Detailed mapping and geochemical analysis of Oligocene to early Pliocene volcanic rocks in the Little Walker volcanic center, Mono County, California have revealed a complex eruptive history. After eruption of widespr ...

The Three Sisters region of the Oregon High Cascades has developed three compositionally and petrogenetically distinct silicic (i.e., SiO₂ ≥ 58%) magma systems within the last 600 k.y. These silicic systems evolved fro ...

The Upper Cretaceous to Eocene Montgomery Creek Formation is exposed between the Klamath and Cascade Mountains in the vicinity of Big Bend and Montgomery Creek, northern California. The formation is divided into a no ...

Steens Mountain is a major horst block near the northern terminus of the Basin and Range geomorphic province of southeastern Oregon. A section of Miocene volcanic rocks totaling 5000 feet in thickness are exposed in a fa ...