Age of the Coso Formation Inyo County California

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Report: Age of the Coso Formation Inyo County California

Abstract

The late Tertiary Coso Formation consisting of sedimentary and volcaniclastic rocks occurs in the Coso Range and at the south end of Owens Valley, Calif. Potassium-argon dating of the volcanic rocks that overlie, are intercalated with, and intrude the Coso indicates that the Coso Formation contains strata at least as old as 6.0 m.y. (million years) and no younger than 2.5 m.y. Within the Coso Formation, Blancan fossils from a locality on the northern slope of the Coso Range are probably 3.0 m.y. old and a Hemphillian fossil was recovered northeast of there from beds between 3.6 and 5.3 m.y. old. A rhyodacite and four rhyolite plug domes that intrude sedimentary rocks of the Coso on the northern flank of the Coso Range range in age from 5.7 to 6.0 m.y. The late Miocene fluvial and lacustrine sedimentary rocks of the Coso Formation suggest that a shallow basin had formed in southern Owens Valley by about 6 m.y. ago. Airfall tuff and coarse clastic sedimentary rocks of the Coso Formation within the Coso

Range suggest that block faulting had begun by about 3 m.y. ago.

Authors 
Charles R. Bacon, D. M. Giovannetti, W. A. Duffield, G. B. Dalrymple and R. E. Drake





Organization 
U.S. Geological Survey



Published 
U.S. Government Printing Office, 1982



Report Number 
Bulletin 1527


DOI 
Not Provided
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Online 
Internet link for Age of the Coso Formation Inyo County California

Citation

Charles R. Bacon,D. M. Giovannetti,W. A. Duffield,G. B. Dalrymple,R. E. Drake (U.S. Geological Survey). 1982. Age of the Coso Formation Inyo County California. Washington, District of Columbia: U.S. Government Printing Office. Report No.: Bulletin 1527.