Debate over the timing and causes of extinction of Australia’s Pleistocene megafauna has become polarised in part due to a paucity of reliable geochronological information for the extinct forms. Thus, it is difficult to accurately test leading extinction hypotheses in relation to human continental colonisation and climate change events.
The Neds Gully megafauna site on the Darling Downs, southeastern Queensland, has a central role in the extinction debate. Although it is commonly regarded as the continent’s youngest megafauna-bearing deposit (possibly dating to around 40-50 thousand years ago), the provenance of existing dates to the fossils and general stratigraphy of the site has never been formally demonstrated. Thus, the significance of the deposit with respect to the broader extinction debate remains unclear.
So there remains the question: Is Neds Gully really the youngest megafauna fossil site in Australia? Providing the answer to this important question has been the focus of some of my recent work on the Darling Downs.
The Neds Gully fossil deposit was excavated in the 1990’s, long before I was even interested in studying palaeontology. Numerous specimens were collected and accessioned into theQueenslandMuseum. Unfortunately, a comprehensive description of the site was never published. Over the past couple of years, I’ve been revisiting the site to try to determine exactly where the fossils and dating samples were collected from. Fortunately, I have had the help of my friend and colleague, Ian Sobbe. Ian wears a couple of different caps- one as a local farmer, and the other as an amateur palaeontologist. Ian was one of the original excavators of Neds Gully, so finding the site again was no problem.
We reopened the site, bringing in some earth moving equipment to clear overgrowth and sediments that built up over the deposit. We were able to identify the stratigraphic horizon that produces the fossils and even found some new specimens in the process. Armed with some aluminum tubes and a sledge hammer, Ian and I took some new sediment samples for dating. The samples were sent to my colleague, Dr Andrew Murray atAarhusUniversityinDenmark. Andrew is a specialist in optically stimulated luminescence (OSL) dating and was able to produce some new dates for us.
In additional to the OSL dates, I also produced new uranium-thorium (U/Th) dates directly on the fossils using the thermal ionization mass spectrometer (TIMS) at the Radiogenic Isotope Facility (The University of Queensland). The new dates are particularly exciting for us and match perfectly with the OSL dates.
Without giving too much away, the results broadly support the idea that Neds Gully is one of the youngest megafauna deposits inAustralia. However, we have not found evidence for a mass extinction event as commonly as been suggested. I’m currently in the process of writing this work up, with a view to submit it to a scientific journal very soon, so watch this space!
