Late Quaternary orbital-scale variation of magnetic minerals in the northern Coral Sea

In the study, we describe the environmental variation for the last 380 ka in the northern Coral Sea, Papua New Guinea (PNG). Both analyses of paleomagnetic studies and wavelet spectra are applied to the magnetic parameters from the core MD052928, including magnetic susceptibility (χ), SIRM, ARM/χ and S-ratio. From the magnetic results, we observe that changes in characteristics of the magnetic minerals show relationship to different environmental conditions: In interglacial periods, the sediments coming from central New Guinea and Gulf of Papua (GOP) would be transported by the Hiri Current and then imported into the northern Coral Sea. Magnetic minerals were relatively fewer and finer due to this farther transportation process. In glacial periods, however, the route of the Hiri Current might regress seaward and the sediments source might shift to southeastern PNG nearby the core site. The magnetic minerals would therefore become more and coarser. Besides, the finest magnetic grains, considered as resulting from the aerosols, imply that stronger monsoon might prevail in MIS 7, MIS 5 and MIS 1. For the wavelet analyses, all spectra of the parameters, except for the S-ratio, present the clear Milankovitch periods though the 20-ka period is relatively ambiguous. It indicates that the variation of the magnetic minerals should be mostly controlled by the orbital forces in the northern Coral Sea. Dominant periods centered at 100-ka and 40-ka imply that changes of global sea-level and regional precipitation may both play important roles controlling the source variation of the magnetic minerals near southern PNG.