Figure Caption: Late Quaternary basaltic lava flows in Pisgah, Cima, and Amboy volcanic fields of the Mojave Desert, California (left panel) and optical microstratigraphies of rock varnish from these flow surfaces (right panel). Varnish-based age estimates indicate that the placement of these dated lava flows occurred around 24-30, 46-60 and 74-85 ka (Liu, 2003), which are in good agreement (within one sigma error) with cosmogenic Cl-36 dating results for the same flows (Phillips, 2003).