Chronology and evolution of the world's largest sand island: K'gari (Fraser Island), South East Queensland, Australia

Abstract

K'gari in South East Queensland, Australia, is the world's largest sand island and a UNESCO World Heritage Area. The island is covered by extensive coastal dune fields that have been divided into seven morphological units (the Awinya, Yankee Jack, Bowarrady, Triangle Cliff, Freshwater, Station Hill, and Cape). Optically-Stimulated Luminescence dating of the dune sequences indicate that the Awinya unit is > 340 ka, and the Yankee Jack and Bowarrady units are ca. 180 ka old. Holocene dune sequences comprise Triangle Cliff (ca. 8.5 ka); Freshwater (ca. 4 ka); Station Hill (ca. 1.5 ka) and Cape (ca. < 0.5 ka). Combining these data with dune ages from the adjacent Cooloola Sand Mass, we demonstrate that for at least the last three glacial cycles the dunes were emplaced during intermediate to high sea-levels. At shorter time intervals (decades to centuries), some dune formation is affected by storminess. Initial formation of the dune field occurred in the mid-Pleistocene, but the most recent widespread stabilisation of dunes occurred late in Marine Isotope Stage 7 (MIS 7: 190–240 ka). The preservation of dunes relates to antecedent topography coupled with the duration and height of individual interglacial high sea-stands. This research confirms K'gari as an outstanding example of geomorphological processes and supports its World Heritage listing.