新近纪以来中国黄土高原的风尘记录

通过对黄土高原中部两个典型的风尘堆积序列的岩性和磁性地层研究 ,认为中国黄土高原风尘堆积的开始发育年龄至少约为 7.2 Ma B.P.。以红粘土和黄土—古土壤交互出现的风尘沉积 ,不仅真实地记录了东亚季风气候的形成演化 ,而且可能包含了青藏高原的阶段性隆升、北半球冰盖形成演化及大冰期发生等构造气候事件的印记。反映粉尘源区的干燥度及携带粉尘的大气环流强度的风尘沉积速率自 7.2 Ma B.P.开始、尤其是 4.5 Ma B.P.以来逐渐增大 ,似乎暗示了自新近纪以来亚洲内陆粉尘源区干旱化的逐级发展和东亚冬季风环流强度的逐渐增加

EOLIAN RECORD OF THE CHINESE LOESS PLATEAU SINCE THE NEOGENE

Two eolian deposit sequences since Neogene were studied for the lithostratigraphy and magnetostratigraphy. This paper shows that the marker loess/paleosol and red clay layers of the two sections are well correlated with other profiles on the Chinese Loess Plateau, and the bottom age of eolian sequences is about 7.2MaB.P., which may mark the initiation of eolian accumulation on the Chinese Loess Plateau. The red clay loess paleosol sequences not only record the formation and evolution of East Asian paleomonsoon, but also include the imprints of the step wise uplifting of Tibetan Plateau and ice volume change of Northern Hemisphere from Neogene. The sedimentation rate of eolian deposits reflects the aridity of dust source regions and intensity of the past atmospheric circulation. It gradually increased from 7.2MaB.P. and especially since 4.5MaB.P., which indicated that the dust source region of inner Asia was becoming more aridity, and the intensity of east Asia winter monsoon was becoming stronger and stronger from Neogene to Quaternary.