Introduction
The eight papers that follow continue the series of U.S. Geological Survey (USGS)
reports on investigations in the geologic sciences in Alaska. 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 Geologic Studies in Alaska cover a broad spectrum of topics from all parts of the
State (fig. 1), which serves 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 Resources, Geologic Framework,
and Environment and Climate. Such an organization is intended to reflect the scope
and objectives of USGS programs currently active in Alaska. Resource papers include one
that presents detailed observations from a Mississippian Zn-Pb-Cu-Ag occurrence in the
Brooks Range (Werdon). Mineralogic, chemical, and isotopic data provide the basis for a
proposed relationship between this vein-breccia deposit and the shale-hosted massive sulfide
deposit type, which includes the active Red Dog mine in the western Brooks Range. Also
included under the topic of Resources is a paper that presents geochemical and isotopic data
from the Greens Creek and Woewodski Island volcanogenic massive sulfide deposits in
southeastern Alaska (Newberry and Brew). The depositional environment and sedimentological
setting of Tertiary coal beds in the Matanuska and Susitna Valleys is the focus of a third
paper under the topic of Resources (Flores and others).
Geologic Framework studies provide background information that is the scientific basis
for present and future studies of the environment, mineral and energy resources, paleoclimate,
and hazards in Alaska. One paper presents the results of sedimentologic and paleontologic
comparisons of lower Paleozoic, deep-water-facies rock units in central Alaska
(Dumoulin and others). The authors show which of these units are likely to correlate with
one another, suggest likely source regions, and provide a structural restoration of units that
have been fragmented by large fault motions. A second framework paper provides a map,
rock descriptions, and chemical compositions of volcanic rocks in a newly recognized,
geologically young volcanic center in the Aleutian volcanic arc (Hildreth and others). A third
paper presents an interesting summary of gravity changes that occurred in south-central
Alaska during the great earthquake of 1964 and for the following 25 years (Barnes). Gravity
changes correlate with land-elevation changes in some cases, but not in others, which means
that different processes are responsible for the gravity changes.
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First posted November 14, 2012
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