Sea-level changes caused by melting ice sheets hundreds of thousands of years ago triggered the formation of K'gari (Fraser Island) - the world's largest sand island - and the creation of Australia's iconic Great Barrier Reef, a new study has found.
Professor Jamie Shulmeister augering (sand sampling) on K'gari.
An international team of scientists led by University of Canterbury (UC) Professor Jamie Shulmeister, and paper lead author Dr Daniel Ellerton from Stockholm University, has provided new insights into the origins of K'gari (Fraser Island) and the Great Barrier Reef, which they suggest date back to a time of climate change on Earth over 800,000 years ago.
UC's Head of the School of Earth and Environment, Professor Shulmeister says the timing and drivers of the formation of these two significant landscape features has been poorly understood until now.
"The Great Barrier Reef is regarded as one of the most significant global biodiversity hotspots and carbon sinks, and K'gari is the world's largest sand island and a UNESCO World Heritage area, so it's really important to gain a better understanding of how they came about," he says.
"What we've discovered with this research is that these landforms were created during the Middle Pleistocene Transition, a period of global climate change about 800,000 years ago. Rising sea-levels associated with melting ice sheets triggered large volumes of sand to be released on the east Australian coast north of Brisbane."
Professor Shulmeister says this process created massive dune fields that became the Cooloola Sand Mass and nearby K'gari, in Queensland.
"The creation of K'gari also acted as a groyne, preventing sediment from being transported north of the island which provided the clear waters and conditions needed for coral growth in the area that now forms the southern and central parts of the Great Barrier Reef," he says.
The team of scientists mostly from Australasian and American universities - which includes University of Canterbury PhD graduate Dr Nicholas Patton, who is now a postdoctoral researcher at the University of Nevada, US,- studied sediment and soil samples from coastal dunes on the Cooloola Sand Mass and K'gari. The scientists used a dating technique called 'optically stimulated luminescence' to provide an estimate of the last time these quartz-rich sand sediments were exposed to light.
The research was funded by an Australian Research Council Discovery Grant and published today in the journal Nature Geoscience.
Professor Shulmeister says the findings have implications for future climate change scenarios because they demonstrate that rising sea-levels sea-level can cause coastal responses that are apparently unconnected to the sea-level rise itself. These types of changes are very hard to predict and plan for.
"For this reason, they represent a serious threat to communities around the world. We need to better understand how natural systems work if we're going to deal with these changes in the future."
The major coastal sedimentary system reorganisation is not expected to be unique to Queensland and the research team believes it should be investigated in other coastlines, such as the Wilderness Embayment coastline of South Africa and the extensive coastline of eastern Brazil.
K'gari is the land of the Butchulla people, and the work was completed with the permission of the Butchulla Aboriginal Corporation.
The new paper is titled 'Fraser Island (K'gari) and initiation of the Great Barrier Reef linked by Middle Pleistocene sea-level change', Nature Geoscience, DOI: 10.1038/s41561-022-01062-6. (Once published, the paper will be available at: https://www.nature.com/articles/s41561-022-01062-6)
The cliffs at Rainbow Beach taken from the Carlo Blowout, Cooloola Sand Mass, south-east Queensland. Photo credit: Jamie Shulmeister
