We have obtained paleomagnetic data for the southern tiip of the middle Tertiary Chilliwack Composite Batholith, located on the Canada-United States border about 125 km E of Vancouver, B.C. Thirty-four separately oriented samples were collected along a road traverse 1.5 km long located along State Highway 22, about 20 km NE of Marblemount, Washington. The mean direction after magnetic cleaning is: D, 182.8°; I, -65.0°; α95 , 1.5°. This corresponds to a paleomagnetic pole at 87.5°N, 267.5°E, close to other poles for Tertiary plutons from the North Cascades and only slightly displaced from Tertiary reference poles from the craton. We conclude that the North Cascades block has not been rotated or suffered major internal disruption since perhaps late Eocene time, in marked contrast to all the terranes that surround it.
Geophysical Research Letters
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Published by American Geophysical Union
Beck Jr., Myrl E.; Burmester, Russ R.; and Schoonover, Ruth, "Tertiary Peleomagnetism of the North Cascade Range, Washington" (1982). Geology. Paper 26.