A Holocene fluvial archive of the Mulgrave River, Notheastern Australia: Influence of tropical cyclones and sediment delivery to the Great Barrier Reef

The sedimentology, geomorphology and chronology of late Quaternary fluvial landforms and sedimentary sequences within the Mulgrave River catchment in northeast Queensland suggest that episodic stripping or wholesale erosion of Holocene floodplains is a major mode of sediment delivery to the Great Barrier Reef lagoon. The last major phase of Holocene valley sediment removal likely occurred sometime between approximately 1200 and 250 years ago and was possibly associated with a phase of heightened tropical cyclone activity and consequent riverine flooding that occurred between AD1400 and 1800. Since then relative tropical cyclone quiescence may be the cause of a phase of valley aggradation that has been occurring over the past two centuries. The results of this investigation suggest that in this catchment there have been alternating phases of Holocene valley floodplain stripping and subsequent aggradation, with the latter being the current dominant mode. This suggests that at least here, in this relatively confined valley, sediment delivery to the Great Barrier Reef may be relatively low compared to other periods over the past millennium and this may be due to low levels of tropical cyclone activity over the past 200 years.