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Geology topics

Frederic H. Wilson

Publications and source records attributed to Frederic H. Wilson.

At least 73 records · Page 4Linked to original sources
USGS1995

Geologic map of Port Moller, Stepovak Bay, and Simeonof Island quadrangles, Alaska Peninsula, Alaska

Geologic mapping of Port Moller, Stevopak Bay, and Simeonof Island 1° by 2° quadrangles on the Alaska Peninsula was conducted as part of the Alaska Mineral Resource Assessment Program (AMRAP). Geologic observations was obtained by using helicopter overflights, vertical aerial photography, and enhanced and extensively processed Landsat imagery (York and others, 1984; Wilson and York, 1985). Helicopter-supported field investigations were conducted from Sand Point in 1982 and 1986 and from both Sand Point and Port Moller in 1985 and 1985. In addition, field work was conducted from the U.S. Geological Survey Research Vessel Don J. Miller II in 1983 and 1984. The mapping of Burk (1965), Kennedy and Waldron (1955), and Moore (1974) provided an excellent basis for the AMRAP mapping. The present map duplicates both Moore’s map of the outer Shumagin Islands and Kennedy and Waldron’s map of the Pavlof Volcano area with minor additions. However, important changes have been made to Burk’s pioneering work.

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USGS1994

Sample locality map and analytical data for potassium-argon ages in the Port Moller, Stepovak Bay, and Simeonof Island quadrangles, Alaska Peninsula

Potassium-argon age determinations for 84 volcanic, intrusive, and hydrothermally altered rocks from the Port Moller, Stepovak Bay, and Simeonof Island quadrangles are reported here. Of these age determinations, 78 samples were analyzed as part of Alaska Mineral Resource Assessment Program (AMRAP) studies in the Port Moller, Stepovak Bay, and Simeonof Island quadrangles. Age deter- minations for 6 of the samples have been previously published (Burk, 1965; Kienle and Turner, 1976; Wilson and others, 1981). This report consists of a sample location map, analytical data (table 1), and rock descriptions (table 2).

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USGS1994

Geologic framework of the Aleutian arc, Alaska

The Aleutian arc is the arcuate arrangement of mountain ranges and flanking submerged margins that forms the northern rim of the Pacific Basin from the Kamchatka Peninsula (Russia) eastward more than 3,000 km to Cooke Inlet (Fig. 1). It consists of two very different segments that meet near Unimak Pass: the Aleutian Ridge segment to the west and the Alaska Peninsula-the Kodiak Island segment to the east. The Aleutian Ridge segment is a massive, mostly submerged cordillera that includes both the islands and the submerged pedestal from which they protrude. The Alaska Peninsula-Kodiak Island segment is composed of the Alaska Peninsula, its adjacent islands, and their continental and insular margins. The Bering Sea margin north of the Alaska Peninsula consists mostly of a wide continental shelf, some of which is underlain by rocks correlative with those on the Alaska Peninsula. There is no pre-Eocene record in rocks of the Aleutian Ridge segment, whereas rare fragments of Paleozoic rocks and extensive outcrops of Mesozoic rocks occur on the Alaska Peninsula. Since the late Eocene, and possibly since the early Eocene, the two segments have evolved somewhat similarly. Major plutonic and volcanic episodes, however, are not synchronous. Furthermore, uplift of the Alaska Peninsula-Kodiak Island segment in late Cenozoic time was more extensive than uplift of the Aleutian Ridge segment. It is probable that tectonic regimes along the Aleutian arc varied during the Tertiary in response to such factors as the directions and rates of convergence, to bathymetry and age of the subducting Pacific Plate, and to the volume of sediment in the Aleutian Trench. The Pacific and North American lithospheric plates converge along the inner wall of the Aleutian trench at about 85 to 90 mm/yr. Convergence is nearly at right angles along the Alaska Peninsula, but because of the arcuate shape of the Aleutian Ridge relative to the location of the plates' poles of rotation, the angle of convergence lessens to the west (Minster and Jordan, 1978). Along the central Aleutian Ridge, underthrusting is about 30° from normal to the volcanic axis. Motion between plates is approximately parallel along the western Aleutian Ridge. In this paper we briefly describe and interpret the Cenozoic evolution of the Aleutian arc by focusing on the onshore and offshore geologic frameworks in four of its sectors, two sectors each from the Aleutian Ridge and Alaska Peninsula-Kodiak Island segments (Fig. 1). We compare the geologic evolution of the segments and comment on the implications of some new, previously unpublished data.

