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Author Topic:   Dating Question For Members
Buzsaw
Inactive Member


Message 1 of 77 (610141)
03-26-2011 6:54 PM


In Message 39 of the Great Debate between Moose and me, I posed the following question:

quote:
If any given beach sand were dated via the same method old rock is dated, what would the dectection show as the date of the beach sand which was dated?

Would the sand rock date old or very young? Would each grain of sand have a different date or would the aggregate of sand in a given beach area show an aggregate date?

("Detection" changed in quote for clarity. )


Replies to this message:
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Message 2 of 77 (610143)
03-26-2011 8:45 PM


Thread Copied from Proposed New Topics Forum
Thread copied here from the Dating Question For Members thread in the Proposed New Topics forum.
    
Dr Adequate
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Joined: 07-20-2006
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Message 3 of 77 (610144)
03-26-2011 8:47 PM
Reply to: Message 1 by Buzsaw
03-26-2011 6:54 PM


The sand would date to the time of formation of the igneous parent rock.

If there were multiple parent rocks with different dates of formation contributing to the beach, the different grains would have different dates.

However, I'm not sure that it's actually possible to date most grains of ordinary sand, which is mostly composed of quartz. In order for radiometric dating to work, you'd need long-lived radioactive isotopes to be including in the mineral at the time of its formation, and I don't think that happens with quartz. You'd want to find a grain of garnet or something like that.


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jar
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Posts: 29147
From: Texas!!
Joined: 04-20-2004
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Message 4 of 77 (610146)
03-26-2011 8:57 PM
Reply to: Message 3 by Dr Adequate
03-26-2011 8:47 PM


TL dating
You might be able to use Thermoluminescence dating for some sands, for example relatively static dunes, sea beds, fossil dunes, but active sea side beaches are not a great prospect.

AbE:

Also, any TL dating would not give an age for the sand itself, but rather only when it was covered so not exposed to the sun.

Edited by jar, : AbE:


Anyone so limited that they can only spell a word one way is severely handicapped!
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Coyote
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Message 5 of 77 (610148)
03-26-2011 9:13 PM
Reply to: Message 1 by Buzsaw
03-26-2011 6:54 PM


Dating sand
My main field in dating is radiocarbon, and it would be of no use on sand.
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Buzsaw
Inactive Member


Message 6 of 77 (610152)
03-26-2011 10:38 PM


Related Dating Questions
Thanks for the replies, folks. What led up to my question was Moose's statement that fossils were dated from the time of deposit of the organism.

From searching, I learned that most fossils consisted of sedimentary rock and were void of original organic matter. This raised the question in my mind as to why the aggregate age of the rock or sand grains in the sediment would not be calculated as the age of the fossil rather than the time the organism was deposited.

If Moose is correct, in that fossils are dated from the time of deposit, why wouldn't that apply to sea shore sand and for that matter, even a house built of stone, some of which had aged fossils in it.

I am considering this as a possible problem in dating methodology.


BUZSAW B 4 U 2 C Y BUZ SAW.
The Immeasurable Present Eternally Extends the Infinite Past And Infinitely Consumes The Eternal Future.
Replies to this message:
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 Message 9 by arachnophilia, posted 03-26-2011 11:37 PM Buzsaw has not yet responded
 Message 11 by Dr Adequate, posted 03-27-2011 12:23 AM Buzsaw has responded

  
subbie
Member (Idle past 181 days)
Posts: 3508
Joined: 02-26-2006


Message 7 of 77 (610155)
03-26-2011 10:44 PM
Reply to: Message 6 by Buzsaw
03-26-2011 10:38 PM


Re: Related Dating Questions
And I'm quite certain that you, someone with zero education in geology, sitting at your computer, will think up all kinds of problems that people with PhDs will never be able to solve.

Hubris much?


Ridicule is the only weapon which can be used against unintelligible propositions. -- Thomas Jefferson

We see monsters where science shows us windmills. -- Phat

It has always struck me as odd that fundies devote so much time and effort into trying to find a naturalistic explanation for their mythical flood, while looking for magical explanations for things that actually happened. -- Dr. Adequate

...creationists have a great way to detect fraud and it doesn't take 8 or 40 years or even a scientific degree to spot the fraud--'if it disagrees with the bible then it is wrong'.... -- archaeologist


This message is a reply to:
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Buzsaw
Inactive Member


Message 8 of 77 (610156)
03-26-2011 10:58 PM
Reply to: Message 7 by subbie
03-26-2011 10:44 PM


Re: Related Dating Questions
subbie writes:

And I'm quite certain that you, someone with zero education in geology, sitting at your computer, will think up all kinds of problems that people with PhDs will never be able to solve.

Hubris much?

Subbie, unless you have something constructive to contribute to this topic I'd appreciate it if you'd find something else to do.


