Orbital-scale variation in the magnetic content as a result of sea level changes in Papua New Guinea over the past 400 ka

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 δ 18 O 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.

Precessional control on ocean productivity in the Western Pacific Warm Pool for the last 400 kyr: Insight from biogenic magnetite

“…Transportation and deposition of magnetic minerals may be controlled by the path and strength of the New Guinea Coastal Undercurrent, which may vary with reorganization of global deep-water circulation on glacial-interglacial timescales. Also, the supply of magnetic minerals from New Guinea may be influenced by sea-level changes [Huang et al, 2015]. The k ARM /SIRM ratio, which is influenced by magnetic grain-size changes, undergoes small increases in interglacial periods in addition to the dominant precessional frequency (Figures 3c and 4c; note that the axis is Geochemistry, Geophysics, Geosystems 10.1002/2016GC006446 inverted).…”

“…Huang et al . [] interpreted magnetic mineral concentration variations in terms of sea‐level changes in New Guinea.…”

“…For example, Kissel et al [2010] discussed paleoprecipitation and bottom-current strength variations and their relation with East Asian Monsoon activity and deep ocean circulation mainly based on magnetic grain size and anisotropy of magnetic susceptibility variations. Huang et al [2015] interpreted magnetic mineral concentration variations in terms of sea-level changes in New Guinea.…”

Special issue on “Recent advances in environmental magnetism and paleomagnetism”

“…The results provide excellent constraints on the initial properties of dust sources that are transported either to the CLP by the Asian winter monsoon or to the North Pacific Ocean by westerly winds. Huang et al (2015) presented the environmental magnetic variation around Papua New Guinea for the past 400 ka based on magnetic parameters and the δ 18 O record of core MD05-2928. Rock magnetic analyses indicate that magnetic minerals were fewer and finer in interglacial periods, whereas the opposite is the case for glacial periods.…”