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Author Topic:   Young earth explanations for Angular Unconformities
edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 93 of 202 (425135)
09-30-2007 5:16 PM
Reply to: Message 88 by CTD
09-27-2007 12:34 AM


If something like this were to happen underneath some horizontal rocks, what would the result look like?

This is an igneous rock and it depends on the depth of intrusion. I've seen things like this cutting through thin sedimentary sequences as vertical dikes in a volcanic field, but sills, parallel to bedding are also possible. Not a problem for geologists. But very interesting.


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edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 98 of 202 (796478)
12-30-2016 12:09 PM
Reply to: Message 95 by Faith
12-30-2016 3:01 AM


Re: Siccar Point angular unconformity video
The breccia embedded in the upper horizontal section is proof itself that it did not form millions of years after the lower vertical strata. There had to be some kind of friction to break it off and embed it.

Then why are the breccias found in beds at all, and why are they all above the unconformity? Why are there not fragments of the upper beds found within the lower?

This fits my theory, not Hutton's: all the strata were in place horizontally, and still damp and malleable from the Flood, when tectonic force pushed the lower segment upright, abrading the vertical rocks at the point where the different kinds of rock met, that being the point of least resistance, so that the whole formation was divided between the two kinds of rock.

In that case, if the lower beds were so ductile, why are they not deformed at the contact? They should be bent in the direction of motion, should they not?

The other evidence that he was wrong is how similar the weathering is for both sections. The multiple millions of years that supposedly mark each layer show NO difference in weathering whatever.

Actually, that is not necessary and in most places you are incorrect. Erosion at a rocky shoreline is quite rapid, easily exceeding the weathering process, so that just before the red beds were deposited the underlying rocks had only recently been eroded. And some rocks are simply more susceptible to weathering.

The lower rocks should be completely disintegrated, or at the very least far more decrepit than the upper.

Not really. We have a lot of fresh rocks exposed at the surface of the earth. Mount Rushmore is holding up quite well even though they have been around for a very long time.

Nope, there is no evidence there for the great age of the rocks that has become dogma based only on gullible human imagination.

But, in fact, some of the pictures we have shown you of the Great Unconformity in the Grand Canyon show weathering under the contact, and we have repeatedly referred you to paleosoils in the geological record. That they exists is not in dispute.

This message is a reply to:
 Message 95 by Faith, posted 12-30-2016 3:01 AM Faith has replied

Replies to this message:
 Message 102 by Faith, posted 12-31-2016 4:23 PM edge has replied

  
edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 99 of 202 (796479)
12-30-2016 12:11 PM
Reply to: Message 97 by herebedragons
12-30-2016 11:57 AM


Re: Siccar Point angular unconformity video
These materials can have completely different sources, ie. compositions. This would imply that first sediments need to be deposited, then lithified, then broken into clasts, then more sediment deposited between the clasts, and then the entire structure lithified.

Heh, heh, so much for the lower beds being ductile.

Not very well thought out for YECs in this case.

Edited by edge, : No reason given.


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edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 106 of 202 (796591)
12-31-2016 9:28 PM
Reply to: Message 102 by Faith
12-31-2016 4:23 PM


Re: Siccar Point angular unconformity video
Then why are the breccias found in beds at all,...

Cuz of the layering that would have contained them I would suppose


But it is a layer concordant with the overlying beds.

And it consists of a matrix identical to the sandstone, but not fragments of the red sandstone. In other words, they are actually a part of the red sand deposition.

Furthermore, there are layers and channels of older rocks cobbles within the red sand sequence.

Why are there not fragments of the upper beds found within the lower?

Because it was the lower strata that folded and got broken as a result of being forced upward and along the lower surface of the upper. The upper didn't break, but were rather lifted by the folding lower layers which would have scraped the sediment of the bottommost layer at the unconformity.


The problem here is that the unconformity is not planar. It is highly irregular due to variable resistance to erosion of different layers in the older sequence.

I have seen plenty of sheared surfaces, some of them parallel to bedding and they are not so irregular. Irregularities of the type visible at Siccar Point forbid the possibility of shear.

I should say the lower were folded rather than tilted, but their upper surfaces would have broken off in that case too. Some pictures from that same area some distance from Siccar Point itself do show a bending of the lower layers where you can still see the fold itself, ....

Actually, I'm not talking about the large-scale folds. I'm discussing the drag folds along your shear plane.

They don't exist. If you hole a deck of cards vertically and then drag the top edge, you form drag folds in the cards that tell you the direction of movement. There are no such drag folds in the older sequence.

