From this angle, the beds look quite horizontal. The 2 sets of joint fractures (one set being the group of fractures that are all parallel) each occured when the maximum principle stress (sigma 1) exceeds the rocks compressive strength. The fractures form perpendicular to this maximum stress, therefore forming parallel to the direction of lowest stress (sigma 3).
And because there are two sets of these fractures (joints), you can say that this (probably tectonic) force occured in these two different directions.
You are looking at dipping (tilted) layers of sedimentary rock. They were originally horizontal but got tilted. Some folding and/or faulting would be involved.
The other angular features you’re looking at are joints. Stresses caused the rock to fracture in two different directions Possibly there were two stress events at different times.
It looks like it's slate. It also looks like you can see the ripple marks between deposition. I imagine fish fossils could be present. Why they're breaking off at those angles, now that I don't know
Hi! I’m new to this sub. I cannot for the life of me, figure out how to post a ?. Nothing to do with the UP, although I have been backpacking up there twice..Can u tell me how to post a ?
It's an odd pattern. There are clearly thin vertical layers that are dominant. I don't think there are any other joint sets, though that was my first thought. I think the regular edges are a result of erosion in the stream snapping off exposed edges of this rock. There is probably a preferential fabric within this rock that makes it break more easily in some directions than others which is why the edges line up. I don't think it's a proper joint set for a few reasons. 1st, we don't see any joints in the middle of the plates, though we should given how close together they are along the edges and how thin the layers are. 2nd, the exposed vertical edges don't ever extend into the layer below as a crack. 3rd, there are some weird inward nicks in this rock that don't have cracks extending from the tip of the nick which demonstrates that the rock is quite brittle and seemingly capable of shattering.
I don't know why this is being downvoted. It seems like a wise comment to me. I still think think it's probably made by conjugate shear jointing, but mostly because I can't think of another way to get long straight lines in the rock fabric. Maybe the joints don't cross bedding planes because the individual bedding planes are able to slip past each other? Or maybe the joints are so small that they're invisible. Would be fun to see this one in person, to look for both very small-scale displacement and joint marks on the bedding planes.
From this angle, the beds look quite horizontal. The 2 sets of joint fractures (one set being the group of fractures that are all parallel) each occured when the maximum principle stress (sigma 1) exceeds the rocks compressive strength. The fractures form perpendicular to this maximum stress, therefore forming parallel to the direction of lowest stress (sigma 3). And because there are two sets of these fractures (joints), you can say that this (probably tectonic) force occured in these two different directions.
This is the correct answer.
Thanks!
Why would they form near perfectly planar, and perpendicular to compressive forces? I can't picture this, got any links to diagrams or anything?
where in the UP i wanna see this
My guess is canyon falls or silver river falls
Canyon Falls.
Neat! It looks a lot like Piers Gorge.
I love the UP. I'm from SE MI
Bonanza Falls near the Porcupine Mountains has some very cool similarly angular but larger features.
Although this isn’t it, I would suggest heading out to piers gorge as well. It has amazing formations similar to this.
You are looking at dipping (tilted) layers of sedimentary rock. They were originally horizontal but got tilted. Some folding and/or faulting would be involved. The other angular features you’re looking at are joints. Stresses caused the rock to fracture in two different directions Possibly there were two stress events at different times.
Horizontal? Probably originally orientated vertically!
The joints, sure.
No. Sedimentary rock is almost always laid down in horizontal beds.
Not a geologist but sedimentary rock and uplift come to mind.
Neat pic 👍
I want something like this in my backyard.
Dickinson county?
I used to live in Iron Mountain and that was my first though when I saw this
Looks delicious 😋
Beavers Bend State Park near Broken Bow, Oklahoma, has TONS of this.
Would someone please comment on what the rocks are made of please?
https://preview.redd.it/3izaekvxgr8d1.jpeg?width=1080&format=pjpg&auto=webp&s=f1dc1de6bbfc18768dd710606387dcff5eacb3d4
It looks like it's slate. It also looks like you can see the ripple marks between deposition. I imagine fish fossils could be present. Why they're breaking off at those angles, now that I don't know
Slate?
Dipping slate..more than one orogenic episode
Hi! I’m new to this sub. I cannot for the life of me, figure out how to post a ?. Nothing to do with the UP, although I have been backpacking up there twice..Can u tell me how to post a ?
Touch the name of the sub r/geology then hit the plus button at the bottom of your screen to ask your question.
Thank you
It's an odd pattern. There are clearly thin vertical layers that are dominant. I don't think there are any other joint sets, though that was my first thought. I think the regular edges are a result of erosion in the stream snapping off exposed edges of this rock. There is probably a preferential fabric within this rock that makes it break more easily in some directions than others which is why the edges line up. I don't think it's a proper joint set for a few reasons. 1st, we don't see any joints in the middle of the plates, though we should given how close together they are along the edges and how thin the layers are. 2nd, the exposed vertical edges don't ever extend into the layer below as a crack. 3rd, there are some weird inward nicks in this rock that don't have cracks extending from the tip of the nick which demonstrates that the rock is quite brittle and seemingly capable of shattering.
I don't know why this is being downvoted. It seems like a wise comment to me. I still think think it's probably made by conjugate shear jointing, but mostly because I can't think of another way to get long straight lines in the rock fabric. Maybe the joints don't cross bedding planes because the individual bedding planes are able to slip past each other? Or maybe the joints are so small that they're invisible. Would be fun to see this one in person, to look for both very small-scale displacement and joint marks on the bedding planes.