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Author Topic:   The Story in the Rocks - Southwestern U.S.
edge
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Posts: 4002
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 2.7


Message 106 of 121 (782051)
04-14-2016 5:08 PM
Reply to: Message 105 by jar
04-14-2016 4:24 PM


If you have a specific issue I would be happy to address it.

Edited by edge, : No reason given.


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jar
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Posts: 29623
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.0


Message 107 of 121 (782054)
04-14-2016 8:46 PM
Reply to: Message 106 by edge
04-14-2016 5:08 PM


I'm simply looking for information.

You have said that there are layers of coal found between layers of volcanic ash and also layers of sandstone.

We saw pictures that show a layer of ash with sandstone above and below.

The topic is the story in the rock. Tell us the story (hopefully with actual pictures not drawings) that those rocks tell you?


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

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edge
Member
Posts: 4002
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 2.7


(2)
Message 108 of 121 (782089)
04-15-2016 3:11 PM
Reply to: Message 107 by jar
04-14-2016 8:46 PM


You have said that there are layers of coal found between layers of volcanic ash and also layers of sandstone.

Yes, let's just say that they are interbedded.

We can also see layers within the ash package, probably due to a number of factors such as multiple eruptions, amount of water present at deposition, degree of oxidation, contamination by silt, etc., etc.

We saw pictures that show a layer of ash with sandstone above and below.

In the picture of the Lee Ranch Mine that I showed you, there is a sequence of coal, sandstone and mudstone, without apparent ash layers. The idea is to imagine the same sequence expanded by a number of very thick ash deposits.

Note that I say 'deposits'. I'm pretty sure that some are 'ash fall', some are 'ash flow' and others are 'water lain' ash, or they are otherwise contaminated by silt and sand. Because the beds are so thick and continuous, I'd say that most of them were deposited in large basins, at least partly containing water. This would facilitate turning the glass to clay.

In this picture, you can see what they call 'popcorn' texture caused by dessication of bentonite on the land surface. If you look closely, it isn't very pure, but there is enough clay to make a distinctive surface. In rain storms this terrain is almost impossible to traverse.

Here is a clue as to what the environment looked like. In among the the clay beds there are petrified trees. While the ash altered to clay, the trees were replaced by silica and now weather out as petrified logs in the clay beds.

You can see some coal beds in the background.

The next picture shows interbedded sandstone, ash and coal in the Bisti Badlands. The basal clay is quite organic (dark gray) suggesting that it was a paleosoil of some kind, probably derived from the bentonite deposits.

The last picture is an image, again in the Bisti Badlands, of clinker where a coal seam has burned and fired the clay around it. The rock is now fragmental because the overlying rock has collapsed into the burning coal.

The topic is the story in the rock. Tell us the story (hopefully with actual pictures not drawings) that those rocks tell you?

The geology of volcanic rocks is very complex and rife with jargon suggesting all of the different combinations of deposition, alteration, age, fragment size, etc., etc. However, the types of rock we see in these places are pretty suggestive of large intermontane basins such as the Green River Basin which we have also discussed with respect to fossils. The accumulated a large amount of transported volcanic ash with successive forests and swamps between volcanic events.

Edited by edge, : No reason given.


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Tanypteryx
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Posts: 1590
From: Oregon, USA
Joined: 08-27-2006
Member Rating: 4.1


Message 109 of 121 (782092)
04-15-2016 4:54 PM
Reply to: Message 108 by edge
04-15-2016 3:11 PM


Wow, good information. The Bisti Badlands look like a spot I would like to visit. Straight south of Farmington.

I found some material at Wikipedia about these deposits.

This area was on the west shore of the Western Interior Seaway 70 million years. If I understand this correctly the an ancient river delta left deposit 430 m thick after the seaway dried up.

It seems to me that the alternating nature of these layers between obviously forming in the seaway and above sea level, over long periods of time, including the burning of some of the lignite coal layers is support for the explanation that geological science gives us and is direct evidence against a recent global flood.

I would expect that since some of these deposits form on a river delta we should see some of the type of layering described by Walther's Law.


What if Eleanor Roosevelt had wings? -- Monty Python

One important characteristic of a theory is that is has survived repeated attempts to falsify it. Contrary to your understanding, all available evidence confirms it. --Subbie

If evolution is shown to be false, it will be at the hands of things that are true, not made up. --percy


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jar
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Posts: 29623
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.0


Message 110 of 121 (782094)
04-15-2016 7:30 PM
Reply to: Message 108 by edge
04-15-2016 3:11 PM


You mention a coal seam burned. Is there evidence to show that the coal seam was buried when burned and not simply a wild fire?

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

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edge
Member
Posts: 4002
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 2.7


Message 111 of 121 (782096)
04-15-2016 10:39 PM
Reply to: Message 110 by jar
04-15-2016 7:30 PM


You mention a coal seam burned. Is there evidence to show that the coal seam was buried when burned and not simply a wild fire?

