Effective range of carbon dating
Radiocarbon measurements are based on the assumption that atmospheric carbon-14 concentration has remained constant as it was in 1950 and that the half-life of carbon-14 is 5568 years.
Calibration of radiocarbon results is needed to account for changes in the atmospheric concentration of carbon-14 over time.
They can determine the exact calendar year each tree ring was formed.
Dendrochronological findings played an important role in the early days of radiocarbon dating.
Carbon consists of 99% carbon-12, 1% carbon-13, and about one part per million carbon-14.
It is also worth noting that the half-life used in carbon dating calculations is 5568 years, the value worked out by chemist Willard Libby, and not the more accurate value of 5730 years, which is known as the Cambridge half-life.
Although it is less accurate, the Libby half-life was retained to avoid inconsistencies or errors when comparing carbon-14 test results that were produced before and after the Cambridge half-life was derived.
BP stands for “Before Present” or “Before Physics” as some would refer to it.
It should be noted that a BP notation is also used in other dating techniques but is defined differently, as in the case of thermoluminescence dating wherein BP is defined as AD 1980.
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For the period after 1950, a great deal of data on atmospheric radiocarbon concentration is available.