陕西旬邑晚新生代红土-黄土序列磁化率特征与环境变迁

研究陕西旬邑下墙完整的晚新生代红土-黄土剖面后证实,磁化率也可以作为分析红土气候特征的一个替代性指标,但最好的办法是以磁化率为主,同时参考粒度、地球化学等资料进行综合分析。本区新近系红土的磁化率曲线特点是高频率、低幅度、短周期,第四系黄土-古土壤的则是低频率、长周期。结合岩性、古生物、粒度及地球化学等资料得出,新近纪的气候在总体暖湿背景下有凉干-暖湿的交替,而第四纪的气候则是在总体冷干背景下的冷干-暖湿的交替。进入第四纪的气候突变及之后的气候亚突变,主导因素是该时期青藏高原的剧烈隆升,北极冰盖的形成与扩大也起着重要的作用。

SUSCEPTIBILITY OF THE LATE CENOZOIC RED EARTH-LOESS SEQUENCE IN XUNYI, SHAANXI PROVINCE AND ENVIRONMENTAL VARIATION

The study of a complete late Cenozoic loess-red earth section in Xunyi County has proved that susceptibility could be used as a substitute index to analyze paleoclimate. The susceptibility curves of Neogene red earth are characterized by high-frequence, low-ampititute, and short-cycle, indicating an alternation of cool-dry and warm-humid phases against a generally warm-humid background, whereas the susceptibility curves of Quaternary loess are characterized by low-frequence and long-cycle, indicating an alternation of cold-dry and warm-humid phases against a generally cool-dry background. A key factor for Quaternary sudden climate changes and subchanges is intense uplift of the Qinghai-Tibet Plateau during that period, and the formation and amplification of Antarctic ice sheet could also have an important effect.