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Author Topic:   Evidence that the Great Unconformity did not Form Before the Strata above it
edge
Member (Idle past 1706 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 1651 of 1939 (757339)
05-07-2015 12:20 PM
Reply to: Message 1650 by Faith
05-07-2015 12:08 PM


Re: Moderator Clarification
You're going to have to give it all again if you want me to know what you're talking about. I've only seen one viewpoint against mine, and that's the idea the layers deposited in the sloped and tilted position rather than deforming later.
There are two others that I like. One is that they are deposited by water currents and we have a cross-bedded sand bar-type situation. Another is that there is a degree of compaction over the Precambrian high point. A third would be a combination of all of the above, including the direct deposition on a sloping surface.
In all cases, these are what we call 'syndepositional'.
They do not require shearing on the unconformity, nor some odd notion of 'intruding' blocks of gneiss.
No I am not saying that, I'm saying you'll never get a normal even layer that way, such as those seen here and especially in long sequences such as are visible from a distance in the Grand Canyon. That is NOT how sloping layers are formed, they are laid down horizontally and then deformed.
Actually, they are not necessarily laid down horizontallly. However, deformation can occur afterward.
I'm not sure what your point is here.
And again you haven't proved it.
I have not 'proven' it to your satisfaction and never will. In fact, I do not intend to prove anything. I'm only saying that you do not have supporting evidence for your scenario, whereas we do have evidence that you are wrong.

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edge
Member (Idle past 1706 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 1652 of 1939 (757340)
05-07-2015 12:31 PM
Reply to: Message 1649 by Admin
05-07-2015 12:04 PM


Re: Moderator Clarification
I'm just trying to clarify again. This is the Google Street View image of the road cut, this time without the yellow circle. I'm posting this to emphasize the point that the layers appear to tilt upward to the right across the entire image, that there's not really much if any bend at the point that you've been indicating.
Well, I wouldn't say that there is a lot of deformation related to the unconformity.
What is interesting is that the composition of the gneiss varies across the outcrop. The place where there is some irregularity in the unconformity is different from the rest of the cut. This could easily be due to differential erosion.
Still remembering my caveat about not being there...
Others can correct me if I have this wrong, but I don't believe the mainstream view is that the sediment was originally deposited on a pre-existing slope. All that's being said is that there's nothing in the image to indicate that the sediment was originally deposited horizontally. It certainly could have been horizontal, but it also could have been in some other orientation. And as Moose stated earlier, the layers have the appearance of dipping downward away from the rock face, so the tilt isn't exclusively left-to-right.
So just to clarify once more, no one's saying the layers could not have been deposited horizontally. They're saying that there's no evidence that horizontal is the only possible original orientation.
I would say that this is an accurate portrayal. The beds do not have to be horizontal, nor do they have to be inclined.

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Admin
Director
Posts: 12998
From: EvC Forum
Joined: 06-14-2002
Member Rating: 2.3


Message 1653 of 1939 (757344)
05-07-2015 1:17 PM
Reply to: Message 1650 by Faith
05-07-2015 12:08 PM


Re: Moderator Clarification
Faith writes:
No I am not saying that, I'm saying you'll never get a normal even layer that way, such as those seen here and especially in long sequences such as are visible from a distance in the Grand Canyon. That is NOT how sloping layers are formed, they are laid down horizontally and then deformed.
Quoting myself from Message 1639:
Admin in Message 1639 writes:
So now I'm ruling that you can no longer assert that layers could only have sagged or tilted after being deposited until you provide evidence or rationale for original horizontality.
Before continuing on this point, please provide your evidence or rationale for original horizontality. Otherwise put this claim on the back burner for the time being.

--Percy
EvC Forum Director

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ThinAirDesigns
Member (Idle past 2373 days)
Posts: 564
Joined: 02-12-2015


(1)
Message 1654 of 1939 (757349)
05-07-2015 4:45 PM
Reply to: Message 1610 by Faith
05-06-2015 4:32 PM


Re: general reply last few dozen posts
Faith writes:
Most of it is irrelevant, ridiculously irrelevant in the case of ThinAir's misreading of the planes in the picture, and I believe I've answered most of the other arguments already.
That "ridiculous" interpretation of the lines you've drawn has been shown by numerous other members here to be a totally reasonable point -- that point being that you've been attempting to pull fine, relative angle detail from a single picture taken from a single location. Such pictures are subject to quite a number of variables that you aren't even aware exist, let alone are taking into account. While you were expounding in the accuracy of your interpretation and mocking my comments, I was busy looking at that exact spot from literally dozens of different camera angles which as Percy has pointed out allow one to get a far better feel for reality.
Lens and subject surface distortion (unless quantified) make it literally impossible to draw lines 'on the screen' and then measure relative angles between them with reflective accuracy. If you have a distortion map for the lens and a accurate map of the surface, it's them possible to produce a rather complete picture of the surface and lines, but without that you're barking in the wind. The second best solution is to look at a number of different pictures taken from different angles and thus deemphasize such artifacts. Several of us have been looking at dozens of such different picture angles and using that to understand the cut better. You were not. I also am quite confident that you wouldn't know how to integrate a surface/distortion map to mathematically correct for these artifacts even if you were provided one (nor would you recognize it if it were emailed to you).
This is not to say that much can't be learned from pictures -- just that one must be aware of the limitations. Ignorance combined with arrogance are a bad mix.
JB

