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Author Topic:   Exploring the Grand Canyon, from the bottom up.
jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 92 of 283 (296412)
03-17-2006 11:08 PM
Reply to: Message 91 by edge
03-17-2006 10:55 PM


Gotta go even slower for me.
Actually, the contact between the metamorphic Vishnu and the overlying Bass Limestone is a nonconformity, meaning the contact is a hiatus of deposition in which the underlying rocks have undergone a metamorphic event prior to erosion.
I'm still looking for some explanations I can understand.
...meaning the contact is a hiatus of deposition in which the underlying rocks have undergone a metamorphic event prior to erosion.
I asume that means a pause?
This brings a few more questions to mind.
How do you build enough pressure to turn sandstone into schist without piling stuff on top of it?

Aslan is not a Tame Lion

This message is a reply to:
 Message 91 by edge, posted 03-17-2006 10:55 PM edge has replied

Replies to this message:
 Message 94 by edge, posted 03-17-2006 11:23 PM jar has not replied

  
jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 95 of 283 (296415)
03-17-2006 11:28 PM


Need a short break to absorb...
all this stuff you folk are throwing at me. I'll try to post a summary of what I think you folk are saying in the morning.

Aslan is not a Tame Lion

Replies to this message:
 Message 96 by roxrkool, posted 03-17-2006 11:47 PM jar has replied

  
jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 98 of 283 (296476)
03-18-2006 12:36 PM
Reply to: Message 96 by roxrkool
03-17-2006 11:47 PM


Okay, trying another summary
Alright.
Let's see if I have a few first principles down correctly and then try to sum up where we are so far.
The process of making many small things out of fewer large things is erosion.
The products of erosion collect in places lower than the origin in most cases.
So what happens is that rocks get formed and pushed up. Rain, wind, heat and cold erode those rocks and the material collects in lower, realtively level areas.
So far so good?
Next, schist is sandstone that was changed due to heat, pressure and time.
Granite is the result of magma which changed form as it slowly cooled over time.
The two formations we have considered so far are the Vishnu Scist and the Zoroaster Granite. We can tell that the Vishnu Schist is older by several indicators. One is that the formations of the granite are ones that had to happen afterwards, to be intrusions, because they would have been unsupported if there hadn't been something to support them originally.
we can see an example of a granite intrusion here
or here
and the process specific to the Vishnu Schist here.
The 4 dimensions you are talking about are height, width, length and time.
Now for the summary.
We began with the Vishnu Schist because it is the lowest exposed layer. It is schist, so originally it was sandstone. To get sandstone there first had to be some higher rock source which was eroded, accumulated in a basin, was later compressed and metamorphed into schist.
So to this point, rock was created, eroded into smaller and smaller particles until we had sand, washed or blown downhill to collect in a basin, settled, compressed and over time, under pressure and heat became schist.
At sometime during this process, magama pushed through the sandstone or schist and over long periods of time cooled to become granite.
The whole structure, Vishnu Scist and Zoroaster Granite was pushed upward or the whole area was eroded down to where everything was at about the same level. We know this happened because accumulations of the sandstone stopped and the area began to erode. We know that because there is a non-conformity between the Vishnu Schist/Zoroaster Granite and the layers above them. Another indicator that that was what happened is that the Zoroaster Granite does not intrude into the layers above.
Is that a reasonable summary of the Grand Canyon so far?
And now a few other questions related to things mentioned. You good folk mention cross bedding, conglomerates and breccia.
From my limited knowledge, conglomerates and breccia both are simply groupings of other rocks that have changed into a single rock while crossbedding refers to changes in directions of what is being laid down or bending of existing layers.
I think it would be worthwhile to explore just what those mean and how they can be identified.
Is this an example of cross bedded sandstone? Can you explain what we see here and what it tells us?
Here is a picture of a conglomerate
and and one of breccia.
To the uneducated eye these seem to be very different formations. The conglomerate shows rounded stuff incorporated that must have going through considerable weathering and erosion before being cemented back together. The breccia on the other hand shows very angular stuff incorporated.
Can you explain what it is that we should be seeing in these pictures and what that tells us about the processes involved?

