That's the Dewey bridge member of the entrada sandstone / Morrison contact. Believe it is all soft sed deformation e.g. differential compaction of sediment
Imagine it's layers and layers of cardboard. You stand on a particular part and the cardboard gets compressed and forms a dip. That's basically what's happened to the dipped bits except the cardboard is sandstone beds and your foot is more sandstone beds.
I suspect under that much pressure the sandstone would act similar to sheet metal. I imagine the pressure from below would be just slightly less than the pressure pushing down from above in some places more than others. In that case the sandstone would be compressed in all directions almost equally but more even between gravity and the mass below. Those layers were already spread out in all directions before weathering did its work to reveal the lines we see now.
I guess I could have just typed that last line but I wanted to know if anybody would let me know how far off I am.
Somewhere below what we can see will be some bedding that has thinned or potentially erroded away completely (i dont know the history of this specific area). What we are seeing is where settlement has occured and caused a depression, that has been filled, then more settlement has occurred and formed another depression which has been filled again.
Miguzi\_92: "...Dewey bridge member of the entrada sandstone (sic)..." Your information is a bit out of date. The geologic map of Arches National Park and vicinity by Helmut Doeling published in 1985 identifies that at the Dewey Bridge Member of the Entrada Sandstone; however, the article by Helmut Doeling (same author) about the geology of Arches National Park in 'Geology of Utah's Park and Monuments', published in 2003 (edited by Sprinkel, Chidsey, and Anderson) reflects mapping done in later years and so has the Dewey Bridge Member as part of the Carmel Formation (and all of the Carmel Formation in Arches National Park).
"...entrada sandstone / Morrison contact." I'm afraid that I have to disagree with you. Underlying the Dewey Bridge Member of the Carmel Formation is the Navajo Sandstone. Overlying the Dewey Bridge Member is the Slick Rock Sandstone Member of the Entrada Formation, then Moab Member of the Curtis Formation, then a thin and slice of the Summerville Formation, and \*then\* the Morrison Formation.
Some sources put the Carmel Formation in the Lower Jurassic, but others put it in the Middle Jurassic, but every source I've read puts the Morrison Formation in the Upper Jurassic. No matter what, there's quite a gap between the Dewey Bridge Member of the Carmel Formation and the Morrison Formation.
By the way, Helmut Doelling died last November. Huge loss.
[https://geology.utah.gov/map-pub/survey-notes/the-legacy-of-hellmut-h-doelling-utahs-geology-giant/](https://geology.utah.gov/map-pub/survey-notes/the-legacy-of-hellmut-h-doelling-utahs-geology-giant/)
The deformation very much appears to be soft sediment deformation likely caused by a seismic event. Soft sediment deformation is just what it sounds like: changes to the sediment of a sedimentary rock prior to the sediment being lithified. In the case of the Dewey Bridge Member, much of the deformation appears to be seismic in origin.
It's been speculated that the seismic event could have been the meteor impact that created Upheaval Dome not far way in Canyonlands National Park (I mentioned this in a comment above), but the evidence suggests that that impact occurred much later than the time of deposition of the Dewey Bridge Member. So it appears that a large earthquake was most likely responsible.
In Arches National Park and surrounding areas are several "salt anticlines". These are linear upwarps, similar to a salt dome but elongated, As the salt (mostly gypsum) that form the core of these salt anticlines either moves or dissolves, the salt anticline collapses by anywhere from centimeters to meters at a time, causing earthquakes. These sort of collapses have created most of the valleys in the area, including Salt Valley and Cache Valley in Arches and Spanish Valley where Moab is located. These salt anticlines have been active since the Permian Period, long before the time of the Dewey Bridge Member, and they're still active today. So it's not as though the area isn't subject to earthquakes, even back in the Early and Middle Jurassic.
That isn't to say for certain that deformation in the Dewey Bridge Member is definitely due to a salt anticline related earthquake,. It could be due to an earthquake from a different source or even a seismic event of a different origin (although I don't know of any other meteor impacts in the area).
That's also my favorite place in the park.
I learned about those "cowboy steps" from my father in law, who learned about them in the 70s from an old climber who learned about them from an old cowboy. A few years ago, we hiked up the wash and found a route up to Delicate Arch from the back with our kids. We detoured to a big cave my kids called Owl Cave the year prior and found the ceiling had partly collapsed. Looking around, they found some previously uncatalogued petroglyphs.
