利用米兰科维奇旋回划分柴达木盆地第四系层序地层

Division of Sequence Stratigraphy of Quaternary Formation in Qaidam Basin Using the Milankvitch Cycle

对柴达木盆地第四系自然伽马测井曲线的频谱分析结果表明,地层中保存着厚度稳定的地层旋回。按柴达木盆地第四纪沉积速率0.87～0.90m/ka计算,地层中保存的地层旋回厚度在厚度比值和沉积时间周期上都与米兰科维奇旋回周期一致,且主要受控于米兰科维奇旋回中的地轴倾斜度周期,其引起的地层旋回厚度变化范围为25.0～36.1m。据此采用Fischer图解法,求取其可容纳空间变化曲线,以指导层序地层的正确划分。

Using natural Gamma-logging curves to analyse sedimentary cycles is a new developing research field. With the frequency spectral analysis of the Gamma-logging curves of the Quaternary formation, Qaidam basin, the results indicate that the sedimentary cycles which have stable thickness are conserved very well in the strata. According to the sedimentary speed of the Quaternary formation, Qaidam basin, the sedimentary cycle in the strata consist with the Milankvitch cycle, and the sedimentary cycles are mainly controlled by the obliquity cycle of the Milankvitch cycle. The thickness of sedimentary cycles that caused by the obliquity cycle is in the range of 25.0-36.1 m. Therefore, the accommodation change curves of the terrigenous sequences obtained using Fischer diagram can guide the division of the sequences.