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Author Topic:   The Story in the Rocks - Southwestern U.S.
edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 3 of 121 (775928)
01-06-2016 6:09 PM
Reply to: Message 1 by Tanypteryx
01-05-2016 8:55 PM


The formations in this photo are in north central Arizona along a stretch of Hwy 89, south of Navajo Bridge over the Colorado River and north of Cameron.

I think this valley may have had a number of layers volcanic ash-like material deposited that has been eroded leaving these short buttes that are composed of soft non-lithified material that almost looks like it is melting in the occasional summer rains.

(ABE: Looking in my Roadside Geology of Arizona I see this is the Chinle formation and it is volcanic ash.)

We have similar looking formations in Oregon around the John Day Fossil Beds.


These formations are indeed volcanic ash, now altered to smectite clays, such as the commonly known bentonite. It make devilish roads and trails, undrivable with the least amount of rain. Sticks to everything.

Here is a photo from the Bisti Badlands in NW New Mexico.

Sometimes flowing water will funnel into pipes that eventually flow out at lower elevations. This is has been called "pseudo-karst."

The first time I ran into that term was regarding some of those more bizarre badlands in China with bright colors and almost a layered, cotton-candy type of appearance. When the article called it karst, I freaked out until I realized that they meant pseudo-karst. In lots of these places, you can find bunch of petrified wood.


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edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(2)
Message 5 of 121 (776033)
01-07-2016 7:39 PM
Reply to: Message 4 by Tanypteryx
01-06-2016 7:18 PM


It seems to me that the way these formations erode shows what the strata of the Southwest would all look like if it was deposited by a flood only a few thousand years ago.

Well, possibly. They were certainly never lithified.

quote:
Is this material, bentonite, good for radiometric dating?

Yes, being potassic, they would be amenable to K-Ar methods. However, this article says that there are analytical errors. I haven't read it but it turns out that U-Pb and Ar-Ar on associated zircons and sanidine crystals give more reliable dates.

http://www.gov.mb.ca/iem/geo/field/roa13pdfs/GS-12.pdf

In oil exploration, bentonite helps form definitive marker beds in the stratigraphy because of the large amount of potassium that they contain. It is easily recognized by gamma ray detectors.

quote:
Are there components of the material that are water soluble?

Bentonite, being a smectitic clay can adsorb and release a large amount of cations which can change with the amount of water and whatever solutes it might contain. This may be part of the problem with dating bentonite directly.

quote:
Is there a way to tell if these deposits occurred in water or on dry land?

Good question. I think that the preservation of such large deposits would require some kind of transport into a basin since volcanic ash is so erodable. A big clue is the presence of other layered clastic sediments such as the sandstones that form the tops of the mesas that you see in some of the photos. There has certainly been plenty of water present in the ash layers as that is a component to the alteration of glass to clay. If the deposits were subaerial, they might be associated with some welded tuffs which would be much more resistant to weathering and erosion.

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edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 10 of 121 (777425)
01-30-2016 7:26 PM
Reply to: Message 9 by Tanypteryx
01-28-2016 11:13 PM


Re: The Kayenta Formation & Dinosaur Tracks
That way what I thought also.

Well, here are a couple of things that I found in a younger sandstone a year ago in NM.

This is petrified cannonball. Well, it could be...

Actually, it's a sandstone concretion formed by overgrowths of a center of cementation. They litter the ground in some places. A weak carbonate(?) cement grew outward from a 'seed' in concentric layers, most likely.

Here is a barite nodule from the same formation:


The growth pattern here is different in being radial rather than concentric. I'm not sure how the enclosing sediments were excluded from the nodule itself. It may have formed in mudstone.

This is an agglomeration of concretions from the same sandstone:


Again, it consists of cemented sandstone. Actually, the form is hollow and may have formed around a clay ball in sandstone.

I guess my point is that we find a lot of weird 'forms' in younger sandstone that has not been overly lithified and/or metamorphosed and you can compare them to common objects. I think that the objects you are seeing are things that formed early in the lithification process. It would be necessary to look at them in person and possibly break some rocks to really see what's going on.

I know that sometimes wet sands can actually liquefy and flow into the surrounding mudstones and claystones. Now, that's confusing...


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edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(2)
Message 11 of 121 (777477)
02-01-2016 7:53 PM


Just for fun:

Dinosaur (according to some) at the top of the Jurassic Entrada Formation, Colorado National Monument.


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edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(2)
Message 14 of 121 (779324)
03-03-2016 11:33 AM
Reply to: Message 13 by Tanypteryx
03-02-2016 7:15 PM


I do not understand the process involved with the lithification of sand dunes that preserves the cross-bedding pattern.

Sand dunes are manifest in the geologic record as large-scale cross-beds such as the ones in your pictures.

Lithification of Jurassic sandstone on the Colorado Plateau is pretty basic. It consists simply of weak cementation, mostly by calcium carbonate. In dry climates they can be preserved as positive topographic features. Even slight differences in the degree of cementation and/or fracturing can result in some of the spires and buttes that are common on the CP.


