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Author | Topic: Several specific questions about RadioCarbon Dating using AMS | |||||||||||||||||||||||||||||||||||||||||||||||
OverallyEvolvedAPE Junior Member (Idle past 873 days) Posts: 10 Joined: |
Coyote: That's interesting. That makes it harder to fact check cause then the reader would have to know whether that person properly collected samples to avaoid bias. Of course that's true for every field of study.
A perfect example would be the problems with the young volcano rocks Snelling/Austin sent in imporperly to be tested for K40/AR40 knowing they would fail.
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Percy Member Posts: 22881 From: New Hampshire Joined: Member Rating: 6.6 |
I found I couldn't be certain what Coyote actually meant and would like to get more clarity. He seemed to be saying that 5900 BP and 9400 BP shells can exist at the same level and location at some archeological sites, but that doesn't seem possible without some inter-level contamination, so I think he must have meant something else. Maybe that you can't know a level's date range unless you are thorough in submitting samples for dating? Still, a date range for a level that spans 3500 years seems very extreme and unlikely. So I'm left uncertain what Coyote meant.
--Percy
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JonF Member (Idle past 386 days) Posts: 6174 Joined:
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Dr. Bertsche, who posts here occasionally, has a good discussion of the issues in re the RAT claims at RATE’s Radiocarbon: Intrinsic or Contamination?
Edited by JonF, : No reason given.
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Coyote Member (Idle past 2324 days) Posts: 6117 Joined:
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To answer Percy's question: almost all of the sites I work in have some degree of "bioturbation," which is disturbance by burrowing animals. The smaller items, such as mussel shell, can be moved about vertically. One site we examined had almost zero correlation between sample age and depth.
But the abalone/mussel problem I mentioned in my previous post reflects a cultural phenomenon--it seems the prehistoric inhabitants did not start using abalone until about 5900 BP, while they began using mussels by at least 9400 BP. Hence, if you date abalone shells you simply can't identify the earliest components in these sites. This is just one of the problems that can come from poor sample selection.Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge. Belief gets in the way of learning--Robert A. Heinlein In the name of diversity, college student demands to be kept in ignorance of the culture that made diversity a value--StultisTheFool It's not what we don't know that hurts, it's what we know that ain't so--Will Rogers If I am entitled to something, someone else is obliged to pay--Jerry Pournelle If a religion's teachings are true, then it should have nothing to fear from science...--dwise1 "Multiculturalism" demands that the US be tolerant of everything except its own past, culture, traditions, and identity.
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Percy Member Posts: 22881 From: New Hampshire Joined: Member Rating: 6.6
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Thanks for the reference to Bertsche's RATE’s Radiocarbon: Intrinsic or Contamination?. It fills in a few very useful details, which I attempt to summarize here. I occasionally add some additional information and my own comments.
Typical sample sizes are 1 mg of carbon. A poppy seed found in an ancient jar might weigh around 0.3 mg, and I'm guessing the carbon content would below 0.1 mg. Bertsche says that small an amount is manageable, but precision begins to "suffer below about 0.1 mg of carbon due to counting statistics."
Beta Analytic Radiocarbon Dating requests sample sizes of 20 mg because the pretreatment reduces the mass significantly. Contamination in situ, during collection and during storage can be significant. This makes a lot of sense. The poppy seed in an ancient jar might have been isolated from modern carbon for millennia, but once opened modern carbon floods in. Carbon is everywhere, in the air, in people, in animals, in bacteria, and even in the sterile gloves an archaeologist might wear while collecting samples. Contamination is measured in units of pMC (percent modern carbon). Apparently contamination is always assumed to be modern carbon (high 14C content). Samples will inevitably have widely varying pMC's. A sloppily gathered sample could easily contain more modern carbon than sample carbon (Coyote's comments about this possibility might be valuable). Laboratory contamination contributions vary, but values around 0.1 pMC are typical AMS instrument contamination contributions also vary, but values around 0.03 pMC are typical. Bertsche's purpose is to critique John Baumgardner's RATE claims. Baumgardner reanalyzed "90 previously purblished radiocarbon AMS dates of old samples," and RATE gathered new samples and had them AMS dated. Baumgardner claims that all material, even non-biological, contains intrinsic radiocarbon. Bertsche's reference 1 and 2 are Baumgardner's papers, and I provide links here:
