汤原断陷下第三系构造活动对层序的控制作用

通过层序地层学分析,汤原断陷下第三系可划分出4个三级层序。由于这些层序在形成时经历了拉张裂陷、快速沉降、挤压回返等不同的构造阶段,因此层序发育特征各有特点。在拉张背景下形成的简单裂陷层序发育巨厚的粗碎屑低位沉积体系域;在快速沉降背景下形成的层序发育下细上粗的湖泊收缩体系域;而在挤压回返背景下形成的简单坳陷层序规模较小,湖泊相不发育。在断裂活动和基底沉降共同作用下形成的快速坳断层序和快速断坳层序都能形成良好的生储盖组合,但快速坳断层序的生储盖组合更好。

CONTROLING THE TECTONIC ACTIVITY TO SEQUENCES LOWER TERTIARY OF IN TANGYUAN FAULTED DEPRESSION

According to sequence stratigraphic analysis,4 sequences of thirdorder could be identified from the Low Tertiary in Tangyuan faulted depression.These sequences are different from each other in scale and composition since they underwent different tectonics.In extension rifting background,fault depressed sequences are mainly composed of thick coarse fragments of lowstand system tract(LST);in rapid extension subsiding background,the sequences are characterzed by finegrain in lower part and coarsegrain in upper part;in the compression uplift background,sequence scale is small and lacustrine facies is poorly development.The most favorable sequence types are quickly depressed faulted sequences and quickly faulted depressed sequences,for they both contain best source,reservoir and seal rocks.