New lead on Great Barrier Reef’s origin

Researchers have discovered that K’gari (Fraser Island) and the nearby Cooloola Sand Mass in southeastern Queensland formed 1.2 and 0.7 million years ago and their formation allowed the development of the southern and central Great Barrier Reef.

Scientists had always been puzzled as to why the Great Barrier Reef only formed around half a million years ago when Australia had the condition appropriate for reef growth for much, much longer.

It turns out the answer might be K’gari, according to a new article in Nature Geoscience led by international experts including Dr Daniel Ellerton from the University of Stockholm, University of Queensland, Flinders University Professor Patrick Hesp and Associate Professor Graziela Miot da Silva and other researchers from Australia, NZ and the US.

They say the development of K’gari dramatically reduced sediment supply to the continental shelf north of the island and this facilitated widespread coral reef formation in the southern and central Great Barrier Reef.

“We found 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,” says Dr Ellerton, whose PhD project at the UQ was supported by Australian Research Council Discovery grant.

During this time, sea-level changes associated with the growth and decline of polar ice sheets changed dramatically.

“This work highlights that rising sea levels under predicted global warming may cause other major changes to the coast in addition to simple sea-level rise,” says Dr Ellerton.

“If we are going to manage coasts under climate change we need to understand how these complex responses occur.”

Location map and diagram from the new Nature study.

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 – thus setting conditions for the formation of the Great Barrier Reef.

Organisation involved in the study were University of Queensland, University of Utah, Clarkson University, University of Canterbury, ANU, Flinders University, University of WA and Stockholm University, Sweden.

The article, Fraser Island (K’gari) and initiation of the Great Barrier Reef linked by Middle Pleistocene sea-level change (2022) by DT Ellerton, TM Rittenour, J Shulmeister, AP Roberts, G Miot da Silva, A Gontz, PA Hesp, P Moss, N Patton, T Santini, K Welsh and X Zhao has been published in an open access article in Nature Geoscience DOI: 10.1038/s41561-022-01062-6

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