The abstract of reference 1 briefly describes Baumgarders results and conclusions, which I paraphrase here:
All organic samples from the Phanerozoic (500 million years ago until the present) contain "significant and reproducible amounts of 14C." The technical literature describes many instances of 14C/C ratios between 0.1 and 0.5 percent of the modern ratio. Because these levels are a factor of 10 above the threshold levels of most AMS labs they represent real 14C levels when none should be present according to uniformitarian principles. Another problem is that the ratios are uncorrelated with their position in the geological record. The older the strata in which the sample is found, the less 14C should be present, yet there is no correlation of 14C levels with age of strata. This calls into question the uniformitarian assumption that samples from different geological levels were deposited in different eras. Because these samples from ancient strata date to 44,000 to 57,000 years ago, they must all have been buried relatively contemporaneously only a few thousand years ago during a "global cataclysm." In order for 14C levels to be so low in life only a few thousand years old, the 14C/C ratios must have been much lower then. The most generous thing I can say about this is that Baumgardner is letting his flood assumptions affect his judgment, because he makes very simple and fundamental errors. If I weren't being generous then I would say that Baumgardner is purposefully misrepresenting the data knowing that fellow creationists will either ignore the misrepresentations or not even notice them. Baumgardner says that 0.1 to 0.5 percent of the modern 14C/C ratio is a factor of 10 above AMS threshold levels. By "AMS threshold levels" he means of the AMS instrument itself and doesn't include sample contamination, so his claim that this says something meaningful about AMS reliability is wrong. The instrument threshold is an order of magnitude smaller than sample contamination and so is overwhelmed by it. Betsche notes that Baumgardner improperly lumps geologic samples together with biologic samples when he draws conclusions about the lack of correlation with geologic level. Baumgardner also ignores the fact that both coal and carbonates easily absorb atmospheric CO2, providing extra 14C that skew the AMS results. He needs to treat such samples differently, but doesn't. I've left out a lot from Bertsche's conclusions, but here's the bottom line: There is no evidence that all carbon in the earth contains a detectable and reproducible ... level of 14C. --Percy Edited by Percy, : Fix typos.
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Percy Member Posts: 22881 From: New Hampshire Joined: Member Rating: 6.6
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Okay, thanks, I think I get it. If you take a multi-level site and attempt to date all the different levels using a poorly selected sample array, say only abalone, then you'll get an incomplete and potentially erroneous impression.
--Percy
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kbertsche Member (Idle past 2349 days) Posts: 1427 From: San Jose, CA, USA Joined:
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PhiloNibbler, take a look at this reference from my RATE analysis paper:
[4] R.E. Taylor and J.R. Southon, Use of Natural Diamonds to Monitor 14C AMS Instrument Backgrounds, Nuclear Instruments and Methods in Physics Research B259 (2007) 282-287. Taylor and Southon present a nice categorization of the different possible sources of contamination and background. Making measurements with an empty aluminum sample holder or with the ion source closed off from the rest of the system will allow characterization of SOME, but not ALL of the background. These measurements will give only a lower limit. In the real world, there will be a number of other contributions, specifically:1) there will be some false counts of radiocarbon when large amounts of C-12 and C-13 are present. This will depend on the specific details of the accelerator system, but is usually due to imperfect separation either in the accelerator or in the particle detector at the end of the system. Some of the C-12 or C-13 ends up being wrongly counted as C-14. 2) there will be cross-contamination in the ion source from previous samples ("ion source memory") and from atmospheric CO2. This is what Taylor and Southon were trying to study in the paper above. CO2 likes to stick to surfaces, and they theorized and showed that this would be lessened with diamond, which is hydrophilic. 3) there is always a small amount of modern carbon present in a sample due to the chemical procedures used to prepare the sample. This is why natural graphite usually gives the lowest (oldest) readings; it can simply be cleaned mechanically and pressed into a sample holder without the normal chemistry. Because of these and other background mechanisms, measurements with a blank sample holder are NOT reflective of the true background of an AMS system."Science without religion is lame, religion without science is blind." — Albert Einstein I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously. — Erwin Schroedinger
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Minnemooseus Inactive Member |
I was under the impression that dating shells is a shaky proposition.
