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Author Topic:   Evidence that the Great Unconformity did not Form Before the Strata above it
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


(1)
Message 37 of 1939 (752880)
03-14-2015 7:27 AM
Reply to: Message 36 by kbertsche
03-14-2015 2:09 AM


Re: where did it go?
nature is unreliable as a source of truth.

Actually, they would say it is our interpretation of nature that is unreliable. Ironically, the Bible is much more difficult to interpret than nature because it can be so subjective and we need to try to get into the minds of people who lived many years ago.

But, you are right. When the Bible is believed to be the only reliable source of truth, it makes it difficult to point out even simple scientific facts.

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 36 by kbertsche, posted 03-14-2015 2:09 AM kbertsche has not yet responded

  
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


(1)
Message 103 of 1939 (752995)
03-15-2015 4:39 PM
Reply to: Message 1 by Faith
03-12-2015 12:42 PM


1. The strata were already in place when the uplift occurred that created the mounded rise. Evidence for this is that the strata all follow the contour of the mound.

OK, for the most part yes, this seems to be true. The forces that caused the Kaibab plateau uplift appear to be a fairly recent phenomenon and the sediment at least up to the Kalibab were in place before the uplift.

2. Whatever caused the rise lifted the whole stack of strata as a block. Evidence for this is that the rounded contour is at both the bottom and the top of the canyon: it rises over the Great Unconformity instead of the strata butting in to it, as they would if it was there before the strata were laid down.

First of all, an unconformity represents a "missing" segment of time - which I understand you don't accept. I think you do understand what it means, but you worded the above kind of strangely saying that if the unconformity existed before the strata above it was laid down that it would butt into it (the unconformity). What we need to look at is the layers above and below the unconformity and see how they interact.

But so far, you thought process is ok.

3. This means that the Great Unconformity was NOT there before the strata were laid down. It was lifted right along with the whole stack, and probably tilted at the same time.

Now this is where your logic has failed. In order for the strata above and below the unconformity to be lifted along with the rest of the block, it needed to be there before the lift occurred. If you are trying to make the argument that the unconformity formed during the uplift, this line of reasoning doesn't do it. It doesn't even make sense, here's your logic:

1. The strata doesn't butt up against the unconformity
2. The whole block was lifted as a unit
3. The unconformity wasn't there before it was lifted

How does 3 follow from 1 and 2?

So I conclude that now I’ve finally proved that the Great Unconformity did NOT preexist the laying-down of the strata

Well, let's look at the contact between the Supergroup and the Tapeats (which represents this Great Unconformity).

First, here is a cross section

Note that the Tonto Group (the Tapeats being the lowest member) contacts the Vishnu Basement through the Sixtymile formation. Also note that the Tapeats DOES butt up against the Supergroup. Wikipedia say this of the contact between the Tapeats and the Supergroup

quote:
The contact between the Tapeats Sandstone and Bass Formation and the rest of the folded and faulted Unkar Group is a prominent angular unconformity, which is part of the Great Unconformity. The differential erosion of the Unkar Group left resistant beds of the Cardenas Basalt and Shinumo Quartzite as topographic highs, ancient monadnocks, that are now buried by sandstones, shales, and conglomerates of the Tapeats Sandstone. These monadnocks served locally as sources of coarse-grained sediments during the marine transgression that deposited the Tapeats Sandstone and other members of the Tonto Group. The contact between the Bass Formation and the Tapeats Sandstone forms part of a relative flat surface that lies between the monadnocks.

One of the layers that is not identified in the above image is the Cardenas Basalts

quote:
The lava flows of the Cardenas Basalt represent the subaerial eruption of basaltic and andesitic magma. The interbedded sandstones and hyaloclastites provide evidence that these eruptions occurred in wet coastal environments such as river deltas or tidal flats.

It is 300m thick in some places! These lava flows (subaerial) make up some of the features that were resistant to weathering and formed these monadnock structures that protrude not just into the Tapeats but some even into the Bright Angle Shale!

quote:
Though this surface is typically a plane, differential erosion of the tilted strata of the Unkar Group left resistant beds of the upper layer Cardenas Basalt and the middle layer Shinumo Quartzite as ancient hills, called monadnocks. These ancient hills, which are ridges formed by block faulting, are up to 240 m (800 ft) tall. Thin drapes of Tapeats Sandstone of the Tonto Group either cover or drape onto most of these ancient monadnocks. However, the summits of the highest monadnocks protrude up through the base layer Tapeats Sandstone and are blanketed by overlying Bright Angel Shale as can be seen at Isis Temple.

