS1978

Gazetteer of coastal and offshore features of the Gulf of Alaska north of 54° N latitude

This gazetteer, the first of three to be released, presents names of seafloor features of the Gulf of Alaska and coastal features north of 54° N latitude between Cross Sound to the east and Unimak Island to the west. Also included are Prince William Sound and Cook Inlet but not the fiords, channels, and shoreline of southeast Alaska that make up the "Inside Passage" and Alexander Archipelago.

Alaska↗
USGS1979

A uranium occurrence in the Tertiary Kootznahoo Formation on Kuiu Island, southeast Alaska

Radioactive anomalies as high as 50 times background and uranium-bearing samples were discovered in parts of the nonmarine Tertiary Kootznahoo Formation in southeast Alaska by K. A. Dickinson and John Mitchell. Samples containing as much as 1300 ± 400 ppm uranium, measured by beta eU, were found. These samples have the highest uranium contents so far reported from Tertiary sedimentary rocks in southeast Alaska. Eakins (1975) reported two samples containing 12 and 13 ppm uranium and an anomaly of 13 times background from the same area. The purpose of this paper is to report the results of present studies and to suggest further work.

Alaska↗
USGS1979

Sediment transport in the Tanana River in the vicinity of Fairbanks, Alaska, 1977-78

Measurements of the sediment load of the Tanana River in the vicinity of Fairbanks, Alaska, show that suspended-sediment transport rate in tons per day, relates to water discharge, in cubic feet per second, as: Suspended-sediment transport rate (tons/day) = 5.717 x 10 to the minus 8th power x water discharge (cubic feet/second) to the 2.713 power, (where the correlation coefficient squared = 0.967). The bedload-transport rate is approximately 1 to 2 prcent of the suspended-sediment transport rate. Data collected at Fairbanks and upstream from Fairbanks near North Pole, Alaska, show little difference in size distribution of suspended sediment between the two locations. The median particle size distribution of suspended sediment is generally in the silt range, but at some low-water discharges, the median particle size is in the very fine sand range. The median particle size is in the very fine sand range. The median particle size of bedload near Noth Pole is generally in the gravel range, but at some low transport rates, the median particle size is in the medium sand range. At Fairbanks, data collected in 1977 indicate median particle sizes of bedload comparable to those of the upstream location, whereas data collected in 1978 indicate a marked decrease in median particle size of bedload between the two locations. For both locations and at all water discharges and sediment transport rates, particles constituting the suspended load are significantly smaller than particles constituting the bedload.

Alaska↗
USGS1979

Calc-alkaline plutonism along the Pacific rim of southern Alaska

Field, petrology, and age data on southern Alaska plutonic rocks now enable the delineation of eight calc-alkaline plutonic belts. These belts of plutons or batholithic complexes are curvilinear to linear and trend parallel or subparallel to the continental margin. The belts represent the principal loci of emplacement for plutons of specific ages and although there is spatial or temporal overlap in some cases, they are more commonly spatially and temporally distinct. Intermediate lithologies such as quartz diorite, tonalite, and granodiorite dominate in most of the Belts but granodiorite and granite characterize one. The belts are of Mesozoic or Cenozoic age and plutonism began in six of them at about 195, 175, 120, 75, 60, and 40 m.y. ago; age relations in two are poorly known. Recognition of the belts is important for future studies of regional geology, tectonism, and magmatism along the Pacific rim of southern Alaska.

Open-File Report↗
USGS1981

Results of exploratory drilling at Point MacKenzie, Alaska, 1981

The Matanuska-Susitna Borough anticipates industrial development near Point MacKenzie, Alaska. Because little hydrologic information is available for the area, the Borough contracted for the drilling of two test wells. It was found that: Both wells penetrated unconsolidated stratified clay, silt, sand, and gravel; each well penetrated a shallow unconfined and deeper confined aquifers; the water levels in the wells rise and fall with the tide; the chemical analyses indicate that the water quality meets the Alaska Drinking Water Standards, except for slightly high levels of manganese and pH; and the potential for saltwater intrusion should be evaluated as part of future studies. (USGS)

Open-File Report↗
USGS1981

Eastern Gulf of Alaska seismicity: Annual report to the National Oceanic and Atmospheric Administration for April 1, 1980, through March 31, 1981

The objective of this research is to collect and analyze data on earthquake activity in the northeast Gulf of Alaska (NEGOA) and adjacent onshore areas in order to develop a better regional seismotectonic model and more accurately assess the earthquake potential. This information is critical to the establishment of criteria for the safe development of oil and gas. Large (M s > 7) historical earthquakes have occurred in and around the NEGOA, and recent studies suggest that the NEGOA is a likely site for a magnitude 8 or larger earthquake to occur within the next two or three decades. A great earthquake (Ms>8) associated with low-angle oblique underthrusting of the sea floor beneath continental shelf could be accompanied by strong ground shaking throughout much of the eastern Gulf of Alaska, possibly from Cross Sound to Kayak Island (Page, 1975), and could trigger tsunamis, seiches, and submarine slumping, any of which could be hazardous to offshore and coastal structures (Meyers, 1976).

Alaska↗