Author Topic: Dinosaur footprints found in cave in France  (Read 490 times)

Offline nickwilliams

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Offline Speleotron

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Re: Dinosaur footprints found in cave in France
« Reply #1 on: April 05, 2020, 11:21:40 am »
How did the prints end up on the roof? Have tectonic forces flipped the slab completely?
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Offline langcliffe

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Re: Dinosaur footprints found in cave in France
« Reply #2 on: April 05, 2020, 11:28:26 am »
How did the prints end up on the roof? Have tectonic forces flipped the slab completely?

Err - there wasn't a cave there when they went for their walk?

Online Roger W

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Re: Dinosaur footprints found in cave in France
« Reply #3 on: April 05, 2020, 11:30:15 am »
From the picture, it looks as if the cave has been formed in the layer of rock from the sediment that the dinosaurs walked over and left depressions in.  These were filled with another layer of sediment that became the rock layer forming the roof of the cave.  The footprints that were depressions in the first layer of sediment are now seen as projections from the roof of the cave.

Does that sound right?
"That, of course, is the dangerous part about caves:  you don't know how far they go back, sometimes... or what is waiting for you inside."   JRR Tolkein: "The Hobbit"

Offline Speleotron

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Re: Dinosaur footprints found in cave in France
« Reply #4 on: April 05, 2020, 11:30:59 am »
But footprints are made on the upwards facing side of whatever you're standing on surely? So then the slab is flipped through 180? Or are we seeing the underside of the footprints, i.e. the dino created a depression right through the slab so a positive impression was made on the underside?
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Offline Judi Durber

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Re: Dinosaur footprints found in cave in France
« Reply #5 on: April 05, 2020, 11:35:44 am »
Could they not be depressions but the infill  :-\  Hard to tell what the shadow is projecting.
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Offline langcliffe

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Re: Dinosaur footprints found in cave in France
« Reply #6 on: April 05, 2020, 11:36:04 am »
The footprints were made in soft sediment, compressing that sediment more than that surrounding the footprints. This resulted in them being less vulnerable to weathering / erosion, leaving them proud in the roof.

Offline Bob Mehew

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Re: Dinosaur footprints found in cave in France
« Reply #7 on: April 05, 2020, 11:40:22 am »
As Rodger says, the photo shows the equivalent of a 'plaster cast' sticking out of the ceiling. I observed similar in MacKinnon's cave roof, a sea cave on Staffa. Click on  https://drive.google.com/open?id=1eYejzlLJZbd8UsYjRcKlWFIpGpdzUwBN to see image as I can't figure out how to load it.

In this case the cave was formed in an volcanic ash layer.  I my hypothesis is the surface of that ash layer weathered and was subsequently covered by another ash layer.  The erosion of the cave took advantage of the weakness between the two ash layers so the ceiling fell down to reveal the upper ash layer.

Hope the image shows  :unsure: bugger modified message  :(

Offline Bob Mehew

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Re: Dinosaur footprints found in cave in France
« Reply #8 on: April 05, 2020, 11:55:50 am »
Third time lucky?

Offline mikem

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Re: Dinosaur footprints found in cave in France
« Reply #9 on: April 05, 2020, 09:41:37 pm »
Picture from the article:


Offline Leclused

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Re: Dinosaur footprints found in cave in France
« Reply #10 on: April 06, 2020, 09:16:12 am »
How did the prints end up on the roof? Have tectonic forces flipped the slab completely?

I think the answer is in the article :-)

"The site was then at the planet’s surface, but geological processes have buried and tilted the sediments, and the prints are now on the cave’s roof, 500 metres underground."

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Offline langcliffe

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Re: Dinosaur footprints found in cave in France
« Reply #11 on: April 06, 2020, 09:37:24 am »
I think the answer is in the article :-)

"The site was then at the planet’s surface, but geological processes have buried and tilted the sediments, and the prints are now on the cave’s roof, 500 metres underground."

I find that difficult to believe. That would have meant that the strata would have been totally flipped over so that the oldest is at the top. The limestones in that area are Mesozoic in age, and haven't been subjected to that sort of tectonic treatment. Just looking at the dip of the rock in the photograph, one would be tempted to conclude that the strata is pretty much as it was when originally laid down.

Online Roger W

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Re: Dinosaur footprints found in cave in France
« Reply #12 on: April 06, 2020, 10:00:17 am »
Try this:
"That, of course, is the dangerous part about caves:  you don't know how far they go back, sometimes... or what is waiting for you inside."   JRR Tolkein: "The Hobbit"

Offline Speleotron

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Re: Dinosaur footprints found in cave in France
« Reply #13 on: April 06, 2020, 10:04:18 am »
Thanks
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Offline Leclused

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Re: Dinosaur footprints found in cave in France
« Reply #14 on: April 06, 2020, 11:05:01 am »
Two other articles about this find in french

https://planet-terre.ens-lyon.fr/actualites/breves/sauropodes-Castelbouc

https://hitek.fr/actualite/empreintes-sauropodes-decouvertes-plafond-grotte-hexagone_22229

in the last article they explain how the footprints ended up on the ceiling

"Une boue qui a été recouverte par plusieurs autres couches de boue, avant que la couche la plus basse ne se transforme en roche, soit érodée par l'eau, formant au passage la grotte de Castelbouc, laissant le soin au temps et aux éléments de révéler les empreintes, alors situées au plafond de la grotte. "

So the explantion of Roger W as spot on.

Scientific study

https://www.tandfonline.com/doi/full/10.1080/02724634.2019.1728286?scroll=top&needAccess=true   (if somebody has a account ....)

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Online David Rose

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Re: Dinosaur footprints found in cave in France
« Reply #15 on: April 06, 2020, 11:33:44 am »
There is another explanation. The cave already existed back in dino times, but was often flooded to the roof, creating a layer of thick mud on the roof. The dinosaurs were playful beasts who liked to go into the cave as a bit of a lark. When they did, they lay on their backs and left the footprints. They liked the squelching sound this made. Later developments saw the floods end, and the footprints harden through calcification. 

Offline mikem

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Re: Dinosaur footprints found in cave in France
« Reply #16 on: April 06, 2020, 11:51:22 am »
Shirley, they would have picked the mud up on their feet from off the floor...

 

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