Carbon dating article
Lake Suigetsu's annually formed sediments hold detailed information about environmental changes over the past 50,000 years, which radiocarbon specialist PJ Reimer believes will be as good as, and perhaps better than, samples cores from the Greenland Ice Sheet. report 808 AMS dates based on sediment varves measured by three different radiocarbon laboratories.
The dates and corresponding environmental changes promise to make direct correlations between other key climate records, allowing researchers such as Reimer to finely calibrate radiocarbon dates between 12,500 to the practical limit of c14 dating of 52,800.
Other organic data sets examined have included varves (layers in sedimentary rock which were laid down annually and contain organic materials, deep ocean corals, speleothems (cave deposits), and volcanic tephras; but there are problems with each of these methods.
Cave deposits and varves have the potential to include old soil carbon, and there are as-yet unresolved issues with fluctuating amounts of C14 in ocean corals.
It was the first absolute scientific method ever invented: that is to say, the technique was the first to allow a researcher to determine how long ago an organic object died, whether it is in context or not.
Shy of a date stamp on an object, it is still the best and most accurate of dating techniques devised.
In his spare time, Stephen reads and writes novels.
You have to know what the atmospheric carbon level (the radiocarbon 'reservoir') was like at the time of an organism's death, in order to be able to calculate how much time has passed since the organism died.Beginning in the 1990s, a coalition of researchers led by Paula J.Reimer of the CHRONO Centre for Climate, the Environment and Chronology, at Queen's University Belfast, began building an extensive dataset and calibration tool that they first called CALIB.Reimer and colleagues point out that Int Cal13 is just the latest in calibration sets, and further refinements are to be expected.For example, in Int Cal09's calibration, they discovered evidence that during the Younger Dryas (12,550-12,900 cal BP), there was a shutdown or at least a steep reduction of the North Atlantic Deep Water formation, which was surely a reflection of climate change; they had to throw out data for that period from the North Atlantic and use a different dataset.
Their recent analysis of sediment from the largest freshwater lake in northeast China showed that its carbon clock stopped ticking as early as 30,000 years ago, or nearly half as long as was hitherto thought.