基于锆石U-Pb年龄的黄土高原红黏土沉积序列物源示踪

Provenance Identification for Sedimentary Sequence of Red Clay in Loess Plateau Based on Zircon U-Pb Ages

黄土高原广泛沉积的新近纪红黏土序列对东亚古气候具有重要的指示意义。通过甘肃灵台红黏土剖面7.0、6.5、5.5、3.2Ma沉积物和山西保德红黏土剖面6.56、5.24、3.50 Ma沉积物碎屑锆石U-Pb年龄的对比,表明黄土高原不同区域红黏土沉积物物源在空间上具有一致性,而在时间上具有差异性。通过与周缘潜在物源区碎屑锆石U-Pb年龄对比,可将黄土高原红黏土沉积物物源的差异划分为3个沉积阶段:第一阶段(5.7~7.0 Ma)物源主要为西昆仑山、帕米尔高原;第二阶段(3.4~5.7 Ma)物源主要来自塔克拉玛干沙漠;第三阶段(2.6~3.4 Ma)物源主要为阿拉善区域。红黏土沉积物物源的变化表明2.6~7.0 Ma处于西风逐渐减弱伴随东亚季风逐渐增强的过程,物源的两次变化对应于约5.7Ma墨西拿盐度危机和约3.4Ma青藏高原的隆升,说明青藏高原以及中国西部山脉的隆升和板块运动控制下的特提斯洋演化是影响黄土高原风成沉积的重要因素。

The widely deposited Neogene red clay sequence in Loess Plateau has important directive significance on East Asian paleoclimate.The comparison of the detrital zircon U-Pb ages of 7.0,6.5,5.5,3.2 Ma from Lingtai red clay section in Gansu and 6.56,5.24,3.50 Ma from Baode red clay section in Shanxi was studied;the comparison of the detrital zircon U-Pb ages from red clay in Loess Plateau and the peripheral potential provenance regions was also studied.The results show that the sedimentary source of red clay in Loess Plateau has a spatial homogeneity and temporal variation.According to the difference of sedimentary sources,the red clay sediment in Loess Plateau can be divided into three stages：the first stage（5.7-7.0 Ma）,the main sources are West Kunlun Mountain and Pamir Plateau;the second stage（3.4-5.7 Ma）,the main source is Taklimakan desert;the third stage（2.6-3.4 Ma）,the main source is Alxa area.The variation of provenance from red clay sediment shows that the west wind weakens and monsoon grows at 2.6-7.0 Ma,and the two changes of provenances correspond to Messina salinity crisis at^5.7 Ma and the uplift of Qinghai-Tibet Plateau at^3.4 Ma,respectively.In general,the important factors influencing the eolian deposition in Loess Plateau are the uplift of Qinghai-Tibet Plateau and the western mountains of China,and the Tethys ocean evolution under the control of plate motion.