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Author Topic:   Evidence that the Great Unconformity did not Form Before the Strata above it
edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 129 of 1939 (753037)
03-16-2015 12:32 AM
Reply to: Message 119 by Faith
03-15-2015 9:55 PM


Re: the Great uncomformity proves the Earth is old
Oh that are indicated along the edge of the Supergroup. Now I see it.

Yes, they truncate the Supergroup rocks, but not the Paleozoic rocks. They are, therefor, older than the Paleozoic.

No such intention.

Well, if you reject the superposition of younger over older, then you should explain yourself.

Going to have to come back to this topic when the whole misunderstanding is clearer.

It's actually pretty clear right now. I could imagine ways of localizing deformation within a rock sequence, but in every case, there would be obvious evidence. We are quite good at deciphering such things.

But even without that, you have a problem explaining the unevenness of the Great Unconformity related to erosion resistance of the different layers in the Supergroup. Just look at the section and it's pretty clear.


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 Message 119 by Faith, posted 03-15-2015 9:55 PM Faith has not replied

  
edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 158 of 1939 (753148)
03-17-2015 11:42 AM
Reply to: Message 155 by ThinAirDesigns
03-17-2015 10:02 AM


My understanding (and I just learned this) is that the very geological definition of an unconformity IS the point where there is missing rock.

In the broadest sense, an unconformity is the depositional contact between two rock bodies of different ages, and hence, represents a gap in the geological record. An unconformity would be approximately horizontal (if not deformed), with the younger rocks above it; and does not include intrusive contacts or fault contacts.

There are several different types of unconformities, as shown at:

http://en.wikipedia.org/wiki/Unconformity

As you can see, the upper contact of the Vishnu with the GC Supergroup, or with the Tapeats, could also be called a nonconformity.

With this in mind, I sometimes refer to the land surface on which we live an unconformity as a way of showing YECs that unconformities do actually exist.


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edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 200 of 1939 (753615)
03-21-2015 12:02 AM
Reply to: Message 199 by Minnemooseus
03-20-2015 11:30 PM


Re: From another topic
First of all, I think Edge had an error. I think a sentence above should have been "As to the burial origin of the foliation, if that is due to the Paleozoic section being deposited, then the foliation should be closer to horizontal. The greatest pressure is perpendicular to the foliation.

Heh, heh... rough day to day. Yes, I was thinking that the forces would have been vertical. If I can edit that, I shall.

The metamorphism of the schist require heat and high pressure. The non-metamorphism of the overlying sediments requires the lack of heat and high pressure. The sediments were not there when the schist metamorphism happened.

Exactly. And they are close enough in space that there should be some effect on the Paleozoic section.

And that unconformity is a nonconformity - It is sediments on top of basement metamorphics and intrusives.

Also true. However, I think that nonconformities are a subset of unconformities.

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edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 206 of 1939 (753642)
03-21-2015 11:14 AM
Reply to: Message 203 by Faith
03-21-2015 3:53 AM


Re: Sorry, but there's so much wrong here
So some say. I'll have to look it up again but one source who studied the Vishnu says it is made up of a huge range of different rocks.

Yes, some of which are not found in the Supergroup.

I ran across this earlier and mentioned it in one of these recent threads, guess I'll have to find it.

If that's what it says, it doesn't help you.

Not at all unfortunate. It would solve the puzzle if you were right but everything I've found calls it a metamorphic rock requiring heat and pressure, such as this Google page:

The term 'quartzite' is often used loosely, but if you want to be precise, many quartzites are actually 'quartz arenite', and meteamorphic quartzite are termed 'orthoquartzite'.

The term 'quartz arenite' is derived from the main component (quartz) and arenite, a Latin term for a rock with sand-sized grains. In some literature, these can be called orthoquartzites, a confusing term which usually refers to the metamorphic rock quartzite, though most metamorphic quartzites are diagentically fused from quartz arenites. The term "quartzose sandstone" can also be used for a quartz arenite.(http://en.wikipedia.org/wiki/Quartz_arenite)

This is how I was taught many years ago and it's only coming back to me now as I look up these terms.

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edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(2)
Message 207 of 1939 (753644)
03-21-2015 11:27 AM
Reply to: Message 204 by herebedragons
03-21-2015 8:31 AM


Re: Surface of the Unconformity
This is an excellent post. Thank you for tracking all of this down.

