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Author Topic:   How the geo strata are identified as time periods
MG1962
Inactive Member


Message 91 of 101 (347537)
09-08-2006 11:25 AM


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


Message 92 of 101 (347544)
09-08-2006 11:42 AM
Reply to: Message 91 by MG1962
09-08-2006 11:25 AM


Safety Fast
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

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  • This message is a reply to:
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    pesto
    Member (Idle past 5587 days)
    Posts: 63
    From: Chicago, IL
    Joined: 04-05-2006


    Message 93 of 101 (348880)
    09-13-2006 5:17 PM
    Reply to: Message 90 by Minnemooseus
    09-07-2006 7:30 PM


    Re: Basalt not a radiometricly datable volcanic
    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.
    One thing I don't understand is how we know the original ratios of these elements in volcanic rocks. I understand carbon dating, because of how nitrogen is turned into carbon-14 in the upper atmosphere, but what about the other radioisotopes used to date older strata?

    This message is a reply to:
     Message 90 by Minnemooseus, posted 09-07-2006 7:30 PM Minnemooseus has not replied

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    AdminNosy
    Administrator
    Posts: 4754
    From: Vancouver, BC, Canada
    Joined: 11-11-2003


    Message 94 of 101 (348886)
    09-13-2006 5:36 PM
    Reply to: Message 93 by pesto
    09-13-2006 5:17 PM


    T o p i c !
    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

    This message is a reply to:
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    Coragyps
    Member (Idle past 734 days)
    Posts: 5553
    From: Snyder, Texas, USA
    Joined: 11-12-2002


    Message 95 of 101 (348887)
    09-13-2006 5:38 PM
    Reply to: Message 93 by pesto
    09-13-2006 5:17 PM


    Re: Basalt not a radiometricly datable volcanic
    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: 4754
    From: Vancouver, BC, Canada
    Joined: 11-11-2003


    Message 96 of 101 (348891)
    09-13-2006 5:46 PM
    Reply to: Message 95 by Coragyps
    09-13-2006 5:38 PM


    Getting grouchy.
    The dating details are NOT on topic here and what mention of Basalt was there in your post with it in the post title?

    This message is a reply to:
     Message 95 by Coragyps, posted 09-13-2006 5:38 PM Coragyps has replied

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    Coragyps
    Member (Idle past 734 days)
    Posts: 5553
    From: Snyder, Texas, USA
    Joined: 11-12-2002


    Message 97 of 101 (348894)
    09-13-2006 5:56 PM
    Reply to: Message 96 by AdminNosy
    09-13-2006 5:46 PM


    Re: Getting grouchy.
    Yessir. No more derail.

    This message is a reply to:
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    Jazzns
    Member (Idle past 3911 days)
    Posts: 2657
    From: A Better America
    Joined: 07-23-2004


    Message 98 of 101 (349042)
    09-14-2006 11:46 AM
    Reply to: Message 80 by Faith
    09-01-2006 8:37 AM


    Now What?
    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)

    This message is a reply to:
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    Jazzns
    Member (Idle past 3911 days)
    Posts: 2657
    From: A Better America
    Joined: 07-23-2004


    Message 99 of 101 (350676)
    09-20-2006 12:41 PM


    Bump for Faith
    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)

      
    petrophysics1
    Inactive Member


    Message 100 of 101 (351819)
    09-24-2006 3:20 PM
    Reply to: Message 1 by Faith
    08-28-2006 2:57 AM


    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: 3941
    From: Duluth, Minnesota, U.S. (West end of Lake Superior)
    Joined: 11-11-2001
    Member Rating: 10.0


    Message 101 of 101 (364494)
    11-18-2006 1:46 AM
    Reply to: Message 90 by Minnemooseus
    09-07-2006 7:30 PM


    Basalt not a radiometricly datable volcanic - WRONG!
    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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