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Geology of southwestern Alaska

By
John Decker
John Decker
Alaska Division of Geological and Geophysical Surveys, 794 University Avenue, Fairbanks, Alaska 99709
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Steven C. Bergman
Steven C. Bergman
ARCO Oil and Gas Company, 2300 West Plano Parkway, Plano, Texas 75075
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Robert B. Blodgett
Robert B. Blodgett
Department of Geology, Oregon State University, Corvallis, Oregon 97331
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Stephen E. Box
Stephen E. Box
Branch of Alaskan Geology, U.S. Geological Survey, 4200 University Drive, Anchorage, Alaska 99508
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Thomas K. Bundtzen
Thomas K. Bundtzen
Alaska Division of Geological and Geophysical Surveys, 3700 Airport Way, Fairbanks, Alaska 99709
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James G. Clough
James G. Clough
Alaska Division of Geological and Geophysical Surveys, 794 University Avenue, Fairbanks, Alaska 99709
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Warren L. Coonrad
Warren L. Coonrad
Branch of Alaskan Geology, U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025
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Wyatt G. Gilbert
Wyatt G. Gilbert
Alaska Division of Geological and Geophysical Surveys, 3601 C Street, Anchorage, Alaska 99510
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Martha L. Miller
Martha L. Miller
Branch of Alaskan Geology, U.S. Geological Survey, 4200 University Drive, Anchorage, Alaska 99508
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John M. Murphy
John M. Murphy
Branch of Alaskan Geology, U.S. Geological Survey, 4200 University Drive, Anchorage, Alaska 99508
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Mark S. Robinson
Mark S. Robinson
Alaska Division of Geological and Geophysical Surveys, 794 University Avenue, Fairbanks, Alaska 99709
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Wesley K. Wallace
Wesley K. Wallace
ARCO Alaska, Inc., P.O. Box 100360, Anchorage, Alaska 99510
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Published:
January 01, 1994

Abstract

Southwest Alaska lies between the Yukon-Koyukuk province to the north, and the Alaska Peninsula to the south (Wahrhaftig, this volume). It includes the southwestern Alaska Range, the Kuskokwim Mountains, the Ahklun Mountains, the Bristol Bay Lowland, and the Minchumina and Holitna basins. It is an area of approximately 175,000 km2, and, with the exception of the rugged southwestern Alaska Range and Ahklun Mountains, consists mostly of low rolling hills.

The oldest rocks in the region are metamorphic rocks with Early Proterozoic protolith ages that occur as isolated exposures in the central Kuskokwim Mountains, and in fault contact with Mesozoic accretionary rocks of the Bristol Bay region. Precambrian metamorphic rocks also occur in the northern Kuskokwim Mountains and serve as depositional basement for Paleozoic shelf deposits. A nearly continuous sequence of Paleozoic continental margin rocks underlies much of the southwestern Alaska Range and northern Kuskokwim Mountains. The most extensive unit in southwest Alaska is the predominantly Upper Cretaceous Kuskokwim Group, which, in large part, rests unconformably on older rocks of the region. Volcanic rocks of Mesozoic age are common in the Bristol Bay region, and volcanic and plutonic rocks of latest Cretaceous and earliest Tertiary age are common throughout southwest Alaska.

Two major northeast-trending faults are known to traverse southwest Alaska, the Denali-Farewell fault system to the south, and the Iditarod-Nixon Fork fault to the north. Latest Cretaceous and Tertiary right-lateral offsets of less than 150 km characterize both faults. The Susulatna lineament (or Poorman fault), north of the Iditarod-Nixon Fork

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Contents

DNAG, Geology of North America

The Geology of Alaska

George Plafker
George Plafker
U.S. Geological Survey MS 904, 345 Middlefield Road Menlo Park, California 94025
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Henry C. Berg
Henry C. Berg
115 Malvern Avenue Fullerton, California 92632
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Geological Society of America
Volume
G-1
ISBN electronic:
9780813754536
Publication date:
January 01, 1994

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