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Did dinosaurs once roam the Grand Canyon?

From: Ben Creisler

An online paper and news stories about a new date for the Grand Canyon
that suggests dinosaurs were around when it first formed.
Paleoartists, be inspired! A "Valley of Gwangi" remake seems in order

R. M. Flowers & K. A. Farley (2012)
Apatite 4He/3He and (U-Th)/He Evidence for an Ancient Grand Canyon
Science (advance online publication)
DOI: 10.1126/science.1229390

Grand Canyon is one of the most dramatic features on Earth, yet when
and why it was carved have been controversial for more than 150 years.
We present apatite 4He/3He thermochronometry data from Grand Canyon
basement that tightly constrain the near-surface cooling history
associated with canyon incision. 4He/3He spectra for eastern Grand
Canyon apatites of differing He date, radiation damage, and U-Th
zonation yield a self-consistent cooling history that substantially
validates the He diffusion kinetic model applied here. Similar data
for western Grand Canyon provide evidence that it was excavated to
within a few hundred meters of modern depths by ~70 million years ago
(Ma), in contrast to the conventional model in which the entire canyon
was carved since 5 to 6 Ma.