Detailed mineral magnetic measurements,integrated with grain-size distribution and X-ray diffraction(XRD) analyses,were made on the marine sediments of Core MD98-2172,retrieved from the Eastern Timor Sea.Values of magnetic susceptibility in this core drop sharply down-core from-3.85 m deep below sediment/water interface and are very low at-5.35 m.However,both XRD and grain-size distribution results show no sudden change in terrigenous input during sedimentation.Mineral magnetic results indicate that the depth of-3.85 m may be an oxic/anoxic boundary.Therefore,the sediments below-3.85 m have been subjected to intense reductive diagenesis,whereas the sediments above-3.85 m are seldom affected.The magnetic properties of the sediments shallower than 3.85 m are dominated by pseudo-single domain(PSD) magnetite,with little down-core variation in its content and grain size.Below-3.85 m,the magnetic mineral assemblages that have survived in the sediments may record different stages of the reductive diagenesis:(1) the sediments from the 3.85-5.35 m interval are at the stage of iron oxide reduction;PSD magnetite is the major magnetic contributor,but it becomes less abundant and coarser down-core;(2) the sediments below-5.35 m are at the stage of sulphate reduction;ferrimagnetic minerals almost vanish and paramagnetic minerals contribute to down-core susceptibility variations,including pyrite as evidenced by high-temperature magnetic susceptibility measurements.However,the susceptibility variations below-5.35 m of Core MD98-2172 show obvious periodicity,despite the intense effect of reductive diagenesis.Furthermore,the down-core susceptibility variations are coincident with fluctuations in the quantity of fine detrital particles(<8 μm),which may come mainly from the advection of the Indonesia Throughflow(ITF) and/or river input from Timor.Therefore,for Core MD98-2172,susceptibility variation below-5.35 m,which potentially correspond to fluctuations in the quantity of fine particles,may record the histories of the developmen
