With regard to prehistorical events, boulder age-dating is a more plausible alternative.
Boulder ages then provide only a maximum limit for the age of the event in question [19].
Various sources of errors are outlined that investigators must consider when attempting to use carbonate boulder ages as a surrogate for timing past events.
Furthermore, extreme boulder ages > 5 Ma documented elsewhere in the Atacama were not found in our area and appear to be limited to exceptionally stable boulders or cobbles in either the northern or southern extremes of the Atacama Desert.
These results invalidate the prevailing assumption of no or little surface lowering on sloping unconsolidated landforms over the Quaternary Period and affirm that accurate interpretations of lichen ages and cosmogenically dated boulder ages require keen understanding of the ever-present erosion.
Erosion rates of 0.03 0.06 m Ma−1 are necessary to have produced the measured boulder exposure age if they were deposited at 14.8 Ma.
Desert pavements on the Johnson Mesa surface give exposure ranging from 97±8 to 159±14 ka and are 34 96 kyears younger than the boulder exposure ages.
Incision rates for the Capitol Reef reach of the Fremont River calculated from the boulder exposure ages range from 0.40 to 0.43 m kyear−1 (maximum rates) and are some of the highest on the Colorado Plateau.
For the largest boulder (MK1), the age range spans two and a half centuries (250 years), which might not be surprising considering its size (nearly 5 × 3 × 3 m).
