These maps show variations in the Earth's magnetic field caused primarily
by the uneven distribution of the mineral magnetite in the rocks
that make up the upper part of the Earth's crust. The features and patterns
of the maps reveal details of subsurface geology including the locations
of buried faults, the location of magnetite-bearing rocks (which include many
kinds of rocks of interest to mineral exploration), and the thickness of
surficial sedimentary rocks.
The maps are constructed from grids that combine information
(data processing details).
collected in 85 separate
aeromagnetic surveys conducted between 1945 and 1982.
The data from these
surveys are of varying quality; large regions of Alaska are covered only by
very coarse surveys. An index plot
(see plot)
gives an overview of the flightline spacing of the original surveys.
A data table
(see table)
summarizes the detailed specifications of the surveys.
The images displayed here were prepared by Northwest Geophysical Associates
under contract to the U.S. Geological Survey. In addition to an overview image
of the entire state, 19 separate detailed images display more of the details
in the magnetic field. HPGL plot files for these images can be downloaded
(download plots)
for plotting at true scale (1:2,500,000 for the overview map, 1:500,000 for
the detailed maps).
This project was supported by the Mineral Resources Program of the
USGS in cooperation with the National Geophysical Data Center
(NGDC),
The State of Alaska, Department of Natural Resources, Division of
Oil and Gas
(DOG),
and the State of Alaska, Department of Natural Resources,
Division of Geological and Geophysical Surveys
(DGGS),
| AccessibilityFOIAPrivacyPolicies and Notices | |
 |
|
