中新世以来长江下游和黄土高原地区黏土矿物的时空变化及古气候意义

Temporal and spatial changes of clay minerals since the Miocene in lower reaches of Yangtze River and Chinese Loess Plateau and their palaeoclimate implications

为了认识中新世以来长江、黄河流域沉积物中黏土矿物的时空变化及古气候意义,利用X射线衍射方法分析了中新世以来长江下游河湖相沉积物、黄土高原红黏土和黄土-古土壤的黏土矿物组成。结果表明:中新世以来长江下游、黄土高原沉积物的黏土矿物组成都为伊利石+绿泥石+高岭石+蒙脱石;各地质时期长江下游和黄土高原不同剖面沉积物由不同的黏土矿物组成;各连续沉积剖面黏土矿物均存在伊利石含量逐渐增加的变化趋势,反映中新世以来这两个地区气候逐渐变冷。研究表明,伊利石/高岭石值、伊利石/(蒙脱石+高岭石)值可作为反映气候暖湿—干冷演化的矿物学标志。

In order to investigate the temporal and spatial changes of clay mineral since the Miocene in the Yangtze and Yellow River reaches and their palaeoclimate implications,the X-ray diffraction analysis（XRD）was applied to study the clay minerals in the fluvial-lacustrine sediments in the lower reaches of the Yangtze River and the red clay-loess sequences in the Chinese Loess Plateau.The results show that the clay mineral compositions of the lower reaches of Yangtze River and Chinese Loess Plateau mainly consisted of illite,chlorite,kaolinite and smectite.During each geological stage,the sediments of different deposition profiles in the two study areas have different combinations of clay minerals.In each continuous depositional profile there exists a phenomenon that illite tends to gradually increase which reflects the gradual cooling of climate.The ratios of illite to kaolinite（Ill/Kao）and illite to smectite plus kaolinite（Ill/（Sm＋Kao））may serve as a proxy to evaluate the palaeoclimate.