Shells provide climate clues
First published 31 July 2012
A James Cook University researcher will lead a ground-breaking study into how seashells from tropical Australia and southern Papua New Guinea can help us understand climate change and archaeological patterns.
Dr Sean Ulm, a Lecturer in JCU’s School of Arts and Social Sciences has been awarded $700,000 over the next four yearsunder the Australian Research Council’s highly competitive Future Fellowships program to improve dating marine shells in the tropics using radiocarbon techniques.
Radiocarbon dating is one of the main ways in which archaeologists and environmental scientists estimate the age of ancient organic materials.
All living organisms absorb radioactive carbon, which begins to decay when the organism dies.
Because this process of decay occurs at a known rate, it is possible to estimate how long something has been dead by measuring the amount of radiocarbon left in the organism.
Dr Ulm said a basic assumption of the radiocarbon dating method is that the concentration of radioactive carbon is uniform through space and time, but this was not the case with marine environments.
“Significant variability in the way carbon is distributed in marine environments means there can be hundreds of years of difference between the radiocarbon date of a shell and its actual age,” he said.
“This is what scientists call the ‘marine reservoir’ effect and we currently have no reliable way of accounting for it through space and time.
“Marine shells are a routine source of dates for archaeological and palaeoecological deposits across Australasia, so it’s critical that we have an accurate way of calibrating their radiocarbon ages.”
Dr Ulm’s research will involve locating and then radiocarbon dating shells in museum collections throughout Australia as well as PNG and the United Kingdom.
By comparing the radiocarbon ages of suitable museum specimens with their known ages Dr Ulm said he would be able to construct a systematic model of marine reservoir effects across northern Australia and southern PNG.
“Not only will this calibration model be important for a better understanding of archaeological chronologies in our region, but also for finer-grained reconstructions of sea-levels and climate change through time,” he said.
The Australian Research Council’s Future Fellowships program is designed to attract and retain the best and brightest mid-career researchers in Australia.
In 2012 the program will provide $151 million to around 200 Australian and international researchers to conduct their research in Australia.
Dr Ulm was one of two JCU researchers to be awarded funding under the program in 2012.
He is also a Fellow of the Society of Antiquaries of London, an Honorary Senior Fellow at The University of Queensland, an Honorary Associate of the Queensland Museum and a Fellow of the Cairns Institute.
For interviews, contact Dr Ulm on (07) 4042 1194 or 0417 792 191.
JCU Media contact: Caroline Kaurila (07) 4781 4586 or 0437 028 175