03. Scott Hocknull - Dinosaur Man
CASE STUDY: Comparison between Mt Etna (central eastern Queensland) and Naracoorte (South Australia)
Here is a map of Australia showing several sites from the mid-Pleistocene era (780,000 – 125,000 years ago). One in particular, the Naracoorte Caves World Heritage Area, preserves a rich fauna that spans a very similar time period to Mt Etna. The researchers working on these sites have uncovered a response to climatic changes in southern Australia. However, the responses are not as dramatic as those experienced at Mt Etna.
Mount Etna is an amazing site. It records Australia’s only known evidence of a Quaternary rainforest fauna. (The Quaternary period extends from about 2.5 million years ago to the present. It includes two epochs: the Pleistocene; and the Holocene.) This fauna is significant in many ways.
- It fills a massive gap in our knowledge of the evolution of rainforest fauna
- It provides a base-line understanding of the species we now find in the fragile and threatened rainforests of the Wet Tropics of Queensland and in Papua New Guinea
The fossil record at Mt Etna also records the local extinction of this rainforest, entirely due to climate change.
Therefore, it provides the first and only information we have on how past climate change has affected our country's most diverse habitat, the rainforest.
Mt Etna Caves – change in species over time
The study at Mt Etna that is described below was carried out by Dr Scott Hocknull over the last decade or more.
Mt Etna and the surrounding cave systems of Limestone Ridge are isolated blocks of limestone that formed as part of an ancient reef system some 350-400 Ma (million years ago). This area was covered by the sea at this time. Since then these limestone blocks have been rolled, squeezed and pushed up over hundreds of millions of years of tectonic activity. The rock layers have been rotated from horizontal to near vertical due to these geological forces.
Since the Miocene (11-15 Ma), these limestone blocks have been slowly exposed to the weather. Percolating ground water dissolved huge cavities in the limestone, forming massive cave systems.
Fossilised remains of animals within these deposits are amazingly plentiful and very well-preserved. This allows us to identify the types of species that once lived in the Mt Etna area. Specimens found in sites older than 280,000 years ago were compared with those from sites younger than 205,000 years ago. This period of time shows a change in animal species. Species extinctions are closely matched by their replacement with new species. The trend is for typically rainforest species to give way to more arid or xeric-adapted species.