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At least 1,333 records · Page 74Linked to original sources
USGS1965

Geology of the Romanzof Mountains, Brooks Range, northeastern Alaska

This remote 700 square mile area in the Brooks Range is topographically rugged and geologically diverse; it contains a granitic pluton, low-grade metamorphic rocks, sedimentary rocks, and mafic igneous rocks, as well as glacial features. Rocks of sedimentary origin include from oldest to youngest: 1.Neruokpuk Formation Middle and Upper Devonian(?), more than 4000 feet thick, a variety of units which represent the greenschist facies, including quartzitic- and schistose-feldspathic graywacke; phyllite, argillite, and slate, as well as dark limestone, sandy limestone, and silicified carbonate rocks. The succession of units in parts of the area is uncertain. Correlations between these units and with others in the eastern Brooks Range are provisional. 2.Kekiktuk Conglomerate and Kayak(?) Shale (Upper Devonian(?) to Upper Mississippian), a single map unit, from absent(?) to 400+ feet thick, containing dark shale Kayak(?) in its uppermost part and quartzite, interbedded dark shale, and some pebble- to boulder-conglomerate in the locally absent lower part (Kekiktuk). The unit overlies the Neruokpuk with angular unconformity, which may reflect either a pre-Kayak(?) or pre-Kekiktuk hiatus or both. 3.Lisburne Group, almost entirely carbonate rocks, and relatively thin in this area, 600 to 800 feet thick. Alapah Limestone (Upper Mississippian), to 560 feet thick, includes gray sandy, crystalline, and cherty limestone; minor dark shale; and dark cherty carbonate rocks in the upper part. The lower contact is gradational with the Kayak(?). Wahoo(?) Limestone (Pennsylvanian(?) to Permian) conformably overlies the Alapah, is absent to 200+ feet thick, and is characterized by light-gray crinoidal limestones in its upper part. 4. Sadlerochit Formation, consisting of three intraconformable units: ferruginous sandstone member (Permian) of ironstained orthoquartzite and dark slate, 175 to 240 feet thick which unconformably overlies the Wahoo(?) and Alapah Limestones; shale member of dark shale, slate, and minor quartzite averaging 400 feet in thickness; and quartzite member (Lower(?) Triassic), 700 feet thick, mostly orthoquartzite with minor shale and conglomerate. The basal clastics were probably shed from the north. 5.Shublik Formation (Middle(?) and Upper Triassic), 600 to 700 feet thick, with the thin phosphatic sandstone member overlain by dark phosphatic limestones and limy shales of the limestone member. 6.Kingak Formation (Jurassic), more than 1000 feet thick. The siltstone member, resistant sandstone and siltstone 75 to 150 feet thick, is overlain by an undetermined thickness of black shale. The basal part contrasts sharply with the underlying Shublik, indicating possible disconformity. 7.Ignek(?) Formation (Cretaceous), represented in the foothills where lithic graywacke, shale, and coaly shale constitute the few exposures examined. 8.Glacial and glaciofluvial materials of five advances recognized on the basis of morphology and position, which are tentatively correlated with five glaciations 15 miles west of the area. 9. Recent alluvial and colluvial deposits including fans which appear to represent at least three stages of encroachment. The Ramanzof granite, exposed in the Okpilak batholith and Jago stock, is mostly light-gray quartz monzonite to granite, and contains essential quartz, perthitic microcline, albite-oligoclase, and partly chloritized biotite. Limited modal and chemical data are presented. Three textural facies are: 1) porphyritic (marginal), with abundant large microcline megacrysts; 2) variable (middle to marginal), which exhibits textural and mineralogical banding; and 3) coarse (inner to marginal), which is gneissoid to equigranular. Facies relationships appear to be mostly gradational but may be locally intrusive. Some schistose metasedimentary(?) rock occurs in the granite. Aplite dikes, inclusions, tourmaline veins and replacements, and chlorite and quartz veins are locally common, as well as quartz monzonite and mafic igneous dikes. Contacts with Neruokpuk Formation rocks are mostly abrupt, concordant to cross-cutting, and locally adjoin tactite and hornfels of the albite-epidote-hornfels and hornblende-hornfels facies. Contacts with Kekiktuk Conglomerate are apparently gradational through a schistoze zone. Both primary and secondary structural elements are present in the Romanzof in granite. Textural and mineralogical banding and, in general, feldspar foliation are considered to be primary in origin; biotite foliation, gneissic and schistose foliation, and schistose zones are considered secondary. Lead-alpha age of zircons appears to be Late Devonian, K-Ar age of biotite is Cretaceous, possibly indicating updating by later reheating. Field age relationships are inconclusive but suggest pre-Kayak(?) (Upper Devonian) granite emplacement. The pluton is interpreted to be essentially the product of melt crystallization, synorogenically emplaced by forceful injection with minor stoping, and may include marginally granitized rock. Mafic igneous rocks of altered basaltic composition (greenstones) include dikes in granitic and Neruokpuk Formation rocks, and volcanics(?). A late Paleozoic age is suggested for them. Structural grain strikes east-northeast; south-dipping elements are common. Structures include the major positive nature of the area (first order), relatively broad folds (second order) which contain small tight folds (third order). Related south-dipping cleavage, schistosity, and biotite foliation in granite in the northern part of the area are cut by prominent sets of transverse joints and faults. Other features are longitudinal normal and reverse faults, at least one large-scale overthrust fault, and sheared zones in granite with possible attendant retrograde metamorphism. Although Mesozoic and Tertiary deformational features are dominant in northern Alaska, the Romanzof area may have been part of a Late Devonian orogenic belt continuous with one in northern Canada. Three alternate trends of such a belt in northern Alaska are discussed, but evidence is inconclusive. The mineral potential of the area is largely unknown. Minor amounts of metallic sulfides and oxides are present in granite and Neruokpuk Formation rocks. Analyses of stream silt samples suggest the possibility of tin and beryllium potential. The Shublik Formation contains rock phosphate.

