Australia

Cave Fossils expose New Mysteries of a Paradise Lost
by Graeme Leech, Dec 4, 1999

Fossil evidence found on cliffs near several Sydney beaches has revealed a tropical paradise existed in NSW as recently as 6000 years ago – a virtual blink of an eye in geological terms. The findings by University of New England scientists also suggest answers to a number of historical mysteries. Bob Haworth said the dramatic change in sea levels and in climate could help explain why the ancient Egyptians stopped building the pyramids, why the Bronze Age came to an abrupt halt, why the Dark Ages began and why social collapse seemed to take place wherever civilisations were beginning to emerge. "There were winners and losers. It was a disaster for Egypt but lower sea levels made it easier for people to make trans-ocean journeys in parts of the Pacific," Dr Haworth said. Dr Haworth and colleague Bob Baker first noticed in 1997 fossils of tropical coral worms preserved and encrusted beneath a rock fall below cliffs near Cronulla, in Sydney's south.

The fossils have since been dated to show they were deposited 6000 years ago. The creatures can only survive in tropical conditions similar to coral reefs off the Queensland coast. Further studies south at Bundeena, and north on Broken Bay and the Hawkesbury show that the scientists have also found an accurate record of changes in sea levels that, in turn, shed light on climate change. Around Sydney between 4300BC and 3400BC, the district was a "Garden of Eden", Dr Haworth said. The Homebush site for the Olympics would have been under water and waves would have lapped the edges of what is now the Sydney Cricket Ground. The sea would have been home to dugongs and other tropical marine animals. There was an explosion in the Aboriginal population. The Murray Valley was "buzzing" with activity – until the climate changed and a long period of population decline began.

In an article to be published in the journal Marine Geology, Peter Flood, Dr Baker and Dr Haworth challenge assumption that sea levels have been stable for the past 6000 years. They say their evidence means greenhouse models will have to be rethought. Why did the climate change? Dr Baker said one "purely speculative" explanation was sunspot activity, but he felt it was more likely to be due to a change in the pattern of ocean currents worldwide. "Whatever, it (the article) is going to be very controversial," Dr Baker said.