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Author Topic:   How do geologist know what they are looking at really is what they say it is?
jar
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Posts: 28433
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.6


Message 61 of 88 (790768)
09-04-2016 7:34 PM
Reply to: Message 60 by edge
09-04-2016 6:15 PM


Re: landscapes come and landscapes go?
edge writes:

... from peat to lignite, to bituminous to anthracite and eventually to graphite.

And these different types are recognizable and each results from a different history and process?

Do the different types point to different initial origins or only to the formation process?


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

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Replies to this message:
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Pressie
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From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 1.8


Message 62 of 88 (790814)
09-06-2016 8:43 AM
Reply to: Message 61 by jar
09-04-2016 7:34 PM


Re: landscapes come and landscapes go?
jar writes:

And these different types are recognizable...

Yes. Ultimate and proximate analyses do it very efficiently. Classification.

jar writes:

... and each results from a different history and process?

Yes and no.

jar writes:

Do the different types point to different initial origins ...

Yes and no.

jar writes:

...or only to the formation process?

No. Lots of different processes.

I don't really understand why anyone would think that there's only one process involved in the formation of any rock.

Edited by Pressie, : No reason given.

Edited by Pressie, : No reason given.


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jar
Member
Posts: 28433
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.6


Message 63 of 88 (790816)
09-06-2016 8:48 AM
Reply to: Message 62 by Pressie
09-06-2016 8:43 AM


Re: landscapes come and landscapes go?
If we look at the different "coal" types as presented (peat to lignite, to bituminous to anthracite and eventually to graphite), what would be the original landscape that resulted in each final product and that process paths are involved in each?

Is part of the answer related to where in a series of processes the sample has completed?


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

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Pressie
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Posts: 1479
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 1.8


Message 64 of 88 (790817)
09-06-2016 8:51 AM
Reply to: Message 63 by jar
09-06-2016 8:48 AM


Re: landscapes come and landscapes go?
jar writes:

If we look at the different "coal" types as presented (peat to lignite, to bituminous to anthracite and eventually to graphite), what would be the original landscape that resulted in each final product and that process paths are involved in each?

"The" original landscape? There's not one 'original' landscape. Lots of different landscapes.
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jar
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Posts: 28433
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.6


Message 65 of 88 (790818)
09-06-2016 9:01 AM
Reply to: Message 64 by Pressie
09-06-2016 8:51 AM


Re: landscapes come and landscapes go?
Pressie writes:

jar writes:

If we look at the different "coal" types as presented (peat to lignite, to bituminous to anthracite and eventually to graphite), what would be the original landscape that resulted in each final product and that process paths are involved in each?

"The" original landscape? There's not one 'original' landscape. Lots of different landscapes.

Okay, but then can you walk us through the cycle from some surface landscape to each of the resulting coal types?


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

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edge
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Posts: 3711
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 1.7


Message 66 of 88 (790825)
09-06-2016 9:59 AM
Reply to: Message 61 by jar
09-04-2016 7:34 PM


Re: landscapes come and landscapes go?
Just to elaborate a little on Pressie's responses...

And these different types are recognizable ...

Yes, in fact a child could recognize the differences. However, there is a whole science behind coal analysis at the analytical level.

... and each results from a different history and process?

The degree of process is the most important factor. But again, it's not just simple burial, but other factors can contribute such as deformation.

Do the different types point to different initial origins or only to the formation process?

They can, but the primary difference is in the degree of post-burial processes.

When I went to school, there were entire laboratories dedicated to the detailed study of coal and numerous PhD's were cranked out over the years. This is not a trivial topic no matter how YECs present it.


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edge
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Posts: 3711
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 1.7


Message 67 of 88 (790826)
09-06-2016 10:15 AM
Reply to: Message 65 by jar
09-06-2016 9:01 AM


Re: landscapes come and landscapes go?
Okay, but then can you walk us through the cycle from some surface landscape to each of the resulting coal types?

Any time you can accumulate a pure organic sediment, you can ultimate end up with a coal bed.

Here is a peat deposit in the bogs of Northern Ireland.

There is almost no input of clastic material at this lcoation, just an ages long build up of organic debris. Even the streams in this immediate area have no rocks, sand, boulders, etc.

Just dead grasses, some animals and (once upon a time) trees and roots.

This material is, even today, harvested and used as fuel. In fact, that's why scotch tastes the smokey way it does.

Interestingly, there is sheep skull in the picture. While it is younger than the peat itself, geologically speaking, it is of the same age. With very little imagination, one could see it being buried eventually and become part of the geological record. However, since we see erosion occurring here, it's not too likely in this case.

Certainly, you can imagine other depositional settings, such as swamps or ponds. I understand that there are even some Precambrian coal deposits, though I'm not really sure how they formed, but basically, it's just 'pure' organic carbon residue.


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jar
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Posts: 28433
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.6


Message 68 of 88 (790828)
09-06-2016 10:47 AM
Reply to: Message 67 by edge
09-06-2016 10:15 AM


Spy vs Spy
Great information.

So in the Mad tradition of spy vs spy can we make a general statement that the various forms of coal products are more the result of processing than original source. All begin as marshy wetlands that remain marshy wetlands long enough for deep deposits of dead plant material to accumulate?

