Abstract

The Butler Basin lies along the John Day River in Central Oregon, astraddle the boundary of Wheeler and Grant counties. Strata exposed in this geomorphic basin, formed by an erosionally breached anticline, range in age from Permo-Triassic to Neogene. The basement rocks of the basin are poorly exposed but lithologically similar to the Permo-Triassic Blue Mountains island-arc rocks which crop out to the south and southeast of the basin in the John Day Inlier. Overlying the basement rocks are Early Cretaceous conglomerates with lenses of sandstone and siltstone informally named the "Goose Rock Conglomerate." Pebble and cobble lithologies present in the conglomerate indicate that the source was terranes of the John Day Inlier. A sparse and poorly preserved terrestrial palynoflora recovered from siltstone lenses suggest that the conglomerates are pre-Albian in age and older than the well known mid-Cretaceous rocks of the neighboring Mitchell Inlier. Sedimentary structures along with the terrestrial palynoflora indicate a fluvial depositional system with a southwesterly paleocurrent trend. Based on a whole-rock K-Ar date of 49 million years and lithostratigraphy of the region, the basalt flow and unreworked red tuffs immediately overlying the "Goose Rock Conglomerate" belong to the lower Clarno Formation. The overlying John Day, Picture Gorge Basalt, Mascall, and Rattlesnake formations are only briefly reviewed since they have been the emphasis of many previous works. The large-scale (1:24,000) geologic map of the Butler Basin produced from this study has resulted in the addition of detail and refinement to the stratigraphic and structural relationships in the Butler Basin.

LLU Discipline

Geology

Department

Geology

School

Graduate School

First Advisor

Lanny H. Fisk

Second Advisor

H. Paul Buchheim

Third Advisor

Ivan E. Rouse

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

1990

Date (Title Page)

6-1990

Language

English

Library of Congress/MESH Subject Headings

Geology -- Oregon; Butler Basin (Ore.)

Type

Thesis

Page Count

vii; 50

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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