Aslan is not a Tame Lion

This message is a reply to:
 Message 96 by roxrkool, posted 03-17-2006 11:47 PM roxrkool has not replied

Replies to this message:
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jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 101 of 283 (296524)
03-18-2006 8:06 PM


Well, looks like we gotta pause again before...
we can get beyond these two levels. Moose and Roxrkool done said stuff this old man needs clarified.
I'm sorry if I'm holding you folk back but if I can't understand it there's the possibility that others may not as well.
First off you folk have mentioned weathering several times and you now bring in chemical and mechanical as types of weathering.
Can you explain what the difference is and how you tell which type weathering happened?
Next you say
da moose writes:
I think it was because the protolith was a clay rich variety of sandstone. It is the clay minerals that are metamorphosed into the micas that give the schist the property of schistosity.
So what be the property of schistosity?
Second, IIRC this is the first time clay has been mentioned.
Clay is very different than other dirts or sand. For one thing, I've never been able to see a clay particle. It doesn't seem to be just small rocks like sand. It feels different, sticky and when wet slippery. It also is different than sand in that as it dries out, it retains it's form and doesn't just crumple like an old sand castle.
So what is clay and how is it produced?
Now for a question on Granite. So fast cooling magma yield glass like material and the slower it cools the larger the crystal structure.
This is important because it gives something specific that can be seen and not just wild speculation as some creationists claim.
This message has been edited by jar, 03-18-2006 11:08 PM

Aslan is not a Tame Lion

Replies to this message:
 Message 102 by edge, posted 03-19-2006 1:08 PM jar has replied

  
jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 103 of 283 (296604)
03-19-2006 1:28 PM
Reply to: Message 102 by edge
03-19-2006 1:08 PM


Yep, I'm sure.
Thanks. You did use yet a few more new terms, platy or foliated. Would you say that these drawings are a reasonable illustration of those and why they form?
And are these useful examples of what geologists find when actually looking at the rocks? When you say glass like I assume you mean something like the sample in the lower left box while granier would refer to things like the one on the lower right.
One more question about clays. Clays seem to be very, very fine grained. Is that from reduction in size and weathering?

Aslan is not a Tame Lion

This message is a reply to:
 Message 102 by edge, posted 03-19-2006 1:08 PM edge has replied

Replies to this message:
 Message 104 by edge, posted 03-19-2006 1:58 PM jar has replied

  
jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 105 of 283 (296615)
03-19-2006 2:01 PM
Reply to: Message 104 by edge
03-19-2006 1:58 PM


still on clay
so where does clay come from? How is clay produced?

Aslan is not a Tame Lion

This message is a reply to:
 Message 104 by edge, posted 03-19-2006 1:58 PM edge has replied

Replies to this message:
 Message 106 by edge, posted 03-19-2006 5:50 PM jar has replied

  
jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 107 of 283 (296644)
03-19-2006 5:59 PM
Reply to: Message 106 by edge
03-19-2006 5:50 PM


Okay trying yet another final summary of the lowest two exposed layers.
Okay, great. So the proces that made our sand for the sandstone likely also produced the clay that went into making schist instead of quartzite.
So here is the layers to date.
Now for the summary.
We began with the Vishnu Schist because it is the lowest exposed layer. It is schist, so originally it was sandstone. To get sandstone there first had to be some higher rock source which was weathered, accumulated in a basin, was later compressed and metamorphed into schist. There was clay, which is also a product of weathering mixed in with the sand.
So to this point, rock was created, weathered into smaller and smaller particles until we had sand and clays, washed or blown downhill (eroded) to collect in a basin, settled, compressed and over time, under pressure and heat became schist.
At sometime during this process, magama pushed through the sandstone or schist and over long periods of time cooled to become granite.
The whole structure, Vishnu Scist and Zoroaster Granite was pushed upward or the whole area was eroded down to where everything was at about the same level. We know this happened because accumulations of the sandstone stopped and the area began to erode. We know that because there is a non-conformity between the Vishnu Schist/Zoroaster Granite and the layers above them. Another indicator that that was what happened is that the Zoroaster Granite does not intrude into the layers above.
Is that a reasonable summary of the Grand Canyon so far?

