There are two stories regarding Grand Canyon geology. Part one concerns the actual rock layers, and in particular, when and how they were deposited. This subject has been covered in depth in many other papers. Part two of Grand Canyon geology deals with why the Colorado River happened to pick this particular path allowing it to cut the Grand Canyon.

   This research paper is an attempt to depict the geologic history of the Colorado River, and in particular, how it formed the Grand Canyon. The time period starts with the late Cretaceous and continues through the Tertiary to the "Grand Canyon Event" in the late Miocene. As far as I know, no one else has presented such a model. Since the model is the first of its kind, it should be regarded as a "trial theory" as opposed to generally accepted knowledge. As such it will be subject to future "refinements". Any additional knowledge that other observers may have would thus be appreciated.

   Some of the feedback that I have received disagrees with the conclusions that I have presented in the model. Readers should understand that better models may exist or may be developed. My policy will be to update the model if there is evidence indicating there is a minor problem, or pull the model entirely if there is evidence that can not be resolved. In either case I will pay attention to other conclusions, but evidence must be provided if it involves changing anything.

Photo courtesy of NASA.
Wyoming is at the top right. Utah and the salt deserts are in the upper left – stretching to the Gulf of California in the lower left.

   The linchpin to much of the scenery in the southwestern U.S. as well as the most dramatic event in the river's geologic history is the origin and formation of the Grand Canyon. The only way to appreciate the Grand Canyon’s size is to visit it.

   One of the ways to see the Grand Canyon is to take a raft trip through it. The most dangerous part of such a trip is that it becomes expensively addictive, leading to future trips.
 
   Only when you raft some of the big rapids do you comprehend the power of the river, and this is just a sample of the power that was here before Glen Canyon Dam held back spring runoffs pouring down from the high Rockies.

Power sufficient to move mountains.
How many mountains?
The answer is - All of them.


March 7, 2008 update:
Recent newspaper reports have suggested that the Colorado River began to cut the Grand Canyon 17 million years ago.
These reports are in error!
   A research study conducted at Grand Canyon Caverns came up with the 17 million years ago date which is valid at that location, but Grand Canyon Caverns is in a different drainage system which is controlled by displacement along the Grand Wash Cliffs/Fault to the southwest of Peach Springs, AZ. The attempt to extend the Grand Canyon Caverns observation to include drainage of the Colorado River in the Grand Canyon is not valid.

   Multiple research studies support the model presented here that local erosion in the western Grand Canyon was beginning about 17 million years ago, but a through-flowing Colorado River to the Pacific Ocean did not exist until about 5.4 million years ago. Within this 5.4 million years ago to present timetable, most of the downward cutting has been concentrated in the last 2.5 million years.

For example:



Note: The Wikipedia article about the Grand Canyon ( http://en.wikipedia.org/wiki/Grand_Canyon ) implies that the Colorado River started cutting the Grand Canyon some 17 million years ago. The Wikipedia article was based on an article in the New York Times, but the New York Times reporter confused 17 million-year-old local drainage at the western end of the present Grand Canyon with the Colorado River. The Colorado River didn’t arrive at the present Grand Canyon until about 5.4 (+/-0.1) million years ago.



Nov. 29, 2012 Update
   Multiple newspaper stories are reporting that 60 to 70 million years ago western portions of the Grand Canyon were eroded down to within a few hundred meters of current levels by a river system that flowed from west to east through the Grand Canyon. The reference source for these newspaper reports is an article by Rebecca M. Flowers and Kenneth A. Farley in the current issue of Science.

   Erosion down to this level 60 million years ago by an eastward flowing river through the present Grand Canyon would be IMPOSSIBLE !!! since the river would have to climb thousands of feet uphill to get over preexisting strata to the east of the present Grand Canyon. I haven’t seen the Science article, but there may be a great deal of misinterpretation about what it does say.

   As outlined in the model given here (which has been posted on the Internet since 2001 – for example, see http://web.archive.org/web/20020308011932/http://www.geocities.com/durangobill/Paleorivers_preface.html ), there was erosion going on ABOVE the current western Grand Canyon some 60 million years ago. Sixty million years ago, there was a river system that originated near the present Arizona/California border that continued northeastward to Wyoming. Rim Gravels show that 60 million years ago, river flow was from south to north just to the north of the Peach Springs, AZ area.

   This river system (and is tributaries) eroded away Mesozoic rock layers from over the current Grand Canyon area and redeposited them from Utah northeastward into Wyoming. If this is consistent with the model presented in the Farley/Flowers journal article, then we are in full agreement.

   Also, the ancestral Peach Springs, AZ to Bryce Canyon, Utah river flow patterns of the western Grand Canyon area presented here are virtually identical to those shown in Fig. 5 of Wayne Ranney’s 2008 “A proposed Laramide proto-Grand Canyon” article published in Geomorphology.  http://www.sciencedirect.com/science/article/pii/S0169555X08002407



   
 
   This paper attributes the cutting of the present Grand Canyon to the arrival and spillover of the Colorado River about 5.4 million years ago. In the years since this paper was first posted on the Internet in April 2001, there have been multiple papers that support this model.

For example:

“supports a lake-spillover hypothesis for initiation of the lower Colorado River.”
http://geology.geoscienceworld.org/content/35/1/57.abstract

“Stratigraphic evidence for the role of lake spillover in the inception of the lower Colorado River” http://specialpapers.gsapubs.org/content/439/335.abstract

“Lake-spillover models for the lower Colorado River (House and others; Howard) are increasingly well-documented” (Page 8)
“Robust Geologic Evidence for latest Miocene-earliest Pliocene River Integration via Lake-spillover along the lower Colorado River” (Page 137)
http://pubs.usgs.gov/of/2011/1210/of2011-1210.pdf




 
 
Evolution of the Colorado River and its Tributaries

Appendix to the Evolution of the Colorado River

Cenozoic River Maps (Suggest you print this. Please allow a few seconds to download.)

Image Index  Intro to many different pages - each with computer generated 3-D Pictures/Images, and a short narrative.

Also please see



View area extends from the Gulf of California to central Wyoming
Photographs taken June 6, 2001 (Links updated July 27, 2008)

Low Resolution (1125w x 1450h) - 326 KB
http://veimages.gsfc.nasa.gov/1980/FourCorners.A2001162.1815.1km.jpg

Medium Resolution (2250w x 2900h) - 1.4 MB
http://veimages.gsfc.nasa.gov/1980/FourCorners.A2001162.1815.500m.jpg

High resolution (4500w x 5800h) - 4.3 MB
http://veimages.gsfc.nasa.gov/1980/FourCorners.A2001162.1815.250m.jpg





Southwest U. S. and North American Paleogeography
Maps by Ron Blakey - animation by Steve Perrin
http://www-personal.umich.edu/~sperrin/geology/paleogeography.html




Also, please see “Ancestral River Systems of the World ”
A pictorial world tour of river systems that flow through mountain ranges instead of going around them - and why they do it.



   This research paper was first posted on the Internet in April 2001. To see what my home page looked like in Nov. 2001, click here. http://replay.waybackmachine.org/20011119013229/http://www.geocities.com/durangobill/
Then click on the “Evolution of the Colorado River” link to see the earliest version that was saved in the “Way Back Machine”.
(or click here: http://replay.waybackmachine.org/20020308011932/http://www.geocities.com/durangobill/Paleorivers_preface.html )




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