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Author Topic:   The Story in the Rocks - Southwestern U.S.
edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 45 of 121 (781771)
04-07-2016 2:21 PM
Reply to: Message 40 by Faith
04-07-2016 1:33 PM


Re: A Testament to Erosion
It's also interesting to me that it is like a lot of angular unconformities in that there are no layers above it at this spot.

In fact, we live on an unconformity and in many places it is an angular unconformity.

Right now, it would be easy to see flat lying deposits on top of tilted rock formations as the sea might transgress across the land.

Why not go with that? Something we can actually see and even predict.

You often see upright or angled lower strata with a single slab lying across them. Siccar Point is just one case, there are lots of them.

Not clear what you are saying here. I see several slabs of sandstone above the GU at Siccar Point.

This is normally absurdly interpreted as the lower section buckling before the upper was laid down, but it's so much better explained as the buckling's occurring after the upper was laid down, and not just one layer but the whole stack to the highest and most 'recent" which would have provided the resistance that allowed the lower part to buckle separately, leaving the upper stack intact.

And one slab would hold down the entire stratigraphic section?

Sorry, but that does not pass the giggle test.

Except that the upper stack was also disturbed by the same tectonic force that did the buckling of the lower, and only the one slab remained, having been stuck to the buckled section by the friction between them, while those above washed away in the Flood.

So that rocks below all angular unconformities are pre-flood?

Sorry, but there is no evidence of universal shearing along these unconformities. That would have to be the case as the upper unit would have to be detached from the lower, which is the opposite of what you are saying.

Most of the Grand Canyon's stack remained intact through the tectonic force that angled the lower part of the unconformity, but there are places like that shown in these pictures where the stack above the Tapeats washed away.

No. There is no detachment and there is an irregular surface at the base of the Tapeats.

We have been over this before.

And just as an aside, Siccar Point is interesting for its current state of erosion of the lower section into jagged picket-like sticks of rock. That's what erosion would do, especially in that location that gets such extreme weathering. And any layer depositing horizontally on top of it wouldn't have formed a nice neat horizontal slab, it would have fallen between the pickets and got welded there over time.

That is practically the definition of an erosional unconformity.

Of course there would have been a full stack laid down there too, then the buckling, then the washing away of those above that one weather- shredded tilted once-horizontal upper rock.

This sentence makes no sense.

Oh and Tanypteryx started this "discussion" by accusing me of giving a religious opinion, which shows his brainwashing. It's a perfectly reasonable conclusion from the evidence.

However the only real reason for making this conclusion and clinging to it is religious.

This message is a reply to:
 Message 40 by Faith, posted 04-07-2016 1:33 PM Faith has replied

Replies to this message:
 Message 47 by Faith, posted 04-07-2016 2:33 PM edge has replied

  
edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 46 of 121 (781772)
04-07-2016 2:24 PM
Reply to: Message 44 by Faith
04-07-2016 2:13 PM


Re: A Testament to Erosion
Siccar Point same situation. They are "basically the same material," yes, basically, being both sandstone, but they are two different kinds of sandstone, one called greywacke and the other I forget, a reddish stone I think, enough of a difference to provide a point of what I think of as slippage between the two sections, so that the entire lower section could buckle separately from the upper because they are sufficiently different for that to happen.

There is exactly zero evidence to support this.

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edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 56 of 121 (781784)
04-07-2016 4:10 PM
Reply to: Message 47 by Faith
04-07-2016 2:33 PM


Re: A Testament to Erosion
I am totally convinced of my argument, I know it's right, it's far from some kind of "religious" position.

However, the only reason to do so is because of adherence to a religious text.

Therefore it is a religious viewpoint.

Edited by Admin, : Fix quote.


This message is a reply to:
 Message 47 by Faith, posted 04-07-2016 2:33 PM Faith has replied

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edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 57 of 121 (781785)
04-07-2016 4:25 PM
Reply to: Message 53 by Faith
04-07-2016 3:10 PM


Re: A Testament to Erosion
Subsequent posts all aimed at finding a surface some where flat enough to justify the Party Line. Eventually one was found. But it blew nothing out of the water because getting a flat surface from mere erosion on top of a stack of angled slabs of rock isn't going to happen.

Except when it does. You have been shown a number of examples. You have also seen where the pre-Tapeats surface was irregular.

You ignore all of it.

That's actually kind of insulting, you know.

