CLIMATIC AND OCEANOGRAPHIC CONDITIONS IN THE GULF OF PAPUA, PAPUA NEW GUINEA, DURING THE BøLLING-ALLERøD, YOUNGER DRYAS, AND MELTWATER PULSE-1B: A PALYNOLOGICAL ANALYSIS
Changes in palynomorph assemblages provided data on the climatic regimes that characterized Papua New Guinea (PNG) during the Bølling-Allerød Interstadial (14.5 to 12.5 kyr BP), the Younger Dryas (12.5 to 11.5 kyr BP), Meltwater Pulse-1B (11.5 to 10.5 kyr BP), and the Holocene (10.5 kyr BP to present). The palynological data showed that the climate remained tropical for the past 14.5 kyr and that summer sea-surface temperature remained above 11.5º C, even during the Younger Dryas, although a reduced PNG vegetative cover marked this climatic interval. Decreases in mangrove pollen abundance and increases in marine palynomorphs mark the end of transgression and modern sea level highstand conditions at approximately 5 to 6 kyr BP. Intensification of the El Niño Southern Oscillation (ENSO) and an increase in climate seasonality was observed in the oxygen isotopic results from MD-50 at ~5,000 yr BP. Although pollen evidence for an ENSO-dominated climate was expected, the vegetation remained stable throughout the study. Sediment transport pathways in the GoP remained fairly constant throughout the time interval. When combined with palynological analysis, sediment maturity, which was determined from illite to smectite ratios, helped to determine sourcing for the cores. In particular, MV-41 was comprised of Vailala and Lakekamu river catchment sediments; MV-46 of Fly, Bamu, Turama, Kikori, and Purari sediments; and MD-50 of carbonate sediments sloughed from surrounding reefs.