黄土高原西部典型古土壤与黄土的磁学特征及其古气候意义

Magnetic properties of typical paleosol and loess stratum of western loess plateau and its signification to paleocliamte

探讨并详细对比了位于黄土高原西部的九州台黄土剖面的黑垆土和马兰黄土上部土层的磁学性质,初步探索了黄土高原西部黄土的磁学性质与成壤作用和气候变化间的内在关系.结果指示晚更新世以来黄土高原西部地区黄土风尘沉积物的磁性矿物质量分数总体较低,以磁铁矿为主,同时含有磁赤铁矿、赤铁矿和少量针铁矿;磁晶粒度特征介于单畴与多畴.不同土层的磁学特性存在明显差别:黑垆土中磁铁矿和赤铁矿质量分数高,磁晶粒度相对更细,高矫顽力矿物含量少;马兰黄土上部中磁铁矿和赤铁矿质量分数少,针铁矿质量分数相对较高,磁晶粒度性质更接近于多畴,高矫顽力矿物含量多;过渡层磁晶粒度性质介于上述两段之间,总体磁学性质更接近于马兰黄土的.

The magnetic properties of the Heilu soil unit and upper Malan loess unit of JZT profile located in the west of the loess plateau were compared.The relationship between magnetic properties and pedogenesis was discussed.The results show that the loess depositing after the late pleistocene had the properties that its content is low;the magnetite is the dominating magnetic mineral and maghemite,hematite and goethite contents could be detected;the magnetic mineral domain is intermediate between SD and MD.The magnetic properties are significantly different：Heilu paleosol contains more magnetite,haematite and/or maghaemite and less goethite in concentration,the magnetic domain is more close to the single-domain;Malan loess has more goethite and less ferromagnetic minerals,the magnetic domain is more close to the multi-domain;the transition＇s magnetic properties are between the above-mentioned two soil units and close to Malan loess.