中国第四纪黄土环境磁学研究进展

ENVIRONMENTAL MAGNETISM OF CHINESE QUATERNARY LOESS: A BRIEF RIEVIEW

中国黄土分布广泛、沉积连续性好 ,是进行磁性地层研究和重建古环境、恢复古气候的理想材料。中国黄土高原黄土—古土壤序列的环境岩石磁学性质详细地记录了 2 .5Ma BP以来古气候和古环境变化的信息 ,尤其是黄土和古土壤的磁化率作为很好的气候代用指标已得到广泛应用。古土壤磁化率增强成因机制一直在争论中 ,其中 ,与气候变化关系密切的成壤作用对古土壤磁化率增强起主导作用的观点已被普遍接受 ,目前利用不同方法建立了磁化率气候转换函数 ,从而使重建古降水量和古温度成为可能。

The loess paleosoil sequences in Chinese loess plateau are the excellent archives for studying the magnetic polarity history of the geomagnetic field and reconstructing the paleoprecipitations and paleotemperatures of the north hemisphere in the Quaternary. Their environmental rock magnetic properties recorded the environmental and climatic information since 2.5 million years before the present continuously and sensitively. Especially, being an excellent climatic proxy, magnetic susceptibility has been extensively applied. However, the actual mechanism of susceptibility enhancement remains debatable. Currently, the viewpoint that pedogenesis plays a key role in enhancing magnetic susceptibility of paleosoils has been generally accepted. Some functions of magnetic susceptibilities established by different methods may help to reconstruct the paleoprecipitations and paleotemperatures. Pedogenic magnetite is generally responsible for susceptibility enhancement. Maghemite, meanwhile, is an important contributor to the enhanced susceptibilities of paleosoils. The grain size of magnetic minerals can substantially influence the magnetic susceptibilities too. Additionally, the anisotropy of magnetic susceptibility may be in use of the reconstruction of Quaternary wind field.