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Faith  Suspended Member (Idle past 1473 days) Posts: 35298 From: Nevada, USA Joined: |
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Author | Topic: Evidence that the Great Unconformity did not Form Before the Strata above it | |||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1734 days) Posts: 4696 From: Colorado, USA Joined: |
There is another major misunderstanding here, I just can't quite figure out what it is...
I think it has to do with Faith thinking that the surface, which was obviously smooth and level, has been changed by secondary processes that she refuses to describe or explain. If she did try to do so, she would find that they make no sense. The frightening thing is that understanding Faith is like stepping into Wonderland.
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edge Member (Idle past 1734 days) Posts: 4696 From: Colorado, USA Joined:
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Something I was thinking about...
That's a good point. Erosion was probably different at that time. I'm sure the point still stands that you cannot erode below base level with running water.there is no evidence that land plants had colonized the land even as late as the Cambrian. Of course, that could be an artifact of the erosion that wiped that surface clean, but if that is true, then none of the surface of the GU would have been secured by plant roots and would have suffered extreme erosion, at a far greater rate than we observe today. There is another fly in the ointment that I hesitate to bring up because it will probably make us follow Faith down another rabbit hole. But, casting fate to the wind: There are several lines of evidence suggesting multiple phases of glaciation in the latest Proterozoic, just before the Cambrian. Now if you want to have a nice, smooth, planer surface try that on for size.
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Faith  Suspended Member (Idle past 1473 days) Posts: 35298 From: Nevada, USA Joined: |
Well, then, I'm going to say that the GU in the Grand Canyon is 'too weathered to tell what it originally looked like. The GC doesn't get anywhere near as severe weather as Siccar Point, and much of the GU we see in the GC doesn't get much exposure to weather anyway, such as in the side canyons, but I'm sure it's true that there has been some deterioration of the original GU there too. I'd expect that the contact used to be even more flat than it is now.
But I would expect that when it was first formed that surface would have been level, yes. And I figure that was the case because the upper strata, even in their ruined condition, show that THEY were straight. They aren't shaped to fit into dips in the lower strata.
Let me get this straight. You are saying that the shape of the unconformity has changed since it formed. I'm saying the rock has been so battered by the weather at Siccar Point that it isn't clear that there was originally a straight contact between upper and lower sections, as illustrated by that drawing at my blog I just posted to jar. Siccar Point is the barely skeletal remains of what must originally have been a much broader and deeper stack of strata, but most of it was destroyed, leaving this small pile of heavily weathered rocks.
This is worse than I thought. Is there really any point in continuing here? Perhaps not, if a simple obvious point escapes you. Edited by Faith, : No reason given.
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Faith  Suspended Member (Idle past 1473 days) Posts: 35298 From: Nevada, USA Joined: |
If your argument is that the yellow line does not represent the actual surface of the unconformity but is an illusion caused by the erosion of the exposed surfaces, I guess that's a reasonable argument. I am not sure that is what you are actually saying though. The surface of the unconformity is not subject to weathering itself. It is protected within the rock. Except it isn't. Those in the GC are but Siccar Point isn't. Weather has been battering this small rock formation from all sides for thousands of years and there is no protection left.
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Faith  Suspended Member (Idle past 1473 days) Posts: 35298 From: Nevada, USA Joined: |
So if it is straight and level, it supports your argument. But if it is not flat then it must have been disturbed after its formation and therefore irrelevant? Of course! It wouldn't have been DEPOSITED in that messy condition.
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Faith  Suspended Member (Idle past 1473 days) Posts: 35298 From: Nevada, USA Joined: |
Again, as usual, there is some kind of huge disconnect in this discussion that makes no sense to me. I don't *want* any particular thing, I simply SEE the flatness and levelness and I think it's very clear how it has been lost in some cases by disturbances after it was all laid down, earthquake displacement perhaps, volcanic disturbance perhaps, and in the case of Siccar Point, both those (that light colored column is a magma dike) plus severe weathering. If anybody lives in Wonderland, it's you guys.
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edge Member (Idle past 1734 days) Posts: 4696 From: Colorado, USA Joined:
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The GC doesn't get anywhere near as severe weather as Siccar Point, and much of the GU we see in the GC doesn't get much exposure to weather anyway, such as in the side canyons, but I'm sure it's true that there has been some deterioration of the original GU there too. I'd expect that the contact used to be even more flat than it is now.
So, you know how severe the weathering was in the Grand Canyon are was half a billion years ago? That's fabulous Faith.
I'm saying the rock has been so battered by the weather at Siccar Point that it isn't clear that there was originally a straight contact between upper and lower sections, as illustrated by that drawing at my blog I just posted to jar.
By that reasoning, Faith, every bedding plane in the upper sequence should be battered as much as the unconformity. There should be no original sedimentary features left.
In your picture the sandstone is almost shredded by the weathering, reduced to splinters. The lower strata no longer have the straight upper surface that is shown in that drawing.
So you are comparing a schematic diagram to an actual photograph. How clever!
Siccar Point is the barely skeletal remains of what must originally have been a much broader and deeper stack of strata, but most of it was destroyed, leaving this small pile of heavily weathered rocks.
But your little sketch does not show this, does it? I see nice even layering all through both the upper and lower sequences. Once again, you are saying that an ancient unconformity surface is changing in geometry because of modern erosion. I think someone spiked my orange juice this morning...
