GSA 125 Denver - Tuesday - The River that Formed Grand Canyon Flowed Where? Stunning Proposal by University of Montana Geologist

Tuesdays sessions were devoted to ideas related to the evolution of the Grand Canyon, the Colorado Plateau, and the Rocky Mountains.

Lon Abbott (Univ. of Colorado) presented a fascinating talk on nine travertine deposits that are found on or near the Tonto Platform between Hermit and Boucher creeks. The most interesting of these are the ones perched on top of the Tonto. Curiously, they do not drape over the ledge into the Inner Gorge, suggesting to him that they predate the cutting of the Vishnu Schist here. Abbott determined (through a convoluted but successful series of determinations) that the age of these perched travertines are between 591,000 and 497,000 years old. This could be the age of the Inner Gorge in Grand Canyon, which is quite young. He was also able to suggest a scarp retreat rate for the Muav/Redwall cliff behind the Tonto of about 850 m/Ma (meters per million years). These are fantastic results that show fast rates in the possible recent sculpting of Grand Canyon.

Ryan Crow (Univ. of New Mexico) was next and reported on mantle-driven uplift of the Grand Canyon region. Chemical signatures in basalt rocks for the last 10 million years show a trend through time to sources derived from the lithosphere to aesthenosphere. He painted a picture of a propagating wave of uplift, that progressively raised the margin of the Colorado Plateau from SW to NE. This wave of uplift he suggested, could be the driver of canyon incision.

Lots of talks spoke to the possible causes of the variable stream gradients observed along the Colorado River system. Possible controls on gradient are rock strength (resistance to abrasion), knickpoint migration, uplift, and/or subsidence. Kelin Whipple (Ariz. State Univ.) gave evidence for the importance of rock strength in determining these gradients (the Colorado/Green rivers have four locations of steep gradients - Grand Canyon, Cataract Canyon, Desolation Canyon, and the eastern Uintah's).

Things began to heat up when Brian Wernicke gave his talk, followed immediately by Karl Karlstrom. These two currently are the point men for ideas of an old canyon (Wernicke) or a young canyon (Karlstrom). Wernicke invoked that Grand Canyon is generally a simple landform that did not require a complicated set of processes in its formation. He channeled Ken Hamblin who was the first person to study the lava dams in western Grand Canyon, who noted when a dam was formed, it was removed rapidly but with no additional incision into the canyon walls. Karlstrom responded that if any segment of the Grand Canyon could be shown to be young, then the entire idea for an old canyon falls apart. Karl's current idea is that the western canyon paleochannels went north along the Hurricane fault zone and then followed a paleocanyon beneath modern Toroweap Valley.

Overall, I was impressed that Brian Wernicke and Rebecca Flowers (and a few others in that camp) continue to beat the drum for an old Grand Canyon; this in spite of the fact that most other workers are showing evidence for a younger canyon. They are not backing down. They generally agree on the Helium dates for cooling of the rocks (unroofing) but diagree on the interpretation of that data. For his part, Karl has now backed off from insisting that the entire canyon is less than 6 Ma - he believes there was a paleocanyon in eastern Grand Canyon between 25 and 15 Ma.

Finally, a former NAU Geology grad proposed what likely is the biggest "bombshell" of the entire session. Just when you think that some things might be resolved or that nothing more exotic could be proposed, something comes along that just blows the roof off of everything. Dr. Jim Sears is a person I had heard of before but had never met. While attending the NAU Alumni Reception on Monday night he hinted to me his idea - that the Colorado River in Grand Canyon might have flowed 23 Ma into Nevada, then north through to Idaho, Wyoming, and Montana, then north still into Saskatchewan, toward modern day Hudson Bay and into the Hudson Strait to the Labrador Sea. That's right - river water from the Grand Canyon flowed into the Labrador Sea 27 Ma.

Slide from Dr. Jim Sears talk on Tuesday, October 29 showing the Bell River system as it existed in North America prior to reorganization by glacial cover. Original Beel River system on the left, reorganized (modern) drainage on the right.

 

Close up of the previous Bell River system with added branch of the river in the Grand Canyon region. I will report more on this research in a later posting.

