断陷湖盆陆相层序中体系域构型及其模式新论

泌阳断陷下第三系核三上段可划分为三个陆相层序（Ｓ４、Ｓ５和Ｓ６），除Ｓ６顶界Ｔ４为沉积间断面外，其它层序界面皆为沉积相不连续面．泌阳断陷湖盆陆相层序的体系域具四分性，一个完整的陆相层序通常从低位加积、水进退积到高位加积、水退进积．研究区下第三系核三上段所划三个层序均缺乏低水位体系域，每一层序自下而上发育ＴＳＴ、ＨＳＴ和ＲＳＴ三个体系域，各体系域在三维地震剖面上呈现不同的反射结构和反射构型特征．按“体系域具四分性”论点，发育齐全的四个体系域有五个界面，除顶、底界面归属层序界面之外，其它三个界面皆为体系域界面，即初始湖泛面（ｆ．ｆ．ｓ．）、凝缩段ＣＳ（通常取其底界面Ｂ．Ｃ．Ｓ．）及最大湖泛面（ｍ．ｆ．ｓ．）等．在以特定井（泌２０７井）的位置作为参照物的基础上，根据参照井处湖平面升降幅度、湖岸线上超远近及沉积相迁移特征，建立了陆相层序体系域的认识模式，并将泌阳断陷陆相层序划归二种类型（Ⅰ型和Ⅱ型）．

On the Structure and Mode of the System Tracts of a Continental Sequence in Faulted Lake Basin

The upper member of Eh 3 in Shuanghe～Zhaoao area of Biyang fault depression is divided into three continental sequences. Except for the top boundary of sequence S6 which is sedimentary discontinuity, the other sequence interfaces are all the discontinuity surfaces of sedimentary facies. Generally, a complete continental sequence includes four system tracts of lowstand aggradation, retrogradation, highstand aggradation and progradation. But in the three sequences of the upper member of Eh 3, there is not LST, and TST, HST and RST developed from bottom to top whose reflection features on seismic profile are different each other. There should be 5 interfaces in a complete continental sequence. Top and bottom boundaries are sequence interfaces, and the others are system tract interfaces (i. e. First Flooding Surface (f. f. s.), Bottom of condensed section (B. C. S.) and Maximum Flooding Surface (m. f. s.)). A recognition pattern of the system tracts of continental sequences is established according to the lake level fluctuation amplitude, the lake strandline onlap and the facies migration character at well B207 which is taken as reference. And by using it, the continental sequences in Biyang fault depression are divided into two types, type Ⅰ and type Ⅱ.