Journal of Geophysical Research: Earth Surface

Late Pleistocene and Holocene sedimentation, organic-carbon delivery, and paleoclimatic inferences on the continental slope of the northern Pandora Trough, Gulf of Papua

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Abstract

[1] We investigated sediment and organic-carbon accumulation rates in two jumbo piston cores (MV-54, MV-51) retrieved from the midslope of the northeastern Pandora Trough in the Gulf of Papua, Papua New Guinea. Our data provide a first assessment of mass fluxes over the past ∼33,000 14C years B.P. and variations in organic-carbon sources. Core sediments were analyzed using a suite of physical properties, organic geochemistry, and micropaleontological measurements. MV-54 and MV-51 show two periods of rapid sediment accumulation. The first interval is from ∼15,000 to 20,400 Cal. years B.P. (MV-51: ∼1.09 m ka−1 and ∼81.2 g cm−2 ka−1) and the second occurs at >32,000 14C years B.P. (∼2.70 m ka−1 and ∼244 g cm−2 ka−1). Extremely high accumulation rates (∼3.96 m ka−1; ∼428 g cm−2 ka−1) characterize 15,800−17,700 Cal. years B.P. in MV-54 and likely correspond to early transgression when rivers delivered sediments much closer to the shelf edge. A benthic foraminiferal assemblage in MV-51 from ∼18,400 to 20,400 Cal. years B.P. indicates a seasonally variable flux of organic carbon, possibly resulting from enhanced contrast between monsoon seasons. The oldest sediments, >32,000 14C years B.P., contain TOC fluxes >200 g cm2 ka−1, with >50% of it derived from C3 vascular plant matter. Magnetic susceptibility values are 2 to 3 times higher and benthic foraminiferal accumulation rates are 6 times higher during this interval than at any younger time, indicating a greater influence of detrital minerals and labile organic carbon. The MS data suggest more direct dispersal pathways from central and eastern PNG Rivers to the core site.

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