blike Posted March 17, 2003 Share Posted March 17, 2003 No, this thread isn't about Anna Nichole Smith, sorry From what I understand, fossils older than about 60,000 years have to be dated using methods other than radiocarbon dating. A method they commonly used for dating dinosaurs is measuring the age of the surrounding rocks and the layer in which the fossil is contained. This seems feasable assuming the fossil is in a specific layer than can be measured. But what about fossils of early bipedal apes that have been found? Some of these are found in valleys [can't remember the name of the real famous one] where the fossil is just under the surface. Dating the surrounding rocks seems a bit of a longshot. What happens if I were to slip down the slope and die alone. In 100,000 years someone could come by and date my fossilized bones and mistake them for 10-million year old remains. How is this screened for? Link to comment Share on other sites More sharing options...
Guest TXKP1974 Posted March 17, 2003 Share Posted March 17, 2003 From what I understand about dating hominids, which isn't very much, is that when a fossil is found, it's often in a volcanic ash layer. This type of sediment provides a handy preservation zone for fossils and it can be fairly easily dated using various radiometric dating methods like Potassium/Argon, Argon40/Argon39, Uranium238/Lead206 ( I think). As far as sediments go, volcanic ash tends to solidify relatively fast, which makes the time span nominal that fossils can "seat" in it. I think the area you were thinking of is the Olduvai Gorge in Tanzinia. This area has a fairly well known geochronologic history, and most fossils can be dated accurately within several thousand years or so. While this may sound like quite a time span, in reality, when comparing it to 2 million years or so, it's actually a very small margin of error. I think I remember reading something one time about using one of these methods, I beleive it was the K/Ar method, to date a pig's tooth, which helped significantly to date an area where hominid fossils were found. Link to comment Share on other sites More sharing options...
DocBill Posted March 18, 2003 Share Posted March 18, 2003 Well, yes and no. Dating via Carbon 14 dating or Oxidizable Carbon Ratio Dating, often simply called "carbon dating" has a maximum reliabliity of about 60,000 years. Naturally occurring Carbon 14 decays to Nitrogen 14, with a half-life of 5,730 years. Because Carbon 14 has such a short half-life, it is useful in archaeology for dating artifacts (man-made objects) and the bones of animals up to 50,000 to 60,000 years old. However, it cannot be used on anything older than Middle Pleistocene Epoch in age. In order to date older fossils, scientists must use other radioactive isotopes. A commonly used technique is called Potassium-Argon dating. The element potassium is found in most rock-forming minerals, and the half-life of the radioactive isotope Potassium 40 is 1.25 billion years, allowing measurable quantities of Argon 40 (its decay element, known as the daughter element) to accumulate in potassium-bearing minerals of almost all ages. The amounts of potassium and argon isotopes can be measured accurately, even in very small quantities, making Potassium-Argon dating useful for both very young and very old rocks (and everything in between). Although radiometric dating is much more precise than relative dating, it does have its drawbacks as well. With the exception of Carbon dating, radiometric dating can only be used on igneous rocks, not sedimentary rocks or the actual fossils. Because fossils are found in sedimentary rock, paleontologists have to use radiometric dating information on igneous rocks found below and above the fossils in order to determine an age range for the sedimentary rocks. Bill Link to comment Share on other sites More sharing options...
Guest TXKP1974 Posted March 18, 2003 Share Posted March 18, 2003 Bill, I'm thinking that are in fact ways to date certain sedimentary rocks. Sedimentary rocks that contain glauconite can be dated, due to the fact this mineral is formed as a precipitate during the formation of, once again, certain sedimentary rocks, and contains Potassium. Kyle Link to comment Share on other sites More sharing options...
DocBill Posted March 18, 2003 Share Posted March 18, 2003 Originally posted by TXKP1974 Bill, I'm thinking that are in fact ways to date certain sedimentary rocks. Sedimentary rocks that contain glauconite can be dated, due to the fact this mineral is formed as a precipitate during the formation of, once again, certain sedimentary rocks, and contains Potassium. Kyle And your thinking would be most correct indeed. Bill Link to comment Share on other sites More sharing options...
