Figure 7    Optical microstratigraphies in rock varnish from radiometrically dated geomorphic features in western USA drylands. Age constraints are reported in cal YBP (± 1σ) and sources of age control are given in Table 2. Letters in the varnish images correspond to those in both Table 2 and Fig. 8. Note that black layer WH7 in (N) is absent probably because of postdepositional modification, such as wind abrasion or peeling. The green lines in (C) and (L) identify positions of the probe line profiles for Ba seen in Fig. 6C, D.