利用上超点法重建渤海湾盆地辽中凹陷渐新世湖平面变化

Reconstruction of Oligocene Lake Level Change through Onlap Points: A case from Liaozhong Depression,Bohai Bay Basin

标准层序是指同时包含高位体系域HST、湖侵体系域TST、下降体系域FSST和低位体系域LST的三级层序。通过对标准三级层序各类体系域中上超特征的分析,将一个标准层序的上超点分为5大类,即LST上超点、TST上超点、早期HST上超点、晚期HST上超点和FSST上超点,提出了通过统计层序内各类上超点来反演湖平面变化史的方法。利用这种方法,结合渤海湾盆地辽中凹陷渐新统地层剖面特征,在划分三级层序的基础上,统计上超点并绘制岸线迁移和湖平面升降幅度曲线,并将渐新世划分为4个湖平面升降旋回,对比钻遇沉积物的纵向变化特征,认为湖平变化曲线可信度很高,同时也证实了上超点方法反演湖平面变化在陆相古湖泊学研究中的可行性。

Standard sequence involve HST,TST,FSST and LST.Through analyzing the features of onlap points in the systems of standard third-order sequences,the onlap points of a standard sequence can be divided into five kinds,which are onlap points of LST,onlap points of TST,onlap points of early HST,onlap points of late HST and onlap points of FSST;and bring forward the way of inverting lake level change history by counting onlap points in the sequence.Use this method,which can be used in conjunction with the features of stratigraphic section in Liaozhong depression,the Bohai Bay Basin;on the basis of dividing third-order sequences,count the onlap points and plot a coastal process curve and a lake level eustasy extent curve,and divide Oligocene into four lake level eustasy cycle,then,through contrasting the vertical variation of drilling sediment,we find that the lake level is highly confident curve,it also proves that the way of inverting lake level change by counting onlap points is practicable in the study of continental paleolimnology.