THE SANDS OF TIME. MAPPING FRASER ISLAND; ONE OF THE OLDEST COASTAL DUNEFIELDS IN THE WORLD

Fraser Island is the largest sand island on the planet. It contain a complex sequence of stacked parabolic dunefields, with individual dunes exceeding 200 m in height and with trailing arms in excess of 8 km. Though undated the dunefield is suspected to contain dunes that are several hundred thousand years old and we are currently dating the major dune units using Optically Stimulated Luminescence. This poster presents an updated map of the major dune units on Fraser. It highlights the tri-partite division of the island into a southern section dominated by successive parabolic fields, a middle section comprised of more recently active dunes including some transverse forms sitting within a parabolic field, and a northern area with many shallow lunette lakes and evidence for widespread deflation. By correlation with the Cooloola Sand Mass to the south, we infer that phases of sand accumulation have occurred in the middle and late-Quaternary. The extensive more recent dune activity in the middle of the island poses questions about dune initiation processes. One possibility is that a paleo-channel of the Mary River flowed to the ocean across this section of what is now Fraser Island and that dunes in this area have formed since the diversion of the river to the south. This event may also have cut-off sand supply to the northern part of Fraser. The Mary River river now flows into the southern part of Wide Bay and helps maintain the channel that separates the island from Inskip Peninsula and the Cooloola Sand Mass to the south. The east coast of Fraser Island is currently rotating into swash alignment with late Holocene progradation along the SE coast and gradual scarp retreat along the NE coast. The Wide Bay, west of the island, is maintained by tidal sweeping but is gradually infilling.