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High-resolution environmental magnetic measurements were carried out on Core MD77-181 in the Bay of Bengal, including magnetic susceptibility, anhysteretic remanent magnetization, isothermal remanent magnetization of all samples, and tem- perature-dependence of magnetic susceptibilities and magnetic hysteresis parameters of representa- tive samples. The results suggest that (1) the mag- netic mineral assemblage of the upper 9.82 m sedi- ments (corresponding to the last 160 ka) is domi- nated by pseudo-single domain magnetite, with more abundant coarse grains in glacial periods than in in- terglacial periods; (2) the uppermost 6.50 m of sedi- ments (corresponding to the last 70 ka) shows sig- nificant temporal variations in grain sizes of magnetic minerals, possibly reflecting the teleconnection be- tween variations of the Indian summer monsoon and rapid cold events of the North Atlantic (Heinrich events); (3) the sediments below 9.82 m are domi- nated by paramagnetic minerals (probably including pyrites), suggesting reductive diagenesis. The mag- netic records of Core MD77-181 are comparable to those of Core MD77-180 in the Bay of Bengal, and ODP Hole 722B in the Arabian Sea. This study sug- gests that the paleoceanographic event at ~160 ka significantly changed the redox state of the northern Indian Ocean, from a reductive environment before the event to an oxic or suboxic environment after the event.
High-resolution environmental magnetic measurements were carried out on Core MD77-181 in the Bay of Bengal, including magnetic susceptibility, anhysteretic remanent magnetization, isothermal remanent magnetization of all samples, and tem- perature-dependence of magnetic susceptibilities and magnetic hysteresis parameters of representa - tive samples. The results suggest that (1) the mag- netic mineral assemblage of the upper 9.82 m sedi- ments (corresponding to the last 160 ka) is domi- nated by pseudo-single domain magnetite, with more abundant coarse grains in glacial periods than in grains (3) the uppermost 6.50 m of sediments (corresponding to the last 70 ka) shows sig- nificant temporal variations in grain sizes of magnetic minerals, possibly reflecting the teleconnection be-tween variations of the Indian summer monsoon and rapid cold events of the North Atlantic (Heinrich events); (3) the sediments below 9.82 m are domi- nated by paramagnetic minerals (probably including pyrites), suggesting reductive diagenesis. The mag- netic records of Core MD77-181 are comparable to those of Core MD77-180 in the Bay of Bengal, and ODP Hole 722B in the Arabian Sea. This study sug- gests that the paleoceanographic event at ~ 160 ka significantly changed the redox state of the northern Indian Ocean, from a reductive environment before the event to an oxic or suboxic environment after the event.