BUZSAW B 4 U 2 C Y BUZ SAW.
The Immeasurable Present Eternally Extends the Infinite Past And Infinitely Consumes The Eternal Future.
This message is a reply to:
 Message 7 by subbie, posted 03-26-2011 10:44 PM subbie has responded

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arachnophilia
Member (Idle past 207 days)
Posts: 9068
From: god's waiting room
Joined: 05-21-2004


Message 9 of 77 (610160)
03-26-2011 11:37 PM
Reply to: Message 6 by Buzsaw
03-26-2011 10:38 PM


Re: Related Dating Questions
Buzsaw writes:

From searching, I learned that most fossils consisted of sedimentary rock and were void of original organic matter. This raised the question in my mind as to why the aggregate age of the rock or sand grains in the sediment would not be calculated as the age of the fossil rather than the time the organism was deposited.

If Moose is correct, in that fossils are dated from the time of deposit, why wouldn't that apply to sea shore sand and for that matter, even a house built of stone, some of which had aged fossils in it.

ah. well, i found your problem. you asked a question about sand when you really wanted to know about sandstone. the two are not the same thing.

sedimentary rocks can be dated by the other stuff that collects in it during the sedimentation process -- usually stuff found in the liquid environment that produces it. for relative methods, the fossils and their correlated dates ("index" fossils) can be used, but i know you'll find this circular. the absolute dating method you're looking for potassium-argon dating.

while it can be used to date the source rock as well, potassium also collects during the deposition of the sediment, too. this is particularly easy with glauconite sandstone. so, yeah, ask for what you want to know -- cause you miss stuff when you make intuitive leaps for the sake of argument.

Edited by arachnophilia, : No reason given.


אָרַח

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subbie
Member (Idle past 181 days)
Posts: 3508
Joined: 02-26-2006


Message 10 of 77 (610161)
03-26-2011 11:41 PM
Reply to: Message 8 by Buzsaw
03-26-2011 10:58 PM


Re: Related Dating Questions
I guess I'm hoping (no basis for this hope, I grant you) that some day you will realize the ridiculousness of you trying to out think people who have spent decades studying a complicated subject. But as Jimmy Stewart said in Mr. Smith Goes to Washington, "The only causes worth fighting for are lost causes." I refuse to give up on you, Buz. I'm convinced that you actually do have functioning brain matter and I'm going to keep trying to reach it.


Ridicule is the only weapon which can be used against unintelligible propositions. -- Thomas Jefferson

We see monsters where science shows us windmills. -- Phat

It has always struck me as odd that fundies devote so much time and effort into trying to find a naturalistic explanation for their mythical flood, while looking for magical explanations for things that actually happened. -- Dr. Adequate

...creationists have a great way to detect fraud and it doesn't take 8 or 40 years or even a scientific degree to spot the fraud--'if it disagrees with the bible then it is wrong'.... -- archaeologist


This message is a reply to:
 Message 8 by Buzsaw, posted 03-26-2011 10:58 PM Buzsaw has not yet responded

  
Dr Adequate
Member
Posts: 15947
Joined: 07-20-2006
Member Rating: 3.5


Message 11 of 77 (610163)
03-27-2011 12:23 AM
Reply to: Message 6 by Buzsaw
03-26-2011 10:38 PM


Re: Related Dating Questions
Thanks for the replies, folks. What led up to my question was Moose's statement that fossils were dated from the time of deposit of the organism.

From searching, I learned that most fossils consisted of sedimentary rock and were void of original organic matter. This raised the question in my mind as to why the aggregate age of the rock or sand grains in the sediment would not be calculated as the age of the fossil rather than the time the organism was deposited.

Fossils aren't dated by looking at the sedimentary rock in which they're buried, though of course such a date would provide a maximum possible age for the fossil.

Instead, you look at igneous rocks underlying or overlying the fossil. If you find, for example, that whenever you have a lava flow or a layer of volcanic ash or whatever under a particular species, it is ≥ 100my old, and when you find such rocks over the species, it is ≤ 95 my old, and whenever you find such rocks within strata containing the fossil, they are between 95 and 100my old, then that allows you to put a date on the species of 100-95mya.

Having put a date on that species by this method you can then use its presence to date sedimentary rocks in the absence of igneous clues and so to put dates on the other fossils that they contain (the method of "index fossils").

You should look at a geology textbook sometime, they contain lots of interesting information about geology.


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dwise1
Member
Posts: 2867
Joined: 05-02-2006
Member Rating: 3.8


Message 12 of 77 (610169)
03-27-2011 5:05 AM
Reply to: Message 1 by Buzsaw
03-26-2011 6:54 PM


The exact same (or rather a very similar type) question occurred to me while driving up to Lake Arrowhead for an organized youth activity with my son and observing the exposed strata along the way: all sedimentary rock consists of much older rock that has been physically broken down and redeposited, so how is radio-dating supposed to work with sedimentary rock?

So I started researching the question. I had already long known of William Smith's empirical observations which formed the basis of stratigraphy, such that observable characteristics of the layer of rock could be used to identify it. Furthermore, I already knew of the Law of Supposition, whereby the age of a given stratum relative to other strata was determined. What I then learned through my research was that the age of a given stratum was further narrowed down by the radio-dating of igneous intrusions and whether they occurred above or below the stratum.

It should be noted here that if we question and research scientific ideas, then we find answers to our questions. That is not at all what we discover when we question and research creationist claims.


