Researchers unravel secrets of the past with new international carbon dating standard – sciencedaily


Radiocarbon dating is expected to become more accurate than ever after an international team of scientists improved the technique for assessing the age of historic objects.

The team of researchers from the universities of Sheffield, Belfast, Bristol, Glasgow, Oxford, St Andrews and Historic England, as well as international colleagues, used measurements of nearly 15,000 object samples dating back to 60 years ago. 000 years, as part of a seven-year project program.

They used the measurements to create new international radiocarbon calibration (IntCal) curves, which are fundamental across the scientific spectrum for accurately dating artifacts and making predictions about the future. Radiocarbon dating is vital for fields like archeology and geoscience to date everything from the oldest modern human bones to historical climate models.

Archaeologists can use this knowledge to restore historic monuments or study the disappearance of Neanderthals, while geoscientists at the Intergovernmental Panel on Climate Change (IPCC) use the curves to find out what the climate looked like. in the past in order to better understand and prepare for future changes.

Professor Paula Reimer, Queen’s University Belfast, responsible for 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. The IntCal calibration curves are essential. to help answer the big questions about the environment and our place in it. “

The research team developed three curves depending on where the object to be dated is located. The new curves, to appear in Radiocarbon, are IntCal20 for the northern hemisphere, SHCal20 for the southern hemisphere and Marine20 for the world’s oceans.

Dr Tim Heaton, University of Sheffield and lead author of the Marine20 Curve, said: “It is a very exciting time to work on radiocarbon. Developments in the field have really helped advance our understanding. I can’t wait to see what new information about our past these recalculated radiocarbon timescales provide. “

Previous radiocarbon calibration curves developed over the past 50 years relied heavily on measurements taken from pieces of wood spanning 10 to 20 years large enough to be tested for radiocarbon.

Advances in radiocarbon testing mean that the updated curves instead use tiny samples, such as tree rings spanning a single year, which provide precision and detail previously not possible in the new calibration curves. In addition, improved understanding of the carbon cycle allowed the curves to be extended to the limit of radiocarbon technology 55,000 years ago.

Radiocarbon dating is the most common approach used to date the past 55,000 years and underpins archaeological and environmental sciences. It was first developed in 1949. It depends on two carbon isotopes called stable 12C and radioactive 14C.

When a plant or animal is alive, it absorbs new carbon and therefore has the same ratio of these isotopes as the atmosphere at the time. But once an organism dies, it stops taking in new carbon, the stable 12C remains but the 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, that would be easy. However, it has fluctuated considerably throughout history. In order to accurately date organisms, scientists need a reliable historical record of its variation to accurately transform 14C measurements into calendar ages. The new IntCal curves provide this link.

The curves are created based on the collection of a large number of records which store the past radiocarbon but can also be dated by another method. These records include tree rings dating as far back as 14,000 years ago, stalagmites found in caves, sea corals, and cores drilled in lake and ocean sediments. In total, the new curves were based on nearly 15,000 radiocarbon measurements taken from objects as old as 60,000 years old.

Alex Bayliss, Scientific Dating Manager at Historic England, said: “Accurate, high-precision radiocarbon dating enables the public to enjoy the historic environment and allows for better preservation and protection.

“The new curves have implications of international importance for archaeological methodology and for practices of conservation and understanding of built heritage in wood.”

IPCC’s Darrell Kaufman said: “The IntCal series of curves are essential in providing a perspective on past climate that is essential for our understanding of the climate system, and a baseline for modeling future changes.”


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