四川元坝地区长兴组层序地层特征及Fischer图解

上二叠统长兴组分别与飞仙关组、吴家坪组整合接触,在元坝地区为一套稳定的海相碳酸盐岩沉积建造,有利于开展层序地层学研究。通过地震地层学方法、岩石岩相地层学方法以及Daubechies小波分析方法对元坝地区长兴组层序界面、体系域进行识别及特征研究,共划分出2个Ⅲ级层序(旋回)。进一步在单井上进行米兰科维奇旋回的划分及对比,通过岩石学及Daubechies小波方法解释结果可知db5曲线,由此识别出的36个旋回与人工解释的米兰科维奇旋回良好对应。将解释结果绘制Fischer图解,进一步对所得图解进行元坝地区长兴组地层可容空间演化特征分析,再次证实元坝地区长兴组存在的2次可容空间周期变化。最后以本实例为基础对Fischer图解形态特性、影响因素进行讨论。

SEQUENCE STRATIGRAPHY OF THE CHANGHSING FORMATION IN THE YUANBA AREA OF SICHUAN PROVINCE USING FISCHER PLOTS

The Upper Permian Changhsing Formation in the Yuanba area of Sichuan Province is overlain by the Feixianguan Formation and underlain by the Wujiaping Formation.It is a marine carbonate series suitable for sequence stratigraphic analysis.On the basis of Daubechies wavelet analysis of seismostratigraphic and lithostratigraphic data , we were able to recognize several sequence boundaries and system tracts in the Changhsing Formation.Two third-order sequences ( cycles ) were identified.Further Daubechies wavelet analysis of seismic and well log data revealed 36 Milankovich cycles , which can be correlated with cycles based on lithostratigraphic interpretation.Further analysis using Fischer plots indicates that the Upper Permian Changhsing Formation represents two cycles of accommodation changes.