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Author Topic:   Exploring the Grand Canyon, from the bottom up.
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 230 of 283 (437236)
11-29-2007 11:25 AM
Reply to: Message 229 by JB1740
11-29-2007 8:44 AM


Now onward and upward.
No you did great.
That was very helpful.
The next formation is the Chuar Group. I gather that there are two main formations in this group and many layers.
What can you good folk tell us about this group?

Aslan is not a Tame Lion

This message is a reply to:
 Message 229 by JB1740, posted 11-29-2007 8:44 AM JB1740 has replied

Replies to this message:
 Message 231 by JB1740, posted 11-29-2007 11:45 AM jar has replied

  
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 232 of 283 (437257)
11-29-2007 12:30 PM
Reply to: Message 231 by JB1740
11-29-2007 11:45 AM


Re: Now onward and upward.
Again, the Proterozoic is way not my forte
That's fine since we are not dealing with any terms such as Proterozoic in this thread. We are just looking at the rocks themselves to see what they tell us.
So basically, the Chuar Group consists of about 1600 meters of clastic sediments (these are sedimentary rocks made of up of fragments of pre-existing rocks (e.g., sandstone)) that records some evidence of the breakup of Rodinia (I presume you've been talking about Rodinia--this is a supercontinent like the much later Pangea, where all major world landmasses were crushed together at low latitudes) and provides evidence of late Neoproterozoic life (apparently mostly things like stromatolites...not Ediacaran stuff).
Well, we are not touching on stuff like Pangea or Rodina or Ediacaran or Neoproterozoic so those kinda fall out.
BUT
clastic sediments is important.
We covered this earlier in the thread but I would like to try explaining it in my words just to see if I understand such things.
You recognize clastic sediments because they are made up of once existing rocks that have been further weathered, broken down into smaller pieces, transported somewhere else and reformed into another piece of rock.
The important thing to me in all that is that first it was necessary to weather and even earlier formation, transport, compact and raise the secondary rock formation, then weather, transport, compact and raise the next formation.
Basically clastic sedimentary rocks are second or more generations of reprocessed rocks. Is that correct?

Aslan is not a Tame Lion

This message is a reply to:
 Message 231 by JB1740, posted 11-29-2007 11:45 AM JB1740 has replied

Replies to this message:
 Message 233 by bluescat48, posted 11-29-2007 12:43 PM jar has replied
 Message 235 by JB1740, posted 11-29-2007 1:47 PM jar has not replied

  
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 234 of 283 (437260)
11-29-2007 12:54 PM
Reply to: Message 233 by bluescat48
11-29-2007 12:43 PM


Re: Now onward and upward.
Great.
Now JB said:
It records nearshore environments (so beaches, tidal flats and the like) and the life living in those environments. There is also evidence of major tectonic unrest (I'm presuming (I don't have this article on hand, but can dig it up quickly if needbe) that this evidence is interbedded deposits of more coarse clastics than one would expect to find in nearshore environments (maybe coarse sands and conglomerates with fragments that can be traced to paleohighlands) as well as the ash layers, which not only provide nice age control for the unit but also indicate that this was an tectonically active area at the time.
It appears from that that we are looking at a succession of events, nearshore but also times when it was deeper water. Also the mention of ash layers.
Does anyone of you good folk know the order of such things in the Chuar Group from bottom to top?

Aslan is not a Tame Lion

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 Message 233 by bluescat48, posted 11-29-2007 12:43 PM bluescat48 has not replied

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 Message 236 by JB1740, posted 11-29-2007 1:58 PM jar has replied

  
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 237 of 283 (437282)
11-29-2007 2:04 PM
Reply to: Message 236 by JB1740
11-29-2007 1:58 PM


Re: Now onward and upward.
The rock is mostly shale all the way through. The older unit is the underlying Galeros Formation. The younger unit is the Kwagunt Formation. The significant stuff from this abstract are that the rocks in the older Galeros are coarser than those of the Kwagunt (slightly higher energy) and are sourced to igneous and metamorphic rocks. The overlying stuff is more highly weathered and comes from different sources. There is ash all the way through. So, it is more the older stuff that is interpreted as being evidence of Rodinia's breakup. Sounds like there is inferred to be a lot of time separating the deposition of the two units...seems as though a lot of the older stuff weathered and redeposited into the Kwagunt Formation.
Great and I almost understand such stuff.
Now one more basics question.
Sorry if so much of this seems silly or self evident, but I want us to present the evidence in pretty much the same way that those seeing it for the first time might have approached it.
Generally transport is from a higher to lower location. So to weather a surface it has to be higher than where it deposits the weathered material. Is that generally true?