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edge Member (Idle past 1734 days) Posts: 4696 From: Colorado, USA Joined: |
Again, as usual, there is some kind of huge disconnect in this discussion that makes no sense to me. I don't *want* any particular thing, I simply SEE the flatness and levelness and I think it's very clear how it has been lost in some cases by disturbances after it was all laid down, ...
So, you are saying that you SEE the unconformity changing from smooth to rough? Interesting...
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edge Member (Idle past 1734 days) Posts: 4696 From: Colorado, USA Joined:
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Except it isn't. Those in the GC are but Siccar Point isn't. Weather has been battering this small rock formation from all sides for thousands of years and there is no protection left.
So, the weathering (erosion, actually) that can penetrate the rock mass and change the character of the unconformity, still manages to leave behind clear bedding features in the overlying rock strata. I think I need more of an explanation here... ETA: See how the smooth unconformity in this sketch has been damaged by erosion (according to you) but the upper layers are still intact in the modern picture. Arguably, the uppermost layers of red sandstone have suffered even more erosion than the unconformity plane. Please explain.
Edited by edge, : No reason given. Edited by edge, : No reason given. Edited by edge, : No reason given.
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edge Member (Idle past 1734 days) Posts: 4696 From: Colorado, USA Joined: |
So if it is straight and level, it supports your argument. But if it is not flat then it must have been disturbed after its formation and therefore irrelevant?
The weird thing is that now she's saying that erosion is causing the distrubance...
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Faith  Suspended Member (Idle past 1473 days) Posts: 35298 From: Nevada, USA Joined: |
The GC doesn't get anywhere near as severe weather as Siccar Point, and much of the GU we see in the GC doesn't get much exposure to weather anyway, such as in the side canyons, but I'm sure it's true that there has been some deterioration of the original GU there too. I'd expect that the contact used to be even more flat than it is now
So, you know how severe the weathering was in the Grand Canyon are was half a billion years ago? That's fabulous Faith.
You know, it would probably help communication if you realized that I NEVER think in terms of millions of years. I ALWAYS have around 4500 years in mind for the age of all these formations. Just for the record, if I were thinking in terms of half a billion years I would expect the Grand Canyon long since to have dissolved into a pile of dust. And wouldn't that be in keeping with the idea that erosion over such an enormously long time supposedly explains how the surface of the Vishnu and the tilted Supergroup got level enough for all those strata to build on them as horizontally as they did even from the nice neat flat Tapeats?
I'm saying the rock has been so battered by the weather at Siccar Point that it isn't clear that there was originally a straight contact between upper and lower sections, as illustrated by that drawing at my blog I just posted to jar.
By that reasoning, Faith, every bedding plane in the upper sequence should be battered as much as the unconformity. There should be no original sedimentary features left. The "upper sequence" being the horizontal strata above the vertical? But it certainly IS that battered: those rocks are barely a shadow of their former selves, nothing left but splinters basically. And surely there was once a huge stack of strata above them too, just as in the GC, long since destroyed by tectonic and other forces. And do try to remember: I don't think of each bedding plane as having been exposed for any great period of time.
In your picture the sandstone is almost shredded by the weathering, reduced to splinters. The lower strata no longer have the straight upper surface that is shown in that drawing.
So you are comparing a schematic diagram to an actual photograph. How clever! Well they didn't have photography in those days and those who made such drawings, Lyell for one, did aim to draw what was actually there. A couple hundred years of weathering since then should be sufficient explanation for the greater deterioration we see in your picture.
Siccar Point is the barely skeletal remains of what must originally have been a much broader and deeper stack of strata, but most of it was destroyed, leaving this small pile of heavily weathered rocks.
But your little sketch does not show this, does it? I see nice even layering all through both the upper and lower sequences. Once again, you are saying that an ancient unconformity surface is changing in geometry because of modern erosion. I think someone spiked my orange juice this morning... I'm sure much of your problem must be due to your habit of thinking in terms of millions of years. If you'd just recognize that I don't, it might help you see better what I'm saying. It's "ancient" yes, but only in thousands, not millions, of years. Edited by Faith, : No reason given. Edited by Faith, : No reason given.
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Faith  Suspended Member (Idle past 1473 days) Posts: 35298 From: Nevada, USA Joined: |
Your yellow line in this case may not really define the contact line but a deterioration of what is left of it. The upper section in the photo doesn't even look like it's resting on the lower section, it sort of looks like it's collapsed behind it.
Why would Hutton's drawing show a straight contact line if it wasn't there?
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New Cat's Eye Inactive Member |
I NEVER think in terms of millions of years Well there's your problem; you don't even know your enemy.
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edge Member (Idle past 1734 days) Posts: 4696 From: Colorado, USA Joined: |
Your yellow line in this case may not really define the contact line but a deterioration of what is left of it.
(Sigh...)
The upper section in the photo doesn't even look like it's resting on the lower section, it sort of looks like it's collapsed behind it.
Hunh? Explain or show a diagram.
Why would Hutton's drawing show a straight contact line if it wasn't there?
It's called a schematic diagram.
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edge Member (Idle past 1734 days) Posts: 4696 From: Colorado, USA Joined: |
You know, it would probably help communication if you realized that I NEVER think in terms of millions of years. I ALWAYS have around 4500 years in mind for the age of all these formations.
You know, it would probably help if you realized that I/we always think in terms of long ages... That's what the evidence tells us.
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