有效厚度拟合定量恢复原始地层超覆点位置

地层超覆点的迁移是层序地层分析和海平面变化曲线编制的重要依据。受构造抬升、海平面下降或二者共同作用影响,地层超覆点在沉积后常被剥蚀。如何恢复其原始沉积时的位置,至今尚无定量方法提出。基于地层厚度自盆地边缘向盆地中心依次增大,或先增大、后减小的分布特点,采用指数与线性相结合的分段函数模型,利用未剥蚀区地层厚度数据拟合外推恢复原始地层超覆点位置。该方法适用于被动大陆边缘、大型三角洲沉积区及坳陷型盆地,应用于巽他陆架晚新生代地层分析,取得满意效果.

Extrapolating the Original Positions of Removed Onlap-Offlap Points Using a Piecewise-Constructed Model of Effective Stratal Thickness

The shift of onlap offlap points is a critical factor in sequence stratigraphic analysis and charting sea level curves. Onlap offlap points, however, are easily removed due to tectonic uplift, eustatic sea level fall, and so on. How to recover the original positions of removed onlap and offlap points has still been a pending problem. In this paper, we presented a piecewise constructed function model to depict the lateral changes of stratal thickness along a dip section. It is assumed that the thickness of a stratum decreases exponentially from its maximum towards basin margin, and thins linearly on areas adjacent to the onlap offlap points. Using this model, the positions of removed onlap and offlap points can be extrapolated by fitting the thickness data in non removal areas. This approach is used in the study of the Pliocene to Pleistocene strata on the northern Sunda Shelf, South China Sea, and the results are to our satisfaction.