摘要
利用X射线衍射、扫描电子分析方法，对临夏地区塔湾黄土沉积物的粘土矿物学特征及其古气候指示作用进行了深入研究。结果表明：晚更新世的黄土沉积物风成黄土或经过表生风化改造形成的古土壤，其粘土矿物组成主要为伊利石、绿泥石、伊／蒙混层粘土矿物、高岭石和少量的坡缕石，沉积物中高岭石、伊利石／蒙脱石、伊利石和绿泥石矿物组合，指示物源区经历了气候从湿润变为冷干的转变。沉积物中伊利石结晶度的测量结果显示，其（001）衍射峰的半高宽在0．23°-0．86°之间，不同岩性层中伊利石结晶度存在明显的差别，伊利石结晶度存在着两个明显的峰值区，这表明临夏地区晚更新世的气候变化经历了从湿润→冷干→湿润→冷干的两个周期性的演化，而且晚期与早期相比更加湿润同时又更为冷干。沉积物中既有自生成因的坡缕石，又有碎屑成因的坡缕石。沉积物中自生成因坡缕石和碎屑成因坡缕石均稳定存在的现象表明，本区晚更新世的古气候是以干旱为特征，年均降雨量在300mm左右。
Clay mineralogy of the Late Pleistocene loess sediments in Tawan, Linxia, northwestern China, was investigated using X-ray diffraction （XRD）and scanning electron microscopy（SEM）. The results show that mineral compositions of both the loess sediment and the palaeosol are illite, chlorite, mixed-layer illite-smectite, kaolinite, and minor palygorskite. The mineral assemblage of illite, chlorite, mixed-layer illite-smectite, and kaolinite suggests that the palaeoclimate of the source area changed from warm and humid to cold and arid. The to cold and arid, and the late cycle was more humid and more arid comparative to the former one. Both authigenic and detrital palygorskite occured in the Late Pleistocene loess sediments, the stability of palygorskite indicates that the annual rainfall was around 300 mm during the Late Pleistocene.
出处
《现代地质》
CAS
CSCD
北大核心
2007年第2期406-414,共9页
Geoscience
基金
中国地质调查局项目(1212010610103)
关键词
粘土矿物
结晶度
坡缕石
晚更新世
临夏盆地
clay minerals
crystallinity
palygorskite
Late Pleistocene
Linxia basin
