Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 69 (9101 total)
1 online now:
Newest Member: sensei
Upcoming Birthdays: Tusko
Post Volume: Total: 904,371 Year: 1,252/14,231 Month: 176/1,076 Week: 285/234 Day: 51/86 Hour: 1/1


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Evidence that the Great Unconformity did not Form Before the Strata above it
Coyote
Member (Idle past 1597 days)
Posts: 6117
Joined: 01-12-2008


Message 1726 of 1939 (757521)
05-09-2015 11:48 PM
Reply to: Message 1725 by Faith
05-09-2015 11:46 PM


Re: sedimentation on slope
I could do a dry angle-of-repose experiment now, getting back to Coragyps' challenge, but the others I really can't set up properly and want to wait until family get here toward the end of June. They can also get some of the material I need that would be hard for me to get.
Fair enough.

Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.
Belief gets in the way of learning--Robert A. Heinlein
How can I possibly put a new idea into your heads, if I do not first remove your delusions?--Robert A. Heinlein
It's not what we don't know that hurts, it's what we know that ain't so--Will Rogers
If I am entitled to something, someone else is obliged to pay--Jerry Pournelle
If a religion's teachings are true, then it should have nothing to fear from science...--dwise1
"Multiculturalism" demands that the US be tolerant of everything except its own past, culture, traditions, and identity.

This message is a reply to:
 Message 1725 by Faith, posted 05-09-2015 11:46 PM Faith has not replied

  
Faith 
Suspended Member (Idle past 935 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 1727 of 1939 (757523)
05-10-2015 12:09 AM
Reply to: Message 1694 by edge
05-08-2015 11:42 PM


eh, somehow, I never found this link before:
http://www.gly.uga.edu/railsback/VFT/VFTManitou.html
That's a great find, very similar to the other road cut situation, and the arguments are the same ones we've been pursuing. I didn't even know my own argument already existed.
So they dismiss the idea of a fault on the unconformity line. That pretty much leaves trying to find out if layers like those and the ones in the other road cut really will form by deposition on the slope.
Just wondering: Would you say the layered rocks in the picture are highly compacted?

This message is a reply to:
 Message 1694 by edge, posted 05-08-2015 11:42 PM edge has replied

Replies to this message:
 Message 1728 by edge, posted 05-10-2015 12:46 AM Faith has not replied

  
edge
Member (Idle past 1197 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 1728 of 1939 (757526)
05-10-2015 12:46 AM
Reply to: Message 1727 by Faith
05-10-2015 12:09 AM


That's a great find, very similar to the other road cut situation, and the arguments are the same ones we've been pursuing. I didn't even know my own argument already existed.
Geologists are actually pretty good at thinking up alternatives. The point is that they search for evidence to support different schemes.
So they dismiss the idea of a fault on the unconformity line.
Based on the evidence, yes.
That pretty much leaves trying to find out if layers like those and the ones in the other road cut really will form by deposition on the slope.
Well, you have just seen a demonstration that they can.
Just wondering: Would you say the layered rocks in the picture are highly compacted?
Considering that it's very lithified, yes, I'd say it was compacted. Your point being?

This message is a reply to:
 Message 1727 by Faith, posted 05-10-2015 12:09 AM Faith has not replied

  
edge
Member (Idle past 1197 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 1729 of 1939 (757527)
05-10-2015 12:49 AM
Reply to: Message 1723 by Faith
05-09-2015 11:28 PM


Re: sedimentation on slope
I'm aware of the variations in thickness across huge distances. Nevertheless the impression of the strata over pretty huge distances, such as seen for instance from a distance in the Grand Canyon, is of a remarkable evenness of thickness.
Not in the case of the Tapeats which we see pinching out over short distances as shown by McKee.
Visible variations of thickness within a few hundred or even perhaps thousands of feet would suggest something other than normal deposition patterns to me.
And yet, they happen. Suggestions to you are not evidence.