The original proposal of a Bell River was published in the Journal of Geology, vol. 3, #5 in 1895. Here is the work:

GSA 125 Denver - Monday - The Bouse Formation (Morning) and West of Grand Canyon (Afternoon)

The Special Session regardng the Grand Canyon and Colorado River is called, "Cenozoic Landscape Evolution of the Colorado Plateau-Rocky Mountain Region and the Carving of the Grand Canyon", (Parts I, II, III, and IV).  The entire two-day special session could be considered as the 4th conference ever held to address the issue for how the Colorado River and the Grand Canyon formed. The previous three were held in Flagstaff, 1964; Grand Canyon, 2000; and Flagstaff, 2010. Of course, you can read the results from the three previous symposiums in my book "Carving Grand Canyon", reviews for which here.

Talks the first morning were focused on the lower Colorado River, downstream from the Grand Canyon. The entire Session is set up to work from the lower river regions to upper river reaches.

Along the lower Colorado River corridor, from the Hoover Dam area to north of Yuma, AZ, are deposits known as the Bouse Formation. They have been controversially interpreted as either marine deposits from the early Gulf of California, or deposits from lakes that sequentially filled and spilled from water upstream. The Gulf of California idea is one from the 1960 to 1990's, with the fill and spill being more recent (except Eliot Blackwelder in the 1930's who was the first to propose a young river formed from spillover). Major contributors to the modern fill and spill hypothesis are Kyle House, Phil Pearthree, and Jon Spencer. They have done a bang-up job of looking at sediments in the lower river corridor and showing a sequence that grades upwards from local closed basin alluvium, course debris composed of material from the basin divides, fine-grained limestone grading upwards to delta sands and mud, and finally Colorado River cobbles and gravel. The interpretation is that formerly closed basins were sequentially filled with spillover water and sediment to establish a course for the lower river.

All seemed well and good with this approach until Kris McDougall (USGS - Flagstaff) and Rebecca Dorsey (Univ. of Oregon) related that paleontological evidence from the Bouse Formation has shown marine affinities in the lower basins. This means that a marine origin for the Bouse cannot be totally ruled out at this time, at least for the Blythe basin. It seems that every time a step is taken forward in understanding this river system that an "avalanche" downslope comes along. Dorsey also reminded listeners that modern faults lie astride the Bouse's various basins and that very recent uplift of the deposits cannot be discounted. More work will be needed in this area.

The afternoon session moved upstream to the Hualapai and Muddy Creek basins and the area around the Grand Wash trough, immediately west of Grand Canyon. Jim Faulds talked about the 1.5 miles of salt that lies beneath Red Lake and other basins and showed that these massive salt deposits record closed basin evaporation and deposition before the Colorado River was integrated (approximately 15 to 6 Ma). Others workers discussed the idea that an ancestral Colorado River might have followed the course of today's lower Virgin River but nothing definitive has come of that.

Then came the "fireworks". Tim Raub came to the defense of river systems that have persisted and existed on Earth's surface for 10's of millions, even hundreds of millions of years. Two examples came from Australia, the Murray/Darling system, the Fitzroy system (280 Ma), an Old Red Sandstone system in Scotland (310 Ma), and the paleo-Susquehanna and Potomac systems (56 Ma). Of course, he was defending the idea that the Colorado River could have been in place for up to 70 Ma as proposed by Brian Wernicke and Rebecca Flowers.

I will discuss more controversies in later posting but now it is time for me to attend the 2nd day of this fascinating conference.

Geological Society of America 125th Annual Meeting in Denver

NOTE: A TWO-DAY SESSION ON THE ORIGIN OF THE COLORADO RIVER AND GRAND CANYON WILL BE HELD ON MONDAY AND TUESDAY THIS WEEK. LOOK HERE FOR OCCASIONAL UPDATES. HERE IS A SUMMARY OF MY FIRST DAY AT THE TALKS.

