Formula for calculating carbon dating

The Conventional Radiocarbon Age BP is calculated using the radiocarbon decay equation: Where -8033 represents the mean lifetime of 14C (Stuiver and Polach, 1977).

In an earlier section we mentioned that the limit of the technique is about 55-60 000 years.Should the activity of the sample be indistinguishable from the background activity at 1 standard deviation, it is released as background.Samples whose age falls between modern and background and are given finite ages.The terms "%Modern", or "pm C" and D14C are shown related in this diagram along with the Radiocarbon age in years BP (Before 1950 AD).If the reservoir corrected conventional radiocarbon age calculated is within the past 200 years, it should by convention be termed 'Modern' (Stuiver and Polach, 192).Beukens (1994) for instance has stated that this means the limit of the range for his Isotrace laboratory is 60 000 yr which is very similar to the conventional range.Figure 1: This gif shows the comparison in radioactivity between a sample, or unknown (green area) , a modern standard (dark blue) and a background (small red peaks) derived from beta decay. A radiocarbon measurement, termed a conventional radiocarbon age (or CRA) is obtained using a set of parameters outlined by Stuiver and Polach (1977), in the journal Radiocarbon.Thus, %Modern becomes a useful term in describing radiocarbon measurements for the past 45 years when, due to the influx of artificial radiocarbon into the atmosphere as a result of nuclear bomb testing the 'age' calculation becomes a 'future' calculation.If the sample approaches D14C = -1000 per mille within 2 standard deviations, it is considered to be indistinguishable from the laboratory background, ie, not able to be separated with confidence from the laboratory countrates which result from a sample which contains no radionuclide. An example of a minimum age is 50, 000 yr (Gupta and Polach, 1985).In order to make allowances for background counts and to evaluate the limits of detection, materials which radiocarbon specialists can be fairly sure contain no activity are measured under identical counting conditions as normal samples.Background samples usually consist of geological samples of infinite age such as coal, lignite, limestone, ancient carbonate, athracite, marble or swamp wood.

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