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USGS1994

Geology of south-central Alaska

South-central Alaska is defined as the region bounded by the Kuskokwim Mountains to the northwest, the basins north of the Alaska Range to the north, the Canadian border to the east, and the Chugach Mountains to the south (Fig. 1). This region, hereafter called the study area, includes the Alaska Range, the Wrangell, Nutzotin, and Talkeetna mountains, the Copper River and the Susitna basins, the northern flank of the Chugach Mountains, the Aleutian Range, and the Alaska Peninsula. This chapter describes and interprets the bedrock geology of the region, which consists mostly of a collage of Paleozoic and Mesozoic tectonostratigraphic terranes (hereafter referred to as terranes), Mesozoic flysch basin deposits, late Paleozoic and Mesozoic plutonic rocks, and younger late Mesozoic and Cenozoic sedimentary, volcanic, and plutonic rocks. Cited published sources and new data and interpretations of the authors are utilized for the descriptions and interpretations. The terranes, flysch basin deposits, and younger Mesozoic sedimentary, volcanic, and plutonic assemblages are described first in a general northwest to southeast order. Major faults or sutures are described second. Stratigraphic linkages and structural and tectonic relations between terranes are described last. Definitions of the various stratigraphic, structural, and tectonic terms are stated at the end of this introduction.

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USGS1994

Map and table showing isotopic age data in Alaska

The source of the data reported here is a compilation of radiometric ages maintained in conjunction with the Alaska Mineral Resource Assessment Program (AMRAP) studies for Alaska. The symbol shape plotted at each location is coded for rock type, whether igneous, metamorphic, or other; the color of the symbol shows the geologic era or period for the Sample(s) at each locale. A list of references for each quadrangle is given to enable the user to find specific information including analytical data for each sample dated within a particular quadrangle. At the scale of this map, the very large number of Samples and the clustering of the samples in limited areas prevented the showing of individual sample numbers on the map. Synthesis and interpretation of any data set requires the user to evaluate the reliability or value of each component of the data set with respect to his or her intended use of the data. For geochronological data, this evaluation must be based on both analytical and geological criteria. Most age determinations are published with calculated estimates of analytical precision, Replicate analyses are infrequently performed; therefore, reported analytical precision is based on estimates of the precision of various components of the analysis and often on an intuitive factor to cover components that may have not been considered. Analytical accuracy is somewhat more difficult to determine; it is not only dependent on the actual measurement, it is also concerned with uncertainties in decay and abundance constants, uncertainties in the isotopic composition and size of the tracer for conventional K-Ar ages, and uncertainties in the Original isotopic composition of the sample, Geologic accuracy of a date is Variable; the interpretation of the meaning of an age determination, is important in the evaluation of its geologic accuracy. Potassium-argon, rubidium-strontium, and uranium-lead age determinations on a single sample can differ widely yet none or all may be wrong Given that the basic Conditions of each dating method were met, each method determines an age based on the equilibration of its particular isotopic system, yet these are different systems and they react to heat, pressure, and recrystallization in different ways. This map is a compilation and not a synthesis or interpretation. Its purpose is to help the user determine the dating coverage of areas of Alaska and gain access to the available data for the state or a project area. Interpretation of that data and evaluation of its suitability for use with any particular project is left to the user. Compilations, with sample data, have been published for much of the state; and are as follows: Wilson, and others (1979), southeastern Alaska; Wilson (1981), Aleutian Islands and Alaska Peninsula, Shew and Wilson (1981), southwestern Alaska; Wilson and others (1985), Yukon Crystalline terrane; Grybeck and others (1977), northern Alaska; Dadisman (1980), south-central Alaska.

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USGS1994

Prehistoric Alaska: The land

Many Alaskans know the dynamic nature of Alaska’s landscape firsthand. The 1964 earthquake, the 1989 eruption of Mount Redoubt volcano, the frequent earthquakes in the Aleutians and the ever-shifting meanders of the Yukon and Kuskokwim rivers remind them of constant changes to the land. These changes are part of the continuing story of the geologic growth and development of Alaska during hundreds of millions of years. By geologic time, Alaska has only recently come into existence and the dynamic processes that formed it continue to affect it. The landscape we see today has been shaped by glacier and stream erosion or their indirect effects, and to a lesser extent by volcanoes. Most prominently, if less obviously, Alaska has been built by slow movements of the Earth’s crust we call tectonic or mountain-building. During 5 billion years of geologic time, the Earth’s crust has repeatedly broken apart into plates. These plates have recombined, and have shifted positions relative to each other, to the Earth’s rotational axis and to the equator. Large parts of the Earth’s crust, including Alaska, have been built and destroyed by tectonic forces. Alaska is a collage of transported and locally formed fragments of crusts As erosion and deposition reshape the land surface, climatic changes, brought on partly by changing ocean and atmospheric circulation patterns, alter the location and extent of tropical, temperate and arctic environments. We need to understand the results of these processes as they acted upon Alaska to understand the formation of Alaska. Rocks can provide hints of previous environments because they contain traces of ocean floor and lost lands, bits and pieces of ancient history.

