Sediment Flux to the Gulf of Papua Continental Slope Using Pb-210 Geochronology, Source to Sink Papua New Guinea Focus Area

Zahid Muhammad¹, Samuel Bentley¹, Andre Droxler², Gerald Dickens², Bradley Opdyke³, and Larry Peterson^4
1 Louisiana State University, Baton Rouge, LA
² Rice University, Houston, TX
³ Australian National University, Canberra, Australia
⁴ University of Miami, Miami, FL

The Gulf of Papua is a mixed siliciclastic/carbonate environment where terrigenous sediments from New Guinea rivers are supplied to shelf and slope, intermixing with shallow water barrier and platform carbonates. During a March-April 2004 cruise aboard R/V Melville, multicores and piston cores were collected from a range of depositional settings on the upper and middle slope of the Gulf of Papua. These cores were navigated using dynamic positioning, and a multibeam bathymetric mosaic collected during the cruise. These multicores have been examined using Pb-210 radiochemistry, x-radiographs and granulometry, and diagenetic models for sediment accumulation and bioturbation, in order to constrain carbonate and terrigenous sediment flux to the slope over century timescales.

Preliminary results support the hypothesis that terrigenous sediments are reaching the slope from the northeast Gulf of Papua shelf break, where a core from a shelf-edge clinoform revealed an apparent Pb-210 accumulation rate of 0.4 cm/y. Southwestwards along the upper slope, toward the northern edge of the Great Barrier Reef, sedimentation rates appear to be lower, and carbonate platform influence appears to increase. In the Moresby Trough, a major sediment conduit from the upper Gulf of Papua slope to the Coral Sea Basin, we have documented modern turbidite sedimentation through core x-radiographs and Pb-210 analyses. The depositional sedimentary fabric of the Moresby Trough turbidites contrast sharply with the intensely bioturbated fabric of hemipelagic sediments identified at other core locations.