Advisor

Michael L. Cummings

Date of Award

1986

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Geology

Department

Geology

Physical Description

1 online resource (140 p.)

Subjects

Geology -- Oregon -- Bear Creek Butte Region, Hydrothermal deposits -- Oregon -- Bear Creek Butte Region, Mineralogy -- Oregon -- Bear Creek Butte Region

Abstract

The Eocene Clarno Formation, the Oligocene John Day Formation and basalts of the High Lava Plains are exposed in the Bear Creek Butte area in Central Oregon. In this area the Clarno Formation can be divided into a lower sequence composed of intermediate lava flows with intercalated mudflows and volcaniclastic sediments and an upper sequence of rhyolite and basalt flows and felsic ruffs. Separating the two units is a well developed saprolite. The change from intermediate to rhyolite-basalt volcanism reflects a change in the tectonic environment of the Cascade volcanic arc from compression to relaxation as subduction of the Farallon plate by the North American plate slowed, allowing extension of the continental plate margin to occur.

Description

If you are the rightful copyright holder of this dissertation or thesis and wish to have it removed from the Open Access Collection, please submit a request to pdxscholar@pdx.edu and include clear identification of the work, preferably with URL

Persistent Identifier

http://archives.pdx.edu/ds/psu/20642

wilkening plate 1.jpg (5756 kB)
Plate 1

wilkening plate 1b.jpg (1232 kB)
Plate 1b

wilkening plate 2.jpg (2019 kB)
Plate 2

wilkening plate 2b.jpg (1221 kB)
Plate 2b

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