Figure 13. Geologic map of the paleovalley at Coal Mine Canyon, southeast flank of the Adobe Range (modified from Moore et al., 1982). The sedimentary sequence consists of fluvial, boulder-to-cobble conglomerate overlain by lacustrine shale, claystone, and limestone. The tuff of Coal Mine Canyon is dated at 40.7 ± 0.4 Ma (⁴⁰Ar/³⁹Ar, hornblende; Brooks et al., 1995a, 1995b) and 41.1 ± 0.2 Ma (U-Pb, zircon; Haynes, 2003).