The best evidence is that the roof rocks are also baked and that they collapsed into the burning seam. These fires are extremely hot and virtually impossible to extinguish. They burn today in many coal fields.
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petrophysics1
Inactive Member


Message 112 of 121 (782101)
04-16-2016 8:43 AM
Reply to: Message 110 by jar
04-15-2016 7:30 PM


Yes, the clay both above and below the clinker are fired. This clay looks like ceramic, looks like busted up pieces of your coffee cup. So the organic debris was buried, covered with sediments, turned to coal through compaction and de-watering, and then started on fire and fired the surrounding sediments.

How did it start on fire? Well coal and organic material create a chemically reducing environment. If Fe and S are present pyrite forms. It is not unusual to find coals with very finely disseminated pyrite in them. Can be abundant but still so fine I need a 30-45X scope to identify the pyrite.

Now if this coal is uplifted, and put into a position where it is above the water table and and subject to infiltration by meteoric waters the pyrite will rust/oxidize. It is actually burning very slowly(oxidizing) and the heat builds up until the coal spontaneously com-busts and is now burning underground.

There is a burning coal on the north side of Rocky Flats south of the city of Boulder, Co.. It is within 10 ft. of the surface and where the combustion gases vent at the outcrop it has it's own little ecosystem. It is warm and damp year round and the assortment of bugs living there can't be found anywhere around there especially during the winter.


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jar
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Posts: 29623
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.0


Message 113 of 121 (782102)
04-16-2016 9:17 AM
Reply to: Message 111 by edge
04-15-2016 10:39 PM


So just to check.

There is a layer of sandstone.

Then there a layer of volcanic ash that is many meters deep.

Then a layer of clay or mudstone.

Then a layer that was once a marsh or bog over the volcanic ask that was later covered by another volcanic ash flow and the bog or marsh material compressed and turned into coal.

Clay that was above and below the coal layer was later baked by a coal seam fire.

There are additional layers of Sandstone, volcanic ash, shale or mudstone above the coal seams and in repeated iterations.

And finally there is sandstone at the current surface.

If that is correct, how did the sandstone instead of soil or marsh or bog or woodland like we see when we walk around today get to be the current surface?


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

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 Message 111 by edge, posted 04-15-2016 10:39 PM edge has responded

Replies to this message:
 Message 114 by edge, posted 04-16-2016 3:29 PM jar has responded

  
edge
Member
Posts: 4002
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 2.7


Message 114 of 121 (782110)
04-16-2016 3:29 PM
Reply to: Message 113 by jar
04-16-2016 9:17 AM


There is a layer of sandstone.

Then there a layer of volcanic ash that is many meters deep.

Then a layer of clay or mudstone.

Then a layer that was once a marsh or bog over the volcanic ask that was later covered by another volcanic ash flow and the bog or marsh material compressed and turned into coal.

In a word, yes. The order and timing and thickness vary.

Clay that was above and below the coal layer was later baked by a coal seam fire.

Well, not everywhere, but yes, that is a possibility. Remember you were asking how we know about layers in the ash. The burnt coal beds are often a bright red, creating very distinct layers.

As petrophysics has mentioned oxidizing pyrite or other iron sulfide can oxidize rapidly enough to actually ignite a coal bed. In other cases, when there is uplift of the basin followed by erosion, the coal can be exposed to lightning or wildfires. Some of the modern fires are man-made.

The result is an odd looking formation that we call 'clinker'. And as petrophysics mentioned it does look very like a crushed coffee cup glued into an unrecognizable mass.

Along the North Fork of the Gunnison River east of Paonia you can see a normal looking sedimentary sequence, but notice very extensive, thin layers of red rock that just don't make sense. Then you realize that you are in coal country.

And finally there is sandstone at the current surface. If that is correct, how did the sandstone instead of soil or marsh or bog or woodland like we see when we walk around today get to be the current surface?

Well, not necessarily, but sandstone, being more resistant to erosion would tend to protect whatever is beneath it.

Here is a hoodoo showing how a cap rock of sandstone can resist erosion from above and protect a column of mudstone or ash below it.

Just as an aside to petrophysics, once I drilled an exploratory hole for coal and intercepted a vertical marcasite vein about the width of the core. You can imagine picking up that box after drilling a bunch of coal...

Edited by edge, : No reason given.


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jar
Member
Posts: 29623
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.0


Message 115 of 121 (782111)
04-16-2016 3:50 PM
Reply to: Message 114 by edge
04-16-2016 3:29 PM


edge writes:

jar writes:

And finally there is sandstone at the current surface. If that is correct, how did the sandstone instead of soil or marsh or bog or woodland like we see when we walk around today get to be the current surface?


Well, not necessarily, but sandstone, being more resistant to erosion would tend to protect whatever is beneath it.

Here is a hoodoo showing how a cap rock of sandstone can resist erosion from above and protect a column of mudstone or ash below it.

I understand that but how can sandstone be the top layer instead of the soil and dirt and loam and sand and pebbles be a top layer?

