US Geological Survey Reports on Alaska Released in 2000 - USGS

158 Pages·2012·47.44 MB·English

Cover photograph: Oblique aerial photograph of Mount Griggs stratovolcano. View northward across upper Knife Creek.
Studies by the U.S. Geological Survey in
Alaska, 2000
Frederic H. Wilson and John P. Galloway, Editors
U.S. Geological Survey Professional Paper 1662
U.S. Department of the Interior
U.S. Geological Survey
U.S. Department of the Interior
Gale A. Norton, Secretary
U.S. Geological Survey
Charles G. Groat, Director
Any use of trade, product, or firm names in this publication is
tor descriptive purposes only and does not imply endorsement
by the U.S. Government.
U.S. Geological Survey, Reston, Virginia: 2002
For additional copies please contact
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Cataloging-in-Publication data is on tile with the Library of Congress
Published in the Western Region, Menlo Park, California
Manuscript approved tor publication, February 14, 2002
Text edited by George A. Havach, James W. Hendley II, and Peter H. Stauffer
Production and design by Susan Mayfield and Sara Boore
Contents
I ntrod uc ti on -----------------------------------------------------------------------------------------------------------------1
By Fredric H. Wilson and John P. Galloway
GEOLOGIC FRAMEWORK
East-Central Alaska
Geochemistry and Age Constraints on Metamorphism and Deformation in the
Fortymile River Area, Eastern Yukon-Tanana Upland, Alaska ----------------------------------------------5
By Warren C. Day, John N. Aleinikoff, and Bruce Gamble
South-Central Alaska
Stratigraphy, Age, and Geochemistry of Tertiary Volcanic Rocks and Associated
Synorogenic De posits, M aunt M c Kinley Quadran gI e , Alaska --------------------------------------------19
By Ronald B. Cole and Paul W. Layer
Stratigraphy and Provenance Data from the Upper Jurassic to Upper Cretaceous Kahiltna
Ass em bl age of South-Centra I AI as ka ------------------------------------------------------------------------45
By Kevin R. Eastham and Kenneth D. Ridgway
Southwestern Alaska
Late Triassic (Norian) Mollusks from the Taylor Mountains Quadrangle, Southwestern Alaska----------------55
By Christopher A. McRoberts and Robert B. Blodgett
Southeastern Alaska
Notes on the Bedrock Geology and Geography of the Stikine lcefield, Coast Mountains Complex,
Southeastern AI as ka -------------------------------------------------------------------------------------------77
By David A. Brew and Richard M. Friedman
HAZARDS
Southwestern Alaska
Mount Griggs: A Compositionally Distinctive Quaternary Stratovolcano Behind the Main
Vole an ic Line in Katma i Nation aI Park -----------------------------------------------------------------------87
ByWes Hildreth, Judy Fierstein, Marvin A. Lanphere, and David F. Siems
ENVIRONMENT AND CLIMATE
Northern Alaska
Treeline Biogeochemistry and Dynamics, Noatak National Preserve, Alaska -----------------------------------113
By Robert Stottlemyer, Dan Binkley, and Heidi Steltzer
South-Central Alaska
Environmental Geochemical Study of the Slate Creek Antimony Deposit, Kantishna Hills,
Denali National Park and Preserve, Alaska----------------------------------------------------------------123
By Robert G. Eppinger, Paul H. Briggs, James G. Crock, Allen L. Meier,
Stephen J. Sutley, and Peter M. Theodorakos
BIBLIOGRAPHIES
U.S. Geologic aI Survey Reports on Alaska ReI eased in 2000-------------------------------------------------------143
Compiled by John P. Galloway
Reports on Alaska in Non-USGS Publications Released in 2000 That Include
U.S. Ge o log i ca I Survey Authors -----------------------------------------------------------------------------147
Compiled by John P. Galloway
Ill

Contributors
Anchorage Others
Gamble, Bruce M. Binkley, Dan
Wilson, Frederic H. Department of Forest Sciences
Colorado State University
U.S. Geological Survey
4200 University Drive Fort Collins, CO 80523
Anchorage, AK 99508
Blodgett, Robert B.
Department of Zoology
Denver Oregon State University
Corvallis, OR 97331
Aleinikoff, John N., Mail Stop 963
Briggs, Paul H., Mail Stop 973 Cole, Ronald B.
Crock, James C., Mail Stop 973 Department of Geology
Eppinger, Robert G., Mail973 Allegheny College
Day, Warren, C., Mail Stop 973 Meadville, PA 16335
Meier, Allen L., Mail Stop 973
Eastham, Kevin R.
Siems, David F., Mail Stop 973
Department of Earth and Atmospheric Sciences
Sutley, Stephen J., Mail Stop 973
Purdue University
Theodorakos, Peter M., Mail Stop 973
West Lafayette, IN 47907-1397
U.S. Geological Survey
Friedman, Richard M.