In fact I think it probably occurred the way I keep postulating. The angled rock was sheared by the friction between it and a previously present very deep stack of horizontal sediments when tectonic force caused the buckling of the lower section.

Faith, it is kind of axiomatic that when rocks are deformed the have to go someplace because volumes are changed at any location. Where do you think the rocks go? Reality says that the 'room problem' is taken up by moving vertically. In other words if you take a substance like a marshmallow and squeeze it or stretch it, the upper surface has to move. This would deform the rocks above the deformation.

There is no other way to accommodate the strain.

Moreover that vertical movement is unlikely to be even. The very best case would be a strongly faulted upper layer. And that is not what we have.

When we combine that with a lack of shearing along the unconformity boundary, it's pretty clear that your model is dead on arrival.

We have plenty of cases where there was plastic flow beneath a section of sedimentary rock and guess what ... the upper rocks are severely deformed.

You can stamp your feet and cry all you want, but it isn't going to make a difference to anyone else on the planet. These are direct observations and logical reasoning.

There is no reason whatever for erosion to choose a level to flatten out a bunch of broken upright slabs of rock. Doesn't happen. Nothing but OE Geo fantasy.

Sure there is: erosion to base level, a resistant layer, glacial friction, etc., etc.

This message is a reply to:
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edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(5)
Message 58 of 121 (781786)
04-07-2016 4:38 PM


Here is an image of deformed sediments in a compression.

And here is one in tension.

In both cases, you can see that the uppermost layers are deformed, even more so than the lower layers. Some vertical deformation is required to take up strain.


Replies to this message:
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edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 68 of 121 (781821)
04-07-2016 9:44 PM
Reply to: Message 67 by jar
04-07-2016 9:10 PM


Re: compound/complex forces
If you have access to that set up would it be possible to get some images of compound forces; for example if the stress point was slanted vertically (both slopes) or squeezed at an angle (stress to front/stress to rear)?

I do not have access do this apparatus. In this case, there's something about the setup that looks like it caused the right side to override the left. This may have something to do with the unconsolidated sediment, or the way it was deposited in the box, or the inclination of the driving platten. At any rate, the point remains that both compression and tension will cause vertical movement in the upper layers of the deformed material. Even if the force was only applied to just the lower layers, as per Faith's model, the top layers really should be deformed. I see no way of escaping this result unless the upper units were deposited later.

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 Message 67 by jar, posted 04-07-2016 9:10 PM jar has replied

Replies to this message:
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edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 73 of 121 (781829)
04-07-2016 11:42 PM
Reply to: Message 70 by Faith
04-07-2016 10:18 PM


Re: compound/complex forces
The sediments have to be WET and already fairly consolidated. A test with loose sediment is ridiculous. I think I may have described a test somewhere myself. The force should come from the side against yhe lower strata. YES I EXPECT THE FORCE TO AFFECT THE UPPER PART TOO, I EXPECT IT TO RAISE IT , to LIFT IT UP as I believe evidently occurred as shown on the GC cross section I've posted many times here. The apparatus has to be designed to allow this to happen as it would in nature. The lower strata BUCKLE, the upper strata are RAISED AT THE LEAST, sometimes other things happen to them, such as breaking up and being washed away. THIS IS THE FLOOD AFTER ALL, during or after I'm not sure, but the sediments are STILL WET when this occurs.
I HAVE THOUGHT THIS THROUGH MANY MANY TIMES, you ape-brained self-important geologist who is always getting insulted if a creat;ionist dares to disagree so you're willing to resort to straw man duplicity and other tricks to win at all costs. I resent your straw man model. I'm every bit as smart as you are, possibly even smarter, yes even about things geological, and I've already thought about this and don't need your hostile lame-brained input.

I understand that you are angry. That is my main take-away from your post. I can't do much about that.

This is basically a scale model with its shortcomings, but the point is still valid that the upper layers are uplifted and deformed. Do you see the lines cutting across the surface of the uppermost layer? Those are fault lines. See the fold that has been created? The axial plane of that fold will eventually rupture and form a major thrust fault that has to go somewhere and the only alternative is up.

So, where are those faults cutting the cutting the Great Unconformity? The underlying rocks are weakly to severely folded, so the strain must be very high. You cannot avoid the displacement.

Even if we accept your detachment theory, the strain is not uniform and there should be some implications for the overlying rocks.