I especially enjoyed this part:

Regarding the "Weathering of Ep-Algonkian Surface" (Ep-Algonkian surface is the name used for the surface that would become the Great Unconformity) MacKee summarizes the work of Robert Sharp (1940)

quote:
The principal points are as follows:
1. Weathering of the Archean rocks has extended downward 10 to 12 feet in many places and as far as 50 feet below the surface in some places.
2. Weathering of Algonkian rocks has been slight, presumably because they are composed of minerals that have already survived at least one cycle of weathering.
3. Mineralogical changes in the weathered zone of the Archean rocks involve elimination of feldspars, biotite, and other iron-bearing minerals, and a notable development of iron oxides. Another result of weathering is a large increase in the percentage of insoluble residues.
4. Residual enrichment causing an increase in iron oxide is progressive upward toward the erosion surface.
5. Locally a regolith which consists of a foot or two of structureless, extensively weathered detritus grades upward into basal Cambrian sediments and downward into less weathered Archean rock.
6. Boulders of decomposition consisting of cores of relatively unaltered rock, residual after weathering along fractures and joints, are locally present beneath the true regolith.
7. The weathered material of the regolith probably should be classed as intrazonal or azonal soil, but some of the most maturely weathered detritus may be normal soil. A considerable but unknown amount of it probably was removed by waves as the Cambrian sea advanced.
8. At two localities, features interpreted as being due to surficial creep have been noted in the weathered zone at the base of Pre-Cambrian monadnocks. - pg. 121


Earlier, I have suggested that some of the material just above the unconformity consists of materials derived directly from the underlying rock. While I was reluctant to be too specific in drawing conclusions from a picture, these observations by Sharp give me a lot more confidence in my earlier musings. Nothing like actual field work to generate conclusive data. We could spend all week arguing about a photo (maybe we have...), but these observations put everything into perspective.

Each of these points is strong indication that the Great Unconformity was once exposed to the surface prior to Paleozoic sediment deposition.

This is an inescapable conclusion. Normally, it would be 'end of discussion' but I have a feeling that a certain poster is preparing a bulwark of denial.

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edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 208 of 1939 (753646)
03-21-2015 11:34 AM
Reply to: Message 205 by herebedragons
03-21-2015 9:44 AM


Re: From another topic
Keep in mind that the unconformity itself is the solid black line that represents a period where there was not continuous deposition. Also note, that it is interpreted to mean "missing time" but what it actually represents is a time when deposition was not continuous - in other words, deposition paused, with or with out subsequent erosion. (however, erosion is pretty much inevitable at the surface and the presence of an erosional surface would be an indication that an unconformity exists). So there is actually no "missing time" but simple no deposition.

One could say 'missing rock' that represents the passage of time.

And this also bears repeating:

Also note that there is nothing in that definition that defines long periods of time. Deposition could have paused for 1 minute between flood waves or 1 million years during an uplift.

In other words, the Great Unconformity does not necessarily represent a billion years of erosion, only a billion years of missing record. This is one of the subtleties of unconformities that people often overlook.

To determine time frames we would need to look at processes. But I suggest that we just focus on determining IF the Great Unconformity is really an unconformity or is it something else.

Yes, we should focus the discussion, at least for the time being.

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edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 210 of 1939 (753652)
03-21-2015 12:21 PM
Reply to: Message 209 by jar
03-21-2015 11:55 AM


Re: From another topic
Would it not be more accurate to say that "the Great Unconformity represents at least a billion years of missing record?"

Exactly.

We can say that the time period would be at least as long as shown by the remaining layers of the Super Group but what is left of the Super Group is very likely not all that was there.

Yes, the Supergroup could be considered part of the missing record. Then, of course, we are presented with two unconformities...

I think saw that called a 'biconformity' or something like that.


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edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 223 of 1939 (753687)
03-21-2015 5:16 PM
Reply to: Message 219 by Faith
03-21-2015 4:19 PM


Re: Erosion simply CANNOT explain the flat contact line
ABE: You can bring up all kinds of exceptions, as I already acknowledged, ...

So, how many exceptions do you need?

... but the problem is still how to explain the vast majority that exhibit such a flat horizontal contact -- and even the exceptions are MOSTLY flat and horizontal.

Flat surfaces are common in eroded areas. Just look at vast expanses of the Canadian Shield, or what do you think the Amazon Basin is going to look like an a few million years?

The point is that the unconformity is not flat everywhere which is what we would expect if your scenario were correct.


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edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 229 of 1939 (753698)
03-21-2015 6:19 PM


So Faith says there shouldn't be any 'flat' surfaces of deposition...

How about this along the seashore in Sweden. What if we started building a sandy beach over this expanse?

Here is the Imuruk Basin on the Seward Peninsula in Alaska. Pretty flat? Oh, and notice the meander loops...

And here is the top of the Entrada Sandstone on the Uncompahgre Uplift that we've talked about before.

Flat enough yet?

So, tell us once again why we should not have flat surfaces.


