Naracoorte caves in South Australia's southeast have world, national heritage status for huge fossils trove
The Naracoorte caves, in southeast South Australia, remained a scientic research site but controlled access was allowed to visitors, with reconstructed skeletons displayed from the 5,000 tonnes of bones estimated to have accumulated in the system over 300,000 years.
The South Australian southeast Naracoorte cave system, part of Australian fossil mammal site, was one of 15 world heritage places included in the Australian national heritage list in 2007.
The Australian fossil mammal site was a serial listing of Naracoorte and Riversleigh, Queensland. Among the world’s 10 greatest fossil sites, they were listed as a superb illustration of key stages in evolving the unique fauna of Australia – the world's most isolated continent. They were outstanding for the extreme diversity and the preserved quality of their fossils that helped understanding of the history of mammal lineages in modern Australia.
Naracoorte caves were near Naracoorte township, about 320 kilometres southeast of Adelaide. Naracoorte Caves were gazetted in 1917. The Naracoorte Caves Conservation Park was proclaimed in 1972. Visitor access at Naracoorte was controlled to protect the caves’ scientific, conservation and aesthetic values. The Pleistocene fossil vertebrate deposits of Victoria Fossil Cave at Naracoorte were considered Australia's largest and best preserved and one of the world’s richest deposits.
Visitors to the Naracoorte Caves’ spectacular limestone forms for more than a century were unaware that in nearby hidden chambers a detailed record of the local fauna had been steadily accumulating for more than 3,000 centuries. In 1969, cave explorer Grant Gartrell and palaeontologist Rod Wells of Adelaide's Flinders University were exploring Victoria Cave, hoping to find fossil bones, when they broke through to a concealed passageway. In unexplored caverns beyond, they found the largest, most diverse and best preserved Pleistocene vertebrate fossil assemblage in Australia in what was later called the Fossil Chamber.
Because of the extraordinary richness and potential of its fossil deposits, Naracoorte Caves were declared a world heritage site in 1994. Key stages in the evolution of the Australian climate and biota were included in the time span represented by the Naracoorte assemblage, including when humans first arrived in Australia. During the huge time span, the Australian continent becameincreasingly cool and dry, with occasional warmer and wetter eras towards the Late Pleistocene. The dry and wet periods corresponded to glacial and interglacial periods on the other continents. These climatic changes, in particular increasing aridity, had profound effects on Australian fauna and flora.
By 15,000 years ago, many large mammal species had become extinct. For more than 300,000 years, sediment and animal bones had filled the Naracoore caves' Fossil Chamber through an opening in the ceiling, forming an enormous cone-shaped pile. The cave acted like a huge natural pitfall trap: animals that fell in were unable to escape through the high entrance and died, their skeletons lying nearly undisturbed for millennia. As the cone grew, fans of sediment and animal bones spread over the cave floor. The sediment pile grew up to the ceiling and blocked the entrance about 15,000 years ago, sealing the cave and its contents until discovery.
Over nearly 30 years of excavation and research of the Naracoorte Caves, more than 5,000 catalogued specimens were excavated from only 4% of an estimated 5,000 tonnes of bone-rich sediment. From the three-to-four-metres deep fossil bed, tens of thousands of specimens, representing at least 93 vertebrate species were recovered, ranging from very small frogs to buffalo-sized marsupials.These include superbly preserved examples of the Australian Ice Age megafauna as well as modern species such as the Tasmanian devil and thylacine, wallabies, possums, bettongs, mice, bats, snakes, parrots, turtles, lizards and frogs. The fossil material included complete postcranial and skulls so well preserved that even the most delicate bones were still intact.