Clay Mineralogy and Its Palaeoclimatic Indicator of the Late Paleocene to Early Oligocene Sediments in Yongdeng,
Clay mineralogy of the Late Paleocene to Early Oligocene sediments in Yongdeng, Lanzhou and their palaeoclimatic interpretations were investigated using X-ray diffraction(XRD) and scanning electron microscopy(SEM). The results showed that clay mineral composition of the sediments was dominantly illite, smectite, and chlorite, with minor palygorskite. From the Late Paleocene to Early Oligocene, the sediments illite content showed an upward increase trend, while the smectite content exhibited an opposite trend to that of illite.