Cal bp radiocarbon dating
For the remaining period 12,400-26,000 cal yr BP, the curve is derived from independently dated marine samples such as foraminifera and corals.A new internationally-ratified calibration curve (Int Cal09) covering the whole radiocarbon timescale (~50,000 cal yr) is being prepared by the Int Cal Working Group.This curve covers the past 11,000 cal yr, which is based on the dendrochronologically-dated tree rings for the last millennium and on model ages for the remaining period.The deep ocean waters are isolated from the atmosphere for long periods of time (the residence time of carbon in the deep ocean is ~800 yr).Terrestrial (Int Cal04) and Marine (Marine04) radiocarbon calibration curves for the past 26,000 cal yr BP. Calibrated ages are shown for 1σ and 2σ (68.2% and 95.4% confidence levels, respectively). Details Calibration of a radiocarbon age of 6550 ± 40 BP of a terrestrial sample from the Northern Hemisphere, using Int Cal04 calibration curve and Ox Cal program version 3.10.
Details C concentrations are mainly due to variations in the rate of radiocarbon production in the atmosphere, caused by changes in the Earth's magnetic field and variability in solar activity, and changes in the carbon cycle.
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These variations are due to changes in ocean circulation and the carbon cycles associated with climatic change.
Temporal variations in C was artificially produced when hundreds of nuclear test weapons were detonated in the atmosphere, mostly in the Northern Hemisphere, in the late 1950s and early 1960s.