FIG. 3. Major physiographic units of the Cordillera Occidental, southern Perú, showing the locations of dated tuffs documented in earlier studies and the distribution of Tertiary landform elements within the limits of geomorphologic mapping by Tosdal (1978; simplified after Tosdal et al., 1984). Dated minerals: bi = biotite, hb = hornblende, pl = plagioclase.