K-Ar results from the southern Oregon-Northern California Cascade Range

Abstract

Nearly 180 new whole-rock potassium-argon age dates from the southern Oregon Cascade volcanic province are reported, each with a corresponding major- and trace-element geochemical analysis. K-Ar results from the Klamath River canyon region astride the California-Oregon border delineate no obvious temporal break in volcanic activity. However, 25 mi farther to the north in the Mount McLoughlin-Brown Mountain-Little Butte Creek region, a time gap in volcanic activity has been documented to exist between 17 and 7 Ma. Mafic volcanic activity, which marks the inception of renewed volcanism between 6 and 7 Ma ago, is compositionally quite diverse, ranging from olivine trachybasalt to low-potassium high-alumina olivine tholeiite basalt.

176 samples from this reference