Tracy P. Hamilton
Posts: 1239
Joined: May 2006
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| Quote (afdave @ Nov. 29 2006,17:08) | Tracy... | Quote | Abstract: Measurements of the radiocarbon concentration of several carbonate background materials, either mineral (IAEA C1 Carrara marble and Icelandic double spar) or biogenic (foraminifera and molluscs), show that the apparent ages of diverse materials can be quite different. Using 0.07 pMC obtained from mineral samples as a processing blank, the results from foraminifera and mollusc background samples, varying from 0.12 to 0.58 pMC (54.0-41.4 ka), show a species-specific contamination that reproduces over several individual shells and foraminifera from several sediment cores. Different cleaning attempts have proven ineffective, and even stronger measures such as progressive hydrolization or leaching of the samples prior to routine preparation, did not give any indication of the source of the contamination. In light of these results, the use of mineral background material in the evaluation of the age of older unknown samples of biogenic carbonate (>30 ka) proves inadequate. The use of background samples of the same species and provenance as the unknown samples is essential, and if such material is unavailable, generic biogenic samples such as mixed foraminifera samples should be used. The description of our new modular carbonate sample preparation system is also introduced.
In other words, different species in the same sample will have different amount of C-14. Now why would that be, AFDave? If they were the same "young" age, shouldn't they have the same C-14 content? |
Notice that they call this strange too high C14 "contamination". this is precisely my point. They are committed to Deep Time, yet they see this extra C14 and have to explain it somehow. What are they to do but ASSUME it is "contamination?" |
Dave, is not what you said an ASSUMPTION (i.e. that there should be no C-14 in sample X only because it is very old) . What is strictly correct to say is that IF the only C-14 in a sample is from what remains from C-14 that was originally in the sample, then there should be none left.
Assumptions can be tested. I already asked the question which showed that the sample of two different species in the same time and location have DIFFERENT C-14 levels. This means they did not have the same original C-14 levels (which would be an amazing mystery - care to put forward any testable hypotheses?), if there was no contamination.
Here is another article which may hint at what the REAL situation is about "old carbon"
Title: E/Q and ME/Q(2) interference in the two models of C-14 Tandetron systems: towards the 21st century
Author(s): Nadeau MJ, Lee HW, Litherland AE, Purser KH, Zhao XL
Source: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 223: 328-332 AUG 2004
Document Type: Article
Language: English
Cited References: 18 Times Cited: 2 Find Related Records Information
Abstract: All C-14 accelerator mass spectrometry (AMS) systems exhibit backgrounds mainly from sample contamination and target preparation. The imperfections in the associated mass spectrometric systems are at present lower and near C-14/C similar to10(-16). In view of the increased interest in much lower mass spectrometric background, <10(-18), for the measurement of natural hydrocarbons, a short review of the existing C-14 systems based upon the Tandetron accelerator will be presented. © 2004 Elsevier B.V. All rights reserved.
Now why would somebody need an instrument to measure C-14 in hydrocarbons if they were all young? Current methods are limited to 100,000 years ago. This instrument will get about 7 more half-lives, a total of 40,000 years more. We can explain "too high" levels easily enough - high levels of C-14 are everywhere on this planet, even the air you breathe. Your problem: explaining why there is ANY hydrocarbons without high levels of C-14.
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