HOLOCENE EVOLUTION OF THE SUNSHINE AND FRASER COASTS, QUEENSLAND – INSIGHT FROM PALAEOCHANNELS AND PALAEOSHORELINES

Sea-level variation is the primary driver of coastal environmental change over the Quaternary. Most evident is the >140 m change in sea level since the Last Glacial Maximum. While the northern hemisphere experienced a persistent rise at variable rates since ~22 kya, most of the southern hemisphere experienced a sea level highstand at ~7 kya; +~2 m in Australia. The undeveloped coastal system of Australia’s southeast Queensland coast serves as an ideal location to decipher the evolutionary relationship of landscapes as related to sea level variation and storms.

During the 2014 Austral winter, ground penetrating radar (GPR) data was acquired at several locations along the Sunshine Coast and Fraser Coast, Queensland to locate the geographical position of the Early Holocene highstand and relate the subsequent regressive coastal sequences and features to sea level fall rates, sediment supply, fluvial dynamics and local antecedent geology. Large regressive coastal plains, low-lying wetlands, and large barrier systems were investigated at a reconnaissance level. Early results show large regressive plains incised with numerous palaeochannels that have been abandoned and filled that are correlated as potential tidal areas based on elevation. Additionally, palaeoshoreline deposits were identified that extend over several kilometers containing the record of large erosional events, former cateye pond and back barrier environments that were formed during sea level fall.

Through the integration of LiDAR and GPR, deposits and features have been correlated using the Lewis et al., 2012 sea level curve for southeast Queensland providing evidence for expanded estuarine environments and additional sand islands. Future work will refine the conceptual model of Holocene coastal evolution and integrate climate, fluvial and sediment provenance data to reconstruct palaeogeography of the Early Holocene coastal system and extract changes to storm frequency and magnitude.