Scientific drilling of lake sediments at Darwin Crater in Tasmania
Fieldwork was completed on April 16-25 th 2018 at Darwin Crater, a 1.2 km diameter and 800,000-year-old meteorite impact crater in western Tasmania. The drilling team included two drillers, two PhD students, and two scientists from the University of Melbourne (Dr Michael Fletcher and Dr Agathe Lisé-Pronovost).
Work was performed with lead driller Max Harvey from Delta Drilling, a Tasmanian company based in Zeehan. The team successfully drilled the complete lake sediment sequence filling up Darwin Crater, and brought back more than 130 meters of sediment retrieved from three holes. Darwin Crater is inaccessible by road and located in the UNESCO Tasmanian Wilderness World Heritage Area. Therefore, the drill rig, all equipment, and the team were transported by helicopter to the site.
The drilling team. From left to right: Richard John Lewis (PhD student, University of Adelaide), Tom Mallett (PhD student, La Trobe University), Max Harvey (Delta Drilling), Agathe Lisé-Pronovost (La Trobe University and 2018 McKenzie Fellow in the School of Earth Sciences at the University of Melbourne), Michael Fletcher (Lecturer in the School of Geography at the University of Melbourne), and Adam Debresteli (Delta Drilling).
The long sedimentary archive covers several Glacial/Interglacial cycles and is the backbone of the ARC-funded project “How do the Southern Westerly Winds respond to rapid climate change?” administered by the University of Melbourne. The international research team is using multi-proxy sediment analyses, including paleo- and environmental magnetism, geochemistry, pollen, charcoal, radiocarbon dating, and optically-stimulated luminescence (OSL) dating to reconstruct how the Southern Westerly Winds respond to rapid global warming at the end of Ice Ages in western Tasmania, a key region of the Southern Hemisphere where precipitation is strongly correlated to westerly winds.
Drone picture during drilling operations at Darwin Crater. The drill site and camp near the crater center is visible in white.
The long record of Darwin Crater, coupled with a long record from neighboring Lake Selina (still a lake today) will form the oldest continuous continental record in Australia, and in the Southern Hemisphere. Long Quaternary lake sediment records are extremely rare in Australia because of the aridity and the general absence of glaciers and tectonics able to form deep freshwater basins. Australian lakes are most often ephemeral and the few permanent lakes rarely reach back beyond the last Glacial period (about 20,000 years ago). Further back in time (millions of years ago), the Australian record contains discontinuous paleo-lakes, such as Stony Creek Basin and Lake Bungunnia. The new Darwin Crater archive will bridge a time gap in the Australian paleoclimate record, provide Quaternary climate and paleomagnetic field reconstructions in an under-documented region of the Southern Hemisphere, and provide essential boundary conditions for predictive climate modelling.
More than 130 meters of sediment were recovered and brought back to the University of Melbourne for multi-proxy and high-resolution analysis. The three meters core sections were wrapped in black plastic to protect them from light until sampling for OSL dating.
For more information on this research project:
Dr Agathe Lisé-Pronovost (agathe.lise@unimelb.edu.au)
Dr Michael Fletcher (michael.fletcher@unimelb.edu.au)