And for the other Spy, can we say chalk results from long term deposition of dead micro-organisms with calcite shells in moderately deep water while other forms of limestone result from different original environments?


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

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 Message 67 by edge, posted 09-06-2016 10:15 AM edge has responded

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edge
Member
Posts: 3711
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 1.7


Message 69 of 88 (790833)
09-06-2016 11:50 AM
Reply to: Message 68 by jar
09-06-2016 10:47 AM


Re: Spy vs Spy
So in the Mad tradition of spy vs spy can we make a general statement that the various forms of coal products are more the result of processing than original source. All begin as marshy wetlands that remain marshy wetlands long enough for deep deposits of dead plant material to accumulate?

And for the other Spy, can we say chalk results from long term deposition of dead micro-organisms with calcite shells in moderately deep water while other forms of limestone result from different original environments?


As a general rule.
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Pressie
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Posts: 1479
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 1.8


Message 70 of 88 (790867)
09-07-2016 8:03 AM
Reply to: Message 68 by jar
09-06-2016 10:47 AM


Re: Spy vs Spy
jar writes:

So in the Mad tradition of spy vs spy can we make a general statement that the various forms of coal products are more the result of processing than original source.

Not really. The processes are similar, but the original sources provide different products. In some circumstances leaves tend to be preserved better than branches to form coals later even undergoing similar processes.

In other circumstances branches tend to be preserved to form coal later. They produce different coal products.

Then there's also the bark and stuff like that; which also play a role.

Then also the species of plants growing, dying and getting preserved also play a role. Then depth of burial and modes of preservation and proximity to inflowing inorganic sources. etc. That's why Gondwana coals (Africa, Australia, India) differ so much in everything from northern hemisphere coals. Different plants, different time periods, different outcomes eventually.

Similar processes, though.

Gondwana anthracites have completely different properties than northern hemisphere anthracites, for example. The processes are similar, yet the original sources differ.


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jar
Member
Posts: 28433
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.6


Message 71 of 88 (790870)
09-07-2016 8:24 AM
Reply to: Message 70 by Pressie
09-07-2016 8:03 AM


Re: Spy vs Spy
So when the various types of coal that have been mentioned (peat to lignite, to bituminous to anthracite and eventually to graphite) so far are being considered...

Pressie writes:

The processes are similar, but the original sources provide different products. In some circumstances leaves tend to be preserved better than branches to form coals later even undergoing similar processes.

In other circumstances branches tend to be preserved to form coal later. They produce different coal products.

... which products or product would get produced in each situation; or. are you saying the the characteristics of bituminous coal (as one example) is different in the situations you mention. Is it a matter of specific chemical composition varying by source material?


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

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jar
Member
Posts: 28433
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.6


Message 72 of 88 (790890)
09-07-2016 12:20 PM


a short side trip to satisfy my curiosity.
I'd like to take a short side trip simply to satisfy a question that has haunted me since it was first brought to my attention many many moons ago.

The Rock of Gibraltar is a massive limestone deposit but strangely it seems to be upside down with the oldest rocks at the top and the youngest near the bottom.

?????????????

What is that story? How was that determined?


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Dr Adequate
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Posts: 15474
Joined: 07-20-2006
Member Rating: 3.9


Message 73 of 88 (790897)
09-07-2016 3:44 PM
Reply to: Message 72 by jar
09-07-2016 12:20 PM


Re: a short side trip to satisfy my curiosity.
It's the remains of part of a great big overturned fold. Here's a smaller one so you can see what's happening.


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 Message 72 by jar, posted 09-07-2016 12:20 PM jar has responded

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jar
Member
Posts: 28433
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.6


Message 74 of 88 (790900)
09-07-2016 4:30 PM
Reply to: Message 73 by Dr Adequate
09-07-2016 3:44 PM


Re: a short side trip to satisfy my curiosity.
But how was it determined that things were overturned?

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dwise1
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Posts: 2687
Joined: 05-02-2006
Member Rating: 3.3


Message 75 of 88 (790912)
09-07-2016 8:12 PM
Reply to: Message 74 by jar
09-07-2016 4:30 PM


Re: a short side trip to satisfy my curiosity.
But how was it determined that things were overturned?

Remembering back to something I read two or three decades ago, that is determined by the orientation of fossils and ephemeral markings contained within. There are a number of things that can only be buried top-side-up, so when you find them top-side-down then that would be an indication. Examples would include ripples on stream and lake/sea bottoms, animal tracks, plant root systems, animal burrows on the sea bottom. I seem to recall that trilobites normally get buried right-side-up.

The rock layers themselves can also offer evidence. Just that the layers are in the reverse order that you would expect from everywhere else they occur would be a clue that something may have happened. And layers that were formed by rapid depositation (ie, in a single depositation event) would be expected to exhibit a "peanut jar" distribution of materials with the larger particles on the bottom of the layer, since they would have settled out first, and graduating up to the finer particles which would have settled out last -- ie, actual hydrodynamic sorting. If you find a layer where that order is reversed, then that would be another clue. Or the upper surface of a surface lava flow oriented downwards. Etc.

Of course, you should verify all of that. As I said, I remember having read about that several years ago.


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