Portland State University. Department of Earth Science
Paul E. Hammond
Date of Award
Master of Science (M.S.) in Geology
1 online resource. Digitized manuscript.
Geological surveys -- Washington (State) -- Kittitas County, Petrology -- Washington (State) -- Kittitas County, Geology, Petrology
The southwestern part of the Kachess Lake quadrangle lies between Lakes Cle Elum and Kachess, on the east flank of the central Cascade Range of Washington. The region lies between the North and South Cascade petrologic provinces, and includes rocks typical of each. Pre-Tertiary Easton Schist (called the Shuksan Suite farther north), and the Late Cretaceous-Paleocene Swauk Formation occur widely in the North Cascades, while the Tertiary Silver Pass Volcanics and Teanaway Basalt are typical of South Cascade volcanic sequences. Diabasic dikes of the Teanaway dike swarm occur throughout the vicinity.
The area is bounded on the west by a major fault, the Kachess, and bot.h folding and faulting have occurred in the area proper. Folding is represented by southeast plunging Thorp Mountain anticline; to the north, and Domerie Creek syncline to the south. Several faults have been recognized, the most important being northwest-southeast trending Thomas Mountain fault, which diagonally bisects t.he folds and complicates stratigraphic relationships.
The region has been geologically active during most of its history. Eugeosynclinal rocks were metamorphosed to blueschists and greenschists during a late Paleozoic-early Mesozoic orogeny, and folding, faulting, and unconformable relationships involving Tertiary strata indicate continued diastrophism during the Cenozoic.
Lofgren, David Carl, "The Bedrock Geology of the Southwest Part of the Kachess Lake Quadrangle, Washington" (1973). Dissertations and Theses. Paper 2187.