Curtin researchers have unveiled how long ago drying began on Australia’s Nullarbor Plains, with a new approach that sheds light on how the ancient climate altered some of the driest parts of our planet.
The iron-rich layers that formed in ancient sediments used to shrink when an area dried out in response to climate change, such as the dramatic drop in groundwater in South Australia.
These ‘drying remnants’ indicate that the Nullarbor shifted dramatically to dry conditions 2.4 to 2.7 million years ago, revealing how these environmental changes played a major role in the formation of Australia’s diverse flora and fauna.
Determining the timing of climate change in ancient landscapes has proven difficult for geoscientists around the world, said lead author Dr. Maximilian Dröllner, of the Timescales of Mineral Systems group in the Curtin School of Earth and Planetary Sciences.
“Almost half of the Earth’s surface is dry land, and it’s home to about three billion people,” Dr. Dröllner said.
“Changes in these drylands can have a profound impact on both our society and regional biodiversity, and droughts have been instrumental in shaping the landscapes and ecosystems we see today.”
Determining when climatic events occur in dry lands has been a challenging task for geoscientists, as researchers have relied on indirect observations, such as marine sediments in nearby regions.
Co-author Professor Milo Parham, also of Curtin’s Timescales of Mineral Systems group, said directly measuring landscape drying products could provide a clearer timescale.
“The amount of helium trapped in these iron-rich horizons can be used to determine when they formed,” said Associate Professor Barham.
“Exposing this ‘drying residue’ to a small laser that releases helium, which we can measure to reduce the timing of these dramatic environmental responses to Earth’s climate history.”
Determining when these events occurred can help explain how they affect biodiversity in the region and, in particular in the case of South Australia, provides a timeline for the evolution of many native species.
“The desiccation of Australia’s interior has separated the common ancestors of many species that once roamed Australia freely,” Dr Drolner said.
“This separation led to the independent evolution of these isolated populations on the east and west coasts, eventually giving rise to distinct sister species or species.”
“Today we see many examples of sister species of birds, insects and plants that have common ancestors but now live thousands of miles apart, separated by ecological barriers created by climate change. Ancient.”
