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When this matter is heated to 275°C, the trapped electrons revert to their fundamental level by emitting radiation (luminescence peak).The technique consists in subjecting the sample to additional known irradiation doses, in order to calculate the paleodose (which is to say the irradiation that the sample was exposed to during the period of time since it was last heated (for flint), or since its formation (for calcite).An ultrafiltration technique isolates collagen macromolecules, which often results in much older dates (Higham , 2006; table 2).If the samples are "clean", the different methods give similar results, but if they are very polluted, purification by ultrafiltration can yield ages several thousand years older, which calls into question certain archeological hypotheses, like for example the notion of a Neanderthal "refuge" south of the Ebre (Wood C concentration.C is constant in all living creatures and begins to decrease from their time of death, when there is no further exchange with the environment.Libby (1949) inferred from this that it was possible to determine the date of the death of the organism by measuring the residual proportion of C, what we refer to as "dead carbon", for example from carbonates of geological origin), then the age is older, but this is independent from the age of the sample and the effects are limited (less than 900 years for 10% of dead carbon; figure 1On the other hand, impurities containing recent carbon are a particularly serious source of error, especially for older samples.In sum, the classical method of charcoal preparation, called ABA (three steps consisting of an acid treatment, then basic, then acid again) has now been replaced by a variant known as ABOx-SC (an oxidation stage and step combustion are added to the acid and basic treatment).In nearly all cases, the ABOx-SC procedure yields dates 3000 to 5000For bone dating, a new method of collagen extraction and purification has also been developed.

A second cause of error is due to what we call the reservoir effect of oceans.The effects of this correction become very significant and inaccurate beyond 30 ka.It is for this reason that the period corresponding to the advent of anatomically modern humans () in Europe and the transition from Neanderthal Man to modern Man remains relatively poorly secured on an absolute time scale, opening the way to all sorts of speculation and controversy.A sample with a real age of 40000 years, only containing 1% of recent carbon, would yield an apparent age of 32800 years, which corresponds to a rejuvenation of 7200 years!(figure 1Therefore the main cause of error in radiocarbon dating is the presence of recent carbon leading to more recent dates.

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