The Great Unconformity and Spectacular Geology of Wyoming's Fremont Canyon 

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Thank you.. 2 billion year unconformity is a bit humbling.

John Fremont was a 19th century explorer who'd been tasked with discovering if any rivers connected the Mississippi and its tributaries to the Pacific Ocean. His "Memoirs of My Life and Times" is a jaw-dropping account of his group's explorations in the 1840's up the Missouri River to the Platte, along the Oregon Trail, along the Snake River to the Columbia River, then down the eastern Sierra, across them in winter while near starvation, into California, and back. An amazing journey.

Great little trek - I always appreciate your showing us what is in the roadcuts as well as close by. Pointing out the layers helps train the eye to look at the cuts more closely, rather than just whizzing by.

Wyoming, ya gotta love it. Far less traffic, but the hazards of grus.

I have always love history and to throw in geology it is my passion!

Thank You for posting this during your "time-off" from teaching. Please be safe and I really appreciate it when you let us know how careful you are being. Rocks are not always as solid as they seem! Says the flat lander to the geologist! 😁

As I understand it, it is the Great Unconformity that led to the Snowball Earth hypothesis. Grus, don't bring me down...

Grus. New geo word day for me.

I've seen the Great Unconformity in the Grand Canyon on a raft and on Frenchman Mountain in Las Vegas after taking a small somewhat rugged hike. In Wyoming I can just drive up to it.

This was a beautiful and interesting outcrop! The Great Unconformity is something I need to read more about. Thank you and Happy New Year’s!

I grew up in Montana, Utah, and Wyoming. As a scout and then a USFS firefighter and Geography major,I got to see so much of what you have shown us. Only wish I knew then what I now know, thanks to you. Antelope Island, I've seen the sign a million times, this time I stopped and knew what a special place it is. Thank you.

Thanks again Shawn.

thanks Shawn

Nice narrow canyon, & it's always a thrill to encounter the ancient basement. Then- the drama of a 2billion year gap/juxtapositon makes the mind swirl-

Oh wow. I've been waiting for this one for a while and I didn't even know it.

I sure hope so visit Wyoming this summer. I haven’t been there for a couple of decades and only to YNP and the migmatite of the Wind River Range. Wonderful glaciers there.

The river is diverted through a tunnel to a power plant. 1958 OR SO. I fished it with my dad before it was Opened. Amazing place.

A strikingly pretty area and I'm glad you're describing it. That would have been hard to figure out otherwise. Gruce is a new word. 👍🏻 Again, your mineral and rock identification series is SO helpful! Thank you!

My dad was a soft rock geologist and turned to crystallography in his retirement (a lot of stuff on MinDat), so watching your stuff gives a bit of nostalgia. Thanks for doing these videos. Sandy (get it? Sandy...soft rock, he did his PhD on some sort of clam) in VA.

A great little excursion thanks very interesting

"Don't bring me down...grus!"

Thank you for this road cut lesson. I need to learn more about the unconformity.

Another excellent roadcut. I was expecting you to say the overlying strata was Cambrian age so it was interesting to hear it was Devonian.

It's so Pretty Shawn , One day it's all going to Blow .

Oooh! this canyon was exactly what I needed to see for a project I'm working on (not geology) ... now I have to drive down there and take pictures. :)

Another road cut and an exquisite canyon (loved that phrase for some reason). Thank you.

Shawn, I spend most of my summers on my boat at Alcova and Pathfinder Reservoirs. To really appreciate the canyon, you need to take a boat trip up the 2 1/2 mile canyon to the power plant from the main body of Alcova Reservoir. There is also a smaller but very unusual canyon on the North Platte River arm of Pathfinder Reservoir. During your next trip that you plan to the Casper Area you have to try and see both of these canyons. I am not a geologist but there appears to be some rather large lava dikes in the rose granite that run through the canyon all the way up to the Marina area and Sweetwater River arm area of Pathfinder Reservoir.

I had never considered looking for the great unconformity here. Would be interesting to map other good exposures in Wyoming and further your observations of the nature of the contact.

Hi, Shawn. We just had an earthquake here in NYC. I'd be so grateful if you do a piece about the splitting up of Pangea and how that created different fault lines throughout the NYC/east coast. NYC geology is very exciting but also VERY confusing at times. From the eastcoast - Happy New Year!

That is a really eye-opener of a roadcut professor. There are different unconformities around but it really takes a geologist to decern the area of the Great Unconformity. Check out any videos that mention Snowball Earth for more on that.

Looks like a fun little crag.

Thx Prof ✌🏻 Happy New Year everyone

Layers and waves , big part of a large part of a big picture

One fun thing to think about is that in places like this where the Great Unconformity is exposed at the surface: presumably in time the top layers will be completely lost to erosion and we will end up with an even greater unconformity when the surface is buried again.

Anyone remember Ernie Shirley who had a rockshop in Hanksville? Shirley's Rocks and Indian Artifacts. I got some great Fremont pottery from him, and a few points. He passed about 2009, I think. He had some huge dino bones in the back, too, he showed me.

