GEOLOGIC MAPPING OF THE CRESCENT FORMATION OF THE SOUTHEAST OLYMPIC MOUNTAINS, WASHINGTON STATE

A stratigraphic column and geologic map were created for the Crescent formation of the southeast region of the Olympic Mountains of western Washington State during summer 2002. A total of twelve basalt flows of the Crescent formation were described and mapped. The flows young to the southeast and are intruded by several sills and a dike. The stratigraphic column can be correlated with earlier mapping by Clark and students in nearby regions of the Olympic Mountains. Paleomagnetic analysis of samples from five individual flows produced no consistent directions when analyzed with thermal and alternating field demagnetization. SEM and reflected light analyses of oxides present in the basalt show significant secondary alteration of iron and titanium-iron oxides. Petrographic analysis of thin sections as well as XRF analysis to provide chemical compositions for the rock units is in progress.