Alaska↗
USGS1970

Water-resources reconnaissance of the Kwiguk (Emmonak) area, Alaska

As part of an agreement between the Alaska Department of Natural Resources and the United States Geological Survey, Water Resources Division, a reconnaissance visit was made of the area in the vicinity of the village of Kwiguk (Emmonak), Alaska, during the period June 17-19, 1970, to evaluate the water resources and to suggest methods of developing additional sources of water.

Alaska↗
USGS1970

Petroleum possibilities of the Yukon-Koyukuk Province, Alaska

The recent discovery of major oil resources on Alaska's North Slope has rekindled interest in the petroleum possibilities of the Yukon-Koyukuk province, a vast tract of Cretaceous rocks stretching along the west coast of Alaska from the Brooks Range to the Yukon delta. Attention was first focused on this region in the early 1950's, after oil and gas were discovered in the Cretaceous of the North Slope by the U.S. Navy. The presence of similar Cretaceous strata in the Yukon-Koyukuk province and the possibility that some of the broad alluviated lowlands within the province might be underlain by Tertiary basins were pointed out by Gryc and others (1951) and Payne (1955). Between 1954 and 1961 large parts of the province were reconnoitered by oil company surface parties and a small amount of geophysical work was carried out in the Nulato-Kateel and Bethel areas. The explorational activity culminated in 1960-61 with the drilling of two deep tests, a 12,000-foot hole near Nulato on the Yukon River and a 15,000-foot hole at Napatuk Creek in the Yukon-Kuskokwim Coastal Lowland. Apparently neither test revealed oil shows or favorable reservoir rocks, as exploration and leasing activity in the province declined sharply thereafter. Since 1954 the U.S. Geological Survey has maintained a modest but continuing program of reconnaissance geologic mapping of the province and its borderlands. Nearly all parts of this vast area have been visited either by helicopter or river boat. Although information in many places is still sketchy, the broad outlines of the surface geology are now known. Subsurface data, however, are almost totally lacking. The mapping indicates that the petroleum possibilities over most of the province are limited because of complex structure and scarcity of promising reservoir rocks. Two areas where further exploration seems warranted are the Yukon-Kuskokwim Coastal Lowland and the western part of the Kobuk-Selawik Lowland.