In a dynamic analysis, you would need to explain how you apply the compressive forces to just a lower block. It is not clear how this is possible. What exactly is the vise-like plate that you envision? Please describe the source of the forces.

And I haven't even started on the necessary shear that must accompany your scenario.


This message is a reply to:
 Message 70 by Faith, posted 04-07-2016 10:18 PM Faith has replied

Replies to this message:
 Message 78 by Faith, posted 04-08-2016 1:09 AM edge has replied

  
edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 74 of 121 (781830)
04-07-2016 11:44 PM
Reply to: Message 72 by Faith
04-07-2016 10:37 PM


Re: compound/complex forces
Yes I'm being rude. I can get even ruder.

And what would that do for you?

Alternatively, you could learn something about rocks, time and motion and see how most of the world came to the same conclusions as the rest of us.

Even if you disagree.


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edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 76 of 121 (781833)
04-08-2016 12:10 AM
Reply to: Message 75 by Minnemooseus
04-07-2016 11:52 PM


Re: compound/complex forces
The compression was from moving the left wall. The right wall is fixed.

Yes. In a normal geological situation, I would expect the major sense of motion to be the opposite, rocks on the left overriding the right. That is why I think there might be something in the initial state to have that particular symmetry.

However, if you look closely, the small, almost parasitic folds on the right side of the larger fold do have a left over right sense of motion. These form ridges on the surface of the geological material, effectively disrupting the unconformity surface.

Certainly, the deformation has to be concentrated on the side closest to the forces, so the location of the fold is not surprising. Forces cannot be transmitted very far in unconsolidated, soft (or wet) sediments.

Thanks for making me take a closer look at the resulting structure. (ETA: in fact, this may even help me with a structural problem that I've been dealing with for a couple of years now.)

Edited by edge, : No reason given.


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edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(2)
Message 80 of 121 (781876)
04-08-2016 1:09 PM
Reply to: Message 78 by Faith
04-08-2016 1:09 AM


Re: strain on the upper layers
I don't know for sure what you are talking about, since my eyes may not be good enough to see those lines you, but it sounds like the cracks in the strata I took into account with my many discussions of how I think the GC formed -- that tectonic pressure angled the lowermost strata beneath the Tapeats,

I'm not sure what you mean by 'angled'.

Please describe to us the process by which you deform the lower block while leaving the upper on essentially undeformed. Describe the forces, where they came from and how they were applied.

I don't think I'm the only one who is skeptical of your scenario.

... (your loose sediments model couldn't possibly show this kind of effect --

I'm not sure why not. You are simply saying this as far as I can see. The demonstration shows how layered materials accommodate compressive stresses. Every layer in the model was deformed.

... the sediments have to be consolidated enough to hold together but flexible enough to deform without breaking) ...

But below, you say that the rocks fractured.

And I would say that the sediment did hold together since the layers remain distinct, and yet they seem to have been flexible enough to fold.

... which I ascribe to the difference between the kinds of rock at the point where the force was beginning to dissipate.

What force? How did it dissipate? In general, we would 'dissipate' stress by deformation.

If all one kind of rock was involved I would expect there might not have been a detachment at all and a lot more destruction -- ...

There are multiple rock types below the unconformity. Between the intrusive rocks, the schist and the GC Supergroup, there is a lot of diversity. And truly, every bedding plane is an opportunity for detachment.

So why don't we see it?

... so the angling of the lower strata PUSHED UP the entire stack above it and in the case of the GC somehow that stack remained intact which doesn't seem to have happened anywhere else.

Seems to me that would be clue that it didn't happen at the GC...

Are you saying that the lower block (for lack of a better description) was pushed downward under the upper block?

SO HERE'S THE RELEVANT POINT: The strain of the uplift would have CRACKED THE UPPERMOST STRATA.

So, the rock was hard enough to crack. I thought you said it was soft.

You are saying that it was uplifted probably thousands of feet while the underlying rocks were strained to the point of tight folding and yet there is no real sense of deformation of the Paleozoic rocks.

And there is no detachment between the two blocks. That's pretty amazing. Particularly since we know that the surface was not smooth and planar.

Which is what I suppose you are calling FAULTS.

Not really. Faults would disrupt the bedding planes and the unconformity. And with the degree of strain we see in the pre-unconformity rocks, there should have been swarms of abundant thrust faults, which we do not see by the way. If you are talking about fractures, then they are fractures along which there is no relative motion.

