Analysis of milankovitch cycles of quaternary in sanhu area, eastern qaidam basin
柴达木盆地东部三湖地区四系米兰柯维奇旋回分析

Natural gamma-ray curves that include great amount of geological information can well reflect stratigraphic cycles caused by climate changes.In this paper,the gamma-ray curves of the Quaternary of Sanhu area in eastern Qaidam Basin are analyzed using frequency spectrum analysis method.The time(depth) field of the natural gamma-ray curves can be transformed into the frequency field by the fast Fourier transform,and then the wavelength of every peak frequency and the ratios between these wavelengths are analyzed in order to find the frequencies whose wavelength ratios are the same as or similar to the Milankovitch cycles,and find out that the strata conserve well Milankovitch cycles and the main sedimentary cycles are 100,54,41,29,23 and 19 ka,corresponding with the eccentricity cycle,the obliquity cycle and the precession cycle of Milankovitch cycle.So it is reasonable to deduce that the sedimentary cycles are controlled by palaeoclimate which is caused by the eccentricity cycle,obliquity cycle and the precession cycle.The thickness range of sedimentary cycles caused by the eccentricity cycle is 92.00~115.00 m,that caused by the obliquity cycle is 24.55~63.43 m and that cause by the precession cycle is 16.8~26.35 m.Among the three control factors,the obliquity and the precession have more important effect on Milankovitch cycle of the Quaternary in Sanhu area.