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Science 4 September 1970:
Vol. 169. no. 3949, pp. 971 - 974
DOI: 10.1126/science.169.3949.971
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Articles

Mantle-Derived Peridotites in Southwestern Oregon: Relation to Plate Tectonics

L. G. Medaris Jr. 1 and R. H. Dott Jr. 1

1 Department of Geology and Geophysics, University of Wisconsin, Madison 53706

A group of peridotites in southwestern Oregon contains high-pressure mineral assemblages reflecting recrystallization at high temperatures (1100° to 1200°C) over a range of pressure decreasing from 19 to 5 kilobars. It is proposed that the peridotites represent upper-mantle material brought from depth along the ancestral Gorda-Juan de Fuca ridge system, transported eastward by the spreading Gorda lithosphere plate, and then emplaced by thrust-faulting in the western margin of the Cordillera during late Mesozoic time.

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Science. ISSN 0036-8075 (print), 1095-9203 (online)