Unkar Group

Here are a couple of pictures of the Great Unconformity

quote:
(above, left)Close-up of The Great Unconformity with Vishnu Schist below and Tapeats Sandstone above. Quartz clasts rest right at the surface of the unconformity

quote:
(above, center)Notice the “loose” fragments of Zoroaster pegmatite from the underlying Grand Canyon Metamorphic Suite incorporated within the contact below the basal-most Tapeats Sandstone. Inclusions can often be utilized to recognize a nonconformity such as this.

quote:
(above, right)A small scale channel within the Tapeats Sandstone just above the unconformity. These channels were likely cut as the waves of the Tapeats Sea washed back across the surface.

OK, you get the point... the contact between the Tapeats and the Supergroup was there BEFORE uplift.

A more likely order of events (simplified, of course):

1. Supergroup deposited
2. Supergroup fractured and tilted
3. Surface which would become the Great Unconformity weathered
4. Paleozoic rocks deposited
5. Uplift of Kalibab plateau
6. Cutting of the Grand Canyon

I think that order is pretty well universally accepted. Of course, some of the details and the timing are debated, but it should be absolutely clear that the unconformity did not form during uplift, the surface that would become the unconformity was there before both the uplift and the deposition of the Paleozoic strata.

There are of course many different reasons why the Geologists think the Great Unconformity was there long before the strata were laid down, but if what I've said above is true, it makes all the other reasons wrong.

Those reasons being that they let the rocks tell the story not try to force a preconceived notion onto them.

HBD

Edited by herebedragons, : spelling


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 1 by Faith, posted 03-12-2015 12:42 PM Faith has responded

Replies to this message:
 Message 108 by Faith, posted 03-15-2015 5:47 PM herebedragons has responded

  
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


Message 104 of 1939 (752996)
03-15-2015 4:55 PM
Reply to: Message 100 by Faith
03-15-2015 3:58 PM


Edge is now saying that the Supergroup is NOT composed of layers as you seem to be saying it is, and I thought it was.

Didn't edge say the Great Unconformity was not composed of strata? Not the Supergroup??

Faith writes:

... that is, simply because it's beneath the Paleozoic system, that refers well enough to the strata the G.U. is composed of,

edge writes:

The Great Unconformity is not composed of strata!!!!!!!!!

From Message 91

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 100 by Faith, posted 03-15-2015 3:58 PM Faith has responded

Replies to this message:
 Message 105 by Faith, posted 03-15-2015 5:21 PM herebedragons has not yet responded

  
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


Message 121 of 1939 (753024)
03-15-2015 10:09 PM
Reply to: Message 108 by Faith
03-15-2015 5:47 PM


All right, this needs a lot of clarification. The angular unconformity at Siccar Point is the entire formation that includes both the upper horizontal layer and the vertical layers beneath. This is how I've been regarding the physical presentation of the Great Unconformity as well. To reduce it merely to the eroded contact line makes no sense to me.

In geological terms, an unconformity represents a period of missing time. If say you have a layer dated at 750 mya with a layer dated to 500 mya directly on top of it - in contact with it, then that is an unconformity - 250 million years of "missing time." But you don't detect an unconformity merely by determining there is "missing time" you look at the contact surface.

So it IS the eroded contact line that represents the unconformity.

As for an unconformity representing a missing segment of time, aren't you confusing different kinds of unconformity?

No, I don't think so. Different types of unconformities describe the different ways that the layers above and below the contact relate to each other. The Great Unconformity in the Grand Canyon is an Angular Unconformity because the lower layers are truncated (terminated) at the contact at an angle.

The kind I reject is the kind that represents an entire segment of rock that OE theory says is supposed to be there but isn't.

An erosional surface has removed material, obviously that's how erosion works. So if the contact is an erosional surface, there is a segment of rock that is missing. It does not necessarily mean that there is an entire layer of rock missing. It could be a time where there was no deposition occurring. An unconformity does strongly suggest, however, that the layer was exposed at the surface - which usually results in erosion.

As for your proofs, they are very much the standard view, though maybe I'm not giving them enough attention at the moment.

This is part of the "let the rocks tell the story" comment. Look back at what I presented regarding the contact between the Supergroup and the Tonto Group and ask "what does this tell me about what happened?" Forget about what you are trying to prove, or what you expect it to say, find out what it says!

Nevertheless, despite the presence of these dramatic pieces of rock, the overall presentation of the surface of the G.U. where it contacts the Tapeats, is still a lot more flat and horizontal than I would expect.