This message is a reply to:
 Message 1723 by Faith, posted 05-09-2015 11:28 PM Faith has replied

Replies to this message:
 Message 1730 by Faith, posted 05-10-2015 12:54 AM edge has replied

  
Faith 
Suspended Member (Idle past 935 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 1730 of 1939 (757528)
05-10-2015 12:54 AM
Reply to: Message 1729 by edge
05-10-2015 12:49 AM


Re: sedimentation on slope
Are you talking about variations in thickness from DEPOSITION or from deformation after deposition? Forces, pressures, compaction after deposition can thin out a layer for instance.
Edited by Faith, : No reason given.
Edited by Faith, : No reason given.

This message is a reply to:
 Message 1729 by edge, posted 05-10-2015 12:49 AM edge has replied

Replies to this message:
 Message 1732 by edge, posted 05-10-2015 1:04 AM Faith has replied

  
edge
Member (Idle past 1197 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 1731 of 1939 (757529)
05-10-2015 1:01 AM
Reply to: Message 1722 by Faith
05-09-2015 11:16 PM


Re: Sedimentation Video
ABE: I'll grant that there is more drape effect in the experiment than I would have expected, ...
Considering that you expected there would be no drape effect, yes, there is 'somewhat more'.
... but unlike the McKee drawings it's so evenly distributed it just comes off as thinly coating the slopes on the way down to pooling in the depressions, rather than forming draped layers as in the drawings.
I'm not sure that your eyesight isn't deceiving you. When I look at McKee's drawings, I see layers thinning to the point where they completely pinch out in some cases.
I know this seems picky but that's how it hits me. Maybe you need to get something more asymmetric to make your case. /ABE
Something hitting you is not evidence, although we have tried that. Again, I'm not sure what you are looking at, but I see assymetric deposition of layers in the demonstration akin to the ones in McKee's diagrams.
As for the draped sandstone I'm not sure how it should be set up. I DON'T see the same draped effect in the video experiment; I DON'T see sediment pooling in the depressions on the drawings, just draped layers.
Again, I'm thinking you are looking at a different video. Some of the layers on the basement high are quite thin compared to the depressions.
"Drape upon drape" means to me something more like layers of equal thickness that start thin at the top but drape down into the depressions with equal thickness like actual layers except they're draped, if that conveys anything. That's what I see in the McKee drawings. Maybe steeper "monadnocks" are needed for the experiment.
I'm not sure what you mean by being of equal thickness if they 'start thin at the top...'.
And what do you mean by draping 'into the depressions with equal thickness'? Equal to what?
In other words it's got to prove your argument or it's not worth it?
I think he is referring to your tendency to dismiss evidence and conclusions without explanations other than 'it kinda, sorta looks that way'.

This message is a reply to:
 Message 1722 by Faith, posted 05-09-2015 11:16 PM Faith has not replied

  
edge
Member (Idle past 1197 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 1732 of 1939 (757530)
05-10-2015 1:04 AM
Reply to: Message 1730 by Faith
05-10-2015 12:54 AM


Re: sedimentation on slope
Are you talking about variations in thickness from DEPOSITION or from deformation after deposition?
Seeing as there is no evidence of forced folding, it would be at deposition.
ABE: (interpretation) The geometry is from deposition./ABE
Forces, pressures, compaction after deposition can thin out a layer for instance.
Most compaction is gravity related and not forced folding.
And yes, this is what I've been saying all along. Compaction is a process which can produce drapes. But it is not tectonic.
ABE: (interpretation) Yes, this is what I've been saying all along, but compaction is not tectonic in this case.
Edited by edge, : No reason given.

This message is a reply to:
 Message 1730 by Faith, posted 05-10-2015 12:54 AM Faith has replied

Replies to this message:
 Message 1733 by Faith, posted 05-10-2015 1:12 AM edge has not replied

  
Faith 
Suspended Member (Idle past 935 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 1733 of 1939 (757533)
05-10-2015 1:12 AM
Reply to: Message 1732 by edge
05-10-2015 1:04 AM


Re: sedimentation on slope
You've lost me every time you've said this about compaction and "forced folding." Sometimes I'll look up your terms but sometimes they are so unrelated to what's on my mind at the moment I just let them go. Anyway, if you want me to understand what you are saying here you need to translate.