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edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 18 of 121 (779350)
03-03-2016 4:11 PM
Reply to: Message 16 by Tanypteryx
03-03-2016 2:54 PM


I thought the process that forms sandstone is as much a chemical process that forms a binding matrix as it is a physical process that applies a force to compact the sand.

It depends on your definition of 'rock'. But in general, yes, it takes some kind of binding material. However, I can imagine pressures high enough to begin melding like grains together. Sometimes you can get sand to cohere with just a little bit of surface tension from moisture, though I wouldn't really call that 'rock'.

If you google 'compressed sand' you can get some idea of how they make some building material and art media. However, in most cases, I think they still use some kind of a binder.

quote:
I wonder how much force it would take to compact sand into stone without melting it?

No idea.

quote:
I would think that modern explosives apply more force per area than a cannon shot. Bombing ranges all over Nevada should have noticeable evidence if compaction alone causes sandstone to form.

Well, if you had a pure sand deposit that might work. Problem is that most of the dirt out there has clay and organic material in it; and it's not exactly a controlled situation.

Let's just say that it's a process, and has several contributing factors such as time, heat, solutions and compression.

I can say that the Jurassic rocks are not that lithified compared to older rocks, but are somewhat more so than younger rocks. Some late Mesozoic sandstone and younger can be gouged with a fingernail, even in pristine samples.

Here is one of my favorite pictures of the Entrada Fromation on the north end of the Uncompahgre Uplift.

This is the Slick Rock member and just above it in the distance are the very flat beds called the 'board beds'. And above that is the Wanakah Formation, a series of mudstone and sandstone. The Entrada is an aquifer and also contains many of the uranium deposits in the area.


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edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 22 of 121 (779358)
03-03-2016 4:32 PM
Reply to: Message 21 by Dr Adequate
03-03-2016 4:24 PM


At any rate, it seems difficult to produce rock from pure sand simply by pressure until we reach pretty massive loads, and it is an ongoing process that takes time.

That is one reason why younger rocks are noticeably softer and recognizable as being younger in the field. Again, the rocks do talk.


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edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 26 of 121 (779388)
03-03-2016 8:00 PM
Reply to: Message 24 by Tanypteryx
03-03-2016 5:12 PM


That is a sweet shot. Is Mesa Vere a part of the same formation? It looks similar.

Actually, that is the Mesa Verde Supergroup formation know locally as the Cliff House Formation. It is quite a bit younger, late Cretaceous.

http://www.nps.gov/meve/planyourvisit/upload/geology_web.pdf

Do you know, is the uranium associated with zircon crystals or sand? The reason I ask is, for years I worked in the analytical lab of a zirconium refinery and one of the byproducts of extracting zirconium from zircon sand was uranium that had to be disposed of at a facility at the Hanford Nuclear reservation. I guess what I'm asking is what minerals contain the uranium?

The uranium comes in from elsewhere basically in groundwater that has passed through weathering igneous rocks.

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edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 27 of 121 (779539)
03-05-2016 12:54 PM
Reply to: Message 25 by Tanypteryx
03-03-2016 7:50 PM


Re: Back tracking a bit
This is looking south toward the dry alkali lake that you can barely see in the above shot. The vegetation where I am standing is lush because there is a small spring with water flowing in a stream for about 0.5 kilometers before disappearing. This is extreme desert at about 6,000 ft elevation. It is about 25 miles north of Death Valley.

Tall sage...

Hate the stuff.


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edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 30 of 121 (779565)
03-05-2016 8:17 PM
Reply to: Message 29 by Tanypteryx
03-05-2016 7:29 PM


Re: Hematite Nodules?
Somewhere I read about hematite (Fe2O3) nodules forming in sandstone that contains iron. I have not been able to find the source where I got that.

Could these black rocks be examples of that? This is the Navajo Sandstone in Snow Canyon, Utah again.

There are volcanic rocks overlying the sandstone close by so that may be what we can see here.


The rocks look like basalt and are pretty clearly transported. Not sure how, but they came from somewhere else.

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edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(2)
Message 31 of 121 (779774)
03-08-2016 10:10 AM
Reply to: Message 23 by Faith
03-03-2016 5:10 PM


Maybe, or perhaps they simply did not undergo the pressure and compaction of harder rocks.

I assure you that there are more exceptions than you can imagine, but the general rule still stands.

But sometimes they don't speak English, or you don't hear them right.

Of course they don't speak English. That's why we study them ... just like we would study any foreign language. And who would 'hear' them better? Someone who has studied them, or someone who reads creationist websites for information?

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edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(2)
Message 32 of 121 (780766)
03-20-2016 11:52 AM


A Testament to Erosion
Here is a close-up of gravel deposits on the west flank of the Panamint Range in California. They are derived from erosion of the rising Panamint Mountains which currently reach an elevation of over 3350m. On the other side of the range is Death Valley with a minimum elevation of -85m (that would be below sea level). Most of this elevation differential has occurred in the last 3 million years resulting in monumental erosion and huge gravel deposits such as this.