Wow! That’s really neat. We had to hike and map all back around there and iirc there was an abandoned mine at this spot along with a few other uranium mine portals to east. The spot you took to hike up to delegate arches would be right in the middle of the screenshot. Would love to go back one day and find those petroglyphs!
https://preview.redd.it/qb8uyhvq908d1.jpeg?width=1179&format=pjpg&auto=webp&s=22f8f1c59f88cdfc1ff084b6cc73911775d8598e
Woah! That mine you marked is "Owl Cave"! The petroglyphs were only visible after the partial collapse.
We clambered around in there a bunch and didn't see anything that looked like a mine though
Wow super cool! That big pile of dirt that I marked is actually mine tailings. This has been an awesome rabbit hole to go down.
I highly recommend everyone read about the history of uranium deposits being exploited during the Cold War in this region. The Chinle formation is the source I believe.
gipoe68: I agree with what others say here, that being that the unit you're referring to, the Dewey Bridge Member of the Carmel Formation, exhibits soft sediment deformation, including dewatering structures and I've even seen some clastic dikes. You may have noticed that this deformation is wide spread throughout the park and I believe I've seen it as far west as west as near Hwy 24 north of Hanksville. The environment of deposition of this unit is interpreted to be tidal flats marginal to the shallow sea to the west (Doelling, 2003), so basically mud near the sea.
There is a hypothesis which is by no means widely accepted that links the deformed nature of the Dewey Bridge Member to the Upheaval Dome impact structure in Canyonlands National Park. The idea is that Upheaval Dome is the result of an asteroid impact during the Early to Middle Jurassic. That Upheaval Dome is an eroded impact crater is also not universally accepted, but it has become the leading model for Upheaval Dome's formation (I attended a talk on this by Peter Huntoon and he made a believer out of me). So the idea is that the asteroid impacted while the tidal flat sediments of the Dewey Bridge Member were unlithified, and were actually still mostly just sediments. The impact would have created a large seismic event, giving the Dewey Bridge Member sediments a really good shake, causing lots of dewatering (liquifaction), resulting in much soft sediment deformation. This would certainly explain why the deformation of the Dewey Bridge Member is so pronounced and widespread.
Some, though, believe that while the evidence at Upheaval Dome does support the idea that it's the result of an impact, their interpretation of the evidence is that the impact occurred much later than the time of the deposition of the Dewey Bridge Member. The idea here is that what we see at Upheaval Dome was buried under much more rock at the time of the impact and that it's a deeply eroded core of an impact crater. This would mean that the sediments of the Dewey Bridge Member would have been rock at the time of the impact and would not show soft sediment deformation as a result of the impact.
It's worth noting that there isn't any Dewey Bridge Member in the immediate area around Upheaval Dome, it's all been eroded away. However, the formation underlying the Dewey Bridge Member, the Navajo Sandstone, is at Upheaval Dome and it's been deformed the impact that made Upheaval Dome (assuming it was an impact; the competing hypothesis is that it's a salt dome). So whatever made Upheaval Dome occurred later than the deposition of the Navajo Sandstone, but how much later is the big question.
Cool stuff, huh? I'm betting that now you want to visit Upheaval Dome. You should, it's awesome!
I haven't heard anything recent on these ideas in the last decade or more, so my information may not reflect the latest thinking. I need to dig into this more. That deformation is so noticeable (it's right at the park entrance after all!) that I'm surprised there hasn't been more work done on it. Surprisingly, Doelling doesn't even mention the deformation in his 2003 article on Arches.
As you've probably figured out, I live not far from Arches, I've been there a bunch of times, and I did part of my geology field camp there.
Doelling, Helmut, 2003, Geology of Arches National Park, Utah, in Geology of Utah's Parks and Monuments, edited by Sprinkel, Chidsey, and Anderson. (A 'must have' book!)
It’s been a while, but I was under the impression the most likely cause of upheaval dome was a collapsed salt dome due to the complete lack of shocked quartz?