Quoting myself from here:
As for the carbon dating of mollusk shells. I have posted on this before, at one of the radiometric dating topics. I pulled the info from my isotope geology text. For radiocarbon dating to be accurate, the carbon in question must have been in equilibrium with the atmosphere at the time of the life forms death. Or in the above case, while the mollusk is living. But the carbon content of seawater is often not in equilibrium with the atmosphere of the time. Rather, the carbon ratios perhaps reflects an atmosphere contact of the past. Or perhaps the carbon ratios of the sea floor sediment. There are also other potential problems. Reference:Principles of Isotope Geology, Gunter Faure, 1977, John Wiley & Sons, Inc. The dating of shells is discussed on pages 315-317. MooseProfessor, geology, Whatsamatta U Evolution - Changes in the environment, caused by the interactions of the components of the environment. "Do not meddle in the affairs of cats, for they are subtle and will piss on your computer." - Bruce Graham "The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness." - John Kenneth Galbraith "Yesterday on Fox News, commentator Glenn Beck said that he believes President Obama is a racist. To be fair, every time you watch Glenn Beck, it does get a little easier to hate white people." - Conan O'Brien "I know a little about a lot of things, and a lot about a few things, but I'm highly ignorant about everything." - Moose
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Coyote Member (Idle past 2324 days) Posts: 6117 Joined:
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Dating marine organisms of any kind can produce dates artificially old as they usually contain reservoir carbon, which has been isolated from the atmosphere.
The source you cited was 1977, but since then there has been a lot of research done on marine shells and other marine organisms. One of the ways to correct for the reservoir effect is to date shells collected from the area you're working, but you have to have shells from the pre-atomic bomb era. From dating a series of shells of known ages you can come up with a calibration. A website with this information is http://calib.qub.ac.uk/marine/ We test these calibration rates all the time. A few years back I came across a feature containing abalone, mussel, and charcoal in a context that showed they were contemporaneous. So, I dated all three materials and when all calibrations were applied the dates fell with a range of 14 years. That gives quite a bit of confidence in our local calibration figures. Another problem though is organisms that have both marine and terrestrial diets--including people and any dogs/coyotes that scavenge from their meals. Using the C14/N15 ratios obtained from the samples (usually bone in this case), we can estimate the percent of marine organisms in the diet and apply an appropriate correction for the reservoir effect. All of this is built into our main tool for calibrating or recalibrating dates--Calib. 7.1, available on the web at http://calib.qub.ac.uk/calib/calib.html Another problem with dating shells is dating freshwater shells that may be absorbing carbon from old limestone or other mineral deposits which is in the groundwater. Those certainly can date too old. I have tended to avoid dating those entirely.Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge. Belief gets in the way of learning--Robert A. Heinlein In the name of diversity, college student demands to be kept in ignorance of the culture that made diversity a value--StultisTheFool It's not what we don't know that hurts, it's what we know that ain't so--Will Rogers If I am entitled to something, someone else is obliged to pay--Jerry Pournelle If a religion's teachings are true, then it should have nothing to fear from science...--dwise1 "Multiculturalism" demands that the US be tolerant of everything except its own past, culture, traditions, and identity.
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RAZD Member (Idle past 1623 days) Posts: 20714 From: the other end of the sidewalk Joined:
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I was under the impression that dating shells is a shaky proposition. Indeed. You have the problem of the reservoir effect, and this is difficult to quantify for past data. There is a compilation of known present day reservoir effects due to the delay in moving CO2 from the atmosphere into the water and where sea water wells up from deep ocean currents Corrections to radiocarbon dates. and an interactive map http://radiocarbon.pa.qub.ac.uk/marine/ but this doesn't help you with fresh water reservoirs or where the carbon is accumulated from old dissolved calcite, limestone and the like. one can assume that they are the same now as in the past, but that is an assumption that should be tested by other correlations. Enjoy Edited by RAZD, : .by our ability to understand Rebel☮American☆Zen☯Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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OverallyEvolvedAPE Junior Member (Idle past 873 days) Posts: 10 Joined: |
Percy:
purposefully misrepresenting the data knowing that fellow creationists will either ignore the misrepresentations or not even notice them Aside from Baumgarder's motives I do think you're correct that most creationists do not attempt to read/understand the issues better because they simply rely on people like Ken Ham and Snellings, and Baumgarder to answer their questions and assume they are knowledgeable and being truthful. Of course it aligns with their interpretation of scripture. kbertsche: Thanks for the great response. I'll read over it tonight. I've come across your work before and found it interesting. One thing I did pick up on is how YEC sources portray all radiometric samples as closed systems and then accuse scientists of the same assumptions.