Can sandstone form at a topmost layer or the surface?

Edited by jar, : fix attribution edge not edfe


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

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 Message 114 by edge, posted 04-16-2016 3:29 PM edge has responded

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edge
Member
Posts: 4002
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 2.7


Message 116 of 121 (782113)
04-16-2016 4:13 PM
Reply to: Message 115 by jar
04-16-2016 3:50 PM


I understand that but how can sandstone be the top layer instead of the soil and dirt and loam and sand and pebbles be a top layer?

Because sandstone, being composed largely of quartz grains does not alter to weaker material like clay. And being cemented by either silica or carbonate, it is more resistant to weathering.

Now, if you developed a modern soil, of course, that would be at the surface. I don't think that any of the places we are talking about have soil.

Can sandstone form at a topmost layer or the surface?

Not sure. I doubt it. In some places they turn compacted sand into building material, but I know of no true rock unless it was somehow cemented by silica from a hot springs deposit or something like that.

Edited by edge, : No reason given.


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edge
Member
Posts: 4002
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 2.7


Message 117 of 121 (782454)
04-23-2016 4:38 PM
Reply to: Message 115 by jar
04-16-2016 3:50 PM


Can sandstone form at a topmost layer or the surface?

As I mentioned earlier, I'm not sure that it happens, but here is a landslide debris deposit that has been cemented by travertine (a carbonate) that has permeated the debris, and can now be considered a new rock, and it is certainly at the surface.

It would not be hard to imagine a sandstone forming this way, but I haven't found any references.


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edge
Member
Posts: 4002
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 2.7


(2)
Message 118 of 121 (786222)
06-19-2016 12:05 AM


Yes, this is a little off-topic, but I thought I'd relate some reading that I've done lately.

This summer is the 200th anniversary of the writing of Frankenstein by Mary Shelley. That year (1816) was known as the is known as the 'Year without Summer' because of the eruption of Tambora in April of the year before. It turns out that she was cavorting around a lake in Switzerland with Percy Bysshe Shelley and Lord Byron, among others, but the weather was so disagreeable that they couldn't enjoy the weather so they sat around campfires and told ghost stories. Well, they decided to see who could write the best horror story as a kind of game. At the age of 18, she composed the story of Frankenstein and his monster. The rest is history.

I post this simply to show that the earth has not only dictated the evolution of our species, but also has affected our culture in more recent times.


  
Tanypteryx
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Posts: 1590
From: Oregon, USA
Joined: 08-27-2006
Member Rating: 4.1


Message 119 of 121 (786743)
06-26-2016 2:25 PM


Unconformities?
Can an unconformity be easily identified as anywhere where both level and tilted strata are exposed?

These first two shots were taken along Hwy 26 in Wyoming, following the Wind River, west of Shoshone. I wasn't sure whether it is better to post this here or in the Road Trip - Dragonflies - Photography - Geology thread.....

N43.5787481 W109.7755929

One thing I noticed on this road trip was that there are huge (covering a large area), often thick layers of volcanic ash that is being exposed by erosion throughout the western U.S. These deposits are sandwiched between other sedimentary layers, so they should make radiometric dating relatively easy at many locations.

I had no idea that these igneous deposits were so common. The implications are that they must be from truly massive eruptions that blanketed huge swaths of territory with deposits many meters deep. Eruptions on this scale are unprecedented in human history.

Further west along Hwy 26 is another example that I assume shows several unconformities. N43.7236648 W110.0423707

One thing that is clear (to me) in these images is that the strata were not deposited in nice, level, flat, evenly thick layers. The deposition surfaces were often tilted and uplifted and eroded between deposition events or periods and this process is continuing today.

Edited by Tanypteryx, : Fixed clumsy wording


What if Eleanor Roosevelt had wings? -- Monty Python

One important characteristic of a theory is that is has survived repeated attempts to falsify it. Contrary to your understanding, all available evidence confirms it. --Subbie

If evolution is shown to be false, it will be at the hands of things that are true, not made up. --percy


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Minnemooseus
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Posts: 3562
From: Duluth, Minnesota, U.S. (West end of Lake Superior)
Joined: 11-11-2001
Member Rating: 4.2


(1)
Message 120 of 121 (786815)
06-27-2016 5:59 PM
Reply to: Message 119 by Tanypteryx
06-26-2016 2:25 PM


Re: Unconformities?
Just because you see tilted rocks and (apparently) flat lying rocks in the same view doesn't automatically mean angular unconformity. You might, for example, be seeing a tilted limb of an anticline in the foreground and the flat lying crest of the same anticline in the distance. I think you need to see more detail to make a judgement.

Also, topography/perspectives can create illusions. You can look at a rock face and the bedding may appear to be flat, when it is indeed dipping steeply. This is the difference between apparent dip and true dip.

I've been through that area of Wyoming, albeit 20+ years ago. I think you MIGHT have an example of a monocline there.

Moose


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