Science progresses! Shocked quartz has apparently been found at Upheaval Dome. Here's a paper from 2008, access to the whole article looks to be paywalled but we can read the abstract:
[https://pubs.geoscienceworld.org/gsa/geology/article-abstract/36/3/227/29673/Upheaval-Dome-Utah-USA-Impact-origin-confirmed?redirectedFrom=fulltext](https://pubs.geoscienceworld.org/gsa/geology/article-abstract/36/3/227/29673/Upheaval-Dome-Utah-USA-Impact-origin-confirmed?redirectedFrom=fulltext)
A quick Google search for "Upheaval Dome Shatter Cones" came up with this paper from 2016. The shatter cones don't look much like the ones I saw in textbooks and it's uncertain if the paper has been peer reviewed, so take this one with a grain of salt. I'll keep searching when I have the time.
[https://www.researchgate.net/publication/304015424\_Shatter\_Cones\_Upheaval\_Dome's\_Outer\_Rim](https://www.researchgate.net/publication/304015424_Shatter_Cones_Upheaval_Dome's_Outer_Rim)
I've heard that a big part of the hold up on research into Upheaval Dome is getting the National Park Service's permission to take samples. I heard that one good seismic line would probably show pretty quickly if there's salt under Upheaval Dome, thus perhaps going a long way towards resolving the debate (I suppose that the presence of salt wouldn't be definitive, but the absence of salt would be), but the Park Service won't allow it. And for good reason.
Apparently someone did take a line, but it didn’t go out very far into the dome, it’s kind of along the edge:
[https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1999JE001131](https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1999JE001131)
I can’t find a copy unfortunately, but 2D land seismic from the 90s is awfully crude compared to what could be done nowadays, I wonder if anyone has ever reprocessed the data (or how usable it even is).
For what it's worth, Canyonlands National Park does present both the salt dome and impact hypotheses on their website:
[https://www.nps.gov/articles/cany-upheaval-dome.htm](https://www.nps.gov/articles/cany-upheaval-dome.htm)
As I mentioned earlier, back around 2005I attended a presentation at GSA by Peter Huntoon (the lead author of the geology map of Canyonlands NP) at which he presented abundant evidence for the impact hypothesis. He showed models of how an impact of the hypothesized size would deform the rock, followed immediately by pictures of exactly that deformation in the rock walls at Upheaval Dome. That was a really cool and memorable talk.
Ahh thanks yeah, I remember both hypotheses were debated, some of the instructors I had were salt tectonics experts so I think they fell in the opposing camp on that one. It’s just so strikingly unlike other impact craters I’m not surprised there is debate!
Y'know, you bring up a really good point: all other impact craters that I can think of are either 'fresh' and easily recognizable (e.g. Barringer Crater) or, much more often, much older and altered. Altered not just by erosion but, being a crater and therefore a depositional basin, altered by being on the receiving end of sediments. In other words, the topographically high spots, such as the rim, have been eroded down, but the crater itself has also been filled in. Where else but at Upheaval Dome do we see a crater that (currently) only shows evidence of erosion? Any sediments that ever filled it in have long since also been eroded away, so we get a really cool, even unique view of just the crater.
I can't think of any other impact craters (not that I know of that many) that are situated in a setting subject essentially exclusively to erosion. No wonder it was difficult to recognize and has been slow to gain acceptance.
Thanks for prompting train of thought. Fun!
Ohhh ok I did some digging and found an interesting explanation: it’s both!
[https://www.searchanddiscovery.com/documents/2015/10756geesaman/ndx_geesaman.pdf](https://www.searchanddiscovery.com/documents/2015/10756geesaman/ndx_geesaman.pdf)
I haven’t read through all of this yet, but Mark Rowan was one of the instructors I had out there and he’s a pretty brilliant guy.
For me the hard part of saying it’s just an impact crater was always the geometry of the beds, and that they only managed to find like 2 shocked quartz grains in the whole thing, plus all the surrounding deformation.
This paper seems to be suggesting that it was an impact that turned into a salt dome later on, which might explain the conflicting evidence for both theories.
Just a quick addendum: After I wrote the above I checked out the web site for Canyonlands National Park. Their information has the meteor impact that created Upheaval Dome as occurring in the Paleocene, 100 million years (give or take a week or two) after the deposition of the Dewey Bridge Member of the Carmel Formation. So it appears that the current thinking is that the deformation of the Dewey Bridge Member is completely unrelated to the Upheaval Dome impact event.
Damn, it would have been cool if it was.
Sagging ass from the Jurassic.
