Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.

Science 19 September 2008:
Vol. 321. no. 5896, p. 1634
DOI: 10.1126/science.1158862
Prev | Table of Contents | Next

Technical Comments

Comment on "Age and Evolution of the Grand Canyon Revealed by U-Pb Dating of Water Table–Type Speleothems"

Philip A. Pearthree,1* Jon E. Spencer,1 James E. Faulds,2 P. Kyle House2

Polyak et al. (Reports, 7 March 2008, p. 1377) reported that development of the western Grand Canyon began about 17 million years ago. However, their conclusion is based on an inappropriate conflation of Plio-Quaternary incision rates and longer-term rates derived from sites outside the Grand Canyon. Water-table declines at these sites were more likely related to local base-level changes and Miocene regional extensional tectonics.

1 Arizona Geological Survey, 416 West Congress Street, Suite 100, Tucson, AZ 85701, USA.
2 Nevada Bureau of Mines and Geology, University of Nevada, Reno, NV 89557, USA.

* To whom correspondence should be addressed. E-mail: phil.pearthree{at}azgs.az.gov

Read the Full Text

To Advertise     Find Products

Science. ISSN 0036-8075 (print), 1095-9203 (online)