YoungStrife Posted March 22, 2003 Share Posted March 22, 2003 Of everything said in relation to radioactive decay, ou all forgot to mention that a substance can be accurately measured by radioactive decay only until the certain thing measured reaches its half-life. Sometimes a fiossil from one time may lay in sediemtns from a different time period, so this isn't 100% accurate. I don't know whether TXKP is right or not, but I guess I'll just agree with Bill. Link to comment Share on other sites More sharing options...
atinymonkey Posted April 10, 2003 Share Posted April 10, 2003 Well, the main reason you cannot carbon date a fossil isn't the 60,000 margin of reliability, it's simply that the fossil is not composed of it's original elements. It is a facsimile of the original bone. That facsimile is created by the sedimentary layer that created the fossil over time, as they both become rock. So it become easier to date the surrounding material than the none existent carbon for the bone that no longer exists. To answer your question about the falling onto rocks far older than yourself when you die, the bone would then be exposed and decay rather than be transposed into fossil. There is specific requirements in fossil formation and the primary one is that the bone is surrounded by sediment or mud almost immediately. It's the mud's age that you want to know, not the fossil itself. Link to comment Share on other sites More sharing options...
DocBill Posted April 10, 2003 Share Posted April 10, 2003 So that's isotopic dating huh? Where did you read that? It has absolutely NOTHING to do with dating whatsoever. This is the old "Creationists" arhument that fell apart in the 1960's. Now to see it here? Link to comment Share on other sites More sharing options...
atinymonkey Posted April 10, 2003 Share Posted April 10, 2003 Well, isotopic dating can be used on calcite, bone etc. As a fossil is not bone, it is pointless to use the method. http://www.sciencenet.org.uk/database/Archaeology/Original/a00056d.html It's the sediment that's tested for fossils, not the fossil itself. As for a creationist argument, I think you have lost the plot. If you like you can join us on an archaeological dig and see the practical application of dating methods, there are digs once a year in York that amateurs can join in on. http://www.yorkarchaeology.co.uk/kilham/ Meantime, back off. I'm not 12 years old, and don't need lecturing. Link to comment Share on other sites More sharing options...
Radical Edward Posted April 10, 2003 Share Posted April 10, 2003 <annoying geordie voice> calm down calm down </annoying geordie voice> out of interest, where does the carbon go? Link to comment Share on other sites More sharing options...
Sayonara Posted April 10, 2003 Share Posted April 10, 2003 Who's dating a fossil? DocBill or Blike? Is it Honor Blackman? Link to comment Share on other sites More sharing options...
DocBill Posted April 10, 2003 Share Posted April 10, 2003 Originally posted by atinymonkey Well, isotopic dating can be used on calcite, bone etc. As a fossil is not bone, it is pointless to use the method. http://www.sciencenet.org.uk/database/Archaeology/Original/a00056d.html It's the sediment that's tested for fossils, not the fossil itself. As for a creationist argument, I think you have lost the plot. If you like you can join us on an archaeological dig and see the practical application of dating methods, there are digs once a year in York that amateurs can join in on. http://www.yorkarchaeology.co.uk/kilham/ Meantime, back off. I'm not 12 years old, and don't need lecturing. Really?? Pray tell me then, where did you recieve your degree(s)? I really, really do not have time for this type of exchange. I am far too busy writing the type of books that people like you most likely refer to. Do me a favor? Do not bother responding..I just don't care that much about what you think you know and what you don't, ok? Life is far to breif to entertain pointless exchanges with lesser minds. "Back off?" Give me a break. If you feel you cannot engage in a civil debate, why should I bother to waste this forums, and what is infinately more valuable, MY time? Have fun with your digs... and grow up. Link to comment Share on other sites More sharing options...
