High Siliciclastic Flux during the Last Sea Level Transgression, Ashmore Trough, Gulf of Papua

Jason M. Francis¹, Brooke Olson¹, Gerald R. Dickens¹, André W. Droxler¹, Luc Beaufort², Thibault De Garidel-Thoron², Samuel Bentley³, Larry C. Peterson⁴, and Bradley Opdyke^5
1 Rice University, Houston, TX
² CEREGE - Université Aix-Marseille III, France
³ Louisiana State University, Baton Rouge, LA
⁴ University of Miami, Rosenstiel School of Marine and Atmospheric Science, Miami, FL
⁵ Australian National University, Canberra, Australia

The continental margins of the Gulf of Papua and northeastern Australia collectively form the world's largest active tropical mixed siliciclastic-carbonate depositional system where rivers supply large amounts of terrigenous sediment to a shelf with substantial carbonate production. Our MARGINS Source-to-Sink - Gulf of Papua study comprises the first large-scale effort to quantify sediment fluxes on the northern portion of this margin, particularly Ashmore Trough. Over the last 30 kyr, the flux and composition of sediment shed from these margins to surrounding slopes and basins has changed dramatically. This is not unexpected given the two dominant sediment sources and the large amplitude variations in sea level. Research on slope cores off the northeast Australian margin have demonstrated that, in contrast to reciprocal sedimentation models, siliciclastic sediment accumulation is highest during the late sea level transgression ca. 12-7 ka rather than LGM lowstand ca. 25-18 ka. Our research reveals that cores across the slope of Ashmore Trough also record increased siliciclastic fluxes during the late transgression. Considering the previous work to the south, this appears to be a super-regional phenomenon spanning more than 10° of latitude. Ultimately, by combining core and shallow seismic data, our work will aim to tie siliciclastic sources and sinks from the Fly River to Ashmore Trough.