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Author Topic:   Geology- working up from basic principles.
edge
Member
Posts: 4607
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.5


Message 151 of 156 (542934)
01-13-2010 10:55 PM
Reply to: Message 150 by RAZD
01-13-2010 6:58 PM


Re: Sanity Check
So if I understand correctly ....

As the sea level rises (or land subsides) specific areas can transition from land to swamp to shore to shallow marine to deep marine - these geological "habitats" move horizontally with the shoreline.

Same in reverse when sea level falls (or land rises), and once again the geological "habitats" move horizontally but in the other direction.

In each case the geological "habitats" can leave sediment deposits characteristic of their "habitat."

So you get a "swamp" layer that is from different timelines as the shoreline moves in and out, and it cuts diagonally through the timelines of the deposits at different elevations in different areas, but we still see sediment deposited on top of what was there.


In general, the change of depositional environment will happen relatively rapidly if the paleoslope is gentle. In such a case, the lithostrat unit approaches identity with the chronostratigraphy.

And I'll stop there in case I'm way off base.

For the purposes of this discussion you are on target.
This message is a reply to:
 Message 150 by RAZD, posted 01-13-2010 6:58 PM RAZD has acknowledged this reply

  
petrophysics1
Inactive Member


Message 152 of 156 (542985)
01-14-2010 9:25 AM
Reply to: Message 150 by RAZD
01-13-2010 6:58 PM


Re: Sanity Check & Layer Cake Stratigraphy
In each case the geological "habitats" can leave sediment deposits characteristic of their "habitat."

So you get a "swamp" layer that is from different timelines as the shoreline moves in and out, and it cuts diagonally through the timelines of the deposits at different elevations in different areas, but we still see sediment deposited on top of what was there.

And I'll stop there in case I'm way off base.

Now you are getting the idea. It took me a while to find the following slide show, it is excellent. I found it googling "layer cake stratigrahy" a kind of derogatory term used by sedimentary geologists.

It is only 27 slides and you go through left clicking your mouse. Pay careful attention to the rocks and depositional environments ("geologic habitats") shown in the 3 d diagrams. when you get to slide 10, pay careful attention to the bottom where you see the formation boundaries and the time lines.

www.geology.wmich.edu/barnes/geos435/18_G435.pps

You might find this short article of interest as well.

http://clasticdetritus.com/...ptions-layer-cake-stratigraphy

Or this quote from Tanner (Geology Department, Florida State University

“The deposits of the past were not laid down in uniform sheets like a giant layer cake, or, for the earth as a whole, like a giant onion.”

http://www.asa3.org/ASA/PSCF/1996/PSCF3-96Tanner.html
this article is a bit involved for a beginner

You asked our YEC friend to show you somewhere in the real world where that experimental flume deposition occured. Have a look at the Gilbert deltas in Maine. Foreset/crossbeds from 10-25 degrees deposited in water. Check the photos out.

I also know where an excellent one is near McCoy, Colorado. I'm going through there in a few days. I get some pictures.

http://www.maine.gov/...gs/explore/surficial/facts/dec03.htm

Perhaps an off topic comment unless you consider applying geology and discovering new things to be on topic.

I look for and find unknown and undiscovered oil and gas deposits, which of course have no objective verifiable evidence of their existence. If they did they wouldn't be unknown and undiscovered.

So let's do this. First we will read all of the scientific geologic literature and look at the data in an area. Now the papers present a model which explains all of the objective verifiable evidence.

However, I have a belief that the model is probably not complete. So I am going to add "chocolate sprinkles" to the model in the form of an unknown oil and gas deposit which I believe exists.

Now I am going to drill a well on this prospect to see if I'm correct. If I am, we make lots of money, if I'm wrong we don't. Either way I have contributed to the scientific knowledge of the area.

Let's suppose instead we had this attitude, "I don't see any reason to believe in the existence of something for which there is no objective verifiable evidence". All drilling comes to a stop, and so does the expansion of geologic knowledge.

Hey RAZD does any of this ring a bell?

Edited by petrophysics1, : No reason given.

Edited by petrophysics1, : typos

Edited by petrophysics1, : another typo


This message is a reply to:
 Message 150 by RAZD, posted 01-13-2010 6:58 PM RAZD has responded

Replies to this message:
 Message 153 by RAZD, posted 01-14-2010 9:33 PM petrophysics1 has not yet responded

  
RAZD
Member
Posts: 19884
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 5.6


Message 153 of 156 (543047)
01-14-2010 9:33 PM
Reply to: Message 152 by petrophysics1
01-14-2010 9:25 AM


The Core Issue with the Law of Superposition
Thanks Petrophysics1 and edge

Now you are getting the idea. ...

