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Studies by the U.S. Geological Survey in Alaska, 2004
U.S. Geological Survey
Professional Paper 1709

Studies by the U.S. Geological Survey in Alaska, 2004

Edited by Peter J. Haeussler and John P. Galloway


photo of glacier moving toward the viewer
A view of the Tordrillo Mountains and the Trimble Glacier in western Alaska Range. Photo by Peter Haeussler


The collection of six papers that follow continues the series of U.S. Geological Survey (USGS) investigative reports in Alaska under the broad umbrella of the geologic sciences. This series represents new and sometimes-preliminary findings that are of interest to Earth scientists in academia, government, and industry; to land and resource managers; and to the general public. The reports presented in Studies by the U.S. Geological Survey in Alaska cover a broad spectrum of topics from various parts of the State, serving to emphasize the diversity of USGS efforts to meet the Nation's needs for Earth-science information in Alaska. This professional paper is the first “online only” version of Studies by the U.S. Geological Survey in Alaska, reflecting the current trend toward disseminating research results on the World Wide Web with rapid posting of completed reports.


By John P. Galloway and Peter J. Haeussler

The six papers in this volume cover a broad spectrum of Earth-science topics from many parts of Alaska. Houseknecht and Schenk describe Upper Cretaceous strata of the upper part of the Nanushuk Formation, the Seabee Formation, and the lower part of the Tuluvak Formation that are exposed along the Colville River on the east flank of Umiat Mountain in north-central Alaska. In the western Brooks Range, paleosols have been recognized in outcrops of the Endicott Group and Kingak Shale. Dumoulin and White present the first microscopic analysis of paleosols from these units, which provide the first evidence of subaerial exposure of the Siksikpuk and Ipewik Formations. An aeromagnetic study of the Lake Clark Fault by Haeussler reveals a north-trending band of magnetic anomalies that are right-laterally offset about 26 km across the fault in south-central Alaska. The magnetic anomalies correlate spatially with a belt of dated 34–39-m.y.-old granitic plutons. Therefore, the Lake Clark Fault apparently has had ~26 km of right-lateral offset in the past 34–39 m.y. The aeromagnetic data also define another previously unknown fault, which appears to have about 11 km of right-lateral offset. Calvert and others present a series of high-precision 40Ar/39Ar ages of selected lavas from Westdahl Volcano, in southwestern Alaska. A dike cutting an old pyroclastic flow and associated lahar deposits from a precursor volcano yields an age of 1,654 k.y., indicating that this precursor volcano is older than early Pleistocene. A total of 11 geographically distributed lavas with ages ranging from 47 to 127 k.y. date construction of the Westdahl volcanic center. Lava flows cut by an apparent caldera-rim structure yielded ages of 81±5 and 121±8 k.y., placing a maximum date of 81 ka on caldera formation.

Two other papers discuss the framework geology of southeastern Alaska. Himmelberg and Brew discuss thermobarometric constraints on mid-Cretaceous to Late Cretaceous metamorphic events in the western metamorphic belt of the Coast Mountains near Petersburg. The western metamorphic belt, which ranges from a few kilometers to several tens of kilometers in width, records a complex sequence of contact-metamorphic and regional metamorphic events. A second paper by Haeussler and others presents a laser-ablation/ICPMS study of detrital zircons from turbidites in the Sitka Graywacke. This monotonous unit was previously believed to be of essentially one age and to correlate with the Valdez Group, but another part is 25 m.y. older and correlates with rocks of the McHugh Complex in south-central Alaska.

Professional Paper 1709-A, Haeussler, Peter J., and Saltus, Richard W., 2005, 26 km of offset on the Lake Clark Fault since late Eocene time.

Professional Paper 1709-B, Houseknecht, David W., and Schenk, Christopher J., 2005, Sedimentology and sequence stratigraphy of the Cretaceous Nanushuk, Seabee, and Tuluvak Formations exposed on Umiat Mountain, north-central Alaska.

Professional Paper 1709-C, Himmelberg, Glen R., and Brew, David A., 2005, Thermobarometric constraints on mid-Cretaceous to Late Cretaceous metamorphic events in the western metamorphic belt of the Coast Mountains Complex near Petersburg, southeastern Alaska.

Professional Paper 1709-D, Calvert, Andrew T., Moore, Richard B., and McGimsey, Robert G., 2005, Argon geochronology of late Pleistocene to Holocene Westdahl Volcano, Unimak Island, Alaska.

Professional Paper 1709-E, Dumoulin, Julie A., and White, Tim, 2005, Micromorphologic evidence for paleosol development in the Endicott Group, Siksikpuk Formation, Kingak(?) Shale, and Ipewik Formation, western Brooks Range, Alaska.

Professional Paper 1709-F, Haeussler, Peter J., Gehrels, George E., and Karl, Susan M., 2006, Constraints on the age and provenance of the Chugach accretionary complex from detrital zircons in the Sitka Graywacke near Sitka, Alaska.


Dumoulin, Julie A.
Haeussler, Peter J.
McGimsey, Robert G.
     U.S. Geological Survey
     4200 University Dr.
     Anchorage, AK 99508-4667

Moore, Richard B. (retired)
     U.S. Geological Survey
     520 N. Park Ave.
     Tucson, AZ 85719

Saltus, Richard W., Mail Stop 964
Schenk, Christopher J., Mail Stop 939
     U.S. Geological Survey
     P.O. Box 25046, Mail Stop ___
     Denver, CO 80225

Menlo Park
Brew, David A., Mail Stop 901
Calvert, Andrew T., Mail Stop 937
Galloway, John P., Mail Stop 901
     U.S. Geological Survey
     345 Middlefield Rd., Mail Stop ___
     Menlo Park, CA 94025-3591

Houseknecht, David W.
     U.S. Geological Survey
     National Center, Mail Stop 956
     12201 Sunrise Valley Dr.
     Reston, VA 20192-0002


Gehrles, George E.
     Department of Geosciences
     University of Arizona
     Tucson, AZ 85721-0077

Himmelberg, Glen R.
     Department of Geological Sciences
     University of Missouri
     Columbia, MO 65211

White, Tim
     EMS Environment Institute
     17 Earth Engineering Science Building
     Pennsylvania State University
     University Park, PA 16802

For questions about the content of this report, contact Peter Haeussler

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Maintained by: Michael Diggles
Created: October 3, 2005
Last modified: May 5, 2006 (mfd)