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Author | Topic: Salt of the Earth (on salt domes and beds) | |||||||||||||||||||
jar Member (Idle past 393 days) Posts: 34026 From: Texas!! Joined: |
Still hoping for more info.
So far it really appears that there are many layers of salt, each one showing numerous individual layers, and each super grouping separated by some form of sandstone, all buried under thousands of feet of earth. From the pictures it really appears that there were a whole series of inundations, that then evaporated leaving the salt, later to be covered by earth. It looks like a very long term succession of events. Is that a reasonable assumption? Aslan is not a Tame Lion
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bluescat48 Member (Idle past 4189 days) Posts: 2347 From: United States Joined: |
It would appear that way.
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jar Member (Idle past 393 days) Posts: 34026 From: Texas!! Joined: |
Okay. Glad I'm catching on.
Now so far we have been mostly talking about the great salt deposits that underlie Detroit, but as mentioned the salt actually underlies much of the North East. Around Ithaca New York it looks like the salt bed is first hit at a depth of over 2000 feet and that there are seven separate beds that that vary in thickness up to 325 feet thick. In Southwestern NY the salt bed is found at a depth of over 3000 feet. In Northeastern Ohio the bed is about 150 feet thick and found at a depth of 1900 feet to 2800 feet.
source It seems there are several things that are needed to explain this. First, how to evaporate and deposit multiple layers of salt each from 100 to 300 feet thick. Second a model that explains this happening at least seven times, each separated by sufficient time to lay down rock between the beds. Third a model that will explain burying the beds under 1000 to 3000 feet of rock. Does that seem reasonable? Aslan is not a Tame Lion
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bluescat48 Member (Idle past 4189 days) Posts: 2347 From: United States Joined: |
obviously
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jar Member (Idle past 393 days) Posts: 34026 From: Texas!! Joined: |
I hope some of our oil folk will step up now as we move south to Texas.
In Texas we seem to have a large number of Salt Domes. From my admittedly uneducated perspective, Salt Domes seem to add an additional process. It looks to me that what is seen in salt domes is a process that starts as we saw in the Northern salt beds of salt being laid down by an evaporative process, over laid by rock formations, but then gradually moving, floating upwards. Is that the basic idea? Aslan is not a Tame Lion
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bluescat48 Member (Idle past 4189 days) Posts: 2347 From: United States Joined: |
Sculpting the Earth from Inside Out-Michael Gurnis 2001 Partial Quote:to determine whether downward flow of the mantle could have caused the dip near Denver, (Christopher) Beaumont teamed up with jerry Mitrovica, then a graduate student at the university of Toronto, and Gary T. Jarvis of York University in Toronto. They found that the sinking of North America during the Cretaceous could have been caused by a plate called the Farallon as it plunged into the mantle beneath the western coast of North America. Basing their conclusion on a computer model, the research team argued that the ancient plate thrust into the mantle nearly horizontally. As it began sinking, it created a downward flow in its wake that tugged North America low enough to allow the ocean to rush in. As the Farallon plate sank deeper, the power of its trailing wake decreased. the continent's tendency to float eventually won out. and North America resurfaced. When the Canadian researchers advanced their theory in 1989, The Farollon plate had long since vanished into the mantle, so its existance had only been inferred from geologic indications on the bottom of the Pacific ocean. At that time. no seismic images were of high enough resolution to delineate a structure as small as a sinking fragment of the sea floor. Then, in 1996, new images of the mantle changed everything. Stephan P. Grand of the University of Texas at Austin and Robert D. van der Hilst of M. I. T., seismologists from separate research groups, presented two images based on entirely different sets of seismic measurements. Both pictures showed virtually identical structures, especially the cold-mantle downdwellings associated with the sinking slabs of seafloor. The long-lost Farallon plate was prominent in the images as an arching slab 1,000 miles below the eastern coast of the U. S. This is one way that the ocean can flood the continent and then recede leaving the salt behind. Edited by bluescat48, : No reason given. Edited by bluescat48, : No reason given. Edited by bluescat48, : Correction of spelling
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jar Member (Idle past 393 days) Posts: 34026 From: Texas!! Joined: |
Okay, but not sure how any of that relates to the question of forming salt domes and specifically, the salt domes of Texas and the Gulf of Mexico.
Aslan is not a Tame Lion
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bluescat48 Member (Idle past 4189 days) Posts: 2347 From: United States Joined: |
It is referring to the uplift of the continent, after the inundation, just the initial cause not the full effect.
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jar Member (Idle past 393 days) Posts: 34026 From: Texas!! Joined: |
Okay, very interesting.
But I really want to find some information on the mechanics of salt domes. Aslan is not a Tame Lion
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jar Member (Idle past 393 days) Posts: 34026 From: Texas!! Joined: |
Sure could use some help on the mechanics of salt domes.
So far we have been looking at salt beds, and we have been able to figure out a few things. We can say they were caused by evaporation so the water needs to have been at the surface at the time. We can say that they are the result of multiple events because we can see the evidence of individual layers. We can see that in some of these events, after the bed consisting of many layer was laid down, something happened and the whole structure was covered by rock, and we can see that even this happened many times because we can see multiple salt beds separated by rock formations. Finally, in the case of the North East Salt beds, the whole collection of formations has been buried under thousands of feet of rock. But what about salt domes? What is the mechanism that transforms a salt bed to a salt dome? Aslan is not a Tame Lion |
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jar Member (Idle past 393 days) Posts: 34026 From: Texas!! Joined: |
Help!
Immigration has been a problem Since 1607!
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The Matt Member (Idle past 5541 days) Posts: 99 From: U.K. Joined: |
I can't tell you much, but the key seems to be the minerals having higher relative buoyancy than surrounding rocks causing them to rise. I'd imagine dissolution and recrystalisation has a hand in it also, but I'm just guessing there.
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jar Member (Idle past 393 days) Posts: 34026 From: Texas!! Joined: |
Still looking at the models that explain the salt beds and domes we see today.
Anyone so limited that they can only spell a word one way is severely handicapped!
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Coragyps Member (Idle past 734 days) Posts: 5553 From: Snyder, Texas, USA Joined: |
How did I miss this three years ago?
I have always understood that salt domes like those along the Texas coast are emplaced from flat evaporite deposits that are overlain by denser sediments. The salt's bouyancy and plasticity let it "float" up through the rock. There are domes in Iran that come to surface and even form "glaciers" of salt. (Lot's wife, anyone??) The strata near the Texas domes are pretty obviously broken from below - there have been about four zillion oil wells drilled into the edges of salt domes over around Beaumont, and well logs and seismic surveys mapped out the shapes pretty accurately several decades ago.
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jar Member (Idle past 393 days) Posts: 34026 From: Texas!! Joined: |
So question.
In the great salt beds we find thick layers that make up a bed separated by more rock and soil, as many as seven discrete beds each hundreds of feet thick and consisting of hundreds of individual layers all buried under another thousand feet or so of rock and soil. In the mappings of the salt domes do we find anything similar? Anyone so limited that they can only spell a word one way is severely handicapped!
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