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USGS1992

Preliminary geologic map of the Cold Bay and False Pass quadrangles, Alaska Peninsula

This map of the Cold Bay and False Pass 1:250,000-scale quadrangles on the Alaska Peninsula is a compilation based in part on the mapping conducted as part of the Alaska Mineral Resource Assessment Program (AMRAP) and the Geothermal Energy Program. Field studies by the authors began as early as 1973 in the quadrangles, but systematic mapping was not begun until 1988. Systematic mapping remains to be completed for much of the southwest part of the map area and the vicinity of southeastern Cold Bay. Previous geologic mapping in the region, which constitutes an invaluable data base for our studies, was conducted by Kennedy and Waldron (1955). Waldron (1961). Burk (1965). McLean and others (1978), and DuBois and others, 1989. Most of the new mapping for this map was done by helicopter-supported foot-traverses and with helicopter spot landings. Coverage of areas between surface observations was made using helicopter overflights and interpretation of vertical aerial photography and Landsat imagery. Field investigations were conducted from bases at Cold Bay (1990), King Cove (1988), and False Pass (1991). In addition, some field work in 1984 was also conducted using the U.S. Geological Survey Research Vessel Don J. Miller II in the vicinity of Belkofski Bay.

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USGS1990

The Alaska Mineral Resource Assessment Program: Background information to accompany folio of geologic and resource maps of the Ugashik, Bristol Bay, and western part of Karluk quadrangles, Alaska

The Ugashik, Bristol Bay, and western part of Karluk quadrangles (1:250,000) are a part of the Alaska Peninsula in southwestern Alaska. This circular, in conjunction with a companion folio of MF-series maps, two I-series geologic maps, and three bulletins, represents the results of integrated field and laboratory studies on the geology, geophysics, geochemistry, paleontology, geochronology, and mineral resources of the quadrangles. These studies were undertaken to provide a modern assessment of the mineral and energy resources of the quadrangles. Each map contains descriptive text, explanatory material, tables, diagrams, and pertinent references. This circular provides background information for the mineral resource assessment map (MF-1539-1) and integrates the component M F- and I-series maps. A comprehensive bibliography cites both specific and general references relevant to the geology and resources of the quadrangles.

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USGS1988

Geology and mineral resources of the Port Moller region, western Alaska Peninsula, Aleutian arc: A section in USGS research on mineral resources - 1989: Program and abstracts

Geologic mapping of the Port Moller, Stepovak Bay, and Simeonof Island quadrangles was begun under the auspices of the Alaska Mineral Resource Assessment Program (AMRAP) in 1983 . Two important mineral deposits are located in the Port Moller quadrangle; the Pyramid prospect is the largest copper porphyry system in the Aleutian Arc, and the Apollo Mine is the only gold mine to reach production status in the Aleutian Arc.

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USGS1988

Brief descriptions of mines, prospects, and mineral occurrences in the Port Moller and Stepovak Bay quadrangles, Alaska peninsula

This report contains brief descriptions of known mines, prospects, and mineral occurrences in the Port Moller and Stepovak Bay quadrangles on the Alaska Peninsula. These quadrangles, and the adjoining Simeonof Island quadrangle to the south were the subject of an Alaska Mineral Resource Assessment Program (AMRAP) mapping and mineral resource assessment project. This compilation of descriptions was made from the published literature (Wilson and others, 1986) and unpublished reports and data of The Aleut Corporation, the U.S. Bureau of Mines, and the U.S. Geological Survey. The initial compilation was primarily based on data from Cobb (1972) and MacKevett and Holloway (1977), however information provided by The Aleut Corporation and data gathered during the Port Moller AMRAP project added most of the information in the descriptions and the database. Compilation of this database is an ongoing process and this is a progress report of work completed to date. The authors would appreciate any corrections or additional information that users may be able to contribute. To facilitate active use of the descriptions, where information is not available for a particular field in the database, it is left blank so that the use can write in data as they obtain it.

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USGS1987

[Book review] The geochronology and evolution of Africa

This book was written 'to provide an up-to-date data bank from which those wishing to construct models concerned with the evolution of Africa .... can draw.' As such, it attempts a survey of 'integrated geology and geochronology' of the African continent throughout the Precambrian and into the Phanerozoic. Political and language divisions often hinder the synthesis of continent-wide data, therefore, this well-indexed inventory of selected data and synthesis of present geochronological knowledge for Africa as a whole provides an important reference for researchers and explorationists, many of whom have limited access to complete collections of the geological literature of Africa.

Precambrian Research↗