P.O. Box 25046, Mail Stop_
Department of Earth and Ocean Sciences
Denver Federal Center
University of British Columbia
Denver, CO 80225
Vancouver, B.C. V6T 1Z4 Canada
Layer, Paul W.
Fort Collins
Department of Geology
Stottlemyer, Robert University of Alaska
U.S. Geological Survey Fairbanks, AK 99775
240 W. Prospect Rd.
McRoberts, Christopher A.
Fort Collins, CO 80526
Department of Geology
State University of New York
Menlo Park Cortland, NY 13045
Brew, David A., Mail Stop 901 Ridgway, Kenneth D.
Fierstein, Judy, Mail Stop 910 Department of Earth and Atmospheric Sciences
Galloway, John P., Mail Stop 901 Purdue University
Hildreth, Wes, Mail Stop 910 West Lafayette, IN 47907-1397
Lanphere, Marvin, Mail Stop 937
Steltzer, Heidi
U.S. Geological Survey Department of Forest Sciences
345 Middlefield Rd., Mail Stop _ Colorado State University
Menlo Park, CA 94025 Fort Collins, CO 80523
v

Studies by the U.S. Geological Survey in Alaska, 2000
U.S. Geological Survey Professional Paper 1662
Studies by the U.S. Geological Survey in
Alaska, 2000
Frederic H. Wilson and John P. Galloway, Editors
Introduction
By Frederic H. Wilson and John P. Galloway
The collection of eight papers that follow continue the series1 of U.S. Geological Survey
(USGS) investigative reports in Alaska under the broad umbrella of the geologic sciences. The
series presents 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.
Reports presented in Studies by the U.S. Geological Survey in Alaska cover a broad spectrum of
topics from various parts of the State (fig. 1) , serving to emphasize the diversity of USGS efforts
to meet the Nation's needs for earth-science information in Alaska.
The papers in this volume are organized under the topics Geologic Framework, Resources, and
Environment and Climate. This organization is intended to reflect the scope and objectives of current
USGS geologic programs in Alaska. In particular, Geologic Framework studies provide background
information that is the scientific basis for present and future earth-science investigations.
Day and others discuss the geochemistry of and age constraints on metamorphism and
deformation in the Fortymile River area, eastern Yukon-Tanana upland. Determining the age of
deposition of many of the major rock types within the Fortymile River area is a major challenge
for understanding the geologic evolution of the Yukon-Tanana lithotectonic terrane of east-central
Alaska. New geochemical data have helped to characterize the bedrock units, along with new U
Pb zircon ages on two critical units within the Fortymile River area. U-Pb-isotopic data on zircons
from the early (pre-D Steele Creek Dome Orthogneiss, as well as from a late-tectonic (late-D
1) 2)
epidote-bearing leucogranite intrusion, help constrain the youngest possible age for supracrustal
rocks and regional D deformation. The Steele Creek Dome Orthogneiss crystallized at 343±4
2
Ma, indicating that the supracrustal sequence is partly at least Early Mississippian in age. The
leucogranite crystallized during the waning states ofD deformation at 196±4 Ma. U-Pb data on
2
this Early Jurassic leucogranite also show that the inherited zircons have a complex history, with
analyses yielding ages of 359±5 and 232±7 Ma. These data confirm earlier 40 ArJ39A r ages that
suggest an Early Jurassic timing for the intense regional D metamorphism and tectonism.
2
Cole and Layer present new field, petrographic, and geochemical data on two Tertiary vol
canic-rock units and underlying sedimentary rocks in the southeast comer of the Mount McKinley
quadrangle. The volcanic-rock units include late Paleocene and early Eocene rocks of the Foraker
Glacier and the late Eocene and early Oligocene Mount Galen Volcanics. New 40ArP9Ar data on
two samples from the lower part of volcanic rocks of the Foraker Glacier yield ages of 56.9±0.2
and 5.55±0.1 Ma. Volcanic rocks of the Foraker Glacier unconformably overlie a 550-m-thick
sequence of Late Cretaceous(?) sedimentary rocks that dip steeply north and unconformably
overlie Paleozoic metamorphic rocks with a schistosity that dips steeply south. The Mount Galen
1From 1975 through 1988. Geologic Studies in Alaska was published as a series of USGS Circulars, which were
titled The United States Geological Sun1ey in Alaska: Accomplishments During 19.u. From 1989 to 1994, the series
was published as more formal USGS Bulletins. As a result of a reorganization in 1995 of USGS publications, the series
is now being published as USGS Professional Papers.
