Researchers unlock secrets of the past with new international carbon
dating standard

Date:
August 12, 2020
Source:
University of Sheffield
Summary:
Radiocarbon dating is set to become more accurate than ever after
an international team of scientists improved the technique for
assessing the age of historical objects.



FULL STORY ========================================================================== Radiocarbon dating is set 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 at the Universities of Sheffield, Belfast,
Bristol, Glasgow, Oxford, St Andrews and Historic England, plus
international colleagues, used measurements from almost 15,000 samples
from objects dating back as far as 60,000 years ago, as part of a
seven-year project.

They used the measurements to create new international radiocarbon
calibration (IntCal) curves, which are fundamental across the scientific spectrum for accurately dating artefacts and making predictions about
the future.

Radiocarbon dating is vital to fields such as archaeology and geoscience
to date everything from the oldest modern human bones to historic
climate patterns.

Archaeologists can use that knowledge to restore historic monuments
or study the demise of the Neanderthals, while geoscientists on the Intergovernmental Panel on Climate Change (IPCC), rely upon the curves to
find out about what the climate was like in the past to better understand
and prepare for future changes.

Professor Paula Reimer, from Queen's University Belfast and head of the
IntCal project, said: "Radiocarbon dating has revolutionised the field
of archaeology and environmental science. As we improve the calibration
curve, we learn more about our history. The IntCal calibration curves
are key to helping answer big questions about the environment and our
place within it." The team of researchers have developed three curves dependent upon where the object to be dated is found. The new curves,
to be published in Radiocarbon, are IntCal20 for the Northern Hemisphere, SHCal20 for the Southern Hemisphere, and Marine20 for the world's oceans.



==========================================================================
Dr Tim Heaton, from the University of Sheffield and lead author on
the Marine20 curve, said: "This is a very exciting time to be working
in radiocarbon.

Developments in the field have made it possible to truly advance our understanding. I look forward to seeing what new insights into our
past these recalculated radiocarbon timescales provide." The previous radiocarbon calibration curves developed over the past 50 years, were
heavily reliant upon measurements taken from chunks of wood covering 10
to 20 years big enough to be tested for radiocarbon.

Advances in radiocarbon testing mean the updated curves instead use tiny samples, such as tree-rings covering just single years, that provide
previously impossible precision and detail in the new calibration
curves. Additionally, improvements in understanding of the carbon cycle
have meant the curves have now been extended all the way to the limit
of the radiocarbon technique 55,000 years ago.

Radiocarbon dating is the most frequently used approach for dating
the last 55,000 years and underpins archaeological and environmental
science. It was first developed in 1949. It depends upon two isotopes
of carbon called stable 12C and radioactive 14C.

While a plant or animal is alive it takes in new carbon, so 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 level of atmospheric 14C were constant, this would be
easy. However, it has fluctuated significantly throughout history. In
order to date organisms precisely 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 collecting a huge number of archives which store past radiocarbon but can also be dated using another method. Such archives include tree-rings from up to 14,000 years ago, stalagmites
found in caves, corals from the sea and cores drilled from lake and
ocean sediments. In total, the new curves were based upon almost 15,000 measurements of radiocarbon taken from objects as old as 60,000 years.

Alex Bayliss, Head of Scientific Dating at Historic England, said:
"Accurate and high-precision radiocarbon dating underpins the public's enjoyment of the historic environment and enables better preservation
and protection.

"The new curves have internationally important implications for
archaeological methodology, and for practices in conservation and
understanding of wooden built heritage." Darrell Kaufman of the
IPCC said: "The IntCal series of curves are critical for providing a perspective on past climate which is essential for our understanding of
the climate system, and a baseline for modelling future changes."

========================================================================== Story Source: Materials provided by University_of_Sheffield. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Timothy J Heaton, Peter Ko"hler, Martin Butzin, Edouard Bard, Ron W
Reimer, William E N Austin, Christopher Bronk Ramsey, Pieter
M Grootes, Konrad A Hughen, Bernd Kromer, Paula J Reimer,
Jess Adkins, Andrea Burke, Mea S Cook, Jesper Olsen, Luke C
Skinner. MARINE20--THE MARINE RADIOCARBON AGE CALIBRATION CURVE
(0-55,000 CAL BP). Radiocarbon, 2020; 1 DOI: 10.1017/RDC.2020.68 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200812144122.htm

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