STRATIGRAPHIC ARCHITECTURE OF THE FRASER ISLAND DUNE COMPLEX, SOUTHEAST QUEENSLAND, AUSTRALIA USING HIGH-RESOLUTION GROUND PENETRATING RADAR

Fraser Island is the world’s largest sand island and the northern terminal feature of a down-drift sand transport system that begins south of Sydney in New South Wales. UNESCO named Fraser Island a World Heritage Site in 1992 based on the intrinsically unique aspects of vegetated dunes that tower 240 m above sea level, blowout features and rainforest vegetation, among other aspects. In 2015, a comprehensive project was begun to understand the stratigraphic relationship of dune sequences, chronology of periods of aeolian activity and relationships between island evolution, sea level and climate.

Since 2015, the research team has collected over 100 km of high-resolution 160 MHz ground penetrating radar (GPR) on Fraser Island and neighboring Cooloola Sand Mass in order to understand the subsurface architecture of the surficial expression of dune sequences. Fraser Island proved to be an ideal location to employ GPR as penetration exceeds 25 m with the 160 MHz system.

GPR data revealed a system of stacked and interfingering aeolian features and units including various palaeosol sequences. The dune complex provided excellent preservation of primary sedimentary structures as expressed by high-angle cross bedding in stratigraphically higher units with stratigraphically lower units showing overprinting of soil formation.

Comparison GPR data collected over active aeolian features including foredunes, parabolic dunes, transverse dunes and trough blowouts with heavily vegetated and inferred stable areas provided insight into how the Island evolved over time. The understanding of the stratigraphic architecture as well as palaeo-landforms has allowed the team to strategically collect shallow and deep cores to analyze the geochemistry of former soils and develop a chronology through optically-stimulated luminescence dating. The coring, geochemistry and dating are ongoing.