That remains a mystery waiting to be solved." Samples from Jinmium were tested using both radiocarbon (C14) and optically-stimulated luminescence - or OSL, a new, powerful dating method developed largely in Australia, capable of dating the time of burial of individual grains of sand.
OSL works on the principle that sunlight releases the natural energy stored as trapped electrons in the crystal lattice of tiny grains of quartz sand.
This research involves the collection of sediment samples in locations as diverse as Arctic Canada, BC's central coast, Australia, and Patagonia.
These samples are then dated, and the age information is used to help understand the nature of long term environmental change.
As a cross-check, fragments of charcoal from the site were dated using a second method, C14 or radiocarbon dating.
This minute amount of energy can be artificially released by stimulating the sand grains with a green light, explains CSIRO scientist Dr Jon Olley.While luminescence is an accurate method of dating the sand grains in sediment, there are a number of pitfalls associated with using this dating method to determine the age of sites.For a start, 3000 sand grains are required, and the sample will likely contain a mixture of earlier and later grains, especially if it is taken from less than 20cm below the ground surface, or within 20cm of bedrock.Deposits below the shelter contained artefacts down to a depth of 1.6 metres, including an engraved sandstone fragment.Initial tests used a technique known as thermoluminescence and indicated a possible age for the lowest layers containing artefacts of between 116-176,000 years.Where radiocarbon dating has a ‘barrier’ of about 40,000 years, luminescence can be used to date material millions of years old.Many older sites in Australia are being dated using a combination of luminescence and radiocarbon, to ensure the accuracy of dates.The older OSL dates are probably due to some grains not being exposed to sufficient sunlight before burial.Based on these results, the researchers conclude that human habitation of the Jinmium site is certainly no older than 10,000 years (ie end of the last ice-age), and probably quite a bit younger, with the oldest inhabited level being perhaps 6000 years old - about the time farming began in the Middle East.The laboratory welcomes visiting colleagues from other universities, and, from time to time, undertakes limited contract work. The laboratory absorbed, and replaced, the Optical and TL Dating Laboratory in the Physics Department at Simon Fraser University which closed due to the retirement of its director, Prof.