Heinrich 1(H1)事件,是末次冰消期内一个重要的千年尺度的古气候事件.南海不同海域沉积物磁学性质对H1事件的响应存在差异,因而磁学参数的多解性应予以关注.本文选取南海西北部陆坡具有良好年龄框架的PC338岩芯顶部370 cm段(底部年龄20. 5 ka B. P.),进行详细的磁学性质分析,并利用IRM获得曲线组分分离方法和高场磁化率值等参数,试图为区域气候变化的沉积物磁学响应给出合理解释.结果表明,在H1事件发生时,碎屑成因的磁铁矿(IRM (C2+C3))和顺磁性组分(xp)明显降低,这反映了源区化学风化的减弱,指示南海北部冷干的气候条件;另外, H1事件发生时,南海西北部陆坡的赤铁矿含量较高,这与海平面降低造成的红河源区的赤铁矿输入增多和暴露的大陆架处于氧化条件有关. H1事件时期,东亚季风区呈现末次冰消期以来最干旱的气候特征,主要受控于大西洋经向翻转环流的减弱迫使热带辐合带南移和热带太平洋类La Nina的气候条件这两个因素.
Sediments of core YSJD-86GC(referred to as86GC)collected from the southern South China Sea were selected for environmental magnetic studies.Combined with the published chronological framework,sediment magnetic properties were revealed for the study area since the MIS3 stage.The rock magnetic results indicate that low-coercivity magnetite is the main magnetic mineral within the sediments.Also,a certain amounts of hematite are present.The King plot and Day plot,which reflect the magnetic particle size,show that fine-grained pseudo-single-domain phase magnetic particles dominate the magnetic minerals in the sediments.Comparison of magnetic parameters and geochemical indicators show that magnetic properties of core 86GC sediments reflect a terrigenous input.Simultaneously,magnetic characteristics of the studied sediment are influenced by the quantity of terrigenous sediment input,oxidation-reduction conditions of the provenance area,and the transportation environment and distance.Sea level fluctuation caused by global climate change was the main factor for variation in concentration of magnetic minerals and magnetic particle size of thestudied core sediments.Thus,variation of sediment magnetic properties in the study area can be used as an indirect indicator of sea level fluctuation.
Tingping OuyangChengjing TianZhaoyu ZhuYan QiuErwin AppelShuqing Fu
