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Faith  Suspended Member (Idle past 1474 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 | |||||||||||||||||||||||||||||||||||||||||||||||||
Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7 |
Faith writes: That's beautiful. Now find us one that has a level flat surface. And hard as schist too. Dr Adequate's image does appear as if it may be composed of soft material, and additionally the bending must be due to deformation. So I don't think his image is evidence for boundaries between layers forming unevenly. You've given participants the impression that your position is that layers do not form unevenly, that they only become uneven later. But what you've just said, that you want evidence of a level flat boundary, puts this interpretation into question, so perhaps it would help if you reexplained your position. By calling what looks to be a contradiction to your attention I'm trying to avoid you finding yourself in the position where you believe no one is listening to what you're saying.
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7 |
Faith writes: No, but it does have to be level if not totally tabletop flat and smooth. I go by the STRAIGHT lines shown in Message 213. I'm not replying to Faith, just clarifying. Faith's point here is that erosion cannot produce flat landscapes upon which sediments could be deposited to form the layers we find in the geological record. Briefly recapitulating the discussion, Message 213 contained images like this of straight contact boundaries:
Faith later posted images like this to show how erosion makes a landscape uneven:
The responses were a bit scattered (i.e., each response only included part of the explanation), but the explanation was that the very flat landscapes were produced by erosion, that if those landscapes later became buried that you'd have a very flat contact boundary with occasional stream and river channels cut into it, as is found in the geological record. Because the explanation was spread about, I'm not sure Faith understood that this is what people were trying to say.
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7 |
Faith writes: But other evidence is the straightness of the upper strata too, showing no signs of having had to conform to irregularities in the lower section, as I already mentioned. Just to be sure you don't miss it, Edge recently commented on this in Message 447:
1.) Why are the bedding planes in the uppermost layers in the photograph not similarly roughened by the same process that has made the unconformity rougher (according to Faith). Demonstrably, they should have been exposed to more severe weathering than the unconformity itself. And yet, there they are just as straight as when Hutton first described them. Please explain.
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7
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Faith writes: Anyway, the challenge was to show that erosion alone could produce such remarkably level and flat surfaces on top of distorted strata or lumpy hard rocks like schist. I want to clarify what other participants, especially Jar, have been pointing out about landscapes like the ones you showed in Message 345, like this one:
You've been calling attention to eroded ditches in images like this one to call attention to how erosion makes landscapes uneven. Others have been trying to call your attention to the incredibly flat plains stretching off into the distance in the backgrounds of your images. These flat plains were caused by the flip side of erosion, namely deposition. It perhaps hasn't been expressed clearly, but when people say these plains are the result of erosion they do not mean that they were created by wind and water eroding away the surface in an incredibly even manner. What they mean is that the material on the plain is eroded material carried and deposited there from more highly elevated regions. Hills and mountains are eroded and the material is carried away by wind and water to become deposited on the plains below. Plains become flat because they are areas of deposition of eroded material from elsewhere, not because their surfaces are eroded flat.
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7 |
Faith writes: Reading out of context of course. I've been encouraging people to repeat and clarify as often as necessary.
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7
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Faith writes: I quoted amply for him to get the context. This is what you said that Tanypteryx quoted:
Faith writes: I thought that's what Percy wanted me to indicate: to explain the unevenness of the lower section as the result of erosion after the deposition of the above section. I'm sure you are still free to offer a different interpretation. If I understand you correctly, you're referring to your belief that it is possible for erosion of a cliff face to affect the shape of an exposed boundary between two layers of solid rock. Participants like Tanypteryx and Edge have been saying that this makes no sense. If it actually does make sense then some clarification or explanation would be welcome.
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7 |
edge writes: That's why there are so many stumps of the upright lower strata.
That was when they were exposed to weathering during Cambrian time. I'm not sure you and Faith are referring to the same "stumps". I think your stumps might be where the vertical strata below the unconformity actually meet the unconformity. Faith may be referring to the parts of the gray rock near the center of this image that are not actually anywhere near the unconformity boundary, except near its top:
This gray rock is the same one Hutton drew from a different angle that appears in the "Bottom Layers" part of his diagram as a thick vertical stratum a little to left of center:
Here's an image that seems to come closer to replicating the angle from which the Hutton diagram was drawn:
After looking at so many images of Siccar Point it's apparent that the diagram is pretty good but only approximate. Some erosion of anywhere from 2 to 10 inches of rock would have taken place over a couple centuries, but the angle of that tall section of big gray strata could not have changed. Edited by Admin, : Change author.
