Earth Musings – My Travel and Geology Blog: Fall River Rafting through the Desolate Gray Canyon of the Green River, Utah

During the last week of September, I served as a geology interpreter on a six-day river trip through Desolation and Gray Canyons on the Green River in Utah. It was a wonderful time of year, when the swarms of mosquitoes had already flown south, the aspen trees were turning red, and the days were warm and the nights cool. This is a fantastic geologic transect through relatively young rocks. Check it out.

The trip began with a scenic flight over the river at sunrise. Floating over the valley

Early morning light begins to wash over the Book Cliffs.

The Green River exits Desolation Canyon (bottom) and flows into Gray Canyon (top). Note the large alluvial fan draining from Sleaford Canyon into the river channel. It flowed to the left. The river flowed to the right (west) and the remaining boundary flowed into the river. See this huge alluvial fan flowing from the River Sleaford Rapids from above. This mailbox.

A view of the cliffs meandering along the Green River – we hiked this loop later on in our trip

We landed on Horse Mesa Bench, a geological marker. Green River Formation

There is a 1.5 mile hike from the runway to the river. Brilliant!

We enjoyed some great views of the river during our hike. Note the Horse Mesa Bench in the middle of the cliffs (the small central cliff face).

Note the hiker (above) and his shadow (below)

Along the famous Green River Formation

The Green River Formation is a rock unit found in the tri-state area of ​​Utah, Colorado, and Wyoming. It represents a series of freshwater lakes that formed in a topographic basin between about 55 and 45 million years ago (megayears, or millions of years ago). At that time, the Mogorrion Highlands were in southern Arizona, and the Rocky Mountains were rising to the north and east. The lake basin was between these two positive areas and received sediments from the entire highlands. Prior to the 2010 study, the Mojave Desert source area was not known to exist (discussed below). See the following map by Ron Blakey for this lacustrine environment of the Green River Formation.

Paleogeographic map of the Colorado Plateau approximately 50 million years ago

Sunrise from a camp in the Green River formation

River Reflection

A typical camping scene on a beautiful sandy beach

As we continued downstream, the Colton Formation began to emerge from beneath the river.

Along the way we visited some amazing petroglyph panels

Remember the aerial photo of the severed serpentine road in the fourth photo of this post? Here we hike a loop on an abandoned meandering trail.

Panoramic view of the abandoned serpentine road near Chicken Rock – see notes Next photo

The yellow line shows the old meander curve (the dashed line is hidden behind it). The meandering “island”

The “downstream” portion of the old Green River channel. The meander is very close to the present riverbed. It was abandoned relatively recently.

Amazing view of the Green River in Desolation Canyon. Inside the far wall The reddish Colton Canyon at the bottom of the canyon the upper light-colored Green River Formation and the upper light-colored Green River Formation.

Another beautiful campsite. Sleeping on this beach is awesome!

The Colton is primarily fluvial and deltaic deposits and is slightly older than the Green River. Lake. Formerly known as the Wasatch Formation, this nomenclature Limited to the Wasatch Front area nowColton has an interesting theory. It comes with that.

The Colton Formation is made up of arkosic sandstone and mudstone (i.e. It is rich in pink feldspar derived from granite. Zircon crystals can be traced back to the time of their formation. The only source of these particular crystals is in the eastern Mojave Desert. Southwestern Arizona and southeastern California. Davis et al. Continental-sized rivers carried sediment out of the region. From the Mojave Desert to near Bryce and the Uinta Basin, from about 56 to 55 million years ago. The California River (shown by the thick dashed line). They did not claim it. As to the exact location of the supposed river, all we know is that it must have flowed. Various Laramide Upwarps (KU=Kaibab Upwarps, MU=Monument Upwarp, CCU=Circle Cliff Upwarp, SRS=San Rafael Swell). References: Davis, Stephen, J. (2010) “Paleogene California Rivers: Evidence for Mojave-Uinta paleodrainage from U-Pb ages of sedimentary rocks Zircon,” Geological Society of America, Geology, Volume 38, Issue 10, Pages 931-934.

Note the gradational change between the reddish corton layers (lower and upper). Mainly in formation slope) and the light-colored Green River Formation above it (shelf).

As the colton layer that forms the slope becomes higher and more developed, The canyon widens, giving you a wider view.

Above Sleaford Rapids. A large debris flow from the Sleaford valley sweeps the river. Continue to the right (west) and the wreckage forms the largest rapid in the river (not visible).

Camping above Sleaford Rapids

Red rock sunset seen from camp

A majestic butte made up of the Colton Formation

A final view of the upper reaches of Desolation Canyon

Entrance to Gray Canyon – Older rocks emerge – Mesa Verde Group

Our last night’s camping included a short hike through the rocks to a window. To the Green River and our camp

A view downstream of Gray Canyon. The plateau caprock is made up of Blue Castle. The upper slopes of the sandstone beds of the Price River Formation Backton; the central cliff is Castlegate Sandstone, the lower half is The landscape is made up of the Blackhawk Formation, all of which are Upper Cretaceous in age.

The trip ended with a view of Gunnison Butte, a famous landmark in the area. It was a fantastic trip (6 days!) with a great group of “students”.