But there is no reason to expect ANYTHING because you don't know what happened there. Your expectations come from having a preconceived notion about what happened. It also comes from ignoring the details and focusing only on the big picture. Yes, it is surprising that that surface is so flat. Yes it is surprising that the area did not experience major tectonic disturbance for long periods of time. But that is the story the rocks tell!

Accusing me of "forcing" anything is not fair. I do my best to understand the actual lay of the rocks and how it all fits together.

You think that is what you are doing, but its not. You are trying to explain it in the context of a global flood, which is not necessarily wrong, but unless you are willing to give up trying to explain it with the flood, you have no choice but to "force" your observations to fit your preconceived notion. When you stop and say "what do the rocks actually say?", then you will be able to understand them. Who knows, maybe you will find that there was a global flood...

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 108 by Faith, posted 03-15-2015 5:47 PM Faith has not yet responded

  
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


Message 126 of 1939 (753031)
03-15-2015 11:29 PM
Reply to: Message 124 by Faith
03-15-2015 10:43 PM


Also, no avoidance going on, I simply believe there was only one major tectonic event that caused the Kaibab Uplift and all that massive erosion above the Permian, and the tilting of the Supergroup beneath the canyon.

You don't still believe this do you??? After you have been shown that the Great Unconformity is an erosional surface?? That it has features that protrude up to 240m (800ft.) into the layers above??? That there are large Vishnu clasts that have been incorporated into the Tapeats at the point of contact???

Sure sounds like avoidance to me.

(Unless you were merely pointing out what you WERE thinking before you were shown it could not have happened that way )

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 124 by Faith, posted 03-15-2015 10:43 PM Faith has not yet responded

Replies to this message:
 Message 128 by Coyote, posted 03-16-2015 12:25 AM herebedragons has responded

  
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


Message 134 of 1939 (753050)
03-16-2015 10:21 AM
Reply to: Message 128 by Coyote
03-16-2015 12:25 AM


can we coin a new word for what we see here, Christian apologistics? I propose the term Christian apologistics as a field of Christian theology which attempts to present a multitude of irrational bases for the Christian faith, defending the faith against objections.

No need to invent a new term, we already have one that fits this description... Creation Science.

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 128 by Coyote, posted 03-16-2015 12:25 AM Coyote has acknowledged this reply

  
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


(2)
Message 135 of 1939 (753051)
03-16-2015 10:27 AM
Reply to: Message 131 by Faith
03-16-2015 2:19 AM


I'm giving up on this thread at this point. I've concluded I didn't have the OP thought out and don't have the evidence I thought I had. Thanks.

Fair enough, but I suspect you have not given up on your belief regarding the formation of the Great Unconformity and the tilting of the Supergroup etc... You just realize you can't continue to argue it here. In 6 months or so, you will be trotting this whole idea out again, whether at EvC or at your blog or whatever, as if none of this discussion ever happened.

I hope I am wrong about that...

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 131 by Faith, posted 03-16-2015 2:19 AM Faith has not yet responded

  
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


Message 147 of 1939 (753122)
03-17-2015 7:40 AM
Reply to: Message 141 by Faith
03-16-2015 11:31 PM


TAD writes:

In their day and age, Martin Luther, John Calvin, Philipp Malanchthon, Bellermine and ALL the giants of Christianity believed and insisted that the earth sat unmoved and the heavens rotated around us. They declared those who disagreed to be apostate and even devil possessed. They claimed that if science and the bible contradicted, it wasn't the bible that was going to be altered because all science had to be measured against the bible. The verses proclaiming geocentricity were "divine evidence" and who has the authority to argue against the divine?

Faith writes:

You really should provide some quotes in evidence for all that.

I have provided you with quotes that are evidence of this (at least for Calvin and Luther) and wondered why you held beliefs (heliocentricism) that were contradictory to the Bible.

You just dismissed it. So what would be the point of Thin Air providing quotes?

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 141 by Faith, posted 03-16-2015 11:31 PM Faith has not yet responded

Replies to this message:
 Message 148 by ThinAirDesigns, posted 03-17-2015 8:12 AM herebedragons has responded

  
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


Message 150 of 1939 (753128)
03-17-2015 8:45 AM
Reply to: Message 148 by ThinAirDesigns
03-17-2015 8:12 AM


It wasn't so much that she denied that they believed it, or that they had said those things but that there was any relevance to it.

The discussion was around here: Message 49

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 148 by ThinAirDesigns, posted 03-17-2015 8:12 AM ThinAirDesigns has not yet responded

  
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


Message 189 of 1939 (753454)
03-20-2015 1:06 AM
Reply to: Message 188 by Faith
03-20-2015 12:39 AM


Re: The Reformers on Science
I think the whole problem has to do with treating the Bible's simple observations as if they were scientific.

