非海相沉积层序的成因和构型特征

根据东部盆地的地质、地球物理特征,初步对非海相层序地层学应用研究进行了总结.非海相沉积层序的形成要素,既有外旋回、又有自旋回,构造和气候因素很重要,强调了环境因素.沉积基准面在海上为海平面,在陆上为潜水面、湖平面、河流平衡剖面.相对基准面的周期性变化引起了可容纳空间的周期性变化,并由之形成了一系列旋回式的层序.大多数情况下内陆基准面的变化不受海平面变化的控制,在全球最大海泛期有某种联系.湖盆小而沉积速率高,形成层序的频率高于海相.以沾化凹陷为依据,提出了5种层序构型特征:冲积-河湖型,(半)盐湖-淡水湖泊过渡型,海流-深湖型,半深湖-缓坡型,河流-冲积平原型.在盆地主要发育期,断阶式坡折对沉积体系有明显的控制作用.除低水位扇外,低水位楔是构成隐蔽圈闭或复合圈闭的有利场所。

Genetic & Architectural Characteristics of Non-marine Depositional Sequence

Based on the geological and geophysical data,the authors summarized the applied seCuence strati graphy of non- marine basins in China. the controls on non- mari ne seCuences included both allocyclic and autocyclic processes. the most important factors Were tectonics and climate,but the environmental factor Would also be taken into account. the accommodation changed periodically With changing base level,resulting in the for mation of a series of genetically and spatially related depositional seCuences. Basically,base level of inner continent Was not controlled by changes of relative sea level. there Would be some relations bet Ween changes in relative sea level and continental base level during eustacy floodi ng,hoWever,a time lag existed betWeen the changes from marine basin to inner continent basin. the lake basin Was smaller than marine basin and the velocity of sedimentary supply Was higher, so the numbers of non- marine seCuences Were much more than those for med in marine facies during the same period. We have to pay attention to recognizing the systems tracts f or t he st udy of hi gh precision or hi gh-resolution seCuence strati graphy,especially to analyze t he loWstand systems tract Wit h its depositional systems. The genetic characteristics of seCuence boundary Were subaerial exposure,strati graphic truncation and subaCuatic erosion. According to the depositional feat ures of Zhanhua Depression,5 seCuence architect ures have been provi ded in this paper,Which are alluvial-fluvial/lacustri ne architecture，transitional architecture formed betWeen brackish lake and fresh lake,marine duration- deep lacustrine architecture，ramp architecture and fluvial-alluvial plain architecture. During the major development of non- marine basin，the step faulting breaks controlled depositional systems.Usually,loWstand complex fan,progradi ng Wedge and highstand turbidity f an Were located close to the third stepping break,it Was bypass of incised valley in loWstand period and then filled With adj acent sandy bar by the second stepping break,and at the first stepping break the sedi ments Were bypass Which could form favorable subtle or complex traps as the basin floor fan,and their economic significance Would be proved by boreholes in Bohai Bay Basin.