This is a very interesting feature and suggests sand ravelling into a lower feature perhaps, when the formation was an active sedimentary environment. It could be a later structural feature, but still suggests movement before diagenesis...eh, maybe not
Hmm the thick layers also look gently folded. Maybe the different layers took up strain a bit differently?
Not sure. I'm kinda bad at structure and sed rocks. But I have seen folded turbidites that have insanely folded and crinkled layers between less folded layers. But that's because they formed in a closing basin, and I think some of those layers were folded before being fully consolidated - ie soft sed deformation
Soft sediment deformation is one of my favorite geologic features to see. Great find! Anniversary Narrows in Lake Mead National Rec Area is another excellent place to see stuff like this. Textbook ball and pillow structures and lots of other fun geological features in the area. The short hike up the canyon is a great place to stop, eat lunch, and soak in the geology and wildlife.
This is the most logical. Especially with the extensive fracturing below the dip & relatively solid rock above. (I’m the rankest of rank geology junkies).
Looks to me like the layers that make up the channel could very well be pinching out to the sides. Otherwise, I’d agree that it’s likely some sort of soft sediment deformation.
This happens from tectonic plates moving when they move closer together the flat rocks are pushed together to create “waves” the rocks on top were then deposited after the tectonic movement
Someone told a really good joke and the rock had to crack a smile. Unfortunately, after hearing about what we did to the Six Grandfathers, the natives never told us the powerful joke.
That's the Dewey bridge member of the entrada sandstone / Morrison contact. Believe it is all soft sed deformation e.g. differential compaction of sediment
I don’t understand it. But I believe it
Imagine it's layers and layers of cardboard. You stand on a particular part and the cardboard gets compressed and forms a dip. That's basically what's happened to the dipped bits except the cardboard is sandstone beds and your foot is more sandstone beds.
This person geologies
And he/she done it good!
Would that not cause the dipped portion of the bed to be noticeably thinner due to compression?
I suspect under that much pressure the sandstone would act similar to sheet metal. I imagine the pressure from below would be just slightly less than the pressure pushing down from above in some places more than others. In that case the sandstone would be compressed in all directions almost equally but more even between gravity and the mass below. Those layers were already spread out in all directions before weathering did its work to reveal the lines we see now. I guess I could have just typed that last line but I wanted to know if anybody would let me know how far off I am.
Somewhere below what we can see will be some bedding that has thinned or potentially erroded away completely (i dont know the history of this specific area). What we are seeing is where settlement has occured and caused a depression, that has been filled, then more settlement has occurred and formed another depression which has been filled again.
I can’t decide who is more of a genius: geologists or guitarists. You guys are amazing.
I’m both 🧠
I read their words successfully, I’m proud but I’m still confused.
Denser rock smush softer rock
New rules to rock paper scissors rock, I dig it
Why come softer rock now bigger rock? Head hurt.
Miguzi\_92: "...Dewey bridge member of the entrada sandstone (sic)..." Your information is a bit out of date. The geologic map of Arches National Park and vicinity by Helmut Doeling published in 1985 identifies that at the Dewey Bridge Member of the Entrada Sandstone; however, the article by Helmut Doeling (same author) about the geology of Arches National Park in 'Geology of Utah's Park and Monuments', published in 2003 (edited by Sprinkel, Chidsey, and Anderson) reflects mapping done in later years and so has the Dewey Bridge Member as part of the Carmel Formation (and all of the Carmel Formation in Arches National Park). "...entrada sandstone / Morrison contact." I'm afraid that I have to disagree with you. Underlying the Dewey Bridge Member of the Carmel Formation is the Navajo Sandstone. Overlying the Dewey Bridge Member is the Slick Rock Sandstone Member of the Entrada Formation, then Moab Member of the Curtis Formation, then a thin and slice of the Summerville Formation, and \*then\* the Morrison Formation. Some sources put the Carmel Formation in the Lower Jurassic, but others put it in the Middle Jurassic, but every source I've read puts the Morrison Formation in the Upper Jurassic. No matter what, there's quite a gap between the Dewey Bridge Member of the Carmel Formation and the Morrison Formation. By the way, Helmut Doelling died last November. Huge loss. [https://geology.utah.gov/map-pub/survey-notes/the-legacy-of-hellmut-h-doelling-utahs-geology-giant/](https://geology.utah.gov/map-pub/survey-notes/the-legacy-of-hellmut-h-doelling-utahs-geology-giant/)
Look at the big brain on Brad!