Message 151 For the purposes of this discussion you are on target.

So if we focus on a single point and go down through the layers, then - barring some mechanism that mixes up the deposition process (like earth quake faults) - the layers lower are older than upper layers.

If we take a core at any one location, the horizontal sample size is so small that it will be similar to a line going down from recent to old to ancient.

If we take another core a mile away, we get the same relative relationship of the layers from young top to old bottom. We may also see similar layers to the first core, but at different elevations, and possibly (probably?) from different timelines.

Timelines in cores could consist of volcanic ash deposits, as there are distinct "signatures" in the ash for particular eruptions and they do "fall from the sky" at the same time over wide areas.

Message 137: ... I consult for them in the Jonah gas field in west central Wyoming, Green River Basin. ...

One of the things I noticed in this article on the Green River Varves:

http://www.indiana.edu/~ensiweb/lessons/varve.ev.pdf (click here if fails to load)

quote:
The laminations in Green River oil shale consist of pairs of laminae, one being richer in organic matter than the other. ... The richest grades of oil shale are characterized by the thinnest laminae because the organic matter compresses more than the mineral fraction of the rock during burial.

Bradley also notes that larger-scale variations displayed by these laminated rocks suggest correlations with astronomical cycles including the 11-year sunspot cycle and the 21thousand-year eccentric orbital cycle of the earth which lends further evidence that the paired laminae are indeed varves, or annual units of sedimentation. Units of laminated oil shale are laterally very persistent. Individual laminae within certain units of oil shale have be correlated in drill cores over distances of 100 kilometers.


So in this one case we have (a) a strong horizontal pattern, and (b) a cyclic pattern matching the solar cycle. The latter being of interest in terms of correlations of age dating systems (see Age Correlations and An Old Earth, Version 2 No 1). The long term seasonal variations could be another correlation to add to that thread (although I may need to use other "rhythmites" with strong seasonal evidence, such as pollen.

I would think these 11-year cycle correlations could make it easier to track the oil rich layers.

But this is getting off the topic - the law of superposition. I think it has been fairly well demonstrated that no matter the horizontal pattern, that the vertical pattern still demonstrates the validity of the law of superposition.

You asked our YEC friend to show you somewhere in the real world where that experimental flume deposition occured. Have a look at the Gilbert deltas in Maine. Foreset/crossbeds from 10-25 degrees deposited in water. Check the photos out.
http://www.maine.gov/...gs/explore/surficial/facts/dec03.htm

quote:
Sediments that were carried all the way to the front of the delta cascaded down into deeper waters, forming the sloping foreset beds on the delta front. The foresets are inclined in the general direction of sediment transport and delta growth, and are typically composed of sand or mixed sand and gravel (Figures 7 and 8).

Figure 8. Close-up of foreset beds in marine delta south of Erskine Academy, South China, Maine.

And I would (previously) have assumed that the layers were tilted after formation instead of formed at these angles with the sediment running (pouring?) downslope as the delta formed. So those layers could be older to the left and younger to the right, even though the right end is lower than the left end?

So the law of superposition holds for any vertical core through those deposits, but the timeline\age will be different for the same depositional environments ("geologic habitats") for a core 5 or 10 feet to the right.

Maine low bush blueberries, yum. Lived in Castine ME for a (too short) while. Cool stuff.

Hey RAZD does any of this ring a bell?

Heh. Using subjective evidence and guessing ... making up stuff you know.

Enjoy.


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This message is a reply to:
 Message 152 by petrophysics1, posted 01-14-2010 9:25 AM petrophysics1 has not yet responded

Replies to this message:
 Message 154 by edge, posted 01-14-2010 10:10 PM RAZD has acknowledged this reply
 Message 155 by edge, posted 01-14-2010 10:15 PM RAZD has acknowledged this reply

  
edge
Member
Posts: 4607
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.5


Message 154 of 156 (543051)
01-14-2010 10:10 PM
Reply to: Message 153 by RAZD
01-14-2010 9:33 PM


Re: The Core Issue with the Law of Superposition
But this is getting off the topic - the law of superposition. I think it has been fairly well demonstrated that no matter the horizontal pattern, that the vertical pattern still demonstrates the validity of the law of superposition.