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ThinAirDesigns
Member (Idle past 2373 days)
Posts: 564
Joined: 02-12-2015


Message 1655 of 1939 (757350)
05-07-2015 4:56 PM


I've been out backpacking for a couple days but I scanned the thread to catch up. I didn't find where Faith posted the answer to this question (It's actually an HDB question that I did a zoomed in sketch for) so I'll try again:
(The lines and yellow arrow were drawn by Faith, the red circle and red arrow were added by me for emphasis)
Faith, if rock represented by your yellow lines stayed in place while the rock represented by the orange lines fell as you assert, where is the gap between the lines (in the red circle) that would be created?
JB

Replies to this message:
 Message 1656 by Faith, posted 05-07-2015 5:25 PM ThinAirDesigns has replied

  
Faith 
Suspended Member (Idle past 1444 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 1656 of 1939 (757352)
05-07-2015 5:25 PM
Reply to: Message 1655 by ThinAirDesigns
05-07-2015 4:56 PM


What I think I said was that they must have stretched that small distance, the rock being soft.

This message is a reply to:
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Replies to this message:
 Message 1657 by ThinAirDesigns, posted 05-07-2015 5:33 PM Faith has replied

  
ThinAirDesigns
Member (Idle past 2373 days)
Posts: 564
Joined: 02-12-2015


Message 1657 of 1939 (757353)
05-07-2015 5:33 PM
Reply to: Message 1656 by Faith
05-07-2015 5:25 PM


Faith writes:
What I think I said was that they must have stretched that small distance, the rock being soft.
Stretched? -- we're not talking about a change in shape here Faith, we're talking about a change in *volume*. How does 1 cubic yard of soft rock increase it's volume?
JB

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Replies to this message:
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Faith 
Suspended Member (Idle past 1444 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 1658 of 1939 (757357)
05-07-2015 6:04 PM
Reply to: Message 1657 by ThinAirDesigns
05-07-2015 5:33 PM


Rock can stretch and rock can compress or compact, when still soft enough.

This message is a reply to:
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Replies to this message:
 Message 1659 by ThinAirDesigns, posted 05-07-2015 6:15 PM Faith has replied

  
ThinAirDesigns
Member (Idle past 2373 days)
Posts: 564
Joined: 02-12-2015


Message 1659 of 1939 (757358)
05-07-2015 6:15 PM
Reply to: Message 1658 by Faith
05-07-2015 6:04 PM


Faith writes:
Rock can stretch and rock can compress or compact, when still soft enough.
Yes to all of the above -- but none of those three solve your problem.
The question is not 'did the rock "stretch" between the lines?' - stretching doesn't increase it's volume (play with putty to see this)
The question is not 'did the rock "compress" or "compact" between the lines?' - that doesn't increase it's volume.
The question is "how did the rock between the lines INCREASE it's volume?
JB

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Minnemooseus
Member
Posts: 3941
From: Duluth, Minnesota, U.S. (West end of Lake Superior)
Joined: 11-11-2001
Member Rating: 10.0


(1)
Message 1660 of 1939 (757360)
05-07-2015 7:12 PM
Reply to: Message 1640 by Admin
05-07-2015 8:59 AM


The red line is wrong
Here's the image again. The jog upward in the red line is the portion above the letters "P" through "m" in "Precambrian":
I don't follow the relevance of that detail, but that portion of the red line is flat out wrong. It should be pretty much straight across. Any "jog(s)" there are much more minor.
Moose

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Replies to this message:
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Faith 
Suspended Member (Idle past 1444 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 1661 of 1939 (757362)
05-07-2015 8:00 PM
Reply to: Message 1659 by ThinAirDesigns
05-07-2015 6:15 PM


It wouldn't have increased its volume, if you're talking about quantity of sediment. But stretching WOULD increase its volume in the sense of absolute measurements, the way beating egg whites or adding yeast to bread dough increases volume.
Edited by Faith, : No reason given.
Edited by Faith, : No reason given.