Aslan is not a Tame Lion

This message is a reply to:
 Message 106 by edge, posted 03-19-2006 5:50 PM edge has replied

Replies to this message:
 Message 108 by edge, posted 03-19-2006 6:46 PM jar has replied

  
jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 109 of 283 (296652)
03-19-2006 6:59 PM
Reply to: Message 108 by edge
03-19-2006 6:46 PM


Thanks and moving on.
You realize this will be a very long thread.
Yes it will be, may even need a continuation or two, but people like Walt Brown and Steve Austin like to keep it simple so that they can con folk out of good money to pay for worthless books and videos. I think it's important to take whatever time is needed to explain things.
So next up, the Houtata Conglomerate.
Roxrkool brought this up and ao I'd like to deal with it before the Bass Limestone layer.
Does anyone have any pictures or information on this layer?
What does "pinch out" mean?
Why would that be significant?

Aslan is not a Tame Lion

This message is a reply to:
 Message 108 by edge, posted 03-19-2006 6:46 PM edge has replied

Replies to this message:
 Message 110 by edge, posted 03-19-2006 7:19 PM jar has not replied

  
jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 112 of 283 (296769)
03-20-2006 10:23 AM


To the Bass Formation.
As we move on to the next layer, I have a few questions.
First, the article referenced says that there is a big chunk of material missing betwen the Vishnu Schist and the Bass Formation. Since it is not there, just what is the evdence that at one time something was there?
Second, the article says that the Bass Formation was created by an intruding and then retreating sea. It even provides the directionality of the event.
How is that determined? What evidence led to that conclusions?
Third, Roxrkool mentioned a layer pinching out. What does that mean and how are such things identified?

Aslan is not a Tame Lion

Replies to this message:
 Message 114 by edge, posted 03-20-2006 8:52 PM jar has not replied
 Message 115 by roxrkool, posted 03-20-2006 10:58 PM jar has replied

  
jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 116 of 283 (296972)
03-20-2006 11:17 PM
Reply to: Message 115 by roxrkool
03-20-2006 10:58 PM


Re: To the Bass Formation.
jar writes:
First, the article referenced says that there is a big chunk of material missing betwen the Vishnu Schist and the Bass Formation. Since it is not there, just what is the evdence that at one time something was there?
to which Roxrkool replied:
I'm not sure, but my guess is that it's simply an assumption based on the amount of time the disconformity represents - 500 million years.
Well, I'd sure like to get more than that.
First, the time period is something we're not dealing with yet and it certainly wasn't something that the people that decided that what was seen couldn't be explained under a Young Earth Concept would have known about.
So is the missing material a new concept that was added after the physical layering was determined and based on dating techniques? If so, then we can just move on for now.
Or is there, as edge implied, evidence that there should be something there? Are there other places where there is stuff between the Vishnu Scist and the Bass Layer?
AbE:
One more thing. Your drawing points to one more thing we haven't discussed yet. Between the Vishnu Schist and the Bass Formation it shows som Ash layers.
Okay, what is Ash and what does an Ash layer tell us?
This message has been edited by jar, 03-20-2006 10:25 PM

Aslan is not a Tame Lion

This message is a reply to:
 Message 115 by roxrkool, posted 03-20-2006 10:58 PM roxrkool has replied

Replies to this message:
 Message 117 by roxrkool, posted 03-21-2006 12:40 AM jar has not replied

  
jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 118 of 283 (297079)
03-21-2006 1:39 PM


