First Advisor

Martin J. Streck

Date of Award


Document Type


Degree Name

Bachelor of Science (B.S.) in Geology and University Honors




Geology -- Oregon -- Wasco County, Geochemistry -- Oregon -- Wasco County, Igneous rocks, Lava -- Oregon -- Wasco County -- Analysis




The Dalles Formation is a sequence of volcanic, volcaniclastic and sedimentary deposits of the late Miocene to Pliocene. The unit stretches along the eastern flanks of Mount Hood from Maupin, northward to the Columbia River, near The Dalles, Oregon (Figure 1). The Dalles Formation consists of lavas that are generally dacitic in composition and are composed of block-and-ash flows, debris-flows, and reworked fluvial sediments. Past workers have mapped the unit as the Dalles Formation "Undivided". The scope of this project has been to investigate the geochemical and petrographic characteristics and whether they may suggest distinct units. A section of the Dalles Formation in the Dufur West quadrangle has been mapped and geochemical data and thin sections were analyzed. The clustering and spread of the geochemical data along with mineralogical indicators such as texture and phenocryst abundance suggest the unit can be divided into different lava types.


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