Eocene flows of intermediate composition are sporadically present across the evaluation area. In the central portion of the area, Middle Eocene hornblende andesite flows associated with intrusive andesite and basalt are exposed at Prospect Ridge within the Eureka district (Nolan, 1962).

To the north in southwestern Elko County, flows of latitic composition resembling basalt in the field have been mapped in the Tuscarora and Independence Mountains area in the Sugarloaf Butte, Lake Mountains, Stampede Ranch, and Reed Station Quadrangles (Coats, 1985). These flows are dense, black and aphanitic, and are often vesicular. They contain plagioclase, augite, olivine and hypersthene in a glassy or crystalline groundmass of feldspar. These flows unconformably overlie Eocene tuffs and have been dated in one locality at the southern end of Independence Valley at 35.4 +/- 1.0 Ma, straddling the Oligocene/Eocene age boundary.

In the Tuscarora mining district and to the southwest at the southern end of Independence Valley in the Reed Staton and Mahala Creek West Quadrangle, altered biotite-pyroxene andesite, hornblende-biotite-pyroxene andesite, and biotite andesite are exposed (Coats, 1985). To the north in the Owyhee and Mountain City Quadrangles, pyroxene andesite, pyroxene-hornblende-biotite andesite, bioite-pyroxene andesite vitrophyre and vent breccias are present. These rocks have been mapped as the andesites of Summit Creek in the northern portion of the Owyhee Quadrangle (Coats, 1971; Coats, 1985). Several of the dark gray to black, aphanitic, pyroxene andesites are associated with uranium deposits in several areas (Coats, 1985).