COMING OF AGE: RADIOCARBON IN 2011

The radiocarbon dating technique is now more than 1% of a ¹⁴C half-life old, and in many ways it remains the gold standard for geochronology for the last 50kyr, since it provides chronologies that are based on one of the major elements of all life forms. Starting in the early 1980’s, the advent of Accelerator Mass Spectrometry (the so-called third radiocarbon revolution) has led to thousand-fold decreases in sample size and increases of 10-30 in throughput; and measurement precisions that were once attainable by just a handful of radiometric ¹⁴C labs worldwide are becoming relatively routine with AMS. However, many of the problems that were uncovered by the earliest pioneers in the field are still with us, and in some cases they have been exacerbated by increases in precision, reductions in sample size, and new efforts to tackle the dating of materials requiring complex chemical extractions, such as bone, pollen, biomarkers, etc. The long-standing question of “What is my blank?” is just as important as it ever was, and even more so for small samples and complex pretreatment procedures. Calibration of radiocarbon dates to calendar years is critically important for correctly comparing radiocarbon-dated records with archives dated by U/Th measurements or layer counting in ice cores, but calibration beyond the current`~14kyr limit of dendrochronology remains challenging. Furthermore, it appears that variations in ocean-atmosphere ¹⁴C offsets over time were more widespread than previously thought, which has major implications for dating of marine materials; and the potential for significant (though much smaller) regional offsets in terrestrial materials must now also be taken seriously. But in spite of these difficulties, demand for ¹⁴C analyses far exceeds supply (at least in North America) which suggests that there’s a lot of life left in the old dog yet.