Amen!!!


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 188 by Faith, posted 03-20-2015 12:39 AM Faith has responded

Replies to this message:
 Message 190 by Faith, posted 03-20-2015 3:14 AM herebedragons has not yet responded

  
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


(2)
Message 204 of 1939 (753629)
03-21-2015 8:31 AM
Reply to: Message 203 by Faith
03-21-2015 3:53 AM


Surface of the Unconformity
everything I've found calls it a metamorphic rock requiring heat and pressure

Shinumo Quartzite

quote:
Red-brown, purple, and gray, cliff-forming sandstone. Includes four undivided informal members as defined by Daneker (1975)... All members cemented with silica, making sandstone as hard as metamorphic quartzite, but unit is not metamorphosed.

Have you given any more thought as to how the Shinumo Quartzite could protrude through the Tapeats and be overlain with Bright Angel Shale?

Shinumo Quartzite

quote:
Making up Cheops Pyramid above the Shinumo are the Paleozoic Bright Angel Shale, Muav Limestone and Temple Butte Formation, concealed for the most part beneath a good deal of talus, capped by a steep walled prominence composed of Redwall Formation. The normally ubiquitous Tapeats Sandstone is missing from below the Bright Angel Shale where hard, resistant quartzites and sandstones of the Shinumo eroded to a hilly topography with highs poking through and pinching out the much later deposited and subsequently eroded Paleozoic Tapeats.

Below is a photo of Cheops Pyramid marked up with the different strata present.

At first I wondered about the brown band at the top of the Shinumo Quartzite thinking it looked much like Tapeats Sandstone. However, the upper unit of the Shinumo is characterized as:

quote:
Finally, the upper member of the Shinumo Quartzite is composed of reddish brown and locally purple sandstone and an overlying well-cemented gray quartzite

And it has weathered almost identically as the formation below. The Tapeats would be much softer than the Shinumo and I would expect it to weather noticeably different.

ABE: (I could be wrong about the Tapeats in this photo. It may actually be Isis Temple in the background where the Tapeats is missing - a little confirmation from someone else would help)

Structures like this are really difficult to find adequate pictures to illustrate the phenomenon. As you can see, they are massive! We often need to rely on descriptions from people who have studied these up close. Edwin MacKee published "Cambrian History of the Grand Canyon Region" in 1945. Mac Kee has done extensive work studying the GC long before the internet. His books are difficult to come by, you have to go to a library in the dust, old books section. However, this book is available on Google Books as a free e-book.

quote:
“These monadnocks of the Cambrian plain may be compared with the Baraboo ridges of Huronian quartzite which by virtue of their homogeneity and hardness still stand as prominences which have weathered repeated cycles of erosion.” The maximum height of these monadnocks in the Shinumo quadrangle he gives as 600 feet. Schuchert,” after visiting an area farther east, refers to hills up to 700 feet, and Wheeler and Kerr “’ describe one north of Grand Canyon Village which rises approximately 800 feet above the base of the Tapeats sandstone. Wheeler and Kerr, moreover, call attention to the fact that at the start of Cambrian deposition these hills must have been still higher, because their upper parts were subsequently continuously reduced by erosion during the time involved in the deposition of some hundreds of feet of marine sediments - pg. 119

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

Each of these points is strong indication that the Great Unconformity was once exposed to the surface prior to Paleozoic sediment deposition. If you have questions as to why they are problematic for continuous sedimentation, please ask and we can discuss further.

Anyway, you are not likely to find a lot of details on these features on the web except as what you might call the "Old Earth Party Line." Edwin Mac Kee spent his whole career studying the Grand Canyon, analyzing it and writing about it. Details about WHY he came to his conclusions could be found in his books. Those that have studied the region close up and in detail have determined that the Great Unconformity is an erosional surface and not a slip fault (which is more like what it would be if the basement rocks rotated underneath the Paleozoic formations).

HBD

Edited by herebedragons, : subtitle

Edited by herebedragons, : disclaimer

Edited by herebedragons, : new link to image


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 203 by Faith, posted 03-21-2015 3:53 AM Faith has responded

Replies to this message:
 Message 207 by edge, posted 03-21-2015 11:27 AM herebedragons has not yet responded
 Message 214 by Faith, posted 03-21-2015 3:30 PM herebedragons has not yet responded

  
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


(3)
Message 205 of 1939 (753637)
03-21-2015 9:44 AM
Reply to: Message 201 by Faith
03-21-2015 12:19 AM


Re: From another topic
So, on top of the basement metamorphics and intrusives the contact with the sedimentary strata is a nonconformity, but on top of the tilted Supergroup it's an angular unconformity? Is that the idea?

