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Date of Award

Spring 1980


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Document Type

Thesis: EWU Only

Degree Name

Master of Science (MS) in Geology




A portion of the Inchelium quadrangle was mapped during the 1979 field season. The area is located 15 km southwest of Colville, in Stevens County, Washington. This thesis is part of a larger project to prepare a geologic map of the Inchelium quadrangle. The purpose of this study is to identify the stratigraphic units in the miogeosynclinal rocks so that the details of their structure can be better understood. The following lithologic units are recognized: Addy Quartzite (Early Cambrian), Maitlen Phyllite (Early Cambrian), Metaline Limestone (Middle Cambrian), Ledbetter Slate (Middle Ordovician), and unnamed quartz monzonite, granodiorite, quartz latite, and rhyodacite intrusive rocks of probable Cretaceous age. Evidence gathered during this study indicates that mature sediments and carbonates were deposited in a shallow, subsiding basin. Conditions fluctuated between those favoring clastic sedimentation and those favoring carbonate deposition, during Cambrian-Ordovician time. The sedimentary rock units strike north and dip west. Mapping data delineates a large isoclinal syncline in the eastern half of the area, as well as small related chevron and drag folds. A large north-trending normal fault system cuts off part of the western limb of the syncline. Northwest- and northeast-trending strike-slip faults displace the normal faults and also the folds. The area is covered in part by glacial debris, alluvium and colluvium.