Reminds me of the contact between the granitic core rocks of the Black Hills and the Cambrian Deadwood Sandstone in Reaves Gulch in Wind Cave National Park southeast of the “Pigtail Bridge” on Highway 87. Very coarse and pebbly bottom beds of weathered quartz unconformably on the pegmatites and schists.

I love you man! So cool

Thanks Shawn. That really is spectacular. 🙂👍 It would be interesting to take a Geiger counter or other radiation detector, and to see how radioactive that pink granite is. I'm in the U.K., and red or pink granite here is known for its radioactivity, from Radon gas which is a fission product of Uranium and other unstable elements. Interestingly, the Precambrian, then the Cambrian and Devonian eras / rocks are named after parts of Great Britain (the correct name of the main island of the U.K.). Devon is a county in the Southwest of England and Cambria is the Latin name of Cymru, or in English, the principality of Wales, which lies to the West of Central England. Both regions are where rocks of the appropriate ages are found.

I see the Great Unconformity often referred to and I pretty much know what it is, but I would really like an in depth look into it, like where it is all seen and the age differences between the rocks and more.

Another good 'un, Shawn! I think the great unconformity is seen in the western half of Glenwood Canyon on I-70, also.

You can tell that the limestone and the material underneath with pebbles, was the river banks, before the uplift had accorded, did you dig up any samples of the pebbles, for gold ??

The river did not cut the canyon as no erosional features are present . The land itself split open and separated which created a natural channel for the water.

It was already gone when I got there.

The GREATER Unconformity!!!

❤ sounds like you're doing unconformity.... I'll come back and watch this in a little bit, I bet it's good!

Shawn, have you ever been to the Sideling Hill road cut on I-70 in Maryland? It is huge for a road cut. Richard West

Nice video, brings back old memories. did you get to climb there? there are some 4-500 ft walls about 1/2 mile downstream, 2-3 pitches, which are really cool, but you can't go wrong climbing near the bridge. A question: Is the pink granite the same as you find in Vedauvoo, south-east of Lararmie off of I-80? it has really big crystals. Have a happy new year!

I’m going to have to look up the Great Unconformity in some sources. “Grus” = be careful out there! TX!

Some say Great Unconformity is from Snow Ball Earth. Do you agree? Nice pink granite at contact with unconformity.

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Love it Shawn! Can you tell from drill cores whether heavies are of natural erosional source vs artificial source? Nile delta cores 8-14 kya show a significant spike which, to my untrained eye, don't appear to be natural black sand deposits. Also. the population density along the Nile Valley goes from "normal" to zero at 14 kya. Repopulation happens after 7.5 kya at 5,500 years ago with the predynastics. My research is leading me toward looking at core samples from the mouth of the following rivers: Mississippi, Amazon, Boyne (Ireland), Thames, Seine, all of which have large complexes of neolithic architecture. Looks like they may have had a little more than copper and iron.

The color banding, lighter/darker sedimentary layers remind me of soil cores taken to survey local ancient climates. Is that the same for the sedimentary layers, light = drier climate, dark = warmer climate?

Shawn, Very interesting video. I assumed the strata at stop 2 was Cambrian Flathead Fm. I would like to read the reference you mentioned where they think it is now Devonian. The white rocks are Madison Formation Limestones. They are across the road and up a little like you mentioned. The mapping does not show Precambrian rocks at Stop #2, so you might be on to something. I was hoping you were going to throw your climbing rope over the edge and then film from above so we can watch you execute your 5.9 moves.

So interesting. Do you ever come upon snakes? And if so, which ones. Greetings from South Africa

🇺🇸🖍📗🔨Dear teacher Sham I've been watching many video from you where you give us so much pleaser to know more about Geology study out of classroom. You are very good MD. I do enjoy to hear from you❤; any time, everyday I can.🔨💚🖍📗🇺🇸

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So is this "Great unconformity" the floor of the inland sea? I'm also curious about the Red desert, where does it lay in comparison to the Great unconformity?

This canyon was probably an old earthquake falt line!

Parts of that canyon, look like it could collapse at any moment.

just wondering when granite is considered basement rock, even though it must have intruded older rock

Is that part of the flaming gorge complex?

Wouldn’t Free ont canyon’s steep sides In resistant rock imply it was formed by tectonic forces rather than erosion?

Did the river actually cut this canyon or is the canyon a fault that a river utilized with the path of least resistance? The vertical walls without the common U or V erosion that occurs with water. With the fracturing, or possible faulting in the granite, could this be indicative for the presence of a fault? Looking at the strata layers, some shows possible uplifting.

Gravel is called "grus" in Swedish, any connection?

You need a head/shoulder mount camera

I don’t think the water cut that. Maybe a fault line?

quarter inch pellets seem to be from a ball mill. expand on this please.

Get ready for another Iceland update.

First shot on second stop looks like face in lower frame. 6:28 looks like giant feet

Have they cracked the case and arrested the thieves yet?

Something hit and formed the moon maybe that erased some history.

Now don't fall down while filming :)

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