Fraser Island (K'gari) and initiation of the Great Barrier Reef linked by Middle Pleistocene sea-level change

The eastern Australia coastline is characterized by impressive coastal landforms and an extensive northward-moving longshore drift system that have been influenced by a stable, long-term tectonic history over the Quaternary period. However, the timing and drivers of the formation of two conspicuous landscape features-Fraser Island (K'gari) and the Great Barrier Reef-remain poorly understood. Here we use optically stimulated luminescence and palaeomagnetic dating to constrain the formation of the extensive dunes that make up Fraser Island, the world's largest sand island, and adjacent Cooloola Sand Mass in southeastern Queensland. We find that both formed between 1.2 Ma and 0.7 Ma, during a global climate reconfiguration across the Middle Pleistocene transition. They formed as a direct result of increased amplitude of sea-level fluctuations associated with increasing global ice volume that redistributed previously stored sediment across the continental shelf. The development of Fraser Island dramatically reduced sediment supply to the continental shelf north of the island. This facilitated widespread coral reef formation in the southern and central Great Barrier Reef and was a necessary precondition for its development. This major reorganization of the coastal sedimentary system is probably not unique to eastern Australia and should be investigated in other passive-margin coastlines.