Aslan is not a Tame Lion

This message is a reply to:
 Message 236 by JB1740, posted 11-29-2007 1:58 PM JB1740 has replied

Replies to this message:
 Message 238 by JB1740, posted 11-29-2007 2:12 PM jar has replied
 Message 239 by JB1740, posted 11-29-2007 2:13 PM jar has not replied

  
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 240 of 283 (437391)
11-29-2007 9:12 PM
Reply to: Message 238 by JB1740
11-29-2007 2:12 PM


Re: Now onward and upward.
Great.
Next, the info you supplied said:
quote:
The significant stuff from this abstract are that the rocks in the older Galeros are coarser than those of the Kwagunt (slightly higher energy) and are sourced to igneous and metamorphic rocks.
So let me try to see if I understand some of what is seen.
We saw the Cardenas Lava Flows which shows an active environment where there are direct lava flows.
Later they get overladen by a formation first of fairly fine sedimentary materials then somewhat coarser ones, and now we see still another change.
One key thing is that this current formation, Galeros and the next higher, Kwagunt , require two things.
First instead of the somewhat slow sea or shore line environment of the Nankoweap, there needed to be some pretty active volcanism to create the igneous rocks that get weathered to make the Chuar group.
Second we seem to see two different transport mechanisms, a more active higher energy one that deposits only the larger material then followed by a slower less energetic period that deposits a smaller finer material.
At various times though throughout the time we see yet another event, volcanic activity but one that is mostly ash flow and not lava flow.
Is that reasonable so far?
Does that also mean that the lower, larger material likely came from a closer, steeper source and as that source was weathered down, away and back from the point of deposition, we see small material that has been transported further and thus more weathered? Also if we were seeing something being worn down, would we see the slope decrease with weathering and so slower, lower energy transport?

Aslan is not a Tame Lion

This message is a reply to:
 Message 238 by JB1740, posted 11-29-2007 2:12 PM JB1740 has replied

Replies to this message:
 Message 241 by JB1740, posted 12-03-2007 4:13 PM jar has replied

  
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 242 of 283 (438270)
12-03-2007 4:20 PM
Reply to: Message 241 by JB1740
12-03-2007 4:13 PM


Re: Now onward and upward.
This is probably true, but doesn't have to be (e.g., if there were preexisting igneous rocks in the Nankoweap or something, that could eliminate the need for active volcanism bewteen Nankoweap and Chuar time.
That makes sense.
What about the ash layers though? Is it common for a volcanic event to produce both ash and lava? Would each ash layer indicate a separate event? If so, I assume that there would be some time between such events to account for the intervening material?
Any chance you can help me over on Salt of the Earth (on salt domes and beds).

Aslan is not a Tame Lion

This message is a reply to:
 Message 241 by JB1740, posted 12-03-2007 4:13 PM JB1740 has replied

Replies to this message:
 Message 243 by JB1740, posted 12-03-2007 4:29 PM jar has replied

  
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 244 of 283 (438275)
12-03-2007 4:49 PM
Reply to: Message 243 by JB1740
12-03-2007 4:29 PM


Next up-Sixty Mile Formation.
Great. I think I understand all this so far.
The last formation in the Super Group is the Sixty Mile Formation and after that we can get to some of the fun stuff I am dying to understand.
I have heard that the makeup of the Sixty Mile formation is somewhat similar to the Chuar group but that it contains more breccias and other conglomerates.
What more can you tell us?

