Impact of climate change on the magnetic mineral assemblage in marine sediments from Izu rear arc, NW Pacific Ocean, over the last 1 Myr

A rock magnetic study was conducted on upper Pleistocene marine sediments from International Ocean Discovery Program Expedition 350 Site U1437 in order to highlight the paleoenvironmental changes in the NW PacificOcean influenced by the East Asian monsoon regime. Remanent magnetization analyses, hysteresis properties,first-order reversal curves and low temperature magnetic measurements were carried out, along with electronmicroscope observations. The results indicate that coarse-grained (titano)-magnetite is the dominant magneticphase in the magnetic mineral assemblage. Time-series analysis supports that this assemblage is modulated byglobal climate changes over the last 1 Myr. During the interglacial stages, magnetic minerals are more abundant;and are dominated by coarse-grained (titano)-magnetite of both terrigenous (likely from mainland China) andvolcanic (Izu arc front, Japan) origin. During the glacial stages, the magnetic mineral content is lower, probablyreflecting partial dissolution of (Ti)-magnetite, and the magnetic assemblage is composed of terrigenouscoarse-grained (titano)-magnetite and of higher coercivity, presumably finer eolian particles (likely hematite)as a result of the enhancement of the winter monsoon in continental Asia. The magnetic mineral assemblage reflects a superimposition of volcanic and global climate signals. Bulk organic-geochemical analyses for total andorganic carbon as well as nitrogen and sulfur contents confirm a climatic signature in the composition of the sediments with more oxygenated water masses being present during glacial periods. Additional X-ray fluorescencemeasurements on bulk samples indicate various origins of the sediment particles with both proximal and distalsources.