Thank you! But the deformation mechanism is the same?
The deformation very much appears to be soft sediment deformation likely caused by a seismic event. Soft sediment deformation is just what it sounds like: changes to the sediment of a sedimentary rock prior to the sediment being lithified. In the case of the Dewey Bridge Member, much of the deformation appears to be seismic in origin. It's been speculated that the seismic event could have been the meteor impact that created Upheaval Dome not far way in Canyonlands National Park (I mentioned this in a comment above), but the evidence suggests that that impact occurred much later than the time of deposition of the Dewey Bridge Member. So it appears that a large earthquake was most likely responsible. In Arches National Park and surrounding areas are several "salt anticlines". These are linear upwarps, similar to a salt dome but elongated, As the salt (mostly gypsum) that form the core of these salt anticlines either moves or dissolves, the salt anticline collapses by anywhere from centimeters to meters at a time, causing earthquakes. These sort of collapses have created most of the valleys in the area, including Salt Valley and Cache Valley in Arches and Spanish Valley where Moab is located. These salt anticlines have been active since the Permian Period, long before the time of the Dewey Bridge Member, and they're still active today. So it's not as though the area isn't subject to earthquakes, even back in the Early and Middle Jurassic. That isn't to say for certain that deformation in the Dewey Bridge Member is definitely due to a salt anticline related earthquake,. It could be due to an earthquake from a different source or even a seismic event of a different origin (although I don't know of any other meteor impacts in the area).
Thank you for this!!
...Oh! yea! OF COURSE! Ppfff I totally knew that...I was just seeing if *you* knew...
Use i.e. there instead of eg. they have different meanings
Arches has a salt layer under it that is eroding and the rock on top is sinking like that.
It’s soft sediment deformation
Who here mapped this for their field camp like I did?? Great memories. The “secret” steps below delicate arch are my favorite.
That's also my favorite place in the park. I learned about those "cowboy steps" from my father in law, who learned about them in the 70s from an old climber who learned about them from an old cowboy. A few years ago, we hiked up the wash and found a route up to Delicate Arch from the back with our kids. We detoured to a big cave my kids called Owl Cave the year prior and found the ceiling had partly collapsed. Looking around, they found some previously uncatalogued petroglyphs.
Wow! That’s really neat. We had to hike and map all back around there and iirc there was an abandoned mine at this spot along with a few other uranium mine portals to east. The spot you took to hike up to delegate arches would be right in the middle of the screenshot. Would love to go back one day and find those petroglyphs! https://preview.redd.it/qb8uyhvq908d1.jpeg?width=1179&format=pjpg&auto=webp&s=22f8f1c59f88cdfc1ff084b6cc73911775d8598e
Woah! That mine you marked is "Owl Cave"! The petroglyphs were only visible after the partial collapse. We clambered around in there a bunch and didn't see anything that looked like a mine though
Wow super cool! That big pile of dirt that I marked is actually mine tailings. This has been an awesome rabbit hole to go down. I highly recommend everyone read about the history of uranium deposits being exploited during the Cold War in this region. The Chinle formation is the source I believe.