... but in any case there's no need to assume a very high degree of ductility, and also, the tectonic pressure should have had the effect of hardening the rock at the same time it folded it.

It doesn't have to be high. But if the rocks are folded in a semi-ductile state (as you profess), one would think that drag folds would be prominent.

Here is an example of drag folding:

The observable evidence at Siccar Point is that there is no visible difference between the degree of weathering of upper and lower sections.

You are simply repeating an irrelevant point.

As I tried to say, the very time the sand was being deposited was just after the underlying rocks were exposed by erosion. There is virtually no difference in this case. That is because the action was all occurring at the shoreline where erosion and deposition both occur.

Which to my mind is evidence for a young earth there as well as at Siccar Point, because in the enormous time spans described by standard theory the lower section of Siccar and Mt. Rushmore too, shouldn't be holding up well at all.

Well, that's the point. Those rocks, while being highly resistant to erosion are also the most recently exposed.

You are creating a straw-man argument.

Creationists have shown that what you call evidence of weathering is chemically different from what you get with weathering.

I'll need a reference on that.

Abraded sediment perhaps but not weathered rock. And I'm sorry but I don't see the relevance of paleosols.

I'm guessing that my explanation above covers this. The process does not include long times between erosion of the lower sequence and deposition of the upper rocks in the case of Siccar Point.

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 Message 102 by Faith, posted 12-31-2016 4:23 PM Faith has replied

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edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 107 of 202 (796592)
12-31-2016 9:57 PM


Just for general information, here is an image of the Great Unconformity where there is evidence of weathering in granite below the erosional surface.

Note the weathering rinds that formed along fractures in the Pikes Peak Granite, ostensibly before the overlying Cambrian sandstone was deposited.

This weathering occurred because the granite was exposed for a long time prior to deposition of the Sawatch sandstone was deposited. This is different from the case at Siccar Point where erosion occurred right up to the point where deposition of the sand started.


Replies to this message:
 Message 108 by Faith, posted 12-31-2016 11:01 PM edge has replied
 Message 110 by Percy, posted 01-01-2017 7:22 AM edge has replied

  
edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 111 of 202 (796605)
01-01-2017 11:24 AM
Reply to: Message 108 by Faith
12-31-2016 11:01 PM


I'm glad you said "ostensibly" because erosion on an exposed surface isn't the only possible explanation. I'd point out for starters how the channels in the granite are capped by similarly eroded sandstone, on their undersides in this case.

Problem is that we see the same granite exposed at the surface elsewhere, without the unconformity present, that do not show such weathering.

If the granite had eroded before the sand was deposited, first the sand would have filled in the depressions, ...

Which, in fact, happens.

Note the irregularities in the unconformity surface in the above image. In detail, the irregularities become even more obvious.

... and second, the underside of the sandstone shouldn't be eroded at that same location. Most erosion between strata can be explained as occurring there after they were all in place, from water runoff between layers at the contacts. That must have happened here too, even cutting into the granite. Whatever cut the granite also cut the sandstone, and at the same time, showing both were already there at the time.

Well, we do have some fractures that cut both the granite and the sandstone but those fractures don't have as severe weathering as the older ones showing spheroidal weathering.

Also the granite is surprisingly flat at the unconformity despite the lumps and depressions. I know you all claim that surface erosion creates flatness. It's never been demonstrated though it's been illustrated from imagination. Abrasion could do it I'd guess. Or maybe it's even possible that the magma welled up after the strata were in place, melting other rocks until it got to this level. Guessing of course, but it's a guess based on the observations above that suggest erosion after deposition of all layers.

The Siccar Point rocks clearly show irregularities that would not be present on a sheared surface.

However, if you want to get technical, the Neoproterozoic was a time of global glaciation and there are many locations where glacial erosion formed nearly flat surfaces. I have shown you some recent glaciated surfaces on the Baltic Shield that look nearly identical to some of the flat surfaces you refer to.

Basically, your problem is that you have no tectonic fabrics to present and you do not explain the geometry of most unconformity surfaces.


This message is a reply to:
 Message 108 by Faith, posted 12-31-2016 11:01 PM Faith has replied

Replies to this message:
 Message 131 by Faith, posted 01-02-2017 11:43 AM edge has replied

  
edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 112 of 202 (796606)
01-01-2017 11:39 AM
Reply to: Message 110 by Percy
01-01-2017 7:22 AM


I wasn't sure where to look in the photo, so consequently I didn't understand this:

The issue was an apparent lack of weathering below the unconformity at Siccar Point. Faith thinks that because the rocks are not so weathered that they were never exposed at the surface. This is support her idea that the unconformity is actually some kind of a shear zone.

