Exploring the Grand Canyon, from the bottom up.

Yep, except: 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. More than likely yes.

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).

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Aslan is not a Tame Lion

No, you're totally right. Volcanoes tend to do one or the other and those require active (duh...) volcanism. I was saying (poorly) that it is possible that you could have an older igneous source weathering to produce the sediment in the lower Chuar that might NOT be related to the activity producing the periodic ash layers. It is a more complicated explanation than necessary but nature does tell Occam to piss off on occasion. I wasn't talking about the ash layers right there but that probably wasn't clear. Yes Yep...exactly. You're a quick study. Hah...you caught me. I've been ignoring that one for the time being because whereas I know a bit about salt deposition, I don't remember all that much detail about salt domes and salt tectonics. I've got an old book that has some stuff on salt tectonics but I haven't been able to put my hand on it. So, the answer to your question is probably...but give me a bit to see what I remember/can find.

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?

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Aslan is not a Tame Lion

Welcome back Jar,This thread has been so wonderfully kept on track that it is a shame to let it slide. I believe a number of the geologists that have provided such valuable input on this topic are still around (perhaps hiding in the wings waiting for a good geology topic).Can someone pick up the dialogue at this point?Enjoy.

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we are limited in our ability to understand
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Rebel American Zen Deist
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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:

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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.

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

This was such an important and useful thread. I would really like to see it continue. If Jar can find a geologist to work off of (Maybe Rox will come back in and help)

Oh I would love to!It's just that when I was able to contribute before, I had access to a lot of literature and a lot more time -- writing these posts can be quite time-consuming -- and these days I'm pretty limited with both. I'll see what I can do. I really enjoyed it and also learned a lot. This is one of my favorite threads. And I'm happy to see jar is back.

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?

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

This is a great thread, and I'd like to see some more progress from the bottom layers.

And I'd love it if the new folk began at the beginning and climbed up with us.

This seems cool. Are you guys starting over again or should I catch up?

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.

Ok, I should be ready by Christmas. My brain hurts from reading this complicated thread but am interested in participating.Can you and RAZD maybe find a few good posts that sum up the thread so far that would bring me up to speed? If not i'll just lurk for a while.

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.