You asked our YEC friend to show you somewhere in the real world where that experimental flume deposition occured. Have a look at the Gilbert deltas in Maine. Foreset/crossbeds from 10-25 degrees deposited in water. Check the photos out.
http://www.maine.gov/...gs/explore/surficial/facts/dec03.htm

quote:
quote:
--------------------------------------------------------------------------------
Sediments that were carried all the way to the front of the delta cascaded down into deeper waters, forming the sloping foreset beds on the delta front. The foresets are inclined in the general direction of sediment transport and delta growth, and are typically composed of sand or mixed sand and gravel (Figures 7 and 8).

Figure 8. Close-up of foreset beds in marine delta south of Erskine Academy, South China, Maine.



This is exactly where our YEC friends become confused. They think that comparing the time of deposition of the lower part of the lamination on the right with the upper part of a lamination on the left refutes superposition. As if no geologist ever noticed this before...

Anyway, each lamination is essentially a time-strat unit, a compositionally uniform deposit occurring essentially instantaneously. And, as it turns out, the real comparison is one lamination with another - superposition holds.

At the same time, each 'bed' which contains laminar elements overlies another 'bed', also with laminar elements, and is younger. Supersposition holds again.

And I would (previously) have assumed that the layers were tilted after formation instead of formed at these angles with the sediment running (pouring?) downslope as the delta formed.

Correct (now), this is a primary depositional feature. Very common in current-laid sediments.

So those layers could be older to the left and younger to the right, even though the right end is lower than the left end?

Correct. However, keep in mind, that in this type of deposit the laminations are usually deposited quickly enough that age difference in the geologic record cannot really be resolved. Coarser-grained deposits such as these can be laid down very quickly.

So the law of superposition holds for any vertical core through those deposits, but the timeline\age will be different for the same depositional environments ("geologic habitats") for a core 5 or 10 feet to the right.

Yes, even though the actual ages might be very slightly different. They are the same bed.

By the way, your 'core' example is a very good way to describe this to the lay person.


This message is a reply to:
 Message 153 by RAZD, posted 01-14-2010 9:33 PM RAZD has acknowledged this reply

  
edge
Member
Posts: 4607
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.5


Message 155 of 156 (543052)
01-14-2010 10:15 PM
Reply to: Message 153 by RAZD
01-14-2010 9:33 PM


By the Way...
Regarding the picture you included in your post. When I first looked at it, I thought to myself, "not eolian", before I read the caption. Do you think our YEC friends could tell us why?
This message is a reply to:
 Message 153 by RAZD, posted 01-14-2010 9:33 PM RAZD has acknowledged this reply

  
hdblue 
Suspended Member (Idle past 2718 days)
Posts: 1
Joined: 04-08-2011


Message 156 of 156 (611474)
04-08-2011 3:59 AM
Reply to: Message 106 by Kitsune
08-05-2009 1:33 AM


Re: Back to horizontality considerations
Kitsune writes:

Thanks for the replies, guys. Sounds like I'm on the right track. Moose, I haven't heard "local yokels" before but I'm sure my sister-in-law has; I'll ask her next time I see her. Her area of expertise is glacial flooding, called a jökulhlaup.

For your own interest/amusement, the creationist I've been debating with thinks that the video (erroneously) illustrating Walther's Law somehow explains all phanerozoic strata. He thinks it's evidence for a global flood too. I listed several other methods of sediment deposition for him and explained yet again what a marine transgression is. If you look at what the video is showing, it's sediment coming laterally or horizontally from the sea and settling in a kind of vertical order, the implication being that the facies would need to be read vertically with the oldest being near the shore and the youngest being furthest out. I suppose this could be close to the real scenario if the diagram were made almost horizontal rather than almost vertical. it then implies that geologists get fooled by facies that "appear" horizontal when the real ones are vertical. (The usual combination of scientific misrepresentation and the "scientists are stupid or liars" claim.)

We've got brachiopod layers washing up into cracks in rocks on mountains and getting stuck too, LOL. This guy isn't too difficult for a layperson to deal with fortunately.

Hi,

Thanks very much for this comment. It help me to think about my ideals.

Apart from that, you also can ref more resources at: Performance evaluation phrases

Tks again and pls keep posting.

Edited by hdblue, : No reason given.

Edited by hdblue, : No reason given.

Edited by Adminnemooseus, : Spam treatment to link.


This message is a reply to:
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