Figure 1. Location of Laguna del Maule and sites of radiocarbon dating discussed in the text.

Figure 2. A glacier carved striations and grooves into the surface of the Mellicos andesite after it erupted ca. 26,000 yr BP. Younger lavas forming the western shore of Laguna del Maule (middle ground) are 23,000 to 21,000 years old and do not show signs of glacial erosion.

Figure 3. 40Ar/ 39Ar age spectra and isochron plots from six incremental-heating experiments. Plateau increments are solid boxes; discordant increments omitted from the plateau and isochron calculations are shown as open boxes. Replicate experiments were performed on the Mellicos and West Peninsula andesite samples with plateau increments shown in diagonal pattern. All errors ± 2s.