Saturday, November 09, 2013

An Autumn Hike in Southeast Utah

Last month I embarked on a fantastic hike in the area of southeast Utah. It had plenty of red rocks, a small stream and some curious ruins and pictographs. The weather was delightful  during the day but below freezing most nights. And the fall colors were at their best. Have a look.

The hike began at 7,000 feet on top of the Shinarump Conglomerate Member of the Chinle Formation. You can see it capping the mesa on the right skyline. The red slope below is cut into the Moenkopi and Organ Rock formations with the Cedar Mesa Sandstone making up all of the light colored rocks inside the canyon.

Another view of the section just described.

Sandstone heaven - the vast majority of the hike was within this one rock unit, deposited near the shore of a Permian age beach.

Heading down.

One of the first things we spotted was an old ranch  house with the wagon still waiting nearby to make a run to town, only 50 miles away. It was amazing to see this wagon returning to the earth from its last position in  the "driveway".

The was lots of well-developed  crytobiotic soil in this little abused section of the desert.

And arches too. Can you spot this one in the distance?

Many alcoves had ruins within them.

A closer look. It was impossible without ladders to get any closer.

Interesting hand prints and dots.

And grinding stations for food stuffs.

View out to the east from an alcove.

The autumn colors in the cottonwood trees was at its peak in the 3rd week in October.

Especially when framed by the sandstone.

Gold for the soul!

Everywhere the color was spectacular.

A nice pictograph from at least 700 years ago.

This one had three other "friends" as well.

Hmm? What could this scat be from? It is pretty large.

Moving on downstream.

A large flood had ripped down the canyon just about a month before.

Yep - there is the one who left the scat on the trail - a brown bear. He was shy and never really showed is face to us.

Pool reflections.

Painted hand prints.

An anthropomorph.

Joe had found this panel while wandering around in  our camp below.

We did not see to many depictions of bighorn sheep but this is one well rendered.

Here is a view of some prehistoric backpackers.

An here are some modern ones.

I am so fortunate to have friends who love to hike and camp in the wilderness. This five-day hike was one of the best ever!

Monday, November 04, 2013

More Details About the Grand Canyon/Bell River Connection

Did the Grand Canyon form 23 million years ago instead of 6 million, as proposed by some geologists? See this updated posting for an interesting scenario in the Colorado River's evolutionary history.  **JUST ADDED: a complete scientific article on this proposal has just been published in GSA Today. You can access the article here where a pdf link is available.

Readers of this blog will recall my last posting about a proposal made by Dr. Jim Sears (University of Montana) at the Annual Meeting of the Geological Society of America in Denver last week. In it he proposed that the ancestral Colorado River might have flowed west through an early incarnation of the Grand Canyon to an area near Nevada, then turned northward toward Idaho and Montana, eventually spilling into the Saskatchewan arm of the pre-Pleistocene (before 2.5 million years ago) Bell River system. The Bell River was an Amazon-scale river system that drained about one-third of the North American continent before glaciers in the last 2.5 Ma reorganized the drainage system.

Here is a map of the Bell River system in pre-Pleistocene Canada, (with an arm of it added by Dr. Jim Sears and colored in red and light blue). It shows how this arm may have run through the Grand Canyon toward Nevada, then along a rift system to Idaho and Montana. The evidence for this? In southwest Montana are Miocene age sediments (about 23 to 17 million years old) in the modern upper Missouri River system. They contain fluvial gravel that is called the Sixmile Creek Formation and they indicate northeast flow directions. They also contain clasts of rocks that are exposed in Nevada. Recent mapping shows that the Sixmile Creek rocks are distributed across 500 miles from the Snake River Plain to the Saskatchewan River area.

This arm of the Bell River thus crossed the present-day Snake River Plain and the Idaho/Montana Continental Divide to connect with the Saskatchewan arm of the Bell River. Note a greatly diminished Mississippi River in the pre-Pleistocene United States.

The Bell River flowed eventually to the area of modern day Hudson Bay and the Hudson Strait to the Labrador Sea. It ended in the Saglek delta which is the largest depositional basin between Baffin Island and Florida. It contains a 5-mile thick section of sediment. Recently released geoinformation from oil companies shows that the Saglek deposits contain Pennsylvanian age (about 300 million years ago) pollen fossils that were transported from their source rocks by this ancient river. Sears surveyed the drainage area of the Bell River and suggested that the likely source area for these transported fossils was the Supai Group rocks in Grand Canyon. One might think that other Pennsylvanian age rocks could have also supplied the material to the Saglek basin but they reside south of the modern Great Lakes and thus on the other side of the drainage divide.

Of course, this idea is not a slam dunk immediately. Further testing of the idea is necessary. But it does dovetail with other proposals by Karl Karlstrom and Brian Wernicke that a paleocanyon in eastern Grand Canyon might have been present during the Miocene.