This message is a reply to:
 Message 1732 by edge, posted 05-10-2015 1:04 AM edge has not replied

  
Admin
Director
Posts: 12870
From: EvC Forum
Joined: 06-14-2002


Message 1734 of 1939 (757541)
05-10-2015 7:48 AM
Reply to: Message 1723 by Faith
05-09-2015 11:28 PM


Re: sedimentation on slope
Faith writes:
With consistent sedimentation rates across the slope, what are you imagining could prevent layers being deposited evenly?
I'd rather not get into an argument about this now, I'd rather see what happens in an experiment if you don't mind.
In that case please put your views about the impossibility of non-horizontal deposition on the back burner until such time as you can provide rationale and/or evidence. Just so it doesn't catch you by surprise later on let me say that this means you can't argue for your view that there's a change in the angle of tilt in the layers of the road cut that could only have been caused by sagging of the layers to the left.

--Percy
EvC Forum Director

This message is a reply to:
 Message 1723 by Faith, posted 05-09-2015 11:28 PM Faith has not replied

  
Admin
Director
Posts: 12870
From: EvC Forum
Joined: 06-14-2002


Message 1735 of 1939 (757543)
05-10-2015 8:23 AM
Reply to: Message 1722 by Faith
05-09-2015 11:16 PM


Moderator Ruling
Hi Faith,
In responding to your post I'm going to make a moderator ruling.
Faith writes:
In other words it's got to prove your argument or it's not worth it?
I think what HBD is saying is that you're dismissing evidence and arguments out of hand while providing specious counter arguments ("it looks like...", "it just comes off as..."), and that if you're going to continue in this way then there's little point in putting effort into providing even more evidence and arguments to you.
I'll grant that there is more drape effect in the experiment than I would have expected, but unlike the McKee drawings it's so evenly distributed it just comes off as thinly coating the slopes on the way down to pooling in the depressions, rather than forming draped layers as in the drawings. I know this seems picky but that's how it hits me. Maybe you need to get something more asymmetric to make your case.
HBD provided this image:
It has asymmetry reflecting flow. Contrary to your claims of even distribution (paraphrasing, just thin coats with pooling in the depressions), the bottommost layer (it's yellow) does become slightly thinner as it rises up the slope, and on the far side it disappears altogether for a while. The next layer up (it's brown) looks precisely like some layers in the McKee diagram.
And the next layer above that (a lighter brown) almost completely pinches out on the far side of the mound.
Ideally both sides in a discussion would bow to the evidence and move on, but as that isn't happening here I'm therefore ruling that unless you can present a rationale for your position that has far more substance and far better correspondence to the evidence than "it just comes off as thinly coating the slopes on the way down to pooling in the depressions" that the geological position that the boundary between the Tapeats and Archean is an erosion unconformity, not an intrusion, has succeeded and that discussion should move on.

--Percy
EvC Forum Director

This message is a reply to:
 Message 1722 by Faith, posted 05-09-2015 11:16 PM Faith has not replied

  
Admin
Director
Posts: 12870
From: EvC Forum
Joined: 06-14-2002


Message 1736 of 1939 (757544)
05-10-2015 8:40 AM
Reply to: Message 1704 by Faith
05-09-2015 1:17 PM


Re: Sedimentation Video
Faith writes:
The first few layers did somewhat drape so that was interesting, but they also filled in the low places. After it was all covered up to a level point then they deposited horizontally, no tilting there. Although you want me to see the result as like the McKee drawing the only similarity I see is the initial draping. There is no filling of the low places in the drawing, or in any of the other drawings either; and there is nothing in the experiment like the drape-upon-drape in the drawing. That drape-upon-drape effect is more apparent in one of the other drawings as I recall but I couldn't find that illustration.
This doesn't appear to have any correspondence to the video at all. It's like you're looking at something completely different than everyone else, or as if you are unable to see obvious similarities in images. In his reply Edge commented similarly.
If you want to pursue the point then you're welcome to argue it again, but some points need significant modification if they're to make sense to anyone. To point out just one example, you say "There is no filling of the low places in the [McKee] drawing," yet everyone else sees the layers thickening the deeper they are in the basins. If you're looking for identicalness between the sedimentation experiment and the McKee drawings then you're not going to find it and should by no means expect it. The experiment was to illustrate general principles of sedimentation, not to replicate what happened in specific regions of the Tapeats boundary with the Great Unconformity. To continue arguing your point you need to make observations that don't cause people to wonder if you're looking at the same images they are, and you need to provide a reasonable rationale for why the sedimentation experiment and the McKee Tapeats diagrams aren't uncannily similar.

