Response to Comments on "Apatite 4He/3He and (U-Th)/He Evidence for an Ancient Grand Canyon".

Apatite 4He/3He and (U-Th)/He evidence for an ancient Grand Canyon.

The Grand Canyon is one of the most dramatic features on Earth, yet when and why it was carved have been controversial topics for more than 150 years. Here, we present apatite (4)He/(3)He thermochronometry data from the Grand Canyon basement that tightly constrain the near-surface cooling history associated with canyon incision. (4)He/(3)He spectra for eastern Grand Canyon apatites of differing...

Comment on "Apatite 4He/3He and (U-Th)/He evidence for an ancient Grand Canyon".

Flowers and Farley (Reports, 21 December 2012, p. 1616; published online 29 November 2012) propose that the Grand Canyon is 70 million years old. Starkly contrasting models for the age of the Grand Canyon-70 versus 6 million years-can be reconciled by a shallow paleocanyon that was carved in the eastern Grand Canyon 25 to 15 million years ago (Ma), negating the proposed 70 Ma and 55 Ma paleocan...

Materials for Apatite 4 He / 3 He and ( U - Th ) / He Evidence for an Ancient Grand Canyon

Comment on “Apatite He/He and (U-Th)/He Evidence for an Ancient Grand Canyon”

Flowers and Farley (Reports, 21 December 2012, p. 1616; published online 29 November 2012) use thermochronometry to propose that the western paleo–Grand Canyon was nearly as deep 70 million years ago (Ma) as today. However, lithologies, facies relations, geomorphology, and paleotopography of Miocene interior-basin deposits near the mouth of the Grand Canyon show that no paleocanyon existed in t...

He/He and (U-Th)/He Evidence for an Ancient Grand Canyon”

We reiterate that geological observations do not require Grand Canyon carving coeval with Colorado River integration. (U-Th)/He data from the western canyon, totaling 29 reproducible analyses from six samples and two labs, compellingly support an ancient canyon. Three dispersed analyses from one anomalous sample do not refute this conclusion, nor do the claimed shortcomings of our modeling have...