2000 km and 600 Ma from Source to Sink: The Eastern Australian Sediment Dispersal System
Ron Boyd1, Kevin Ruming1, and Marianne Sandstrom2
1 University of Newcastle, Callaghan, Australia
2 Australian School of Petroleum, Adelaide, Australia
The modern coastal sediment dispersal system of eastern Australia operates from sources in the Sydney Basin 1000 km northward to sinks on the coastline of south-east Queensland and the adjacent Tasman Sea abyssal plain. Individual sand reservoirs of over 203 km3 have accumulated in less than one million years, from longshore transport rates averaging 500,000 m3 per year. Zircon dating techniques enable the tracing of this entire sediment dispersal system from its original source in Antarctica to its final sink on the floor of the Tasman Sea. Igneous rocks with a characteristic age of around 600 Ma produced zircons and associated source rocks on the current northern margin of Antarctica prior to continental breakup with Australia. Triassic uplift shed sediments and associated zircons 1000 km northward in a braided river before intermediate deposition in the Sydney Basin of eastern Australia. Continental rifting in the late Cretaceous produced the modern Tasman Sea and an uplifted escarpment along eastern Australia, including the Sydney Basin. Escarpment erosion of the 600 Ma zircons and associated quartz sands by river processes feeds the modern Tasman Sea longshore transport system, delivering reservoir quality sand 1000 km north for storage on the SE Queensland shelf. In the Holocene, this “sand river” has intersected the highstand shelf edge and is currently supplying the east Australian longshore transport sands directly to the floor of the Tasman Sea via a network of wave, tide and gravity driven flows through a 4 km-deep network of submarine gullies and canyons.