I am attending this huge gathering of geologists held at the Colorado Convention Center in downtown Denver. There are between 7,500 to 8,000 professional geologists in attendance - the venue itself is huge. During this four-day conference there will be 4,900 talks given and at any one time, 30 talks are underway! I have to choose among those talks to attend one of them. It is a mind blowing geology fest. Here are some pictures from the first day on Sunday, October 27.

This is Harrison Schmitt, the last of the 12 men who have ever walked on the moon. He talked his way into the Apollo program - a program that had identified military test pilots as the best candidates to go to the moon. Dr. Schmitt convinced the program that a professional geologist needed to go to the moon. He gave a talk on the composition of the rocks near the landing spot for Apollo 17. I was amazed to learn that the moon has pyroclastic deposits, as well as the usual basalt rocks.

In the main exhibit hallway are large (8 feet X 8 feet) paintings of ancient Colorado. Here is one from the Morrison Formation 145 Ma (million years ago) showing a Stegosaurus walking on the site of the present-day Rocky Mountains, then a broad low-lying floodplain.

Here is a Triassic depiction of Colorado about 215 Ma.

I conducted an oral history with William (Bill) Dickinson in his hotel room after the first day of talks. Bill received three degrees from Stanford University and then became a professor there during the 1960's. This is when the theory of plate tectonics was being developed and I was interested in learning more from him about the changes that occurred during this pivotal moment in the geosciences. Look here in the future for some excerpts.

Southern Africa Safari - Part 4 - Botswana

The final leg of this great safari is in the country of Botswana where we visited the Linyanti Swamp and the Okavango Delta. The delta is an area I have wanted to visit for a long time since its settingas an inland delta is postulated as a modern analog for the Colorado Plateau's Moenave Formation (found between the Chinle and the Kayenta formations in the western Plateau - the eastern equivalent is the Wingate Sandstone).

 Ima heade out on another adventure so the captions are short. Sorry.

The Linyanti Swamp. The water originates in the Angolan Highlands, just like the water for the Kunene and Zambezi rivers.

The first stop was at King's Pool where the termite mounds here were taller and thinner.

We finally saw giraffes!

And more leopards, this one eating an impala that it just took down.

She is a beautiful specimen and is not bothered one bit by our presence.

Digesting.

She had one small cub with her who was also learning how to hunt.

We followed the leopard to the swamp where it had a drink of water at sunset. The placement by the guide for photos was impeccable.

The next morning, the remains of the impala were hanging in a tree. This is where the leopard brings its kill to keep it away from hyenas.

Mama coming down from the tree.

And looking for her cub.

Next was the hippo pool at the swamp. These can be mean creatures.

And this is why - they are very territorial.

Next we saw a gruesome sight - an elephant taken down during the night.

These are the two who are responsible.

We got very close to them.

Beautiful but dnagerous to anyone walking on two legs.

They were two young males.

One of them spotted some vultures on the kill and they do not like to share.

Chasing the vultures away.

The swamp is actually beautiful.

A parade of elephants crossing over to Namibia - the swamp is the international boundary.

An evening cruise on a boat.

Antelope in the swamp.

Sunset in Botswana.

The next morning we are out again looking for wildlife.

And the mother leopard has yet another impala.

On the way to the airstrip we saw the elusive wild dog.

There are thought to be only 5,000 of these left in the wild in all of Africa.

Next it was off to the Okavango Delta, seen here from the air.

A Maraboo stork.

And the great kingfisher - the largest in the world.

We saw lots of African fish eagles.

Lily pads on the water.

The delta is a wetland of unbound proportions.

Time for a helicopter ride with the doors off for better photgraphy.

Note the "hippo highways" in the water.

A large Nile crocodile.

I spotted one that had recently taken down and antelope and was ready for its meal.

The Cape buffalo.

A hippo moving under water.

A family of elephants

Closer view.

We could get really close to the Wildebeest here, unlike Tanzania where they are more skittish.

And wherever there is Wildebeest, there is Zebra.

We saw two amorous giraffes in a meadow.

This is how the courtship ensues with a next embrace.

I'd better stop here.

Our final lunch was beneath a large ebony tree. It was fantastic.

Sunset on the delta - thank you for reading and again I apologize for the very short captions.