Radiocarbon dating is about to become more accurate than ever after an international team of scientists improved the technique for assessing the age of historical objects.
The team of researchers from the Universities of Sheffield, Belfast, Bristol, Glasgow, Oxford, St Andrews and Historic England used measurements of nearly 15,000 samples of objects dating back 60,000 years as part of a seven-year project. Q>
They used the measurements to create new International Radiocarbon Calibration Curves (IntCal), which are critical across the scientific spectrum for accurately dating artifacts and making predictions about the future. Radiocarbon dating is vital to fields like archeology and geoscience to date everything from the oldest modern human bones to historical weather patterns.
Archaeologists can use that knowledge to restore historic monuments or study the disappearance of Neanderthals, while geoscientists from the Intergovernmental Panel on Climate Change (IPCC) rely on curves to figure out what the climate was like in the past to understand better and prepare for future changes.
Professor Paula Reimer, from Queen's University Belfast and Director of the IntCal project, said:Radiocarbon dating has revolutionized the field of archeology and environmental science. As we improve the calibration curve, we learn more about our history. IntCal's calibration curves are key to helping answer the big questions about the environment and our place within it .
The team of researchers has developed three curves depending on where the object to be dated is located. The new curves are IntCal20 for the Northern Hemisphere, SHCal20 for the Southern Hemisphere and Marine20 for the world's oceans.
Previous radiocarbon calibration curves developed over the last 50 years relied heavily on measurements taken from 10 to 20 year old logs of wood, large enough to be used for radiocarbon.
Advances in radiocarbon testing mean that the updated curves instead use minute samples, such as tree rings covering just one year, which provide precision and detail previously impossible to obtain in the new calibration curves. Furthermore, improvements in understanding of the carbon cycle have meant that the curves have been stretched to the limit of the radiocarbon technique, which goes back to 55,000 years ago.
Radiocarbon dating is the most widely used approach to dating the last 55,000 years and is the foundation of archaeological and environmental science. It was first developed in 1949. It relies on two isotopes of carbon called stable 12C and radioactive 14C .
While a plant or animal is alive it takes on new carbon, so it has the same ratio of these isotopes as the atmosphere at that time. But once an organism dies it stops taking up new carbon, 12C remains but 14C decays at a known rate. By measuring the ratio of 14C to 12C left in an object, the date of its death can be estimated.
If the atmospheric 14C level were constant, this would be easy. However, it has fluctuated significantly throughout history. In order to date organisms, scientists need a reliable historical record of their variation to accurately transform 14C measurements into calendar ages. The new IntCal curves provide this link.
The curves are created from the collection of a large number of archives that store radiocarbon from the past, but can also be dated using another method. Such archives include tree rings up to 14,000 years old, stalagmites found in caves, corals from the sea, and cores drilled from lake and ocean sediments. In all, the new curves were based on nearly 15,000 radiocarbon measurements taken from objects as old as 60,000 years.