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Master of Science (MS)
Beck, Myrl E.
Pevear, David R.
Babcock, R. Scott (Randall Scott)
Paleomagnetic results have been obtained from eight sites in the Miocene (15-18 m.y.) Snoqualmie batholith, Central Cascades, Washington. After ac magnetic cleaning, four magnetically stable sites remained, yielding a pole at 221.0°E, 84.5°N, (δp = 7.9, δm = 9.3, k = 286.4). A stability test was formulated based on the ratio of the intensity of natural remanent magnetism, NRM, (after ac demagnetization) to the weak field susceptibility. This ratio, Qd proved effective in determining magnetically stable samples from samples showing a wide spectrum of stability from within the Snoqualmie batholith, and therefore, was strictly applied to all samples. Experiments with saturation isothermal remanent magnetism indicated that stable NRM is dominated by magnetic grains with single domain characteristics. Paleomagnetic results from the 25.0-26.5 m.y. Grotto batholith (Beske et al 1972) were combined with data from the Snoqualmie batholith to give a Miocene pole for the Central Cascades at 208.5°E, 85,5°N, (δp = 4.5, δm = 5.4, k = 360.4). These poles show no large scale tectonic rotation or translation of the Central Cascades since the Miocene when compared with other Miocene poles from North America, This suggests that the post-mid-Cretaceous movement postulated by Beck and Noson (1972) for the Central Cascades relative to the North American craton ceased by the Miocene. Furthermore, this data does not support the post-Miocene rotational movement of the Nevadan tectonic zone postulated by Watkins (1965b).
Paleomagnetism, Snoqulmie batholith
Western Washington University
Subject – LCSH
Paleomagnetism--Washington (State)--Cascade Range; Petrology--Washington (State)--Cascade Range; Batholiths
Cascade Range; Washington (State)
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Beske, Suzanne J., "Paleomagnetism of the Snoqualmie Batholith Central Cascades, Washington" (1972). WWU Graduate School Collection. 770.