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Author Topic:   Origin of the Flood Layers
Admin
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Message 331 of 409 (753483)
03-20-2015 10:02 AM
Reply to: Message 284 by Faith
03-19-2015 12:56 PM


Moderator Clarification
Though this is a reply to Faith, I'm actually just trying to draw attention to what Faith has been trying to say about the shadows beneath the clasts. I've circled what Faith sees as depressions in the Vishnu Schist in the image. Faith believes that the clasts used to be down in those depressions and were somehow "sucked up" into the Tapeats:

Moving on, I think Faith asks a very relevant question here. It might be answered later on, I don't know, I have to read and respond to posts in order rather than jumping about:

If you are talking about the picture in Message 247, no, they look like veins of quartz in a wall of schist. If something caused the quartz to come out of their veins then they might look like clasts either lying on the schist or stuck in sandstone and not lying on anything.

This is the image Faith is referring to:

She wants to know how pieces of quartz broken off from the veins of quartz embedded within the Vishnu Schist came to be deposited atop the Vishnu Schist.


--Percy
EvC Forum Director

This message is a reply to:
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Replies to this message:
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Admin
Director
Posts: 12534
From: EvC Forum
Joined: 06-14-2002
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Message 332 of 409 (753484)
03-20-2015 10:07 AM
Reply to: Message 285 by Faith
03-19-2015 12:58 PM


Moderator Concern
Faith writes:

Yup, very adept at spieling the party line.

Again, please, not as a message's sole content. Also, consider how it looks. You're dismissing "examining, evaluating and appreciating converging lines of evidence" as the "party line" when it is actually just part of how anyone would want to approach the understanding of anything.


--Percy
EvC Forum Director

This message is a reply to:
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jar
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Message 333 of 409 (753485)
03-20-2015 10:07 AM
Reply to: Message 330 by Faith
03-20-2015 10:01 AM


Re: Formation of schist etc.
I realize that you are not interested in answering the question yet the fact remains, the Vishnu Schist exists and conventional geology does explain its origin and the process that formed it.

How was the material (quartz sand) that make up the Tapeats Sandstone created?

Note that the materials that make up the Vishnu Schist are much finer than the material that makes up the Tapeats Sandstone and remember what you learned about hydrological sorting.


Anyone so limited that they can only spell a word one way is severely handicapped!

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Admin
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Message 334 of 409 (753488)
03-20-2015 10:22 AM
Reply to: Message 292 by edge
03-19-2015 2:16 PM


Moderator Request
edge writes:

I have shown you where they came from. It doesn't look like this picture.

By the time I read this I no longer remembered what "this picture" is of. Posting the image again would have been very helpful, in many posts, not just yours.

Also, and I know I'm asking a lot, but I'm having a great deal of difficulty following your posts because of the brevity of the responses. I understand the desire to be economical in investing one's time given past history, but if you're going to participate then it's worth giving it your full effort. In for a penny in for a pound, as they say.


--Percy
EvC Forum Director

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JonF
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Message 335 of 409 (753489)
03-20-2015 10:26 AM
Reply to: Message 325 by Faith
03-20-2015 9:38 AM


Re: Let's Move Forward
But I'm not interested in arguing about it.

I.e. no depressions, no shrinkage, no pulling schists, but there must have been a fludde what done it.
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Admin
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Message 336 of 409 (753490)
03-20-2015 10:26 AM
Reply to: Message 293 by edge
03-19-2015 2:21 PM


edge writes:

I don't know what to tell you. I see continuous bedding in very soft sedimentary rocks that have been eroded into rather fanciful forms. In the foreground the bedding is vertical and in the distance it is tilted to the left.

Noting again that I'm reading and responding to posts in order and haven't read ahead to see if this issue has been resolved, I think Faith wants to understand how geology thinks the bedding came to be tilted so much as to be vertical in some places, i.e., 90° rotated from its original orientation.


--Percy
EvC Forum Director

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JonF
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Message 337 of 409 (753491)
03-20-2015 10:28 AM
Reply to: Message 323 by Admin
03-20-2015 9:21 AM


The smooth upper surface of the Tapeats does give it the appearance of having been a liquid that flowed into place.

Sure don't look like it tome. Pockmarked, ridges, a bedding plane that Edge pointed out, definitely rough front surface.

Edited by JonF, : No reason given.


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edge
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Message 338 of 409 (753492)
03-20-2015 10:31 AM
Reply to: Message 331 by Admin
03-20-2015 10:02 AM


Re: Moderator Clarification
Though this is a reply to Faith, I'm actually just trying to draw attention to what Faith has been trying to say about the shadows beneath the clasts. I've circled what Faith sees as depressions in the Vishnu Schist in the image. Faith believes that the clasts used to be down in those depressions and were somehow "sucked up" into the Tapeats:

Thank you for translating these questions.

First of all, the shadows are there partly because the quartz pegmatites protrude out from the rock face which is nearly vertical as shown in the image with the geologist. Light coming from above necessarily casts a shadow beneath the fragments.

Second, if the pegmatite pebbles have an original position in the schist as dikes and veins, they would not look like fragments positioned in little depressions (which just happen to be directly on top of the unconformity, by the way). But maybe this isnt' clear...

What if we put those fragments back into their depressions. Would they look like dikes and veins?

She wants to know how pieces of quartz broken off from the veins of quartz embedded within the Vishnu Schist came to be deposited atop the Vishnu Schist.

Probably much the same way as they would look as if they fell out of the cliff face shown and ended up in the river sediments below.

Does that help clarify things, because I'm not sure how to further explain it. The appearance of the fragments now is not in veins or dikes, and if they came from depressions in the schist surface that would not look like the veins or dikes either.