Alaska↗
USGS1972

The status of mineral resource information on the major land withdrawals of the Alaska Native Claims Settlement Act of 1971

This report is an analysis of the adequacy of the present level of geologic knowledge for making mineral resource potential evaluations of 126 federal land withdrawals made under the Alaska Native Claims Settlement Act. The withdrawals considered are Native village and regional deficiency areas (Sec. 11.A.3, ANCSA), classification and national interest study areas for possible inclusion in the four national systems (Sec. 17.d.2) and classification and public interest areas (Sec. 17.d.1). Neither prior withdrawals, utility corridors, state selections, open lands, or Indian Reserves are included. Native village withdrawals are also not included because they were the subject of an earlier report (Cobb, E. H., and Trollman, W. T., 1971). The present report consists of two sections. The introduction explains the method of preparation and presents a summary table and some general remarks on the mineral potential of Alaska. The second part, the discussion of withdrawals, contains listings of the investigations that have been made and analyses of their adequacy in view of what needs to be known about the withdrawals.

Alaska↗
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

Report on the environmental geology OCS area, eastern Gulf of Alaska

In anticipation of oil and gas leasing of the outer continental shelf (OCS lease area 39) in the northeastern Gulf of Alaska, the U. S. Geological Survey began a regional reconnaissance in 1974. The study area, which extends from Prince William Sound on the west to Yakutat Bay on the east, is in a region fraught with natural hazards. The tectonic history of the area suggests that future major earthquakes could pose serious hazards to installations on the continental shelf or along the coast of the Gulf of Alaska. The hazard may be either direct, by ground shaking or fault displacement, or indirect, through ground failure or generation of tsunami waves. Storm waves sometimes are responsible for ground failures, especially in areas of rapid accumulation of sediment.

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

Computer-enhanced LANDSAT imagery as a tool for mineral exploration in Alaska

Recent work in the Nabesna and McCarthy quadrangles, Alaska, indicates that computer-enhanced LANDSAT imagery shows many of the known mineral deposits and can help in the prediction of potential mineral occurrences. False color, "simulated natural color" and color ratio techniques, were used successfully in conjunction with a black and white, single band photomosaic of Alaska. Computer techniques involved 2 stages of digital image processing: 1) atmospheric and sun elevation corrections, noise removal, computer mosaicking and change of the data format; and 2) image enhancement, involving data manipulation for maximum discrimination of surface materials and structure. Application of a new technique called a "sinusoidal" stretch gave information not available in other products having standard contrast stretches. We identified several orthogonal sets of linears and found parallel linears to be regularly spaced at approximately 30-35 km intervals. The locations of known mineral occurrences correlate well with the linears. Extensions of known faults and possible locations of hidden intrusive bodies were identified. Analysis of numerous areas of anomalous light reflectance showed that most are associated with known mineral occurrences, altered zones or geochemical anomalies, whereas some are not and may represent unexplored altered zones or mineralized areas worthy of future exploration.

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↗
USGS1977

Aquatic organisms from selected sites along the Trans-Alaska Pipeline corridor, September 1970 to September 1972: supplement

This report is a supplement to earlier preconstruction studies of benthic invertebrates and water quality at selected sites along the trans-Alaska pipeline corridor. Some of the problems which arose during the course of data collection and analysis are discussed. Benthic invertebrate abundance and community-structure data are presented for 20 sites along the trans-Alaska pipeline for the period September 1970 to September 1972. In addition, a list of invertebrate taxa identified to various taxonomic levels is given for 42 sites along the pipeline. (See also W74-08369) (Woodard-USGS)

Open-File Report↗
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↗
USGS1977

Distribution and character of naleds in northeastern Alaska

An examination of the distribution of river naleds seen in Landsat satellite imagery and high- and low-altitude aerial photography of Alaska's North Slope indicates that these features are widespread east of the Colville River and less abundant to the west. Where naleds occur, stream channels are wide and often form braided channels. Their distribution can be related to changes in stream gradient and to the occurrence of springs. Large naleds, such as on the Kongakut River, often remain through the summer melt season to form the nucleus of icing in the succeeding winter. Major naleds also are likely to significantly influence the nature of permafrost in their immediate vicinity. The map of naleds may serve as a guide to the occurrence of year-round flowing water, a sparse commodity in northern Alaska.

Open-File Report↗