This was published 17 years ago
Joy echoes at discovery that Jenolan Caves are world's oldest
By Deborah Smith Science Editor
THE Jenolan Caves in the Blue Mountains have been dated at 340 million years old, making them the oldest known open caves in the world.
In a five-year study, a team of Australian scientists tested clay from caves regularly visited by tourists, such as the Orient Cave and Temple of Baal Cave, to determine their ancient origins.
Team member, ArmstrongOsborne, of the University of Sydney, said it had been thought for many years that the limestone caves were only a few thousand years old.
Then, about six years ago, geologists estimated they could have formed as long as 100 million years ago.
The new finding was a shock.
"The dates we got are much older than anticipated. It is quite dramatic," Dr Osborne said.
The second oldest known open cave is in the Guadelupe Mountains in New Mexico, US, which is 65 million years old. Most other famous caves, such as Postojna Cave in Slovenia, are thought to be only about 5 million years old, he said.
For the study, CSIRO scientists, led by Dr Horst Zwingmann, used a method they had developed to help oil exploration companies find oil deposits. By testing minerals in mud samples from the floors of the caves at Jenolan, they were able to show that the clay had formed in the distant past from ash blown in from a nearby volcano.
Dr Osborne said 340 million years was a long time, even in geological terms. "To put it in context, the Blue Mountains began to form 100 million years ago; dinosaurs became extinct 65 million years ago and Tasmania was joined to the mainland as recently as 10,000 years ago."
He said the discovery, published in the Australian Journal of Earth Sciences, could assist in a push for Jenolan Caves to gain world heritage listing in their own right, not just as part of the Blue Mountains listing.
"They deserve it. They are one of the world's most complicated cave systems," he said.
Most ancient caves around the world have filled up with rock, and are no longer accessible, Dr Osborne said.