Portland State University. Department of Earth Sciences
Marvin H. Beeson
Date of Award
Master of Science (M.S.) in Geology
1 online resource (149 p.)
Basalt -- Oregon, Geology -- Oregon, Stratigraphic geology
The Clackamas River drainage within the western Cascade Range is approximately aligned with a northwest trending lineation defined by the Portland Hills and the Brothers Fault zone. This area is occupied by an extensive Columbia River Basalt sequence that is deeply incised by the Clackamas River and its tributaries. Two major basalt units of the Yakima Basalt Subgroup, including the Grande Ronde Basalt and the Frenchman Springs Member of the Wanapurn Basalt, are distinguishable in a 515 meter to 550 meter accumulation. Of particular interest is the presence of five trending right-lateral strike-slip faults is consistent with a stress model of north-south compression and east-west extension.
Anderson, James Lee, "The stratigraphy and structure of the Columbia River basalt in the Clackamas River drainage" (1978). Dissertations and Theses. Paper 3511.