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Faith  Suspended Member (Idle past 1764 days) Posts: 35298 From: Nevada, USA Joined: |
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Author | Topic: How the geo strata are identified as time periods | |||||||||||||||||||||||
MG1962 Inactive Member |
Ahh okay thank you for that - I was under the impression there was enough potassium in basalt.
And yeah the comment about fossil dating may have been a little too general. I dont have a reference, but I recall reading some time ago that plankton was being used to improve the dating of deposits. If I can find the article again I will post a link.
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AdminJar Inactive Member |
Welcome to EvC. At the end of this message you will find links to threads on neat stuff like how to include quotes or special characters™, the proper use of a UniSyn™ when balancing SU Carbs, the actual location of the battery and the importance of remembering to retighten the nuts on the choke cable. In addition we have two, not one but two, reply buttons for your convenience. The one on the lower left is a General Reply button, but the one at the lower right of each individual message is the magical LGRB (Little Green Reply Button) which links your response to the exact message you are replying to and (if the other poster has notification turned on in his profile) sends that person a notice that you have replied.
Since you are new here I make a few assumptions, that is was a Model A and not the all new improved B which was introduced that year and that you are well aware that Joseph Lucas truly is the Prince of Darkness. Edited by AdminJar, : h was missing Comments on moderation procedures (or wish to respond to admin messages)? - Go to:
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pesto Member (Idle past 5907 days) Posts: 63 From: Chicago, IL Joined: |
In terms of dating geologic age, basalt is an excellent marker. Using Potasium 40 or Argon dating will get you a fairly accurate date of a volcanic event.
Some volcanic horizons are indeed very useful for radiometricly dating, and for the dating of sediments between volcanic horizons. But basalt, the mafic (high iron and magnesium) end member of the types of igneous rocks is (and someone correct me if I'm wrong) not radiomentrically datable by the common methods, including such as Potasium/Argon, Uranium/Lead, and variations there of. Basalt is very low in Potasium and Uranium.
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AdminNosy Administrator Posts: 4755 From: Vancouver, BC, Canada Joined: |
I'm afraid that the details of dating methods don't belong in this thread.
Have a look over this site and if you have questions open another thread: http://pubs.usgs.gov/gip/geotime/radiometric.html
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Coragyps Member (Idle past 1054 days) Posts: 5553 From: Snyder, Texas, USA Joined: |
Typically you don't need to know the initial ratios: methods like isochrons and concordia diagrams remove that number from the list of variables. Another instance where it doesn't much matter is in dating single zircons. When a crystal of zirconium silicate forms from molten rock, its crystal lattice will exclude any lead very efficiently, but will let some uranium in in the place of zirconium. If you find lead in a well-formed zircon, then, you can bet that it's there as a decay product of uranium, not as an original part of the grain.
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AdminNosy Administrator Posts: 4755 From: Vancouver, BC, Canada Joined: |
The dating details are NOT on topic here and what mention of Basalt was there in your post with it in the post title?
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Coragyps Member (Idle past 1054 days) Posts: 5553 From: Snyder, Texas, USA Joined: |
Yessir. No more derail.
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Jazzns Member (Idle past 4231 days) Posts: 2657 From: A Better America Joined: |
I think this thread died down because we are pretty much done describing in general how the time periods are identified.
The key point to take away I think is that sedimentation is no where near a primary method used to establish time periods. Time periods are established via absolute methods and merely grouped by similarities in paleo-ecology or other factors. The naivety of the standard, "Layers date the fossils and the fossils date the layers" criticism should be quite apparent although I am not suggesting that anyone on this thread was pushing that concept in any pure way. Where did you want to take this next? Of course, biblical creationists are committed to belief in God's written Word, the Bible, which forbids bearing false witness; --AIG (lest they forget)
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Jazzns Member (Idle past 4231 days) Posts: 2657 From: A Better America Joined: |
I don't want this thread to get lost. Please see my previous post. I know you are battling computer problems. Let me know if I can help.
Of course, biblical creationists are committed to belief in God's written Word, the Bible, which forbids bearing false witness; --AIG (lest they forget) |
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petrophysics1 Inactive Member |
The geologic column is divided into only 2 periods.
The formations of Period 1 contain no pollen.The formations of Period 2 contain pollen. Period 2 overlies Period 1 I can go anywhere in the world and by following the contact of Periods 1&2 or taking samples of a formation and analyzing for pollen determine with confidence if it is in Period 1 or Period 2. That directly answers your question. Why is this geology for five year olds important? Well it dissproves inane statements like this: "The entire geologic column was formed by the flood. THAT's the beginning and end of the flood. I don't know where people get the idea they have to get out their microscopes and peer into one particular half inch of one layer to find it. The evidence of the flood is EVERYWHERE. I see it wherever I go.This message has been edited by Faith, 03-11-2006 09:10 AM " Pollen is ubiquitous, it gets into everything. It is also very very durable. Since there were plants at the time of the made up flood there should be pollen in all the formations of the geologic column if "The entire geologic column was formed by the flood". Since Period 1 contains no pollen it could not possibly have been formed by the flood. Edited by petrophysics, : typo
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Minnemooseus Member Posts: 3978 From: Duluth, Minnesota, U.S. (West end of Lake Superior) Joined: |
THIS IS SERIOUSLY GETTING OFF-TOPIC, SO WE NEED A NEW TOPIC IF THIS LINE OF DISCUSSION GOES ANY FURTHER.
From message 1 of the new "A Guide to the Bait & Switch tactics of the Biblical Creationists" topic:
Jar writes: A claim I have seen on many (unfortunately Christian) sites is of dating Hawaiian basalt using the potassium-argon method. The samples were known to be only 200 or so years old yet they got readings that were in the hundreds of thousands of years. The above caused me to look into the radiometric dating of basalts a bit more.
Moose, in message 90 writes: But basalt, the mafic (high iron and magnesium) end member of the types of igneous rocks is (and someone correct me if I'm wrong) not radiomentrically datable by the common methods, including such as Potasium/Argon, Uranium/Lead, and variations there of. Basalt is very low in Potasium and Uranium. "Bolds" newly added. Well, I was wrong (or at least, less than totally right), and no one corrected me. At least sometimes, basalts are datable and dated by the Argon/Argon method (and other methods). In Radiometric Dating there are examples of lunar basalts being dated by the 40Ar/39Ar method, and also by other radiometric methods. In particular, see the above cited for an example of a single rock sample that was dated by a variety of methods. See the "Apollo 11 - High-K basalt 10072" table. Well, I'm not going to go any further here. But I certainly wouldn't mind someone else explaining any proper datings of basalt by the K/Ar, Ar/Ar, and/or Rb/Sr methods. Especially the 40Ar/39Ar method. But it needs to be in a new topic Moose
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