THE BIOTIC RESPONSE TO CLIMATE CHANGE AND EPISODIC VOLCANIC EVENTS DURING THE LATE PLEISTOCENE TO RECENT IN THE NORTHERN PANDORA TROUGH, GULF OF PAPUA, PAPUA NEW GUINEA

The Gulf of Papua is a mixed carbonate-siliciclastic system situated along the northeastern Australia and Papua-New Guinea margin and is one of the focus areas of the National Science Foundation's Margins Source to Sink Initiative. We investigated the response of benthic foraminifera and calcareous dinocysts to climatic change and volcanic events in a jumbo piston core (MV-51) from the northeastern Pandora Trough. Our data provide an assessment of mass fluxes over the past ~32,000 ¹⁴C yrs B.P., variations in organic carbon sources, volcanic events, and the biotic responses associated with all of them. MV-51 shows two periods of high sediment accumulation. The first interval is from ~15,000-20,400 Cal. yrs B.P. (~1.09 m kyr^-1 and ~81.2 g cm^-2kyr^-1) and likely corresponds to lowstand accumulation when rivers prograded closer to the Last Glacial Maximum coast. The second occurs >32,000¹⁴C yrs B.P. (~2.70 m kyr^-1 and ~244 g cm^-2kyr^-1). Lower accumulations rates characterize the very thin Holocene section (~1m thick) and an expanded section from 20,400 to 29,000 ¹⁴C yrs B.P., during the earliest to middle part of the Stage 2 glaciation (LGM).

MV-51 appears to have experienced a greater terrestrial influence during >32,000 ¹⁴C yrs B.P., possibly from river(s) draining the Papuan Peninsula. During >32,000 ¹⁴C yrs B.P., TOC fluxes were >200 g cm^-2kyr^-1, with over 45% of it coming from terrestrial vascular plant matter. Magnetic susceptibility values are two to three times higher and benthic foraminiferal accumulation rates are six times higher during this interval than any younger time indicating a much greater influence of detrital minerals and labile organic carbon.

We note several surprises. First, benthic foraminifera are most abundant during times of highest siliciclastic and terrestrial organic carbon input. Secondly, benthic foraminifera that are usually indicative of “marine productivity”, such as Uvigerina peregrina/hispida, Cibicidoides pachyderma, and Sphaeroidina bulloides, strongly responded to highest fluxes of terrestrial carbon. Finally, four volcanic ashfall events recorded in sediments generally caused sudden declines in TOC, benthic foraminifera, and calcareous dinocysts, but each event affected the faunas differently. We only noted an abundant “recovery” fauna after one ashfall and did not observe major assemblage changes.