--Percy
EvC Forum Director

This message is a reply to:
 Message 1704 by Faith, posted 05-09-2015 1:17 PM Faith has not replied

  
edge
Member (Idle past 1197 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 1737 of 1939 (757575)
05-10-2015 10:13 PM


Just out of curiosity, I was looking at some inclined bedding references and ran across this article on the Lawrence Formation in Kansas. Here is one of the explanatory diagrams.
The caption says:
quote:
"Figure 12--Three patterns of channel fill: A) horizontal layers, common in subaerial channels; B) layers conforming approximately to the channel shape, common in subaqueous channels; C) asymmetric fill by inclined layers, common in tidal regimes (from Reineck and Singh, l975, p. 63; based on McKee, l957)."
Note that the horizontal, flat channel fill sedimentary strata are 'common in subaerial channels'.
So, even though the layers occur as Faith would like them to be, it still implies an unconformity occurring somewhere above sea level.
I rather like the inference of 'tidal regimes' for the assymetric fill because it suggests a shoreline along the Tapeats sea as it rose across the Great Unconformity land surface.
For those interested, here is a schematic strat column for the study area. Note that the age of these rocks is Pennsylvanian, which would be at a time between the Redwall Limestone and the Hermit Shale in the Grand Canyon. That would be at the time when Faith says there was no erosion or tectonism going on in the Grand Canyon and, ostensibly, no where else in the world.
(Ooops, I forgot, we have to ignore what's going on outside of the Grand Canyon).
This is one of the common ways that some detail is added to the normal stratigraphic column by showing erosional channels cut into lower formations. As you can see, it is quite complex.
Edited by edge, : No reason given.

  
edge
Member (Idle past 1197 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 1738 of 1939 (757649)
05-11-2015 6:17 PM


Another video for Faith. At about 2 minutes there is a discussion on the irregular unconformity surface at the base of the Tapeats and how it formed.
https://www.youtube.com/watch?v=ZoaAh0I7rJM

  
edge
Member (Idle past 1197 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 1739 of 1939 (757864)
05-14-2015 9:19 PM


Earlier in the thread someone asked if drag folds could form without faulting. The answer is 'not really', because 'drag' implies friction between two bodies.
However, it is possible that folding may precede faulting and consequent drag folding.
Here is a diagram depicting the stages in development of a 'monocline' (a fold with only one limb).
In this case the fold 'drapes' over the basement fault but shows drag after the fault has developed. One can see that if faulting continued in this diagram, the fault would propagate upward through the remaining sedimentary rock layers.
Note that this 'draping' is different from soft sediment drapes, but the driving force is still gravity. There is no compression such as what we see in normal fold development.
Here is an image of an actual monocline in the northern part of the Uncompahgre Uplift in Colorado.
Often times the hinge zones of these folds are highly fractured (and consequently more eroded) suggesting they were hard rocks when deformed or the strain rates were rapid. Here is an example:
Edited by edge, : No reason given.

  
snapdragon
Junior Member
Posts: 3
Joined: 01-20-2012


(4)
Message 1740 of 1939 (757984)
05-17-2015 9:24 PM


NY roadcut pictures
Today I had the opportunity to visit the area near the St. Lawrence River where the roadside unconformity (discussed earlier) is located. Here's a link to the pictures Microsoft OneDrive - Access files anywhere. Create docs with free Office Online.
They may or may not be useful, but it was nice just to touch and see them firsthand.
ABE:just to clarify
1-4 Head-on walking L-R
5-7 are angled from the Right, with 7 a little closer view
8 is angled from the L
9 is pretty, unweathered sandstone
10-15 are closer shots
16 is the opposite side of the road
Edited by snapdragon, : provide context

Replies to this message:
 Message 1741 by edge, posted 05-17-2015 11:26 PM snapdragon has seen this message but not replied
 Message 1742 by JonF, posted 05-18-2015 7:36 AM snapdragon has seen this message but not replied

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2022 by EvC Forum, All Rights Reserved

™ Version 4.1
Innovative software from Qwixotic © 2023