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Date Permissions Signed


Date of Award

Spring 1981

Document Type

Masters Thesis

Degree Name

Master of Science (MS)



First Advisor

Brown, Edwin H.

Second Advisor

Babcock, R. Scott (Randall Scott)

Third Advisor

Suczek, Christopher A., 1942-2014


Detailed mapping of the Goat Mountain dunite and the western and southern margins of the Twin Sisters dunite indicates that the structural setting of these bodies is dominated by high-angle northwest-trending fault zones. The Goat Mountain dunite overlies rocks of the Chilliwack Group and Yellow Aster Complex as a lowangle, west-dipping slab approximately 2500 feet thick. Cretaceous phyllite west of Goat Mountain overlies Chilliwack Group rocks along a similar low-angle west-dipping fault contact. These structures are both truncated by high-angle fault zones.

The timing of faulting is poorly constrained. High-angle faulting is at least post-Eocene through Holocene (?), and may have begun as early as Late Cretaceous. Thrust emplacement of the Cretaceous phyllite over rocks of the Chilliwack Group may or may not have been contemporaneous with dunite emplacement.




Goat Mountain dunite, North Cascades geology


Western Washington University

OCLC Number


Subject – LCSH

Geology--Washington (State)--Twin Sisters Range; Geology, Structural

Geographic Coverage

Twin Sisters Range (Wash.)




masters theses




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.

Frasse Thesis Map 1 reduced 7272144.pdf (152 kB)
Plate 1 - Geologic Map of the Twin Sisters Area, North Cascades, Washington

Frasse Thesis Map 2 reduced 7272144.pdf (107 kB)
Plate 2 - Geologic Map of the Twin Sisters Area, North Cascades, Washington

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