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Percy Member Posts: 22881 From: New Hampshire Joined: Member Rating: 6.6
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PhiloNibbler writes: Aside from Baumgarder's motives... I should be a bit more detailed about how I really feel about Baumgardner's stance. No one invests a lifetime in a cause they don't sincerely believe in, and so Baumgardner must believe the Earth is only a few thousand years old with all his heart. It's difficult to imagine the machinations his mind must go through to write things like this from 14C Evidence for a Recent Global Flood and a Young Earth:
quote: The obvious and blatant error is that he's ignoring sample contamination. He's making an argument that assumes that every bit of 14C above the instrument threshold level was actually from the sample and not contamination. Baumgardner is a brilliant scientist. Even brilliant scientists can be wrong, even profoundly wrong, but not about things as basic and simple as contamination. He's declaring, "Contamination outside the instrument doesn't exist," when the reality is that sample contamination is at least an order of magnitude larger than instrument contamination. How does Baumgardner reach such a dunderheaded conclusion? It appears he trusts someone else's dunderheaded conclusion, though on some level Baumgardner must know it's wrong. He relies upon Paul Giem's paper Carbon-14 Content of Fossil Carbon. About Giem's paper Baumgardner says on page 590:
quote: A reading of Giem's paper reveals that he understands the possible sources of contamination, but after many words he unjustifiably declares that the contamination problem is solvable (i.e., reduce contamination to indetectable levels) and that therefore contamination can be ignored. But he did no dating himself. He was reviewing papers about dating done by others where they described the contamination problem and definitely did not think it had been solved, as Bertsche's discussion makes clear. So is that why Baumgardner makes the errors he does, misplaced trust? That's a lot of trust. If you were a chemist, would you believe a paper by your most beloved collaborator declaring that dust in beakers doesn't affect experiments? Of course not. Baumgardner has no excuse for accepting such specious declarations about sample contamination. It's inexplicable. --Percy
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JonF Member (Idle past 386 days) Posts: 6174 Joined:
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Somewhat OT, but Baumgardner wrote a program modeling geophysical convection which (at least at the time) was the state of the art and garnered several real publications. He used it with physically impossible parameters to support a runaway subduction model similar to Walt Brown's Hydroplate (AKA Hydropants) "theory".
He also went to Turkey with Ron Wyatt but did not believe that what Wyatt found was the Ark. And he created Mendel's Accountant with John Sanford, which simulated evolution in a manner so as to prove Sanford's genetic entropy nonsense no matter what parameters you put in.
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edge Member (Idle past 1924 days) Posts: 4696 From: Colorado, USA Joined:
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So is that why Baumgardner makes the errors he does, misplaced trust? That's a lot of trust. If you were a chemist, would you believe a paper by your most beloved collaborator declaring that dust in beakers doesn't affect experiments? Of course not. Baumgardner has no excuse for accepting such specious declarations about sample contamination. It's inexplicable. I think that your analysis is spot-on. I would like to add another possible contributing factor. It is possible that Baumgardner doesn't really have an appreciation for contamination and sampling errors because of a general lack of field work and sampling experience. In fact, I've known a few geophysicists like that, and their sterile world of computer screens and databases simply don't carry the metadata of sampling conditions, geological history (natural contamination), or operator errors. These factors are often overlooked while we over-emphasize laboratory error and the labs become the whipping boys. I have one correspondent on another board who is convinced that laboratories and their workers are in on the great conspiracy of old ages. I often shudder to think of all the money I have spent on lab quality assurance/control to insure against the cause of 1% of the error.
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OverallyEvolvedAPE Junior Member (Idle past 873 days) Posts: 10 Joined: |
Percy: When I first found out the truth, I thought the worst of them, esp. Ken Ham and those who definitely should know better like Baumgardner and Snellings. But after reading Glen Morton's demon. The belief is real, but it's hard to tell how much they're deceiving themselves and how much they're knowingly deceiving others. Sadly, Ham sounds a little too much like a used car sales man when he does his presentations and makes me think the latter is true more than the former.
Baumgardner has no excuse for accepting such specious declarations about sample contamination. It's inexplicable. Totally right about that. A great example is when you point out factual errors that having nothing to do with their interpretation - such as miscopied sources - they still refuse to edit it to make it correct. How lazy is that? If I wrote something and someone pointed out I had misspelled a name or copied a quote wrong, I'd fix it and thank that person right away. Even magazines when their reporting information like a review of video games will issue corrections when pointed out. It just shows they don't really care about the truth or they don't actually read the original sources that their fellow YECs use. Totally, irresponsible. Of course, the run of the mill YEC has no idea they're being deceived because Morton's demon won't let them see the truth. I was on a YEC forum and had pointed out the during the Ham/Nye debate Ham had flipped a chart to make it unreadable to the audience (it actually disproved his point) and I found the original source which Ham provided during the presentation. When I pointed it out to them- and one person in responding asked whether the evo source had copied it from Ham! I about fell on the floor from shock.
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