So I figure there were many very deep cracks in those uppermost strata at the top of the uplift, which began to break up and wash away in the receding Flood waters, washing away in all directions to the point of scouring off the limestone surface of the Kaibab Plateau, ...

Problem is that you've got meandering channels which formed near sea level, so the erosion did not occur after uplift of the plateau.

that limestone being another point of resistance in that area since it remained intact and didn't break up, the surface of the "Permian" period ending the Paleozoic, beyond which far to the north some of the stack from the Mesozoic through the Cenozoic remained intact while the tectonic disturbance cut away pieces of the strata to form the Grand Staircase

However, there are cracks throughout the Paleozoic section. If cracking controlled the erosion, why do we see incised meanders? Why did the erosion stop at the Kaibab?

But back to the Gtand Canyon: the cracks that formed right over the center of the uplift broke up everything down to the Kaibab, and one of them became a crack or more likely series of cracks wide enough to become the canyon itself.

Not really.

Fracture controlled drainages would look very different from the incised meanders that we see in the Grand Canyon.

It was then further widened by the chunks of strata breaking off and being washed into this largest crack or collection of cracks. It all washed down and out to the Gulf of California as the Flood receded, scouring out the canyon as it went.

This is mainstream stuff.

Again, the strain of the uplift caused by the upending and pushing up of the lowermost strata caused by the lateral tectonic force, caused the cracking of the uppermost layers two to three miles up, that broke up and washed away, a lot of it into the cracks that became the GC. Have I dealt with your faulting sufficiently? If not, go soak your head.

No. As you can see from the experiment, as folding intensifies (more strongly deformed) the faulting becomes more complicated, more abundant and is attended by folding/disruption of the unconformity.

So, where are those faults cutting the cutting the Great Unconformity?


This message is a reply to:
 Message 78 by Faith, posted 04-08-2016 1:09 AM Faith has replied

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edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(4)
Message 84 of 121 (781919)
04-09-2016 2:39 PM
Reply to: Message 1 by Tanypteryx
01-05-2016 8:55 PM


Going back to the opening post, I thought I'd show a picture from the bentonite (volcanic ash) beds in New Mexico at the Bisti Wilderness.

These beds are the same material as shown in the OP, but in this case you can see where, because of cracks and fossils and other impurities, water has carved out pipes from the top of ridges down into the arroyos. We call it pseudokarst since it is karst-like but not due to dissolution of limestone.

You can see some smaller black gravels laying about the surface that were probably erupted along with the ash.


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edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 86 of 121 (781935)
04-10-2016 11:17 AM
Reply to: Message 85 by jar
04-09-2016 9:05 PM


Re: telling the tale
I'm not very familiar with these particular beds since I was just a tourist at the time, but they probably originated as ash flows or ash falls. That means that they were composeed of fine glass fragments mostly without crystals or rock fragments. The glass reacted with water to form various types of clay. In this case they formed bentonite, a loose term for a class of expansive clays. Devilish stuff to walk or drive on when wet.

The Hawaiian volcanic rocks were not as explosively erupted so ithere was not as much ash formed. They are also much younger.


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edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 95 of 121 (781977)
04-12-2016 11:28 PM
Reply to: Message 90 by jar
04-12-2016 10:04 PM


How can you know that is the case?

Because there are sandstones and mudstones interbedded with the ash flows. You can see the layering with more fluvial sediments in this picture. The reddish beds are more oxidized than the green-gray reduced beds. The tan beds are more resistant sandstone.

I've also seen burnt coal beds mixed in with the ash. Looking for a picture.


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edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 98 of 121 (782017)
04-13-2016 2:05 PM
Reply to: Message 97 by jar
04-13-2016 8:14 AM


So are you saying that in the pinnacle the topmost tan material is sandstone?

Yes, that layer is more resistant to erosion.

Is the greenish part below that volcanic ash?

Yes, and there are several layers of it.

What is the tan material at the bottom?

It is another layer of sandstone.

ETA: By the way, if you google 'volcanic ash', you can get a lot of interesting photographs including fossils.

Edited by edge, : No reason given.


This message is a reply to:
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edge
Member (Idle past 1021 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 100 of 121 (782034)
04-14-2016 12:09 AM
Reply to: Message 99 by jar
04-13-2016 3:19 PM


How do you know there are several layers of it?

Contrasting colors and textures, coal seams, etc.

Maybe pictures don't do it justice...


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Replies to this message:
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