断陷湖盆层序地层研究和计算机模拟──以二连盆地乌里雅斯太断陷为例

SEQUENCE ARCHITECTURE AND DEPOSITIONAL SYSTEMS OF ERLIAN LACUSTRINE FAULT BASINS,NORTH CHINA

断陷湖盆高级别的层序单元可依据不整合面及其对应的整合面来划分。高级别的不整合面主要是古构造运动面。应用二维回剥法恢复盆地构造沉降的速率曲线与层序界面比较分析表明，高级别的层序界面的形成与构造沉降速率的幕式变化和断块掀斜运动有关。湖泛面可作为副层序和副层序组划分的依据，湖平面变化受到气候、沉积物供给和盆地构造沉降相互作用的控制。各级层序界面的确定需要综合地质、地球物理及地球化学资料等系统分析。二连盆地乌里雅斯太断陷内充填了３０００多米厚的陆相湖盆沉积，可划分为５个层序组，识别出９～１１个三级层序，以湖泛面和碎屑体系的废弃为标志划分了副层序组和副层序，建立了湖盆地层格架。系统的沉积学研究概括出三种层序的体系域模式，即深湖盆型层序体系域、浅湖－深湖盆型层序体系域及浅湖－河流型层序体系域模式。不同体系域模式中的沉积体系作有序的分布，并受控于湖平面相对的高低变化和构造格架样式。层序地层模拟是近年来发展起来的一门新兴技术。通过模拟可分析层序的发育和形成机制，揭示构造沉降、海平面或湖平面变化及沉积物供给对层序发育和盆地充填演化的控制作用。以乌里雅斯太断陷为例的模拟验证了构造沉降速率的幕式变化和横向上的差异沉降是高级别层序?

Erlian fault basins,a major oil prospecting and producing area in North China,comprise about 40 grabens or half grabens. The basins formed during Jurassic to EarlyCretaceous were filled with basal volcanic rocks(Jurassic)and fluvial and lacustrine de-posits(Lower Cretaceous),with a thickness of about 3000 m,Based on the integrated in-vestigation of seismic profiles, logging and cores,5 sequence sets and 11 sequences havebeen identified in recognition of unconformities resulted from relative lacustrine levelchanges. The subsident research of the basins by backstripping shows that the major un-conformities mainly resulted from variable stretching rate and differential subsidence. Three types of lacustrine sequences have been identified:(1)deep lacustrine basin se-quences:(2) shallow lacustrine basin sequences and(3)shallow lacustrine and fluvialbasins sequences. The facies configuration and evolution in the basins varied in response tothe evolution of basin structural framework and lacustrine level change.A computer modelling Software has been programmed to test the geological model andto investigate the processes controlling the basins filling and evolution,The study hasshowed that the varied subsident rate of the marginal syndepositional faults is one of themajor factors controlling the geometries and development of the sequences,The computermodel can be also used to predict the facies distribution within sequence framework.