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Percy
Member
Posts: 15646
From: New Hampshire
Joined: 12-23-2000
Member Rating: 2.5


Message 13 of 77 (610171)
03-27-2011 7:17 AM
Reply to: Message 12 by dwise1
03-27-2011 5:05 AM


dwise1 writes:

Furthermore, I already knew of the Law of Supposition...

I suppose there could have been a law of supposition, but if so then I think it may have been superseded.

--Percy


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Buzsaw
Inactive Member


Message 14 of 77 (610173)
03-27-2011 9:46 AM
Reply to: Message 11 by Dr Adequate
03-27-2011 12:23 AM


Re: Related Dating Questions
Dr Adequate writes:

Fossils aren't dated by looking at the sedimentary rock in which they're buried, though of course such a date would provide a maximum possible age for the fossil.

But the sedimentary rock consist of aged grains of sediment much older than the organism which formed the sediment into a fossil. It's all particles of rock compacted into sediment instead of loose, for example, in an ant hill or a beach.

I would assume that since the organic organism is no longer there that what is being calibrated would be the old particles of the sedimentary rock.

Since beach sand is mostly quartz, perhaps a better example would be an ant hill. When I was young I was a geophysical rod man on the Sweetwater wilderness of Wyoming. The large ant hills out there consisted of all sorts of rock, including enough beautiful little red garnets that I robbed the ants of their garnets and saved a bottle of them.

Suppose that during a catastrophe thousands of years ago, an ant hill was buried and became sediment with a leaf in it becoming fossilized. Over the millennia the leaf ceased to be and the sediment formed the fossil. Why wouldn't the dating method calibrate the rock particles making up the sediment of the fossil rather than the time the rock became sedimented?

In short, if dating methodology would date the ant hill by the rock in it, why wouldn't the fossil sediment be dated by the same rock making up the sediment?

We know the ant hill rock was deposited by the ants at the time they existed as ant hills. But dating methodology would not tell us when ant hills are formed, any more than it would tell us when a rock house was built. Why should it be different with the sedimented rock?

Since beach sand is mostly quartz, perhaps a better example would be an ant hill. When I was young I was a geophysical rod man on the Sweet water region of Wyoming. The large ant hills out there consisted of all sorts of rock, including enough beautiful little red garnets that I robbed the ants of their garnets and saved a bottle of them.

Supposing that during a catastrophe thousands of years ago, an ant hill was buried and became sediment with a leaf in it becoming fossilized. Over the millennia the leaf ceased to be and the sediment formed the fossil. Why wouldn't the dating method date the rock particles making up the sediment of the fossil rather than the time the rock became sedimented?


BUZSAW B 4 U 2 C Y BUZ SAW.
The Immeasurable Present Eternally Extends the Infinite Past And Infinitely Consumes The Eternal Future.
This message is a reply to:
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JonF
Member
Posts: 3806
Joined: 06-23-2003
Member Rating: 3.4


Message 15 of 77 (610176)
03-27-2011 11:32 AM
Reply to: Message 14 by Buzsaw
03-27-2011 9:46 AM


Re: Related Dating Questions
It's already been said that dating the individual grains would yield the date that the parent rock formed, many years before the sedimentary or metamorphic rock formed. So scientists are smart enough to avoid doing that.

However, there are some methods for dating when sedimentary rock formed. Not surprisingly they involve dating the "glue" that holds the rock together. The individual grains of sedimentary rock don't stick together by themselves; something forms or precipitates between the grains and holds them together.

Examples include U-Pb dating of xenotime grown on zircons (SHRIMP Uranium-Lead Dating of Diagenetic Xenotime in Siliciclastic Sedimentary Rocks) and K-Ar dating of glauconite (Sedimentary geology: an introduction to sedimentary rocks and stratigraphy, pg 400). The latter is not particulary reliable because argon loss is common, leading to dates that are 10-20% too low (but still incompatible with creationist time scales by orders of magnitude).

Most sedimentary rocks, and the fossils they contain, are dated by a combination of stratigraphy, index fossils, and radiometric dating.

The simplest case is a fossil found in a sedimentary layer that lies between two igneous layers. Suppose the igneous layer above is dated at 500 million years and the layer below is dated as 510 million years; the sedimentary layer and fossil are therefore 500 to 510 million years old. This situation is common, such as in the Rift Valley of East Africa, where so many hominid fossils have been found; the area is loaded with volcanic tuff layers.

An example of a slightly more complex case is the use of index fossils to calibrate, not date, layers. An index fossil is a fossil of an organism that has been found to occur only in some narrow range of dates (by many applications of the technique above). FOr example foraminifera, AKA forams, are widely used and are critical to oil well drilling. Let's suppose we know of an index fossil that is reliably known to be 370-380 million years old. Also suppose we find a fossil of some other organism in a layer that's above a layer containing those index fossils and below an igneous layer that dates to 350 million years. The new fossil is therefore 350-370 million years old.

There are lots of scenarios and variations, but the bottom line is that most fossils are dated by radiometric dating of associated igneous layers, the association being established by various means.


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