Excess 210Pb inventories and fluxes along the continental slope and basins of the Gulf of Papua

Abstract

Sediment samples were collected from continental slopes and marginal basins in the Gulf of Papua and analyzed for excess 210Pb to elucidate transport processes of fine‐ grained particles to this region. Estimated excess 210Pb fluxes of 1.0–12.8 dpm cm−2 a−1 were derived from measured seabed inventories. Highest sediment accumulation rates (0.28–0.35 cm a−1) were measured along the northeastern shelf edge, and they decrease in seaward directions and along isobaths to the southwest. The excess 210Pb flux could result from either focused deposition of high‐210Pb activity sediments from the continental shelf and upper slope or scavenging of 210Pb brought landward from deep‐sea waters. This sediment flux is concentrated in the northeastern Gulf of Papua, where the shelf is narrow and calcium carbonate contents are lowest. Analysis of sedimentary fabric and 210Pb distributions in cores suggests sediment delivery to the slope occurs on a 100‐year timescale as both diffuse hemipelagic deposition as well as turbidity flows. The flux of sediment in turbidity flows is not well constrained but may be producing additional deep‐sea accumulation in the Moresby Trough, as well as export from the study area.