Modern and Pleistocene Turbidite Sedimentation in the Gulf of Papua S2S Study Area: Implications for Modulation of Sediment Sources by Oceanic and Climatic Processes

Samuel J. Bentley¹, Zahid Muhammad¹, Luke Patterson¹, Andre Droxler², Gerald Dickens², Larry Peterson³, and Bradley Opdyke^4
1 Louisiana State University, Baton Rouge, LA
² Rice University, Houston, TX
³ University of Miami, Miami, FL
⁴ Australian National University, Canberra, Australia

Seabed morphology, stratigraphy, and sedimentation patterns in the Pandora and Moresby Troughs of the Gulf of Papua have been studied using a combination of multicores and long piston cores, multibeam bathymetry, and 3.5kHz subbottom profiling. These basins are the deep-sea depocenters for the Papua New Guinea Source to Sink Study Area, and contain a Quaternary record of sediment flux from rivers draining much of Papua New Guinea. Our observations have documented the occurrence of a clinoform along the northeastern shelf edge of the study area that feeds modern turbidites in the troughs downslope. This sediment appears to be delivered by oceanic processes from inner shelf clinoforms to the northwest, fed by the Fly/Strickland Rivers, among others. In contrast, smaller rivers on the nearby Papuan Peninsula to the northeast appear to deliver negligible sediment to the shelf, possibly due to drier conditions in this region at present.

Turbidites deposited near the LGM in the deepest parts of the study area tell a different story, however. These sediments contain high concentrations of pristine mafic volcanic debris, consistent with delivery from the Papuan Peninsula, not the Fly/Strickland rivers, which are more quartzofeldspathic. This downcore change in apparent provenance thus suggests that Papuan Peninsula rivers delivered much more sediment to the deep sea in the past than at present. An important remaining question is whether this shift also reflects a decrease in sediment flux from the Fly-Strickland system, or merely a change in delivery pathways, thus retaining Fly/Strickland sediment closer to the fluvial source.