Introduction
Volcanics consists of basaltic, andesitic, dacitic, and rhyolitic lavas and dacite, and rhyolite
tuff and tuff breccia. New 40 ArP9 Ar data on a basaltic andesite flow 46 m above the base of the
Mount Galen Volcanics yield an age of 43.8±0.5 Ma. The Mount Galen Volcanics is enriched in
Ba, Th, Sr, and light rare-earth elements, has high BalTa ratios, and exhibits a distinct paired Nb
Ta-depletion trend, all of which are common characteristics of subduction-related volcanic rocks.
Cole and Layer interpret that the Late Cretaceous(?) sedimentary rocks record uplift and shorten
ing during the final stages of accretion of the Wrangellia composite terrane to southern Alaska.
Volcanic rocks of the Foraker Glacier represent the final phase of Late Cretaceous and early
Tertiary Alaska-Talkeetna Mountains magmatism, which ended with suturing of the Wrangellia
composite terrane. The Mount Galen Volcanics is part of the northern section of the Eocene to
Oligocene Alaska-Aleutian arc that crosscuts older igneous rocks of the region.
Eastham and Ridgway present stratigraphic and provenance data which suggest that thou
sands of meters of Upper Jurassic to Upper Cretaceous strata which have been grouped together
as the Kahiltna assemblage in south-central Alaska may actually represent several different sedi
mentary basins. The Kahiltna assemblage in the Alaska Range is separated from the Kahlitna
assemblage in the Clearwater and Talkeetna Mountains by a large thrust block of Paleozoic and
Mesozoic strata known as the Chulitna terrane. Easthman and Ridgway interpret the lithofacies
of the Chulitna terrane as representing deposition on a bathymetric high relative to submarine
fan lithofacies of the Kahiltna assemblage in the Talkeetna Mountains and Alaska Range.
McRoberts and Blodgett describe a diverse molluscan fauna of silicified fossils from two
localities in the Taylor Mountain D-3 quadrangle. The molluscan fauna consists of a least 8 spe
cies of bivalves, including one new species, Cassianella cordillerana McRoberts n.sp., and at
least 11 species of gastropods, including two new species, Neritaria nuetzeli Blodgett n.sp. and
Andangularia "vilsoni Blodgett n.sp. Bivalve and gastropod affinities suggest an early Norian
age, with taxonomic similarities to several southern Alaskan lithotectonic terranes (for example,
Alexander and Chulitna), as well as to the South American Cordillera of Peru.
Mount Griggs, the highest peak in Katmai National Park, is a fumarolically active andesitic
stratovolcano that stands 12 km behind the main volcanic chain of the Alaska Peninsula range
crest. (Hildreth and others, report). K-Ar ages indicate that the volcano is as old at 292±11 ka
and thus predates inception of the nearby volcanic-front centers. Geochemical analyses of lava
flows exposed on Mount Griggs and a few near-vent scoria bombs define a typical Ti-poor,
medium-K calc-alkaline arc suite that shows little systematic change over time. Relative to erup
tive products of the nearby volcanic-front centers, those of Mount Griggs are slightly depleted in
Fe, generally enriched in Rb, Sr, AI, and P, and consistently enriched inK and Zr. The magmatic
plumbing system of Mount Griggs is independent of those beneath the main volcanic chain,
probably all the way to mantle depths.
Brew and Friedman present recent field studies and published and unpublished data on
adjacent areas which show that the Stikine Icefield, part of the Coast Mountains of southeast
em Alaska, is underlain by five generalized map: (1) locally foliated and prophyritic granodi
orite, (2) foliated tonalite, (3) migmatitic rocks, (4) unfoliated tonalite and granodiorite, and (5)
polymetamorphic rocks.
Stottlemyer and others discuss treeline biogeochemistry and dynamics in Noatak National
Preserve, Alaska. The objective of their study was to gain an understanding of treeline dynam
ics, structure, and function and to examine the effects of global climate change-in particular,
soil temperature, moisture, and nitrogen availability-on ecosystem processes within an 800-ha
watershed in a boreal biome.
Eppinger and others present a detailed environmental-geochemical study of the Slate Creek
antimony deposit in the Kantishna Hills, Denali National Park and Preserve, Alaska. The purpose
of their study was to focus on identifying and characterizing the environmental and geochemical
signatures associated with this historical mining area. Samples collected included water, stream
sediment, rock, and soil from upstream and downstream of the mineralized area. Natural springs
present within the mineralized area, but outside the disturbed minesite, suggest premining spring
waters that naturally ranged from acidic to neutral pH, had relatively high conductivities, had
varying high total dissolved solids, were iron rich, and were metalliferous.
Two bibliographies at the end of the volume list reports covering Alaska earth-science topics
in USGS publications during 2000 and reports about Alaska by USGS authors in non-USGS
publications during the same period.
2 Studies by the U.S. Geological Survey in Alaska, 2000