Date of Award

1980

Document Type

Thesis

Department

Earth Science

First Advisor

Marvin H. Beeson

Subjects

Geology -- Pacific Northwest, Silver Falls State Park (Or.) -- Geology, Basalt

DOI

10.15760/honors.390

Abstract

Silver Falls State Park is near the southern extent of the Columbia River Basalt Group as mapped in western Oregon. The flows in the park were identified as belonging to subdivisions of the Columbia River Basalt Group on the basis of physical characteristics and trace element geochemistry. The sequence of flows present is as follows: 3-4 flows of the Low-Mg chemical type of the Grande Ronde Basalt, 2 flows of the High-Mg chemical type of the Grande Ronde Basalt, 3 flows of the Frenchman Springs Member of the Wanapum Basalt, and one flow of anomolous geochemistry. The flows dip west to southwest two to three degrees on the limb of an open anticline. Two related trends are represented in the jointing pattern of the flows, N 20 W and N 70 E. A paleostream appearing to follow one of these trends eroded 90 m into the Low-Mg and High-Mg flows before its valley was obscured by the incursion of a Frenchman Springs flow. The possibility arises that this stream drainage may provide access to the coast via the coast range for the Frenchman Springs basalts.

Comments

A thesis submitted in partial fulfillment of the requirements for the University Scholars Program Bachelor of Science degree in Earth Science.

Note: The University Scholars Program at Portland State University was subsequently changed to the Honors College.

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/20344

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