Sunday, April 30, 2017

C-14-dating makeover?

TECHNOLOGY WATCH: Radiocarbon dating gets a postmodern makeover (Emily Litvack, PhysOrg).
For decades, radiocarbon dating has been a way for scientists to get a rough picture of when once-living stuff lived. The method has been revolutionary and remains one of the most commonly used dating methods to study the past.

Charlotte Pearson says it's ready for a makeover.

Pearson, an assistant professor of dendrochronology at the University of Arizona, studies the past lives of trees to better understand the history of civilizations. Dendrochronology and radiocarbon dating have intertwined histories, she explains, with roots firmly planted at the UA.

I don't really see the title's "postmodern" element of the makeover, but more attention to the dendrochronological data may well give radiocarbon dating a more precise anchoring.
A New Method

According to Pearson, recent discoveries of large-scale "spikes" of radiocarbon in certain years have led to a growing need to revisit the way radiocarbon dates are calibrated.

Radiocarbon dating, as of now, dates samples to within a few decades using a calibration curve made up of groups of ten tree rings plotted as series of single points on a graph. The points represent an average amount of radiocarbon present in those rings. This doesn't account for spikes in the data —individual rings with unusually high or low amounts of carbon-14. These spikes in radiocarbon can come from a number of short-term events, such as solar flares, volcanic eruptions and changes in oceanic circulation. By lumping 10 years' worth of radiocarbon data into a single data point, spikes in radiocarbon may inadvertently skew the curve, making dates less accurate.

"Spikes are a potential limitation to how well the current radiocarbon calibration curve works, and we want to investigate that for time periods of archaeological controversy. But they also offer enormous potential to act as a sort of chronological anchor for our floating chronologies," Pearson said.

With funding from the Malcolm Hewitt Wiener Foundation, Pearson is targeting a period in the Bronze Age from 2,400 to 1,400 BC, getting measurements of carbon-14 in single tree rings from a range of growth locations. What this reveals about yearly radiocarbon variation during this time period will then be applied to archaeological controversies and floating chronologies from the East Mediterranean and beyond.

"Tree rings just record. They are impartial recorders of change over time. They have no bias, and they have no political agenda; they just stand at locations all over the world," Pearson says. "They capture a moment. We still have many discoveries, I believe, to make about what they can teach us."
None of this is immediately relevant to ancient Judaism. But there is much potential. A more precise framework of radiocarbon dating could, for example, confirm or complicate the paleographic dating of manuscripts from the Second Temple period.