The thesis area consists of 33 square miles in the south-central Pueblo Mountains of Humboldt County, Nevada and Harney County, Oregon. The Pueblo Mountains are tilted fault block mountains found in the extreme northwestern part of the Basin and Range province and were produced during Early Tertiary Basin and Range orogeny. Northwest and northeast trending faults of Late Tertiary time have since cut the entire stratigraphic sequence. The oldest rocks exposed are metamorphosed Permian to Triassic eugeosynclinal sedimentary rocks. The metamorphic sequence is intruded by several granitic plutons of Late Jurassic to Middle Cretaceous age. A thick sequence of Miocene basalt flows unconformably overlies the pre- Tertiary rocks. A slight angular unconformity separates the basalt sequence from overlying Miocene tuffaceous sedimentary rocks, sillar flows, and welded tuffs. Unconsolidated deposits of Quaternary alluvium include alluvial fan and lacustrine sediments. Mineralization within the area includes several gold prospects, a mercury prospect, and a possible copper deposit. The copper prospect consists of a large gossan (6, 000 feet by 3, 000 feet). Mineralization and alteration from a Cretaceous porphyritic quartz monzonite intrusion has produced potassic and quartz sericite hydrothermal alteration in the host. Oxidation and weathering has removed the sulfides from the surface leaving goethite, hematite, and limonite residues. / Graduation date: 1971