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Distribution and character of upper mesozoic subduction complexes along the west coast of North America

Tectonophysics

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, , ,

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Abstract

Structurally complex sequences of sedimentary, volcanic, and intrusive igneous rocks characterize a nearly continuous narrow band along the Pacific coast of North America from Baja California, Mexico to southern Alaska. They occur in two modes: (1) as complexly folded but coherent sequences of graywacke and argillite that locally exhibit blueschist-grade metamorphism, and (2) as melanges containing large blocks of graywacke, chert, volcanic and plutonic rocks, high-grade schist, and limestone in a highly sheared pelitic, cherty, or sandstone matrix. Fossils from the coherent graywacke sequences range in age from late Jurassic to Eocene; fossils from limestone blocks in the melanges range in age from mid-Paleozoic to middle Cretaceous. Fossils from the matrix surrounding the blocks, however, are of Jurassic, Cretaceous, and rarely, Tertiary age, indicating that fossils from the blocks cannot be used to date the time of formation of the melanges. Both the deformation of the graywacke, with accompanying blueschist metamorphism, as well as the formation of the melanges, are believed to be the result of late Mesozoic and early Tertiary subduction. The origin of the melanges, particularly the emplacement of exotic tectonic blocks, is not understood. ?? 1978.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Distribution and character of upper mesozoic subduction complexes along the west coast of North America
Series title:
Tectonophysics
Volume
47
Issue:
3-4
Year Published:
1978
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
207
Last page:
222
Number of Pages:
16