中文摘要：

对红白山剖面的粒度分析表明,塔里木盆地腹地晚新生代沉积物的粒度曲线中普遍存在一个超细粒组分。其众数粒径分布比较稳定,平均为0.87μm,含量变化介于0.3%～10%,在不同成因的沉积物中和在剖面上都具有明显的变化规律。对同一岩性段而言,超细粒组分含量在风成砂中最低,在黄土中较低,在河流相沉积中较高,在湖相泥岩中最高。尽管受岩性变化的影响比较显著,但不同成因沉积物的超细粒组分含量在剖面上的变化基本一致,暗示了其长周期变化受同一驱动因子控制。化学风化和/或成壤作用强度可能起着关键作用。红白山剖面超细粒组分含量在2.8Ma的快速降低指示了化学风化和/或成壤作用强度的显著减弱,进而反映了塔里木盆地腹地干旱化的显著加强。

英文摘要：

Grain size data from the Hongbaishan section reveal that the late Cenozoic deposits in the central Tarim basin generally contains an ultrafine component,which has an consistent modal size of 0.87μm and a variable proportion of 0.3%~10%.For the same lithological unit,proportions of the ultrafine component are quite distinctive along with the alternation of lithology.Aeolian sand owns the lowest value,loess has slightly higher value but lower than that of the fluvial deposits,whereas lacustrine clay maintains the highest value.Nevertheless,the long-term variations of the ultrafine component in different sediments show a similar trend,implying that same factor contributed to the long-term changes.Intensities of the chemical weathering and/or pedogenisis probably play the leading role in driving the changes.The abrupt decreasing of the ultrafine component at 2.8 Ma indicates a dramatic weakening of the chemical weathering and/or pedogenisis,which in turn suggest a significant strengthening of aridity in the Tarim basin.