There may be some confusion here that the fragments are lying directly on the surface of the unconformity. This is not always the case. I believe there are some images out there showing pieces of the pegmatite farther up in the Tapeats, which is also something that we would expect.

I have looked far and wide to find an image where we might see a pegmatite dike running upward through the schist and terminating against the unconformity, and also showing a trail of pebbles spreading out along that erosional unconformity surface. Perhaps a drawing will suffice. Later.


This message is a reply to:
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Replies to this message:
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Admin
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Message 339 of 409 (753494)
03-20-2015 10:33 AM
Reply to: Message 303 by Faith
03-19-2015 10:08 PM


Moderator Info
Though I'm replying to Faith, I'm really just calling attention to something Faith believes that might be worth addressing. She indicates here her belief that rocks form by drying:

Faith writes:

So I figure the quartz chunks in the picture we are discussing would have been broken out of such a vein here too, with the aid of wet or drying sand that seems to have had a sticky quality to it, at least while it was drying and hardening which I've suggested it did while lying over the quartz vein, then gradually pulling pieces of the quartz with it as it dried and hardened more, shrinking and retracting from the position over the vein.


--Percy
EvC Forum Director

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Faith
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Message 340 of 409 (753495)
03-20-2015 10:35 AM


Hip hip ...
Just want to say Hooray for Percy, he may yet straighten us all out. I hope you have the time to get through the whole mess, Percy.
    
edge
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Message 341 of 409 (753496)
03-20-2015 10:35 AM
Reply to: Message 337 by JonF
03-20-2015 10:28 AM


Sure don't look like it tome. Pockmarked, ridges, a bedding plane that Edge pointed out, definitely rough front surface.

I agree. Perhaps to someone not familiar with rocks, it looks like a flow of taffy or something draped over the schist, but 'smooth' surfaces are fairly common in geology.

Now, if I crashed my bike on that surface and skidded a a few feet, I would probably not characterize the surface as 'smooth'...


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Faith
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Member Rating: 1.1


Message 342 of 409 (753497)
03-20-2015 10:36 AM
Reply to: Message 339 by Admin
03-20-2015 10:33 AM


Re: Moderator Info
Drying is a huge part of lithification, and others with some expertise have agreed on former threads, but I've never said it's the ONLY way rocks harden.
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 Message 339 by Admin, posted 03-20-2015 10:33 AM Admin has acknowledged this reply

    
edge
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From: Colorado, USA
Joined: 01-09-2002
Member Rating: 2.5


Message 343 of 409 (753498)
03-20-2015 10:43 AM
Reply to: Message 339 by Admin
03-20-2015 10:33 AM


Re: Moderator Info
Though I'm replying to Faith, I'm really just calling attention to something Faith believes that might be worth addressing. She indicates here her belief that rocks form by drying:

I read that post also, but couldn't, for the life of me, figure out what she means.

She talks about plucking out fragments of the dikes, but earlier suggested that they came from those 'depressions' in the schist.

If anything was 'sticky' at the time of deposition, it would be the schist. But, unfortunately for Faith, that would mean the the schist had been weathered at an erosional unconformity.

I'm waiting for clarification.


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JonF
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(1)
Message 344 of 409 (753499)
03-20-2015 10:47 AM
Reply to: Message 331 by Admin
03-20-2015 10:02 AM


Re: Moderator Clarification
Though this is a reply to Faith, I'm actually just trying to draw attention to what Faith has been trying to say about the shadows beneath the clasts.

I think everyone understands that. The shadows under the clasts look to me like shadows of the clasts, just like the shadow of th overhand to the left of the clasts. I see no indication whatsoever of depressions under the clasts.

I see the same flattish topography inside the shadows as outside. I don't see and "socket" from which the clast could be magically pulled. I see the same thing under the overhang shadow to the left as I see under the clasts.

Moving on, I think Faith asks a very relevant question here. It might be answered later on, I don't know, I have to read and respond to posts in order rather than jumping about:

If you are talking about the picture in Message 247, no, they look like veins of quartz in a wall of schist. If something caused the quartz to come out of their veins then they might look like clasts either lying on the schist or stuck in sandstone and not lying on anything.

What is the hardness of schist on the mohs hardness scale?

quote:
Schist is a composite material made up of a mixture of several minerals, each of which have different mohs hardness. Schist is made mostly of quartz (mohs 7) and feldspar (mohs 6) but also includes minerals such as chlorite (mohs 2) and hornblende (mohs 5). Schist has no real mohs hardness, but a composite of its constituents of approximately 6.

Seems to me that erosion of the material in which the very hard quartz is embedded it quite possible, probably rounding-off the quartz as we see in the pictures posted so many times, but not enough erosion to wear it away.


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 Message 331 by Admin, posted 03-20-2015 10:02 AM Admin has acknowledged this reply

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Faith
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From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.1


Message 345 of 409 (753500)
03-20-2015 11:01 AM
Reply to: Message 343 by edge
03-20-2015 10:43 AM


Re: Moderator Info
She talks about plucking out fragments of the dikes, but earlier suggested that they came from those 'depressions' in the schist.

That was when I thought the picture was on a much larger scale than it turns out to be, so that I interpreted the depression in front of the clasts as where a vein had been, and the clasts as fragments of that vein that had broken off and been lifted out when stuck in the sandstone. They clearly ARE stuck in the sandstone whatever else you want to say about them, AND they still look like they came out of that depression. The shape and size are right.

If anything was 'sticky' at the time of deposition, it would be the schist.

I figured the sandstone had to be sticky in some way because the clasts STUCK in it. Nothing mysterious here. They ARE stuck in it.

But, unfortunately for Faith, that would mean the the schist had been weathered at an erosional unconformity.

Again the true scale makes that schist only a few square inches instead of the square feet I'd originally thought it was. That small area simply does not look eroded, that was all I said.
]


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