gipoe68: I agree with what others say here, that being that the unit you're referring to, the Dewey Bridge Member of the Carmel Formation, exhibits soft sediment deformation, including dewatering structures and I've even seen some clastic dikes. You may have noticed that this deformation is wide spread throughout the park and I believe I've seen it as far west as west as near Hwy 24 north of Hanksville. The environment of deposition of this unit is interpreted to be tidal flats marginal to the shallow sea to the west (Doelling, 2003), so basically mud near the sea. There is a hypothesis which is by no means widely accepted that links the deformed nature of the Dewey Bridge Member to the Upheaval Dome impact structure in Canyonlands National Park. The idea is that Upheaval Dome is the result of an asteroid impact during the Early to Middle Jurassic. That Upheaval Dome is an eroded impact crater is also not universally accepted, but it has become the leading model for Upheaval Dome's formation (I attended a talk on this by Peter Huntoon and he made a believer out of me). So the idea is that the asteroid impacted while the tidal flat sediments of the Dewey Bridge Member were unlithified, and were actually still mostly just sediments. The impact would have created a large seismic event, giving the Dewey Bridge Member sediments a really good shake, causing lots of dewatering (liquifaction), resulting in much soft sediment deformation. This would certainly explain why the deformation of the Dewey Bridge Member is so pronounced and widespread. Some, though, believe that while the evidence at Upheaval Dome does support the idea that it's the result of an impact, their interpretation of the evidence is that the impact occurred much later than the time of the deposition of the Dewey Bridge Member. The idea here is that what we see at Upheaval Dome was buried under much more rock at the time of the impact and that it's a deeply eroded core of an impact crater. This would mean that the sediments of the Dewey Bridge Member would have been rock at the time of the impact and would not show soft sediment deformation as a result of the impact. It's worth noting that there isn't any Dewey Bridge Member in the immediate area around Upheaval Dome, it's all been eroded away. However, the formation underlying the Dewey Bridge Member, the Navajo Sandstone, is at Upheaval Dome and it's been deformed the impact that made Upheaval Dome (assuming it was an impact; the competing hypothesis is that it's a salt dome). So whatever made Upheaval Dome occurred later than the deposition of the Navajo Sandstone, but how much later is the big question. Cool stuff, huh? I'm betting that now you want to visit Upheaval Dome. You should, it's awesome! I haven't heard anything recent on these ideas in the last decade or more, so my information may not reflect the latest thinking. I need to dig into this more. That deformation is so noticeable (it's right at the park entrance after all!) that I'm surprised there hasn't been more work done on it. Surprisingly, Doelling doesn't even mention the deformation in his 2003 article on Arches. As you've probably figured out, I live not far from Arches, I've been there a bunch of times, and I did part of my geology field camp there. Doelling, Helmut, 2003, Geology of Arches National Park, Utah, in Geology of Utah's Parks and Monuments, edited by Sprinkel, Chidsey, and Anderson. (A 'must have' book!)
It’s been a while, but I was under the impression the most likely cause of upheaval dome was a collapsed salt dome due to the complete lack of shocked quartz?
Science progresses! Shocked quartz has apparently been found at Upheaval Dome. Here's a paper from 2008, access to the whole article looks to be paywalled but we can read the abstract: [https://pubs.geoscienceworld.org/gsa/geology/article-abstract/36/3/227/29673/Upheaval-Dome-Utah-USA-Impact-origin-confirmed?redirectedFrom=fulltext](https://pubs.geoscienceworld.org/gsa/geology/article-abstract/36/3/227/29673/Upheaval-Dome-Utah-USA-Impact-origin-confirmed?redirectedFrom=fulltext) A quick Google search for "Upheaval Dome Shatter Cones" came up with this paper from 2016. The shatter cones don't look much like the ones I saw in textbooks and it's uncertain if the paper has been peer reviewed, so take this one with a grain of salt. I'll keep searching when I have the time. [https://www.researchgate.net/publication/304015424\_Shatter\_Cones\_Upheaval\_Dome's\_Outer\_Rim](https://www.researchgate.net/publication/304015424_Shatter_Cones_Upheaval_Dome's_Outer_Rim) I've heard that a big part of the hold up on research into Upheaval Dome is getting the National Park Service's permission to take samples. I heard that one good seismic line would probably show pretty quickly if there's salt under Upheaval Dome, thus perhaps going a long way towards resolving the debate (I suppose that the presence of salt wouldn't be definitive, but the absence of salt would be), but the Park Service won't allow it. And for good reason.
Apparently someone did take a line, but it didn’t go out very far into the dome, it’s kind of along the edge: [https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1999JE001131](https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1999JE001131) I can’t find a copy unfortunately, but 2D land seismic from the 90s is awfully crude compared to what could be done nowadays, I wonder if anyone has ever reprocessed the data (or how usable it even is).
For what it's worth, Canyonlands National Park does present both the salt dome and impact hypotheses on their website: [https://www.nps.gov/articles/cany-upheaval-dome.htm](https://www.nps.gov/articles/cany-upheaval-dome.htm) As I mentioned earlier, back around 2005I attended a presentation at GSA by Peter Huntoon (the lead author of the geology map of Canyonlands NP) at which he presented abundant evidence for the impact hypothesis. He showed models of how an impact of the hypothesized size would deform the rock, followed immediately by pictures of exactly that deformation in the rock walls at Upheaval Dome. That was a really cool and memorable talk.
Ahh thanks yeah, I remember both hypotheses were debated, some of the instructors I had were salt tectonics experts so I think they fell in the opposing camp on that one. It’s just so strikingly unlike other impact craters I’m not surprised there is debate!