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7 |
edge writes: Abrasion between upper and lower sections as already explained somewhere back there.
Except that there should be evidence of abrasion. Why is there evidence of cross-bedding? I want to better understand this exchange. When I read Faith's post I wasn't sure what she meant, but I decided not to pursue it. In your view is Faith saying that there should be abrasion between two adjacent layers of rock buried within a stack of strata? Or is she saying that abrasion can happen only where the boundary between two layers is exposed in a cliff face? Or is she referring to abrasion long ago when the upper layer was being being deposited upon the lower layer?
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7 |
jar writes: Well, actually Faith, no you haven't and it seems you simply have no clue what the words explanation, model, method, mechanism, process, procedure or evidence mean. Please let the discussion be about the topic rather than assessments of the quality of others' contributions.
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7 |
Faith writes: I need to see this from another angle, or as HBD suggested, without the yellow outline. HBD made the same request. I was able to find this:
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7 |
Reposting images into your message is extremely helpful. It makes no difference that the image has been posted a dozen times already, it is really helpful to have it right there in your message. It is even more helpful to annotate the image if you're calling attention to a specific part. When annotating, if it wouldn't be too ambiguous you might consider using circles, ovals, boxes and so forth instead of lines to identify boundaries, because at least in this particular discussion obscuring the boundary seems to raise doubts in the minds of some of what they're actually seeing.
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7
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Faith writes: I think this particular photo is a problem because there is no indication of where the top and bottom are,... This is the photo:
This image is from a different part of Mosaic Canyon, but it provides a rough idea of the context. The sand with the embedded rocks was deposited atop the light-colored dolomite:
It might be helpful to clarify this portion:
But at least now that the outline has been removed, the dolomite doesn't look like it's separated from the sandstone, now it looks like it's embedded in it. It isn't clear what you're implying when you say you previously thought the dolomite and sandstone layers were separated. Why do you think it possible for rock layers to be separated (I assume you mean by air - of course rock layers can be separated by other rock layers), what do you think that implies about the angular unconformity, and what do you think the absence of a separation implies?
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7 |
Faith writes: I'm not sure I'm implying anything, just saying the photo looks odd and I need to see it in its immediate context to be able to have a clear opinion about it. I have looked at pictures of Mosaic Canyon and that general area so I know that it's characterized by these rocks but haven't found a picture that shows anything like this unconformity. My attempts to elicit clarifications from you are only leaving me more confused. Okay, the images look odd to you for some reason, but is your focus on their minute details leading anywhere, because if not then it might better aid understanding if your comments addressed the larger message they convey about how angular unconformities form.
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7 |
Faith writes: Not minute details but the overall three-dimensional appearance of the whole picture. Okay, let me rephrase the question. Is your focus on the overall three-dimensional appearance of images leading anywhere, because if not then it might better aid understanding if your comments addressed the larger message they convey about how angular unconformities form.
It doesn't support my view but it also isn't enough to challenge it. I don't think we know what your view really is. Earlier in this thread, after some discussion deriving from your opening post, you posted this in Message 131:
Faith in Message 131 writes: I've concluded I didn't have the OP thought out and don't have the evidence I thought I had. So if your view is not represented in the opening post I think it would be helpful if you described your view of how angular unconformities form. We know you think the Great Unconformity formed as a result of tectonic forces and uplift, but there are open questions, and there are many angular unconformities around the world not in a region of uplift. Again, I'm not trying to debate the issues. I'm more just trying to identify the issues, which it seemed were getting lost in all the discussion about what was actually in the images. Questions can be raised about almost any image (e.g., "Is that a shadow or a recess?"), but I'm working at trying to keep the focus on those parts of the images relevant to the discussion.
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7 |
Faith writes: And all this is off topic in this thread. In the view of this moderator, discussion of other angular unconformities around the world seems important to a better understanding of the processes that cause them.
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