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A high-density remote reference magnetic variation profile in the Pacific northwest of North America

Physics of the Earth and Planetary Interiors

By:
, , , ,
DOI: 10.1016/0031-9201(89)90016-2

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Abstract

During the summer of 1985, as part of the EMSLAB Project, Brown University conducted a detailed magnetic variation study of the Oregon Coast Range and Cascades volcanic system along an E-W profile in central Oregon. Comprised of a sequence of 75 remote reference magnetic variation (MV) stations spaced 3-4 km apart, the profile stretched for 225 km from Newport, on the Oregon coast, across the Coast Range, the Willamette Valley, and the High Cascades to a point ??? 50 km east of Santiam Pass. At all of the MV stations, data were collected for short periods (16-100 s), and at 17 of these stations data were also obtained at longer periods (100-1600 s). Data were monitored with a three-component ring core fluxgate magnetometer (Nanotesla), and were recorded with a microcomputer (DEC PDP 11/73) based data acquisition system. A 2-D generalized inversion of the magnetic transfer coefficients over the period range of 16-1600 s indicates four distinct conductors. First, we see the coast effect caused by a large sedimentary wedge offshore. Second, we see the effect of currents flowing in the conductive sediments of the Willamette Valley. Our inversion suggests that the Willamette Valley consists of two electrically distinct features, due perhaps to a horst-like structure imprinted on the valley sediments. Next we note an electric current system centered beneath the High Cascades. This latter feature may be associated with a sediment-filled graben beneath Santiam Pass as suggested by some of the gravity and MT results reported to date. Finally, we detect the presence of a deep conductor at mid-crustal depths which laterally extends westward from beneath the Basin and Range Province, and terminates beneath the western Cascades. One view of this last result is that it appears that modern Basin and Range structure is being imprinted on pre-existing Cascade structure. ?? 1989.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
A high-density remote reference magnetic variation profile in the Pacific northwest of North America
Series title:
Physics of the Earth and Planetary Interiors
DOI:
10.1016/0031-9201(89)90016-2
Volume
53
Issue:
3-4
Year Published:
1989
Language:
English
Publisher:
Elsevier
Publisher location:
Amsterdam, Netherlands
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Physics of the Earth and Planetary Interiors
First page:
305
Last page:
319
Number of Pages:
15