塔中地区石炭系东河砂岩层序地层研究

东河砂岩是沉积于早海西期角度不整合面之上的第一套旋回性地层单元，它是由最底部的低水位体系域（ＬＳＴ）、海侵体系域（ＴＳＴ）及高水位体系域组成的Ⅰ类标准沉积层序，相当于三级海平面旋回的沉积地层。ＬＳＴ以缺失其早期的盆底扇、斜坡楔状体等为特征，仅发育其晚期的陆上河流充填沉积；ＴＳＴ中不发育凝缩层段，副层序在垂向上以弱退积至加积方式堆叠。一个完整的海平面相对升降旋回导致区内不同时期、不同地区的沉积体系及沉积特征不同。

Sequence Stratigraphy of Carboniferous Donghe Sandstone in Tazhong Area,Tarim Basin

Donghe Sandstone in Iarim Basin is a set of fine elastic reservoir rocks which deposited on the regional unconformity of early Hercy progeny. The origional basin where the Donghe Sandstone deposited is an intracratonic depressional basin. The basin with the characterstiris of shallow water and low slope was formed by the compression between the north and south plates.basin.The Tazhong area located in the east part is one of the components in the origional The sequence stratigraphy of longhe Sandstone within a depressional basin was depicted in this paper on the basis of study of seismic data,well logging 70-120 m,while and drilling materials. The thickness of Donghe Sandstone vanes between the maximum thickness is more than 165 m,it overlaped eastward and on the buried hill. The Donghe Sandstone is a standard type 1 sequence,including lowstand system tract,transgressive system tract and highstand system tract. It is analogous to the stratigraphyic unit formed by the third order cu-static fluctuation. Compared to the passive continental margin sequence stratigraphic model, the lowstand tract of this sequence only developed the fluvial deposits on land and lacked the early submarine fan,slope wedge,progradational complex and incised valleys which developed on shelf. There is no condensed sections in the transgressive system tract owing to the plenty of source materials and adjacent to the source area. Because of the transgression,the delta and estuary are the main depositional system which formed in the different locations and periods from the east to the west. The parasequences have the stackingg patterns from slight retrogra elation to aggradation. The highstand system tract which is mainly littoral depositional system is widely distributed,its parasequences have the progradational stacking pattern. During the late stage of highstand system tract,the infiiling of deposits and falling of sealevel lead to the basinward movement of estuary line and equlibrium point, which accounts for new land accom-mondation and developed the fluvial and alluvial deposits.