Okay, trying a summary and see if we are ready to move on.
So let me summarize where we are at this point.
We began with the Vishnu Schist because it is the lowest exposed layer. It is schist, so originally it was sandstone. To get sandstone there first had to be some higher rock source which was weathered, accumulated in a basin, was later compressed and metamorphed into schist. There was clay, which is also a product of weathering mixed in with the sand.
So to this point, rock was created, weathered into smaller and smaller particles until we had sand and clays, washed or blown downhill (eroded) to collect in a basin, settled, compressed and over time, under pressure and heat became schist.
At sometime during this process, magama pushed through the sandstone or schist and over long periods of time cooled to become granite.
The whole structure, Vishnu Schist and Zoroaster Granite was pushed upward or the whole area was eroded down to where everything was at about the same level. We know this happened because accumulations of the sandstone stopped and the area began to erode. We know that because there is a non-conformity between the Vishnu Schist/Zoroaster Granite and the layers above them. Another indicator that that was what happened is that the Zoroaster Granite does not intrude into the layers above.
Then we began to look at the next level.
The Bass Formation is actually a a composite of several types of material including limestone, conglomerates, ash and other materials. At the very bottom of the Bass Formation is a layer of Ash. This would indicate a period of volcanic activity somewhere and the ash was brought in, likely by wind, and layered over the eroded surface of the Vishnu Schist.
One of the layers is the Houtata Conglomerate which again layers over the Vishnu Schist and likely simply filled eroded valleys in the Vishnu Schist and so is seen to be pinched out, or gradually disappear, in some areas. Conglomerates, as we learned earlier, are made up of rocks that have been worn down and weathered, have rounded edges, that are then cemented into some matrix under pressure, temperature and over time. We can see an example of a conglomerate here.
The important issues are that the Vishnu Schist being eroded at the top shows that biulding up had ceased. It was no longer accumulating things but was higher than the surrounding areas and so was wearing away.
The Bass Formation shows an intruding, and then a retreating sea. We can tell that by looking at the composition of the formation as we move from top to bottom as outlined in Message 115.
This means we see the land lowering to allow the sea in, and then later in the process gradually rising again to make the sea retreat.
Is this a reasonable summary of what we see so far?
This message has been edited by jar, 03-21-2006 03:33 PM

Aslan is not a Tame Lion

Replies to this message:
 Message 119 by Jazzns, posted 03-21-2006 4:09 PM jar has replied
 Message 124 by roxrkool, posted 03-21-2006 5:47 PM jar has replied

  
jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 120 of 283 (297099)
03-21-2006 4:20 PM
Reply to: Message 119 by Jazzns
03-21-2006 4:09 PM


Reasonable point
I agree that it's certainly a reasonable variation on the summary.
So...
for out geologists.
Is there something that could tell us whether what is seen in the Bass Formation is the result of changing land levels, changing sea levels, or some combination of both?

Aslan is not a Tame Lion

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 Message 119 by Jazzns, posted 03-21-2006 4:09 PM Jazzns has not replied

  
jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 122 of 283 (297106)
03-21-2006 5:05 PM
Reply to: Message 121 by Minnemooseus
03-21-2006 4:56 PM


Re: Cause of sea level changes and marine transgressions onto land
Thanks moose, and yes it could be a thread in and of itself. In this case though we are looking at one very specific incident.
In the case of the Bass Formation, is there any way we can tell what happened? If not, then we just include both possibilities.

Aslan is not a Tame Lion

This message is a reply to:
 Message 121 by Minnemooseus, posted 03-21-2006 4:56 PM Minnemooseus has not replied

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jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 125 of 283 (297128)
03-21-2006 6:57 PM
Reply to: Message 124 by roxrkool
03-21-2006 5:47 PM


Okay, summing the summary.
roxrkool writes:
So basically, the GC Supergroup transgressive-regressive sequences appear to be the result of tectonics.
So basically we can say that there is evidence that the Bass Formation and the other ones we will discuss in looking at the Grand Canyon Supergroup are the result of tectonics, the actual movement to the surface up, down, and as we will see once we get to the end of the Supergroup, side-toside and tilting.
And I stand corrected on the conglomerates and will correct that in the next summary.

Aslan is not a Tame Lion

This message is a reply to:
 Message 124 by roxrkool, posted 03-21-2006 5:47 PM roxrkool has not replied

  
jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 126 of 283 (297143)
03-21-2006 9:10 PM


Got yet another question for you.
A new term, two infact, came up in Roxrkools last post.
Horsts and Grabens.
From what I can find out they are the result of faulty, the Horst being the relatively upthrust body while the Graben is the relatively lowered one. Together they would form a series of hills and valleys bounded by fault lines.
It would seem that these are very indicative of tectonic activity.
Is this what is refered to in the discussion of the Bass Formation?
Is what is shown this page an explanation of Horsts and Grabens?
Finally, on the page referenced above there is an animation called Fold Trains in Ireland.
On the lower left of the picture I notice that many of the layers seem to be cut off at the overlay. Is this the kind of evidence that shows an Unconformity, that part of what was there is missing?

Aslan is not a Tame Lion

Replies to this message:
 Message 127 by edge, posted 03-21-2006 10:01 PM jar has replied
 Message 129 by roxrkool, posted 03-21-2006 10:22 PM jar has replied

  
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