河流相层序地层模式与地层等时对比

Fluvial Sequence Stratigraphy Mode and Isochronous Strata Correlation

已有的河流层序地层模式在层序发育的控制因素、体系域的划分等方面存在一定的问题。通过对苏里格气田盒8段河流相准层序对比,发现河谷中存在阶梯状河流阶地。现代河谷地貌的研究表明,这种阶地是构造抬升过程中,次级间歇性构造抬升导致河流下蚀与侧蚀—沉积交替的结果。而构造下降过程所引起的基准面上升和可容空间增速的变化又影响了河道砂体的展布特征。考虑构造运动在河流层序形成过程中的作用以及河流阶地与相邻地层之间的接触关系,修正了Wright等河流相层序地层模式,认为构造运动控制了河流层序的发育,构造上升半旋回形成水退体系域,为一系列相对等时的阶地,构造下降半旋回形成低位体系域、水进体系域和高位体系域,低位体系域为构造抬升早期形成的河谷充填物,水进体系域和高位体系域与Wright等的含义一致。

There exist some faults about the factor controlling sequence and the system tract partition in the former fluvial sequence stratigraphic models.The author finds that there are some terrace staircases in the fluvial valley during the fluvial parasequence correlation of He 8th in Sulige gas field.Studies about modern valleyform show that the secondary intermittent tectonic uplifts during the first tectonic uplift led to the alternation of vertical erosion and lateral erosion-deposition,which forms the terrace staircases.And the first tectonic fall led to base level uplift and the change of new space added,which will control the sandbody distribution.According to the role of tectonic during forming fluvial sequence and the contact relationship between terrace staircases and their surrounding formations,the author modifies Wright,et al（1993） fluvial sequence stratigraphic model,and he thinks that the tectonic movement controls the fluvial sequence.The hemicycle of tectonic uplift forms the regressive systems tract that is made of a series of relative isochronous terraces staircases.And the hemicycle of tectonic fall forms the lowstand systems tract,transgressive systems tract and highstand systems tract.The lowstand systems tract includes some filling sedimentary compound in the fluvial valley.The transgressive systems tract and the highstand systems tract are the same as the corresponding systems tract in the Wright,et al（1993） model.