[JimBob (OP)]

From "Science" - Amer. Assoc. Advancement of Science weekly Magazine Notifications email

Grand Canyon Dates

The incision history of the Grand Canyon has been an unsettled issue, in part because common dating methods that rely on the analysis of basalt flows and travertine do not provide any information on samples older than about 1 million years. In order to overcome this limitation, Polyak et al. (p. 1377; see the Perspective by Atkinson and Leeder) take advantage of technical advances in uranium-lead dating methods to date cave mammillaries, a type of speleothem that forms only in caves at or near the depth of the water table. Because these structures are common throughout the canyon, the authors could construct a history of its incision that extends back 17 million years for much of the length of the canyon.

[DoctorBeaver]

 []

Thats... interesting.

[Bass]

Especially since 17 million years is the beginning of Columbia River Flood Basalts, inception of the Yellowstone hotspot and the time of greatest crustal extension in the Great Basin

[DoctorBeaver]

Wasn't that also when Happy Days was first shown?  []

But seriously, does that shed any new light on the canyon?

[JimBob (OP)]

It adds a wrinkle to the tectonic history of the western US. There uplift of the Colorado plateau is a geologic mystery, having never been been explained adequately.

[DoctorBeaver]

Yeah, I read a bit about it in, I think, The Times Online. Apparently it's older than was previously thought.

[Bass]

Sorry Doc, I didn't explain that very well (rush to leave).  The Miocene, especially around 17 m.y. ago, was a very active time in the tectonic history of the western US.  As JimBob said, the Colorado uplift is still a bit of a geologic mystery- and I thought it was interesting that this new date on the inception of the uplift (and therefore the downcutting of the Grand Canyon) so neatly coincides with such an active series of tectonic events.

[DoctorBeaver]

I'm a total thicko where geology is concerned (where anything is concerned  [] ), but I would have thought that a period of intense activity would be a prime candidate for such an uplift.

[Bass]

My point exactly!  But thanks, Doc, for stating it more clearly and succinctly

[DoctorBeaver]

My pleasure  []