Research website of Dr Gilbert Price

Archives for February 2012

Redating the Neds Gully megafauna deposit

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!

Palaeoecology during the Ice Ages in northeastern Australia

Main study sites in northeastern Australia

One of the challenges of working in academia is the constant need and pressure to secure research project funding. The main research funding body in the country is the Australian Research Council (ARC). They offer a number of schemes for supporting research, all of which are incredibly competitive.

In 2011, I applied for funding under a new ARC scheme called the Discovery Early Career Research Award (DECRA). The DECRA’s are intended for junior researchers, generally with less than five years post-PhD research experience. There was an incredible number of applicants in the round – over 3180 – for just 277 awards (success rate of less than 9%). The outcomes were announced in mid-November, and to my surprise and delight, my application was successful! My funding will secure my research program for the next three years.

My study will focus on developing a baseline understanding of faunal responses to climate change and environmental perturbations through the Quaternary in northeasternQueensland. The region is unique for the concentration of a vast array of well-documented Quaternary palaeoclimatic archives (e.g., deep marine pollen cores, records in lacustrine sediments, rainfall archives from speleothems, offshore ostracod and foraminifer geochemical records). Such records extend back several hundred thousand years, through numerous glacial-interglacial cycles, and document how the region’s climate and environments have evolved through to the present. Strikingly, they provide key information on the timing and duration of prehistoric dry intervals, and document a long-term trend in the weakening of the Australian Monsoon: patterns of climate change that mirror those that are predicted to continue into the future.

Diprotodon skeleton at Floraville

Although there is an increasingly robust model of Quaternary climate change for the region, a lack of well-documented faunal records hampers efforts to understand prehistoric biological responses to the climate perturbations. However, that is not through want of appropriate fossil sites, but rather, lack of investigation. Areas such as Chillagoe are renowned for their unique Pleistocene faunas and contain animals such as the enigmatic Quinkana fortirostrum (extinct terrestrial crocodile) and Propleopus chillagoensis (giant carnivorous rat-kangaroo), two species that are known from nowhere else on the continent. Yet, we have little or no knowledge of their palaeoecology, palaeobiology and extinction simply owing to a lack of significant investigation in the region (the last major studies in the area ceased in the 1970’s). Other areas such as Floraville contain remarkably diverse Plio-Pleistocene faunas (including both megafauna and smaller-bodied species), but only preliminary results have ever been published. Well-documented sites, such as Wyandotte, preserve highly significant faunal assemblages previously thought to date to around the time of terminal megafaunal extinctions, but they now require re-dating because the previously established dates are no longer accepted. It is clear that northeastern Australia can yield critical data for understanding ongoing patterns of faunal change.

A major goal of my project will be to quantify the precise timing, magnitude, rates of climatic and environmental changes, and the long-term response of northeastern Australia’s terrestrial faunas to such events. For this reason, fossil deposits with long depositional sequences and well-preserved faunal remains in potentially easily datable contexts will be the focus of the research. Strategically, this includes targeting fossil assemblages that represent accumulation at different times through interglacial/glacial cycles, both before and after the arrival of humans on the continent, as well as more recent deposits within the timeframe of European colonisation (such as Carrington Cave, a site that contains the introduced house mouse, Mus musculus).

I’m currently planning fieldwork for the upcoming year. In late May, I will be heading up to the BrokenRiverarea. Several fossil deposits have already been identified from caves in the area by my friend Doug Irvin, a long-serving member of the Chillagoe Caving Club. Through June-July, I will be trekking to the Floraville area, just south of the Gulf of Carpentaria. Fossils have been collected from the region for the past 40 years by my colleagues Prof. Michael Archer and Henk Godthelp, both of the Universityof New South Walesin Sydney. We’ll be visiting the main sites, collecting new fossil specimens and hopefully some dating samples. In 2011, we excavated one of Australia’s most complete Diprotodonskeletons. I collected some dating samples at the time, but am still waiting on the results.

Waterfall in the Leichhardt River, Floraville Crossing

I’ve almost completed my first manuscript relating to the project- a direct fossil dating study. The purpose of the study is to determine the age of the specimen and to demonstrate the utility of the direct fossil dating approach of museum specimens using U-series methods. The specimen, a maxilla of the extinct marsupial ‘tapir’ (Palorchestes azael) was collected from the cave in 1977 and curated into the fossil collections of theQueenslandMuseum before being sequestered for dating. The results demonstrate that the specimen is between ~137–199 thousand years old, thus, predating the hypothesised time of final megafaunal extinctions. The result is significant in that it is the most northerly mainland dated recorded for any of the extinct Australian megafauna and represents one of the youngest reliably dated records for the species. The stratigraphic relationship of the dated specimen to other fossils from the cave is unclear. I hope to be able to submit the manuscript to a journal in the next month or so.

With the fieldwork, lab work, and paper writing, it’s bound to be a busy year!