Abstract
We describe the orbital-scale environmental variation around Papua New Guinea (PNG) for the last 400 ka based on the environmental magnetism. Six magnetic parameters and the δ18O record of the core MD05-2928 are presented in the study. Results of magnetic analyses reveal opposite responses to different environmental conditions: Magnetic minerals were relatively fewer and finer in interglacial periods and were more and coarser in glacial periods. The reason could be suggested: In interglacial periods, sediments coming from central New Guinea were transported by the coastal currents in the northern Coral Sea and then imported to the core site location. Magnetic minerals would be relatively fewer and finer due to this longer transportation process. In glacial periods, the routes of the currents might regress seaward with reduced current intensity because of lower sea level. Main sediment sources would shift to the Papuan Peninsula relatively near the core site, and therefore, the magnetic minerals became more and coarser. Further, period analyses using the eccentricity, tilt, and precession (ETP) curves and the wavelet spectra were applied to the study to analyze the periodicities embedded in the parameters. Results of both period analyses clearly present the Milankovitch periods, indicating the dominance of the orbital forcing in this area. The strongest signal of 100-ka period reveals that sea level change played the dominant role in long-term environmental setting for the past ~400 ka. However, influences of 40- and 20-ka periods, possibly related to regional precipitation, should also be considered though they might be second factors affecting the environmental variation around PNG.
Highlights
The Western Pacific Warm Pool (WPWP), with the average sea surface temperatures (SST) over 28 °C (Yan et al 1992), is generally considered to be the global transported engine and important source providing water vapors
From the magnetic results of the core, we can observe that variations of magnetic parameters (χ, saturated isothermal remanent magnetization (SIRM), anhysteretic remanent magnetization (ARM), χARM/χ, and SIRM/χ) are clearly related to the marine isotope stages (MIS) change
This feature denotes that these magnetic parameters could be considered as proxies describing the paleoenvironmental variation around Papua New Guinea (PNG)
Summary
The Western Pacific Warm Pool (WPWP), with the average sea surface temperatures (SST) over 28 °C (Yan et al 1992), is generally considered to be the global transported engine and important source providing water vapors. New Guinea, locating at the edge of the WPWP, is affected by several environmental factors, such as the intertropical convergence zone (ITCZ) migration, the Asian-Australian monsoon system, and the El-Niño Southern Oscillation (ENSO). Papua New Guinea (PNG), with the average precipitation about 2000–3000 mm a−1 (McAlpine et al 1983), is embraced by the Bismarck Sea, Solomon Sea, Coral Sea, and Arafura Sea (Fig. 1). Major rivers, coming from central New Guinea, receive input from rainfall and glacier meltwater, and drain to the Gulf of Papua (GoP) (Brunskill 2004). These rivers deliver more than ~365 mT sediments per year to the GoP (Milliman 1995). Less than 5 % of finer (suspended) sediments may be delivered eastwardly along the shelf by the coastal
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