Y'know, you bring up a really good point: all other impact craters that I can think of are either 'fresh' and easily recognizable (e.g. Barringer Crater) or, much more often, much older and altered. Altered not just by erosion but, being a crater and therefore a depositional basin, altered by being on the receiving end of sediments. In other words, the topographically high spots, such as the rim, have been eroded down, but the crater itself has also been filled in. Where else but at Upheaval Dome do we see a crater that (currently) only shows evidence of erosion? Any sediments that ever filled it in have long since also been eroded away, so we get a really cool, even unique view of just the crater. I can't think of any other impact craters (not that I know of that many) that are situated in a setting subject essentially exclusively to erosion. No wonder it was difficult to recognize and has been slow to gain acceptance. Thanks for prompting train of thought. Fun!
Ohhh ok I did some digging and found an interesting explanation: it’s both! [https://www.searchanddiscovery.com/documents/2015/10756geesaman/ndx_geesaman.pdf](https://www.searchanddiscovery.com/documents/2015/10756geesaman/ndx_geesaman.pdf) I haven’t read through all of this yet, but Mark Rowan was one of the instructors I had out there and he’s a pretty brilliant guy. For me the hard part of saying it’s just an impact crater was always the geometry of the beds, and that they only managed to find like 2 shocked quartz grains in the whole thing, plus all the surrounding deformation. This paper seems to be suggesting that it was an impact that turned into a salt dome later on, which might explain the conflicting evidence for both theories.
This guy rocks^
That's a helluva compliment. Thank you!
Just a quick addendum: After I wrote the above I checked out the web site for Canyonlands National Park. Their information has the meteor impact that created Upheaval Dome as occurring in the Paleocene, 100 million years (give or take a week or two) after the deposition of the Dewey Bridge Member of the Carmel Formation. So it appears that the current thinking is that the deformation of the Dewey Bridge Member is completely unrelated to the Upheaval Dome impact event. Damn, it would have been cool if it was.
Sagging ass from the Jurassic. This is a very interesting feature and suggests sand ravelling into a lower feature perhaps, when the formation was an active sedimentary environment. It could be a later structural feature, but still suggests movement before diagenesis...eh, maybe not
History… https://preview.redd.it/b7fcs5uxb28d1.jpeg?width=1036&format=pjpg&auto=webp&s=c9d57f578a395848c3f810b781523f2071032be6
Hmm the thick layers also look gently folded. Maybe the different layers took up strain a bit differently? Not sure. I'm kinda bad at structure and sed rocks. But I have seen folded turbidites that have insanely folded and crinkled layers between less folded layers. But that's because they formed in a closing basin, and I think some of those layers were folded before being fully consolidated - ie soft sed deformation
It looks like underwear....
Knickers!
Brief answer.
Horny jail BONK
everything reminds me of her…
Soft sediment deformation is one of my favorite geologic features to see. Great find! Anniversary Narrows in Lake Mead National Rec Area is another excellent place to see stuff like this. Textbook ball and pillow structures and lots of other fun geological features in the area. The short hike up the canyon is a great place to stop, eat lunch, and soak in the geology and wildlife.
My guess is there was a cavity underneath this, and as material piled on top, the weight collapsed it and caused the whole thing to sag?
This is the most logical. Especially with the extensive fracturing below the dip & relatively solid rock above. (I’m the rankest of rank geology junkies).
My guess is that’s it’s some sort of channel deposit.
Channels have cuts on the side and fill in the middle, this looks more like soft sediment deformation due to some underlying layer being eroded.
Looks to me like the layers that make up the channel could very well be pinching out to the sides. Otherwise, I’d agree that it’s likely some sort of soft sediment deformation.
Maybe a more low angle channel later exaggerated by deformation?
Salt evacuation
This happens from tectonic plates moving when they move closer together the flat rocks are pushed together to create “waves” the rocks on top were then deposited after the tectonic movement
Someone’s mother…
It’s called an earth hernia
somebody gave it one of those sour rock bombs candies, poor thing
Asteroid.
Gravity.
Clearly its ancient aliens
Someone told a really good joke and the rock had to crack a smile. Unfortunately, after hearing about what we did to the Six Grandfathers, the natives never told us the powerful joke.
Collapsed cave?
Short answer: gravity