大型陆相盆地层序地层学研究──以鄂尔多斯中生代盆地为例

APPROACHES OF NONMARINE SEQUENCE STRATIGRAPHY A CASE STUDY ON THE MESOZOIC ORDOS BASIN

鄂尔多斯盆地是我国最重要的含煤及含油气盆地之一。中生代盆地充填序列可按古构造运动面划分为五个构造层序（ＴＳ－１～ＴＳ－５），分别与盆地构造演化的阶段性相当。受秦岭带中三叠世末期造山运动的影响，盆地西南缘形成了晚三叠世的前渊，不整合于其上的保罗系属于继承性盆地充填，延安组正属于这一阶段的相对稳定期。已发现其上、下界面均为不连续面，并都发现有深切谷，因此延安组恰好是一个三级层序。其内部可进一步划分８～１１个四级层序。延安期层序内部体系域的演化有三分性，但不宜套用源于海相地层的体系域命名。本文就此问题进行了探讨和命名。鄂尔多斯盆地层序地层研究的成果已被有效地用于富煤单元预测、油气储层分析，并在古大陆暴露面优质高岭土矿床的发现和追索中起了重要作用。

The Ordos basin is one of the most important coal-bearing and hydrocarbon-bearing basin in China. The Mesozoic stratigraphy can be divided into five tectonic se-quences (TS) which coincide with the evolution stages of Ordos basin.The Early to Mid-dle Triassic sequences(TS-1)were formed in intracratonic regime,whilethe Upper Triassic(TS-2)sequences were developed in flexural regime under the influenceof orogenic movement of Qinling belt.The Early-Middle Jurassic sequences(TS-3)wereformed in a successor basin under ralatively stable condition which permits the detailedstudy of sequence stratigraphy. A molasse wedge developed in Upper Jurassic time(TS-4)overlied by the Cretaceous red beds(TS-5).The Yanan Formation is a typical nonma-rine sequence in TS-3. which is confined by unconformities at the bottom and top and in-cised valley have been found at the sequence boundaries.8-11 parasequences have beensubdivided from Yanan Formation and the depositional system tracts have been recon-structed.