the following is a short discussion of dating methods used at a burial in which flowers were used to adorn the bodies. the burial was at Mount Carmel in northern Israel: I thought it was informative. Did the collapse of empires in the Early Bronze Age occur earlier than previously thought? These questions are being addressed with the help of advanced equipment – the first of its kind in the entire Middle East – set up recently in the building that previously housed a particle accelerator. The newly-installed technology – the Dangoor-Research Accelerator Mass Spectrometer, or D-REAMS – is used to determine the age of archaeological samples by measuring the concentration of the radioactive carbon, or 14C. The method is based on determining the ratio between 14C and the stable carbon atoms, 12C and 13C: since 14C decays over time while the amount of stable carbon remains constant, the fewer radioactive atoms are found in a sample compared to the stable ones, the older the sample. High precision dating In the past, radiocarbon dating required relatively large amounts of material, at least several grams, because it relied on measuring 14C indirectly, by observing its decay. In contrast, an accelerator mass spectrometer like D-REAMS, which accelerates atoms to high energies before analysis, directly counts the radiocarbon atoms. Its precision is remarkable, considering that for every radioactive 14C there are anywhere between a trillion to a quadrillion stable carbon atoms. As a result, dating can be performed on a sample as small as a few milligrams. “A 5-gram sample, the equivalent of a small sugar packet, could yield about 5,000 measurements,” says Boaretto, who heads the D-REAMS laboratory. “It is even possible to date a single seed.” D-REAMS can shed new light on the distant past thanks to the high precision of its dating. It can, for example, help determine when our ancestors, early Homo sapiens, migrated out of Africa. One of their first stops in the Near East was the site of Boker Tachtit, located in a sun-scorched ravine in Israel’s southern Negev desert. Radiocarbon dating of the material from an earlier excavation of Boker Tachtit in the 1970s suggested that the site was occupied about 47,000 years ago. But the dating method at the time was imprecise, so the question has remained open: When exactly was Boqer Tachtit inhabited?
Posted on: Fri, 19 Jul 2013 19:10:48 +0000
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