Abstract

Tectonic fragments of schist and amphibolite that occur in the North Cascades of Washington near Groat Mountain, and in southern British Columbia on Vedder Mountain, yield Rb-Sr dates of 229 to 285 Ma. K-Ar dates are somewhat younger, ranging from 219 to 279 Ma. Mineral compositions and assemblages indicate high-pressure metamorphism, variable from blueschist to amphibolite facies. Rocks of the same age and metamorphic grade occur as tectonic slivers in the San Juan Islands (Garrison Schist) and as tectonic fragments at several localities in fault zones in the Chilliwack Group. The rocks are neither Yellow Aster Complex sensu striclo nor Shuksan Metamorphic Suite, with which parts were previously correlated. They are a separate high-pressure metamorphic unit of late Paleozoic age, herein called the Vedder Complex, which through the process of Mesozoic orogeny has become highly disrupted and imbricated with older and younger rocks over an extensive region.

First Page Preview

First page PDF preview
You do not currently have access to this article.