4 types of unconformities.

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.

Does that help clear things up?

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. 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.

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 201 by Faith, posted 03-21-2015 12:19 AM Faith has not yet responded

Replies to this message:
 Message 208 by edge, posted 03-21-2015 11:34 AM herebedragons has not yet responded

  
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


(2)
Message 211 of 1939 (753666)
03-21-2015 2:41 PM
Reply to: Message 206 by edge
03-21-2015 11:14 AM


More terminology clarification
The term 'quartzite' is often used loosely, but if you want to be precise...

Something else that needs to be clarified... terms like quartzite, granite, sandstone, etc. are general categories for rock classification. Its like the terms fish, insect, mammal, etc. in biology (well maybe not quite that broad, but close). They are classified because they have certain characteristics in common, but there can be considerable variation in their actual make up.

For example, here is the description of the Tapeats Sandstone from the USGS. It is much more than just "sandstone."

quote:
Tapeats Sandstone (Middle and Lower Cambrian)—Brown and red-brown, cliff-forming sandstone and conglomerate. Includes an upper slope-forming transition zone of nearly equal distribution of brown sandstone of Tapeats Sandstone lithology and green siltstone and shale of Bright Angel Shale lithology, and a lower unit of cliff-forming sandstone and conglomeratic sandstone. Lower cliff unit consists mainly of medium- to coarse-grained, thin-bedded, low-angle planar and trough cross-bedded sandstone and conglomeratic sandstone; sandstone beds 6–24 in. (15–60 cm) thick. Unconformable contact with underlying Middle and Late Proterozoic surface that forms the Great Unconformity. The Tapeats fills in lowland areas and thins across or pinches out against young Proterozoic highlands. Variable thickness 0–400 ft (0–122 m)

Quartzite is kind of a strange category, there can be metamorphic quartzite and unmetamorphic quartzite. I think that makes the terminology confusing and it is understandable why Faith thought the Shinumo Quartzite was metamorphic.

Geologists

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 206 by edge, posted 03-21-2015 11:14 AM edge has not yet responded

  
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


(1)
Message 212 of 1939 (753668)
03-21-2015 3:00 PM
Reply to: Message 203 by Faith
03-21-2015 3:53 AM


The Tapeats
Another thing to point out real quick.

In Message 211 I quote a description of the Tapeats sandstone from the USGS. Here it is again.

quote:
Tapeats Sandstone (Middle and Lower Cambrian)—Brown and red-brown, cliff-forming sandstone and conglomerate. Includes an upper slope-forming transition zone of nearly equal distribution of brown sandstone of Tapeats Sandstone lithology and green siltstone and shale of Bright Angel Shale lithology, and a lower unit of cliff-forming sandstone and conglomeratic sandstone. Lower cliff unit consists mainly of medium- to coarse-grained, thin-bedded, low-angle planar and trough cross-bedded sandstone and conglomeratic sandstone; sandstone beds 6–24 in. (15–60 cm) thick. Unconformable contact with underlying Middle and Late Proterozoic surface that forms the Great Unconformity. The Tapeats fills in lowland areas and thins across or pinches out against young Proterozoic highlands. Variable thickness 0–400 ft (0–122 m)

I bolded a section in that description that describes how the Tapeats blends into the Bright Angel Shale and both materials are found in nearly equal proportions. Contrast this upper contact to the lower contact with the Vishnu and/or the Supergroup.

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 203 by Faith, posted 03-21-2015 3:53 AM Faith has not yet responded

  
herebedragons
Member
Posts: 1517
From: Michigan
Joined: 11-22-2009


Message 215 of 1939 (753672)
03-21-2015 3:45 PM
Reply to: Message 213 by Faith
03-21-2015 3:19 PM


Re: Erosion simply CANNOT explain the flat contact line
I understand your concern here. We have been over this before and without arguing over what "flat" means again, let me ask you a question...

Can you think of an example in our contemporary setting where the surface of the earth that is exposed to erosion is "flat?"

Remember that image that we went round and round about in the other thread (the one where you said it looks like the rock were lifted out of the Vishnu)? Remember how you said it doesn't look like it had even been subjected to erosion? And I pointed out that even though it may not "look like" it had been eroded, we knew for sure it was eroded. Sometimes our expectations of what geological features should "look like" is pretty subjective.

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 213 by Faith, posted 03-21-2015 3:19 PM Faith has responded

Replies to this message:
 Message 216 by Faith, posted 03-21-2015 3:54 PM herebedragons has responded

  
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