频谱分析法确定乌什凹陷白垩系米氏沉积旋回及沉积速率

Applying Frequency Spectral Analysis to Identify Milankovitch Cycle and Calculate Sedimentation Rate of Cretaceous in Wushi Sag

以自然伽马曲线包含的丰富地质信息为基础,通过小波分析与快速傅里叶变换相结合,运用频谱分析法在乌什凹陷白垩系识别出米兰柯维奇沉积旋回,并确定出米氏旋回的厚度,在此基础上精确计算出资料区白垩系各层组沉积速率。其中偏心率周期引起的地层旋回厚度变化为8.70～13.89m;地轴倾角周期引起的地层旋回厚度变化为3.01～5.88m;岁差周期引起的地层旋回厚度变化为1.28～2.44m.4口采样井白垩系地层平均沉积速率为0.09378mm/a.

Based on abundant information of gamma-ray curves, combining wavelet analysis with fast Fourier transform, the Milankovitch cycle and its thickness of Cretaceous in Wushi sag is identified using frequency spectral analysis, then the sedimentation rates of each layer of Cretaceous in studied area are precisely calculated. The results show that the thickness of sedimentary cycle caused by eccentricity cycle ranges from 8.70 m to 13.89 m; the thickness of it caused by obliquity cycle from 3.01 m to 5.88 m; the one of it by precession cycle from 1.28 m to 2.44 m, and the average sedimentation rate of Cretaceous strata from four sampling wells is 0.093 78 mm/a.