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 Message 1663 by JonF, posted 05-07-2015 8:51 PM Faith has replied

  
Faith 
Suspended Member (Idle past 1444 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 1662 of 1939 (757364)
05-07-2015 8:48 PM
Reply to: Message 1649 by Admin
05-07-2015 12:04 PM


Re: Moderator Clarification
I'm just trying to clarify again. This is the Google Street View image of the road cut, this time without the yellow circle. I'm posting this to emphasize the point that the layers appear to tilt upward to the right across the entire image,
Yes, it does give quite a different appearance.
that there's not really much if any bend at the point that you've been indicating.
Which I believe I noted in my previous post.
Please let me know if you need me to add some marks so you can get your bearings in the image relative to the other image of the road cut, but what this means is that it would be incorrect to argue that there is a tilting or sagging that occurs only on the left side of the image. The layers appear to have the same general tilted upward orientation from left to right across the entire image. If you actually go to Google Street View and follow the road cut a little further to where it ends you'll see that the upward tilt to the right continues all the way.
Yes, there is certainly a general tilt to the whole formation that is not at all apparent on the other view. However, there is still a particular sagging on the left as the sandstone climbs up onto the gneiss, much less pronounced than it is in the other image, but not just part of the general tilt. A definite curve or bend. The appearance of tilt on the left in the layer or two above the "sag" can't be seen from this perspective but it couldn't disappear altogether, must be merely even less pronounced than it appears in the other view. So it still remains true that there is a separate but very slight tilt on the left that isn't just part of the overall tilt.
Here's the left side of the street view with the layer marked to show that there is still a recognizable sag though much less steep. Wiggly line isn't intentional.
Others can correct me if I have this wrong, but I don't believe the mainstream view is that the sediment was originally deposited on a pre-existing slope. All that's being said is that there's nothing in the image to indicate that the sediment was originally deposited horizontally. It certainly could have been horizontal, but it also could have been in some other orientation.
Original horizontality is a principle more than something that should need to be proved, but I do nevertheless intend to try to construct some experiments to address all the different claims. But not to lose the point of the distinction: if the layers deposited horizontally and then deformed, that suggests that the deformation was caused by the deformation of the gneiss over which they now lie and to which they appear to be conformed in basic shape. This would be evidence that they were already in place when that deformation occurred, which is the whole point of my argument that there was no appreciable time gap between the two rocks. If, however, they were deposited on top of the already-deformed gneiss, conforming to its contours as seen, that would support the idea of pre-existing gneiss already eroded long before the deposition of the sandstone. I do feel it is necessary to repeat this because otherwise the whole reason for the dispute could get lost. Sorry if it is in the category of what you said I can't repeat. This is not meant as an argument, merely a statement of what the argument is about because otherwise it can all get lost and confused.
And as Moose stated earlier, the layers have the appearance of dipping downward away from the rock face, so the tilt isn't exclusively left-to-right.
I assume this refers to the vertical tilt or incline from top to bottom? Not sure what the significance of this is.
So just to clarify once more, no one's saying the layers could not have been deposited horizontally. They're saying that there's no evidence that horizontal is the only possible original orientation.
Noted.
Edited by Faith, : No reason given.

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Replies to this message:
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JonF
Member (Idle past 168 days)
Posts: 6174
Joined: 06-23-2003


Message 1663 of 1939 (757365)
05-07-2015 8:51 PM
Reply to: Message 1661 by Faith
05-07-2015 8:00 PM


You actually wrote that? On purpose?
I'm speechless.

This message is a reply to:
 Message 1661 by Faith, posted 05-07-2015 8:00 PM Faith has replied

Replies to this message:
 Message 1664 by Faith, posted 05-07-2015 9:09 PM JonF has replied

  
Faith 
Suspended Member (Idle past 1444 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 1664 of 1939 (757366)
05-07-2015 9:09 PM
Reply to: Message 1663 by JonF
05-07-2015 8:51 PM


A little content would be helpful. I have to guess: You don't think it makes sense to talk about an increase in rock volume unless there's actually more sediment added? Granted my analogies aren't that great but stretching versus compaction ought to make the point that volume can increase or decrease simply mechanically.
Edited by Faith, : No reason given.

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Replies to this message:
 Message 1665 by ThinAirDesigns, posted 05-07-2015 9:28 PM Faith has not replied
 Message 1666 by JonF, posted 05-07-2015 9:41 PM Faith has replied
 Message 1682 by edge, posted 05-08-2015 11:41 AM Faith has replied

  
ThinAirDesigns
Member (Idle past 2373 days)
Posts: 564
Joined: 02-12-2015


Message 1665 of 1939 (757368)
05-07-2015 9:28 PM
Reply to: Message 1664 by Faith
05-07-2015 9:09 PM


Faith writes:
You don't think it makes sense to talk about an increase in rock volume unless there's actually more sediment added?
Water changes volumes through changes in temperature. Yeast increases the volume of bread dough by converting sugars into carbon dioxide gas bubble. Soils reduce in volume through compaction. All of these processes are well understood and repeatable.
Granted my analogies aren't that great but stretching versus compaction ought to make the point that volume can increase or decrease simply mechanically.
And what I am repeatedly asking (and you're not answering) is how does rock increase in volume? By what process? By what mechanism?
What evidence do you have for this magical "rocks suddenly grows in size whenever Faith wants to say they did" process. Right now, all you have is a bald assertion because you need it to able to happen. Magic just doesn't count here.
JB
Edited by Admin, : Fix typos.

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