Aslan is not a Tame Lion

This message is a reply to:
 Message 243 by JB1740, posted 12-03-2007 4:29 PM JB1740 has not replied

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 Message 245 by RAZD, posted 07-04-2010 9:42 AM jar has not replied

  
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 246 of 283 (568098)
07-04-2010 10:13 AM


General message
Welcome to any new folk. Just a few points.
Before you jump in, please read through the thread. Yeah, I know that is a lot of messages but there is also a lot of information here.
We are going slow on purpose, step by step working our way up from the bottom of the Grand Canon.
So far we have just reached the Sixty Mile Formation in the Super group.
As mentioned in the OP...
quote:
I'd like for us to discuss the Grand Canyon, beginning with the lowest, oldest layers and then working up to the top, layer by layer. I'd like to see explanations for each layer, it's composition, the environment when it was created, and get questions about that layer answered before we move up to the next layer.

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

  
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 249 of 283 (610052)
03-25-2011 9:03 PM
Reply to: Message 248 by roxrkool
03-25-2011 8:51 PM


Re: Bump
Good to see you back and thanks rox. Sure need your help.
Here's where we are so far, just at the very bottom of the sixty-mile group. Any chance you can tell us about just the bottom layer of the sixty-mile group?

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

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 Message 248 by roxrkool, posted 03-25-2011 8:51 PM roxrkool has not replied

Replies to this message:
 Message 250 by RAZD, posted 09-14-2011 12:11 PM jar has replied

  
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


(1)
Message 251 of 283 (633492)
09-14-2011 12:22 PM
Reply to: Message 250 by RAZD
09-14-2011 12:11 PM


Re: Bump for any new GEOLOGISTS to help out ...
And I'd love it if the new folk began at the beginning and climbed up with us.

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

This message is a reply to:
 Message 250 by RAZD, posted 09-14-2011 12:11 PM RAZD has seen this message but not replied

Replies to this message:
 Message 252 by Chuck77, posted 09-15-2011 2:33 AM jar has replied

  
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


(2)
Message 253 of 283 (633639)
09-15-2011 8:53 AM
Reply to: Message 252 by Chuck77
09-15-2011 2:33 AM


Re: Bump for any new GEOLOGISTS to help out ...
All the material is still the same so if you could begin at the beginning and read through the posts on each layer it will help you. I know there is a lot of material there and that is why we are doing this slowly, one layer at a time.

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

This message is a reply to:
 Message 252 by Chuck77, posted 09-15-2011 2:33 AM Chuck77 has replied

Replies to this message:
 Message 254 by Chuck77, posted 09-17-2011 3:53 AM jar has replied

  
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


(1)
Message 255 of 283 (633932)
09-17-2011 8:33 AM
Reply to: Message 254 by Chuck77
09-17-2011 3:53 AM


Re: Bump for any new GEOLOGISTS to help out ...
The purpose of the thread is to avoid summing up the process.
Yes, this is a difficult thread and yes it is complicated, but it is also really, really important, particularly for you, to understand just what processes are involved in each one of the stages, each layer. Take your time and if possible, touch base with us as you climb up each layer. If you have questions feel free to ask, but remember, only one layer at a time and starting at the bottom.

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

This message is a reply to:
 Message 254 by Chuck77, posted 09-17-2011 3:53 AM Chuck77 has not replied

  
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


(1)
Message 257 of 283 (633944)
09-17-2011 11:16 AM
Reply to: Message 254 by Chuck77
09-17-2011 3:53 AM


Re: Bump for any new GEOLOGISTS to help out ...
Another one that might help is How to make Sand that starts at Message 1.

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

This message is a reply to:
 Message 254 by Chuck77, posted 09-17-2011 3:53 AM Chuck77 has not replied

  
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


(2)
Message 278 of 283 (842227)
10-28-2018 9:17 AM
Reply to: Message 270 by RAZD
10-27-2018 4:44 PM


Re: New Footprints ... in the sand ...
Come on RAZD; how can either of the imaginary floods detailed in the Bible erase real footprints?

My Sister's Website: Rose Hill Studios My Website: My Website

This message is a reply to:
 Message 270 by RAZD, posted 10-27-2018 4:44 PM RAZD has seen this message but not replied

  
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