My point here is that, if you look at the next picture, you can see that the gravels themselves have been uplifted and, in turn, eroded into these steep arroyos. So if anyone has a problem with the effects of erosion go here and explain this...

In the second picture, you can see the Panamint Valley (yeah, not much out there) in the background and thick gravel deposits extending as 'spurs' out into the valley. In the very lower left there is a small outcrop of Precambrian basement rock.

These gravels were once at the elevation of the valley below and even now form (tilted) terraces that one can drive a vehicle on, if you can get across the treacherous gullies.

This is extremely remote and rugged country. Charles Manson hid out in this area for a while.


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edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 38 of 121 (781744)
04-07-2016 10:22 AM
Reply to: Message 37 by Faith
04-06-2016 8:42 PM


Re: A Testament to Erosion
I realize that brainwashing has damaged your ability to think, ...

Now, that's a good way to start a discussion.

... I spoke about the gravel heap and gave the opinion of any reasonable person that it wouldn't have taken millions of years.

Problem is that on one says that it took millions of years to produce that particular deposit.

This is one of the things that completely baffles me about the YEC understanding of geology. For some reason, they seem to think that rapid processes mean young ages.

For instance, I would think that the gravel deposit shown in my picture might have been deposited in hundreds to thousands of years ... a million years ago (actually, in this case, I think those particular gravels are younger, but I know of no dating).

Probably this flaw in reasoning has no impact on the YEC because old ages simply do not exist, are not possible and never will exist. It is a logic barrier. As I remember, Faith also believes that geology has 'ended' and the world is fixed in its present state.

And while I'm at it your photos of the Great Unconformity are quite nice and they also serve to prove your regurgitation of the Party Line about it ridiculous: The lower part of the formation is pretty much upright. Erosion would have eaten away at the indented parts of it and greatly increased them, knocked off a lot of the higher parts into those indentations, and in other words could not possibly, even if given the millions or billions of years allotted to it, ended up with the flat surface on which the Tapeats was later laid.

First of all you are giving us reasons why the surface tends to become planed off.

" ... knocked off a lot of the higher parts into those indentations..."

And in the second place, you are just plain wrong. The Tapeats was not deposited on a planar surface. As we have shown you before, there are 'islands' of Shinumo Quartzite around which the Tapeats was deposited. (Oh, I know ... it's all in the imaginations of brainwashed scientists...)

It would have been rough and lumpy and bumpy and most likely the upper surface besides being a nightmare of peaks and holes, would have followed no straight horizontal line as it apparently does.

Except that it doesn't.

At the very least sand would have flowed into the holes and indentations. This is wonderful evidence for my theory about how angular uncomformities form.

Which you should perhaps explain again, because that sounds exactly like erosion...

Thanks for the great shot that makes it so clear.

Well, it seem to be clearer to some than others.

Oh don't worry, I don't expect the brainwashed to understand anything I say. Carry on.

Ah, nothing like a parting insult to open up conversation.

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edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 41 of 121 (781767)
04-07-2016 1:53 PM
Reply to: Message 40 by Faith
04-07-2016 1:33 PM


Re: A Testament to Erosion
Yes, I was describing what erosion WOULD HAVE done, which would have made the neat flat deposition of the Tapeats impossible. There would not have been a flat surface or a horizontal surface. The sand would have filled in the gaps. But it didn't. The Tapeats sits on it so awfully neatly, straight and horizontal.

There is something here that I haven't noticed before. However, it is still a fallacy.

The material that fills in the depressions is not the same as what forms the depressions. That is, they would be part of the upper (younger) package of rocks even though they are derived from the lower. In detail, the the unconformity is irregular.

I have shown this picture before. What it shows is that the unconformity, the yellow line, is irregular and the sand filling in the low spots is actually considered part of the overlying package of rocks.

This particular picture is from the Death Valley area and shows an angular unconformity that looks (based on the base of the coarse-grained unit) to be planar and smooth. But it isn't really so.

Here is the old picture of Siccar Point, where the Great Unconformity can be seen to be irregular also.

It shows an irregular surface filled in by younger sediments with a very smooth and planar layering above. Note the blue section where a channel of coarser material has run across the finer. All sediments above the unconformity are basically the same material as what is below, probably with some contamination from other sources not in the area of the image. Once again this is an angular unconformity in which the upper sediments have also been tilted.


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edge
Member (Idle past 940 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 42 of 121 (781768)
04-07-2016 2:05 PM
Reply to: Message 35 by Tanypteryx
04-06-2016 8:22 PM


Re: Another testament to erosion
An unconformity is where there is a time gap where material has been eroded away and then later newer material is deposited. It was under water when the deposition occurred and above sea level when the erosion occurred.

I might add something here.

At an unconformity, we cannot tell when the erosion started, we can only tell when sedimentation resumed. A short period of erosion could conceivably remove many millions of years of deposition. So just looking at a picture, we cannot tell how long the erosion took place.


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