Sayonara Posted April 10, 2003 Share Posted April 10, 2003 Once again, DocBill, you are the antagonist here, not the member you're stomping on. Do you really want to know where atm got his degrees? I couldn't care less because he could tell me anything and I'd have to take his word for it, just like I take your word for it that you have a BA in Theology or whatever it was. Stop acting like a spoiled child every time someone with links to sources or a rational argument disgarees with you - it's no way for a moderator to behave. Link to comment Share on other sites More sharing options...
DocBill Posted April 10, 2003 Share Posted April 10, 2003 Originally posted by Sayonara³ Once again, DocBill, you are the antagonist here, not the member you're stomping on. Do you really want to know where atm got his degrees? I couldn't care less because he could tell me anything and I'd have to take his word for it, just like I take your word for it that you have a BA in Theology or whatever it was. Stop acting like a spoiled child every time someone with links to sources or a rational argument disgarees with you - it's no way for a moderator to behave. Really? A spoiled child. Well..we certainly don't need that. Tell you what..let the powers that be simply delete my account here. Won't that be MUCH easier? Stomping? Is that what you brits term being "called" on something? My credentials are easily available in the min. of the Royal Society, the rolls of the AGU, and the UCS. But..why should this board be forced to tolerate a "spoiled child." So long..I just do not have the time. Link to comment Share on other sites More sharing options...
Sayonara Posted April 10, 2003 Share Posted April 10, 2003 "Stomping" is bashing someone for their statements without backing up your own, as well you know. [edit] How about if - unlike on the last forums you 'left' - your account doesn't get deleted, then people from the next forum you land on can see what you're like. Link to comment Share on other sites More sharing options...
DocBill Posted April 10, 2003 Share Posted April 10, 2003 As you wish. I have added your email contacts to my "Ignore" list..do as you want, I have no time left for "forums" of anykind. Link to comment Share on other sites More sharing options...
Sayonara Posted April 10, 2003 Share Posted April 10, 2003 How exactly would you have any member e-mail addresses? Link to comment Share on other sites More sharing options...
atinymonkey Posted April 10, 2003 Share Posted April 10, 2003 http://www.royalsoc.ac.uk/templates/search/websearch.cfm?mainpage=/royalsoc/fel_dird.htm I can't seem to find you, old boy. You may want to specify which royal society. Myself, I'm only a member of the royal society of yachtsmen, as I'm not a Professor. Just stick to topic, if you disagree with what I've said, fine. I've given you evidence. Disagree with the evidence if you like. Throw your rattle out your pram if you like, I really don't have time for self absorbed little self publicists. Or for that matter people with 'degrees' from Springfeild university. If your tired of trying to impress students with the results of your google searches, I don't think I'll miss you much. By the way, how come neither the British Library or The Library of Congress has any of your books? Possible because they are purile? Heretics, all 169 pages, I could have written in one night. While drunk. And if you happen to think I'm being harsh, I'll remind you I asked for you to back off. Thanks for your time. Link to comment Share on other sites More sharing options...
atinymonkey Posted April 10, 2003 Share Posted April 10, 2003 Many apologies, Blike, for the thread hijack. Feel free to delete one of mine, if I ever get an interesting one. Link to comment Share on other sites More sharing options...
atinymonkey Posted April 10, 2003 Share Posted April 10, 2003 Oh, Radical Edward, like bill said carbon deteriorates after 6000 years. It's the calcium that sticks around. Link to comment Share on other sites More sharing options...
Sayonara Posted April 10, 2003 Share Posted April 10, 2003 Originally posted by atinymonkey Many apologies, Blike, for the thread hijack. Feel free to delete one of mine, if I ever get an interesting one. Yeah, sorry about the mess Blike Wasn't expecting so much collateral damage. Link to comment Share on other sites More sharing options...
Radical Edward Posted April 11, 2003 Share Posted April 11, 2003 Originally posted by atinymonkey http://www.yorkarchaeology.co.uk/kilham/ ace, my brother lives in kilham... say hi for me Link to comment Share on other sites More sharing options...
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