Figure 8. Simplified geologic map of the Eocene paleovalley near California Mountain, east side of the Independence Mountains (Muntean and Henry, 2006) with ⁴⁰Ar/³⁹Ar dates from this study (regular type) and Hofstra (1994; italics). The paleovalley, which was 5 km wide and at least 800 m deep, was filled by conglomerate containing rounded boulders to 1.5 m diameter, shale and limestone, the plagioclase-biotite tuff and tuff of Big Cottonwood Canyon, and a thick dacite sequence between the tuffs. The rocks were tilted gently southeastward after 40.0 Ma by several small-displacement, northeast-striking, mostly down-to-the-northwest normal faults. Dashed lines within unit Td are contacts between individual lavas and tuffs.