【作者】 丁仲礼； 杨石岭； 孙继敏；

【Author】 Ding Zhongli Yang Shiling Sun Jimin (Institute ofGeology,Chinese Academy of Sciences,Beijing,100029)

【机构】 中国科学院地质研究所；

【摘要】 最近一些研究表明,黄土高原晚第三纪红粘土沉积与其上覆黄土一样,也为风成成因。因此,中国北方连续风成沉积已从2.6 Ma下推到7.0 Ma前后。为比较中国北方晚第三纪与第四纪时期大气环流格局的差异,我们对黄土高原9个黄土剖面和4个红粘土剖面的粒度组成进行了采样和分析。结果表明,第四纪时期黄土和古土壤的粒度均从北往南变细,进一步支持第四纪黄土是由冬季风搬运的观点。但是,2.6 Ma以前沉积的红粘土的粒度从北到南基本没有变化,表明其受冬季风搬运的作用很小,推测红粘土可能是由西风带从中国西北部干旱区搬运而来。因此,2.6 Ma前后中国北方的大气环流格局发生了重大的变化,这可能由全球冰量增加和区域构造活动增强所致。更多还原

【Abstract】 It has been revealed that Late Eocene Red Clay in the Loess Plateau was eolian origin as Quaternary loess.So the wind-blown deposits in the northern China began about 7.0Ma instead of 2.6Ma.In order to compare the atmospheric circulation difference between the Late Eocene and Quaternary,grain-size analyses of 9 Loess sequences and 4 Red Clay sequences have been carried out.The results show that the grain size of Loess-paleosol become fine gradually from north to south in the Chinese Loess Plateau,confirming the statement that Quaternary loess have been carried by winter monsoon.However,the gain sizes of the Red Clay keep roughly unchanged,indicating that Red Clay has been affected weakly by the winter monsoon and maybe carried from the arid area in the northwestern China by the west wind.So atmospheric circulation in the Northern China has been changed about 2.6Ma due to global ice volume increasing and regional structure activity enhancing.更多还原