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edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 233 of 1939 (753704)
03-21-2015 6:47 PM
Reply to: Message 230 by Faith
03-21-2015 6:22 PM


I said no such thing. I said lumpy bumpy spiky or inclined surfaces would not erode flat.

Well, something is eroding flat...

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 Message 230 by Faith, posted 03-21-2015 6:22 PM Faith has replied

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 Message 235 by Faith, posted 03-21-2015 6:49 PM edge has not replied

  
edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 239 of 1939 (753722)
03-21-2015 7:31 PM
Reply to: Message 234 by Faith
03-21-2015 6:47 PM


Re: Erosion simply CANNOT explain the flat contact line
That's changing the subject. FIRST ACKNOWLEDGE THE POINT, THAT EROSION CAN'T DO IT.

I think what you are really saying is that we should acknowledge that 'Faith is correct'. Isn't that right?

I'm trying to follow your argument, but it doesn't make sense. You say that the unconformity is 'flat', even though it isn't.

Then you say that erosion can't create such a surface, even though we show you places where it has.

You don't seem to be doing much other than just requiring that we agree with you before engaging in civil discourse.


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 Message 234 by Faith, posted 03-21-2015 6:47 PM Faith has replied

Replies to this message:
 Message 241 by Faith, posted 03-21-2015 7:35 PM edge has replied

  
edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 240 of 1939 (753725)
03-21-2015 7:33 PM
Reply to: Message 238 by Faith
03-21-2015 7:30 PM


Re: Erosion simply CANNOT explain the flat contact line
It first needs to be acknowledged that erosion couldn't accomplish what you all claim it did with the Great Unconformity.

Just to clarify, what do we claim the Great Unconformity did?

But at this point I'm not defending my own interpretation, I'm insisting that the absurdity of the conventional interpretation be recognized.

I'm not sure that you know what the conventional interpretation is.

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edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 242 of 1939 (753727)
03-21-2015 7:40 PM
Reply to: Message 241 by Faith
03-21-2015 7:35 PM


Re: Erosion simply CANNOT explain the flat contact line
Look at the pictures for a definition of "flat."

I'm not asking for a definition.

Several lines of evidence have been shown to you that the Great Unconformity is not flat. Even by your pictorial definition.

But you haven't. You've shown flat surfaces but without any evidence that they are the sort I've been talking about.

Then maybe you are not being very clear in what you'd like to see. You have shown several flat bedding planes, so I showed you a couple of images where bedding planes have been exposed by erosion over a fairly large area.

So what do you want?


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 Message 241 by Faith, posted 03-21-2015 7:35 PM Faith has replied

Replies to this message:
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edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 257 of 1939 (753786)
03-22-2015 10:56 AM
Reply to: Message 246 by Faith
03-21-2015 8:15 PM


Re: Erosion simply CANNOT explain the flat contact line
THERE IS NO EVIDENCE OF IT IN THE ROCK RECORD. THERE ARE LUMPY ROCKS WITH FLAT SURFACES. THERE IS NO EVIDENCE OF HOW THEY GOT THAT WAY.

Okay, Faith, I''m trying to determine if you think this is a lumpy surface or a flat surface, and why you think there is no evidence of how it got that way.

If it is lumpy, how did it get to be that way? I am confused by your line of questioning. It seems you say unconformities are flat when everyone else shows that are not necessariy so. Then you say that erosion cannot form flat surfaces when, demonstrably, it can; but we are not saying that it always does.

What is your point? What is your evidence that the Great Unconformity is not erosional (and therefor, NOT an unconformity). All I can see you doing right now is denying our evidence, but providing none of your own. You seem to be only capable of disagreeing in order to be disagreeable.

Edited by edge, : No reason given.


This message is a reply to:
 Message 246 by Faith, posted 03-21-2015 8:15 PM Faith has replied

Replies to this message:
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edge
Member (Idle past 1020 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 258 of 1939 (753787)
03-22-2015 11:09 AM
Reply to: Message 251 by Faith
03-22-2015 12:38 AM


Re: Erosion simply CANNOT explain the flat contact line
If you had bothered to read what I wrote you'd know that I was talking about the impossibility of eroding down to flatness tilted surfaces like the angular strata of an angular unconformity and lumpy surfaces like schist and granite, ...

I'm not sure who was saying that they are 'flat' surfaces.

You do understand that 'flat' is a term relative to scale. Is that your problem?

and specifically said I was NOT talking about naturally FLAT surfaces like the Kaibab which is the upper surface of a limestone layer. I SAID THAT IN SO MANY WORDS. Sheesh.

IIRC, though, it was you who showed us such surfaces in a series of pictures showing how 'flat' layers can be.

This message is a reply to:
 Message 251 by Faith, posted 03-22-2015 12:38 AM Faith has replied

Replies to this message:
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