GPR FACIES FROM THE WORLD’S LONGEST CONTINUALLY ACTIVE COASTAL SAND DUNE SYSTEM, GREAT SANDY COAST, SOUTHEAST QUEENSLAND AUSTRALIA – EVIDENCE FOR CHANGE

Southeast Queensland Australia is home the world’s largest downdrift sand system which stretches 1100 km from southeast New South Wales to the tip of Fraser Island in Queensland. This system provides sand for the world’s three largest sand islands (Fraser, North Stradbroke and Moreton). These islands combined with other large sand islands and coastal sand masses comprise the world’s longest continually active coastal sand dune system which has been active for over ca 1.1 my. Fraser Island and the Cooloola Sand Mass at the northern terminus of the system have been the target of a broad multidisciplinary study that seeks to elucidate the evolutionary history of the sand dune systems and link the phases of activity to variations in the Earth’s climate.

During the past four years, the research team collected in excess of 250 km of ground penetrating radar data, several hundred sediment augers and nearly 100 samples for optical stimulated luminescence dating. This is an extremely rich dataset and much too large to present in its entirety, thus this will focus on the ground penetrating radar.

A considerable portion of the GPR was collected on the western side of the Cooloola Sand Mass. In this area, various GPR facies were identified through correlation with modern analogs and coring. Environments observed included highly eroded and degraded dunes, fluvial systems, transgressive sand sheets and thin repeated soils. In the topographic lowest areas, salt water intrusion restricted the penetration of the GPR, but features potentially related to former marine and estuarine environments were observed. Comparing past landscape elements to the present day landscape has fostered the capability to target areas for chronological sampling and investigation of the rates and chemistry associated with soil formation.