Post by jonsdigs on Oct 11, 2006 19:51:54 GMT -5
Jenolan's ancient archives
Kate Rossmanith
October 11, 2006
The Australian
IN June the Jenolan Caves in the Blue Mountains of NSW were dated at 340 million years old. This makes them the oldest known open caves in the world. One hundred million years before dinosaurs, when amphibians wandered through ferns and forests, warm water rose beneath the east coast of Australia, creating hollows under the earth. When the ground split, spewing molten lava and raining ash into watery openings, a fine clay formed. It is this clay that has made dating the caves possible.
Armstrong Osborne, a speleologist from the University of Sydney, led the research team that made the discovery. He's happily flustered when we meet. He has done three radio interviews, agreed to another four, taken calls from reporters and fielded inquiries from leading international journals. It is his moment. Even in academic terms, where a 50-year-old is a mid-career researcher, his moment has been a long time coming.
For 25 years, Osborne and other speleologists suspected the Jenolan Caves were many millions of years older than the few thousand widely accepted, but they had no way to prove it. He completed his PhD on Jenolan in the 1980s and was told it might not be passed because of its radical proposals. "Most people were convinced the caves were quite young and those of us who thought they were really old couldn't find any evidence. But not even I imagined they'd date as far back as hundreds of millions of years," he says.
Determining the age of a cave is like solving a self-perpetuating riddle, for a cave names an absence. It is well established that the limestone at Jenolan is 430 million years old. But exactly when that rock succumbed to flows of water and air - when, as the traditional owners believe, Gurangatch, the giant creature that's part eel, part reptile, chased rivers and burrowed through stone - was more difficult to estimate.
The way to date a cave is to date the material inside it, in this case clay, the sedimentary substance with grains smaller than .002mm. It wasn't until 1999 that technology developed for the oil industry gave scientists from CSIRO, Sydney University and the Australian Museum the means to determine its age. And so work began.
Seven years ago, Osborne scooped and scraped 500g samples of tan and white clay by hand or trowel from a wall or corner of the caves, sometimes scratching together red dirt clumps of the stuff wedged between limestone. The samples were left in laboratories to sit and separate before tests could begin, and it took about a month to process each of them.
"The dating of clay is determined by tiny amounts of radioactive potassium. Over time the potassium turns to argon, a gas, which remains trapped, allowing us to measure the ratio of radioactive potassium to argon," he explains.
By determining the rate of decay, it is possible to pinpoint the birth of the clay. The researchers are working backwards, observing life's gentle decomposition.
Full Story:
www.theaustralian.news.com.au/story/0,20867,20557865-12332,00.html
Kate Rossmanith
October 11, 2006
The Australian
IN June the Jenolan Caves in the Blue Mountains of NSW were dated at 340 million years old. This makes them the oldest known open caves in the world. One hundred million years before dinosaurs, when amphibians wandered through ferns and forests, warm water rose beneath the east coast of Australia, creating hollows under the earth. When the ground split, spewing molten lava and raining ash into watery openings, a fine clay formed. It is this clay that has made dating the caves possible.
Armstrong Osborne, a speleologist from the University of Sydney, led the research team that made the discovery. He's happily flustered when we meet. He has done three radio interviews, agreed to another four, taken calls from reporters and fielded inquiries from leading international journals. It is his moment. Even in academic terms, where a 50-year-old is a mid-career researcher, his moment has been a long time coming.
For 25 years, Osborne and other speleologists suspected the Jenolan Caves were many millions of years older than the few thousand widely accepted, but they had no way to prove it. He completed his PhD on Jenolan in the 1980s and was told it might not be passed because of its radical proposals. "Most people were convinced the caves were quite young and those of us who thought they were really old couldn't find any evidence. But not even I imagined they'd date as far back as hundreds of millions of years," he says.
Determining the age of a cave is like solving a self-perpetuating riddle, for a cave names an absence. It is well established that the limestone at Jenolan is 430 million years old. But exactly when that rock succumbed to flows of water and air - when, as the traditional owners believe, Gurangatch, the giant creature that's part eel, part reptile, chased rivers and burrowed through stone - was more difficult to estimate.
The way to date a cave is to date the material inside it, in this case clay, the sedimentary substance with grains smaller than .002mm. It wasn't until 1999 that technology developed for the oil industry gave scientists from CSIRO, Sydney University and the Australian Museum the means to determine its age. And so work began.
Seven years ago, Osborne scooped and scraped 500g samples of tan and white clay by hand or trowel from a wall or corner of the caves, sometimes scratching together red dirt clumps of the stuff wedged between limestone. The samples were left in laboratories to sit and separate before tests could begin, and it took about a month to process each of them.
"The dating of clay is determined by tiny amounts of radioactive potassium. Over time the potassium turns to argon, a gas, which remains trapped, allowing us to measure the ratio of radioactive potassium to argon," he explains.
By determining the rate of decay, it is possible to pinpoint the birth of the clay. The researchers are working backwards, observing life's gentle decomposition.
Full Story:
www.theaustralian.news.com.au/story/0,20867,20557865-12332,00.html