My point is that, because erosion was strongly mechanical (wave action) the more weathered rock was being constantly removed right up to the point of deposition of the Red Sand. Consequently, there is little evidence of a long period of erosion.

To emphasize this point, I tried to find a location where erosion was not so mechanical and weathered rock might not be removed by the time the overlying sediments were deposited on the unconformity. The image I showed was of the Pikes Peak Granite just below the Great Unconformity. It shows deep spheroidal weathering (creating rounded boulders) due to long exposure at the surface of the earth. If that granite were not exposed to weathering, this feature would not be present.

Faith has countered with the idea that the weathering has occurred with the modern exposure of the outcropping and affected both sides of the unconformity. That doesn't quite work because then all outcroppings of the granite would show such weathering, not just where the unconformity occurs.

Sorry that I was not more clear in my reasoning. Let me know if you want more explanation.

Edited by edge, : No reason given.

Edited by edge, : No reason given.


This message is a reply to:
 Message 110 by Percy, posted 01-01-2017 7:22 AM Percy has replied

Replies to this message:
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edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 114 of 202 (796609)
01-01-2017 12:14 PM
Reply to: Message 113 by Faith
01-01-2017 11:52 AM


Re: Siccar Point angular unconformity video
That's rather a pedantic point. It's possible for the action I'm describing to have occurred as described and left a more irregular contact. Pieces would still have broken off and been embedded in the upper section which settled into the lower. Besides, if the upper had been deposited long after the lower was eroded, shouldn't we see the red sandstone filling all the spaces in the lower instead of sitting on it as a horizontal formation?

That is what we see. Here is a detailed drawing.

Fig.1. The angular unconformity at Siccar Point, one of the key outcrops for Hutton to demonstrate the validity of his theory. This illustration was made by Sir James Hull in 1788, during an excursion lead by Hutton.

Explain the deposition of layered sediments in the crevices cut in the lower section.

Then tell me which way the upper block moved relative to the lower block.

Here is another image showing similar relationship.

And, in even more detail:


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 Message 113 by Faith, posted 01-01-2017 11:52 AM Faith has replied

Replies to this message:
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edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 117 of 202 (796615)
01-01-2017 1:48 PM
Reply to: Message 116 by Faith
01-01-2017 1:23 PM


Re: Siccar Point angular unconformity video
Another point: if you want to argue that the layering in the crevices proves deposition occurred after the lower irregular section had been there for a while, ...

I'm not, I'm just saying that things are not as you described them.

... I'd point out that some time ago, a couple years by now maybe, HBD proved that sand depositing on an irregular surface would drape over the protuberances and not settle in the crevices in layers as I had supposed.

I don't think anyone proved that it has to be that way. It depends on the thickness of the materials, how much they compact and what the currents are doing.

You cannot dispute that these are sedimentary structures.

However, the layers don't fit my scenario either since they would have been disturbed by the scraping of the "picket" shapes illustrated in your drawing.

Exactly. The irregularities prevent slip.

That suggests that neither explanation works.

Once again the structures are demonstrably sedimentary and not tectonic.

However, the drawing is just a drawing, and nothing in the photos corroborates its presentation of layers in the crevices anyway.

The other photos do demonstrate irregular surfaces, infilling of crevices and the lack of a tectonic structure through the sequence of rocks.

Added from your previous post:

OK, you've shown that there's red sandstone in the crevices. Now I have a different take on it. It would have been the scraping of the lower section, irregular as it is now, against the underside of the upper section, that caused the sand to fill those spaces. For one thing it looks like it came off a horizontal layer that was already there, rather than being deposited as loose sediment into the crevices originally, which would de-emphasize the layered effect, which it didn't.

So, the upper plate rocks just happened to fall into the crevices while just happening to maintain their original orientation compared to their source beds above in every case?

Sure, Faith ...

Edited by edge, : No reason given.


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 Message 116 by Faith, posted 01-01-2017 1:23 PM Faith has replied

Replies to this message:
 Message 118 by Faith, posted 01-01-2017 5:19 PM edge has replied
 Message 119 by Faith, posted 01-01-2017 6:16 PM edge has replied

  
edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 122 of 202 (796627)
01-01-2017 8:49 PM
Reply to: Message 118 by Faith
01-01-2017 5:19 PM


Re: Siccar Point angular unconformity video
At this point I just want to ask, What on earth do you mean by a "tectonic structure" ...

