地层记录中旋回层序界面的识别方法及原理

Detection of Cyclostratigraphic Sequence Surfaces in Stratigraphic Record:Its principle and approach

应用频谱分析技术对测井物理参数记录的沉积旋回在深度域的变化进行了研究,发现沉积速率变化对沉积旋回波长、旋回谱系的组合样式和连续性具有明显的影响。数字模拟实验研究结果表明,在深度域对测井数据进行递进扫描的频谱分析图中,旋回波长和旋回谱系的终止面和转换面,指示沉积速率突变界面,对应地层间断面或沉积体制转型的位置和深度,这是我们识别旋回层序界面的标志,这一结论在深海钻孔中得到了验证。文中详细地介绍了从测井曲线数据中提取沉积旋回信号的数据处理方法和流程,提出根据原始测井曲线建立的极值曲线,可以检测到最明显的旋回波长为10 m级的频谱信号,这一层级的旋回层序界面,可以作为区域等时对比的基准。文中以川西上三叠统须家河组为例,根据自然伽马测井曲线的频谱分析,讨论了旋回层序界面在解决地震层序界面标定中的实用价值。

In this paper spectral analysis methods are used to study sedimentary cycle changes in depth domains in geophysic logging record. We propose that sedimentation rates have important control for cyclic wavelengths, spectrum peak patterns and continuities. Digital simulation tests show cyclic wavelength changes and spectral bands terminations along depth domain by sliding-widow spectral analysis, which indicate abrupt sedimentation rate changes. Its depth location of abrupt surfaces are corresponding to stratigraphic discontinuity and reflect deposifional regime conversion and can be as identification critical maker of cyclostratigraphic sequence surface discrimination. This method has been verified to be validity in deep sea sediment from ODP Site 154. The data processing procedures, which sedimentary cycle signals are extracted and check in spectral analysis, are described and illustrated in detailed. The extreme point data series, which are reconstructed from original logs, can be provided us obvious and stable spectral signals with the cyclic wavelength of 10m scale leveI. The cyclostratigraphic sequence surfaces in this hierarchy can be used a refer- ence surface in regional stratigraphic correlations. The upper Trassic Xujiahe Formation from the western Sichuan fore- land basin as a case study, cyclostratigraphic sequence surfaces are calibrated based on evolutive spectral analysis from natural gamma log of Chuanya Hole 95. It is suggested that this methods have widely practical values compres- sion with traditional seismic sequence.