前陆盆地挠曲沉降正演模型的设计与实现——以库车古近纪陆内前陆坳陷沉降分析为例

本文以二维薄板弹性挠曲模型为基础,对模型进行简化和参数优化选取,并在VC++6.0环境下采用Windows视窗设计,实现了前陆盆地挠曲沉降的正演模拟系统.应用这一系统模拟分析了库车古近纪-新近纪前陆盆地的挠曲沉降过程.模拟结果表明,库车古近纪-新近纪前陆盆地的沉降曲线总体呈上凸型,具有典型前陆盆地沉降的特点,根据沉降速率变化可以把整个沉降过程分为四个部分,分别对应盆地的四个构造层序发育阶段,每一阶段呈不同的沉降特征,相邻两阶段之间存在一盆地回弹隆升、逆冲构造活动终止期,盆地遭受广泛剥蚀形成两个构造层序之间的不整合界面.正演模拟通过将沉降过程时间离散,精细设定不同时间段的构造负载,能够精细恢复前陆盆地的沉降过程和演化.

The Design and Realization of the Forward Model for the Simulation of the Foreland Basin Flexure Subsidence Process: A Case Study of Design and Realization of the Tertiary Kuqa Foreland Depression

Based on the 2D thin board elastic flexure model and simplified and optimized model parameters in the visual C ++ 6.0 environment and using the visual window design idea, the authors built the flexure subsidence dynamic modeling software of foreland basin and applied it to the analysis of the compression flexure subsidence process of Tertiary Kuqa foreland basin. The modeling result shows that the whole subsidence curve and subsidence rate of Tertiary Kuqa foreland basin exhibit an upward convexity shape, indicating a typical flexure subsidence characteristic. According to variation of the subsidence rate, the whole subsidence process may be divided into four phases, corresponding to four tectonic sequence phases respectively. There exist different subsidence characteristics in different phases, with a period of basin upheaval and quiescence of the tectonic activity existent between two adjacent phases which suffered extensive erosion and formed unconformity. Through the time-dispersion of the depositional process and the exact setting up of the tectonic load of different segments, the forward model can exactly restore the subsidence rate and subsidence curve, overcoming the shortcomings of the reward backstripping model which fails to accurately restore the sequence-scale subsidence process due to the impossibility of obtaining the accurate geological age for every surface.