A structure is usually a planar feature in a rock mass.

A tectonic structure would be such a feature caused by tectonism.

In this case, it would be a fault plane, that we would describe as a detachment surface that cuts through the rock mass and its various elements (such as bedding planes, clasts, fossils, etc.) There is no such thing at Siccar.

Such a detachment would have to be very obvious if it were involved in the type of deformation that you are describing in the lower block because of the total amount of strain shown by folding.

... and why can't there be both sedimentary and tectonic features at Siccar Point?

Theoretically, we might see a fold axis, but I have never seen it in any photographs of the location.

This is utter gobbledygook, as well as a brand-new subject never mentioned before.

Actually, it makes sense even if it is not commonly used.

Edited by edge, : No reason given.


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edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 123 of 202 (796628)
01-01-2017 8:58 PM
Reply to: Message 119 by Faith
01-01-2017 6:16 PM


Re: Siccar Point angular unconformity video
The sand was scraped into the crevices, AS I SAID, and just as in all my arguments about how this happened, ...

Then please show us the surface formed by scraping. And explain how the layering is concordant with the overlying rocks in every case.

I'm aware of all those features, I see them mostly as the result of extreme erosion, the photos however do NOT show layering, infilling yes but not layering.

This is not uncommon for photographs at Siccar Point. Unfortunately, no one has been trying to show you the details.

However, I am certain that I have shown you such situations at other locations, some of which were at the Great Unconformity.

When the discussion devolves into irrationality in this way as it so often does with you, I have little interest in continuing it.

I can see that you are, once again, becoming frustrated with your lack of geological knowledge. With that in mind, I will try to refrain from posting responding to you unless you have a direct question.

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edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 125 of 202 (796633)
01-02-2017 5:25 AM
Reply to: Message 124 by Faith
01-02-2017 12:03 AM


Re: No tectonic features?
WHAT ABOUT THE UPRIGHT STRATA FOR PETE'S SAKE?

Do you see a fold?

All I see are bedding planes.

Those would be sedimentary structures.


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edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 136 of 202 (796674)
01-02-2017 9:53 PM
Reply to: Message 131 by Faith
01-02-2017 11:43 AM


Also I don't see why the shearing always has to create a perfectly flat surface. If there's enough resistance it could be pretty lumpy.

It doesn't have to be perfectly flat, but it has to be present and visible. It also should conform to the sense of direction of relative motion.

There is no such surface present at Siccar, nor any other of the places we have discussed.

That whole formation obviously tilted after it was laid down, same as at Siccar Point, since the upper section would have originally been horizontal. Whatever caused that tilting could have affected the surface of the lower section.

Should have. If your scenario were correct.

There is no such structure, there is no rock fabric that tells us that there was relative motion.

Edited by edge, : No reason given.


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 Message 131 by Faith, posted 01-02-2017 11:43 AM Faith has taken no action

  
edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 137 of 202 (796675)
01-02-2017 9:56 PM
Reply to: Message 134 by Percy
01-02-2017 4:37 PM


Re: Edge's photo of the GC
Is Edge referring to those granite boulders when he says, "weathering rinds"? What fractures is he referring to, the ones between layers, or the fracture in the layer to the right of the boulders? Anyway, because I didn't understand this paragraph, I wasn't sure how to interpret the next one either.

Weathering is beginning to form boulders which are visible in the image. This weathering takes time to happen, occurring along fractures in the granite.

Not all outcroppings of granite show this feature.


This message is a reply to:
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edge
Member (Idle past 936 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 138 of 202 (796676)
01-02-2017 10:33 PM
Reply to: Message 132 by Percy
01-02-2017 2:47 PM


This is incorrect. As you can see in your own diagram, some of the layers are nearly upright, some are tilted, but at any rate the degree of tilt doesn't matter. What you're missing is that tilting or bending or buckling of underlying layers without affecting the layers above isn't possible because it requires cubic miles of material to simply disappear into thin air.

The missing material should be present in the section as an identifiable layer of what we call mylonite. It is essentially ground up rock that defines a plane or zone of shearing.

For the total strain evidenced by folding in the rocks (see Faith's diagram) this should be a substantial and identifiable layer in the section. Other features present should be slickensides and polished surfaces, such as the ones shown below.

No such thing is present at Siccar or any other place we have discussed. They are ubiquitous in any area that has been tectonized (which would include Faith's scenario for unconformities).

You are correct. The supposedly ground up material had to go somewhere and by appearances, there must have been a lot of it.

Edited by edge, : No reason given.

Edited by edge, : No reason given.


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