Suggested terminology for quaternary dating methods

47 48 3 DATING METHODS I DATING METHODS Direct measurement of radioisotope or of decay products (^*C, K/Ar) Growth rates (lichenometry) Growth layers (dendrochronology) CHEMICAL PALEOMAGNETIC Incidence of reversals Secular variations 7^ Organic (amino acid racemization) Inorganic Weathering rates (obsidian hydration) FIGURE 3.1 'Fingerprinting' (tephrochronology) Principal dating methods used in paleoclimatic research.

For any one element, the number of protons (the atomic number) is invariant, but the number of neutrons may vary, resulting in different isotopes of the same element.Strenuous efforts must therefore be made to date all proxy materials, to avoid sample contamination, and to ensure that the stratigraphic context of the sample is clearly understood.It is equally important that the assumptions and limitations of the dating procedure used are understood so that a realistic interpretation of the date obtained can be made.A single "absolute" (i.e., numerical) age can therefore never be assigned to a sample.Rather, dates are reported as the midpoint of a Poisson probability distribution; together with its standard deviation, the date thus defines a known level of probability. R, for example, indicates a 68% probability that the true (radiocarbon) age is between 49 yr B.

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