旋回层序地层的控制因素

旋回层序是受天文周期控制的,以最大洪泛面为顶、底界的,由进积叠加到退积叠加构成的有成因联系的沉积地层,是天文周期的真实记录。以鄂尔多斯盆地Sh99井延长组为例,应用离散小波变换方法对GR曲线进行了信号分解,并进行了各细节分量的频谱分析。根据各细节分量的优势频率比值与天文频率比值之间的对应关系,确定了与各天文周期对应的沉积旋回,并在延长组绝对地质年龄约束下划分了旋回层序。研究表明,以天文周期为依据、以小波变换及频谱分析为手段可以合理并有效地开展旋回层序划分。

Controlling factors of cyclic sequence stratigraphy

Cyclic sequence is a set of sedimentary formations with genetic relationship that are deposited in a cycle from prograding to retrograding,controlled by astronomical periods and bounded by maximum flooding surfaces.It records faithfully the shifting of astronomical periods.The article takes the Yanchang Formation in Well Sh99 from Ordos Basin for an example,discusses the signal decomposition and reconstruction of GR curve by using filtering DWT as well as spectrum analysis technique.The correspondent sedimentary cycle of each astronomical cycle is identified based on the relationship between master frequency ratios and astronomical frequency ratios.The cyclic sequences of the Yanchang Formation are identified with the Absdolute geologic age as constraints.The research shows that the division of cyclic sequence can be carried out reasonably and effectively with discrete wavelet transformation and spectrum analysis technique on the ground of the astronomical cycles.