中国黄土磁学与古气候(英文)

近二十年来中国黄土环境磁学的研究基本上是沿着两条主线进行的 ,即磁性地层学和古气候研究两个方面。对早先确定的典型黄土剖面的磁性地层研究表明风成黄土的堆积开始于Matuyama的下界 ,约 2 .6Ma。而近年来对黄土古土壤序列之下的红粘土的进一步研究显示风成堆积的开始比原先认为的要早的多 ,至少可追溯到约 7Ma。尽管目前在古土壤磁化率的增强机制和磁化率如何记录古气候变化等问题上还没有达成广泛的一致 ,而黄土古土壤系列磁化率与深海氧同位素的良好对比可证实中国黄土确是记录全球气候变化非常理想的信息载体。近年来许多学者尝试性提出的其它古气候替代性指标 ,如全岩粒度、稳定同位素组成、FeD/FeT指标、Rb/Sr比值和CaCO3 含量等必将为重建古季风变化和古气候提供重要信息。

CHINESE LOESS MAGNETISM AND PALEOCLIMATE

Over the last two decades two broad lines of enquiry have emerged from magnetic investigation of Chinese Loess Plateau (CLP): magnetostratigraphy and paleoclimate. The classic loess sections cross CLP indicate that wind-blown loess deposition began close to the base of Matuyama (2.6Ma). However, progress is also being made in extending the record down below the loess of the CLP into the so\|called Red Clay, so that the aeolian record can now be carried back beyond 7Ma. Excellent connection between marine oxygen isotope curves and low-field susceptibility from numerous loess-paleosol sequences provides impressive evidence of the global significance of the Chinese record. Whereas the actual mechanism by which magnetic susceptibility becomes a climate proxy remains controversial. Presently several other proxy indicators, such as grain size, stable isotope composition, CaCO 3 content, ratio of citrate-bicarbonate-dithionite (CBD)-extractable Fe 2 O 3 to total Fe 2 O 3 , Rb/Sr and others have been proposed to reflect and reconstruct long-term monsoon changes.