The formation of Fraser Island linked to Middle Pleistocene sea-level change

New research shows that K’gari, previously known as Fraser Island, and part of the Great Barrier Reef was formed over 800,000 years ago. Its formation was tied to a major change in earth’s climate called the Middle Pleistocene Transition. The study is published today in Nature Geoscience.

Research has provided new insights into the origins of K’gari (Fraser Island), the world’s largest sand island as well as a UNESCO world heritage area and linked its formation to the inception of Australia’s iconic Great Barrier Reef.

The work led by Dr Daniel Ellerton, Stockholm University, and including an international team from Australia, New Zealand and the United States has shown that the sand island formed over 800,000 years ago and its formation was tied to a major change in earth’s climate called the Middle Pleistocene Transition.

“The Great Barrier Reef is the world’s largest coral reef ecosystem, yet what I find so interesting is that we still do not really know what caused its initial inception. Previous research has highlighted that several mechanisms are likely responsible and here we demonstrate an additional factor that should be considered,” says Daniel Ellerton.

During the Middle Pleistocene, sea-level changes associated with the growth and decline of polar ice sheets changed dramatically. Prior to the Middle Pleistocene Transition, sea level would fall and rise up to ~75 m during each warm and cold cycle, but this increased to about 120 m per cycle during and following the transition. This resulted in huge areas of continental shelf becoming exposed during low sea-stands.

On the east Australian coast north of Brisbane this increased sea level change triggered large volumes of sand to be redistributed from the continental shelf towards the coast, creating the massive dune fields that became K’gari and the nearby Cooloola Sand Mass. The growth of K’gari directed sand moving north along the Australian coast over the edge of the Australian Shelf and into deep water. This prevented the northwards transport of sand into areas that now form part of the Great Barrier Reef and provided the clear waters needed for coral growth. This set the conditions for the formation of the Great Barrier Reef.

“This research highlights the complex evolution of coastal environments over long timescales. Coastlines globally are at risk from rising sea-levels under predicted global warming which poses a serious threat. If we are going to manage coasts and coral reefs under climate change scenarios, we need to understand how these complex responses occur,” says Daniel Ellerton.

This work was supported by an Australian Research Council Discovery Grant.