伊通地堑的沉积充填序列及其对转换—伸展过程的响应

DEPOSITIONAL SEQUENCES OF YITONG GRABEN (EASTERN CHINA) AND ITS RESPONSE TO TRANSFORM-EXTENSIONAL PROCESSES

陆永潮 任建业 李思田 叶洪波

LU Yong-chao REN Jian-ye LI Si-tian YE Hong-po

中国地质大学国土资源系, 武汉430030

China University of Geosciences, Wuhan 430030, China

伊通地堑处于中国东部第三纪裂谷系向东北延伸的分支,其东侧盆缘断裂为正断层,西侧为高角度走滑断层,其旁侧为扇-扇三角洲楔状体,表明这些断裂控制着沉积充填。第三系在断陷中厚达6000m,油气勘探中已识别出一系列不同级别的间断面及构造反转事件,根据大的区域性间断面划分出3个构造层序,并进一步划分了三级和四级层序,在构造层序界面处识别出了深切谷充填。在层序地层格架的基础上重建了沉积体系域。结合各阶段同生构造的配置揭示了总体伸展背景下构造体制由右旋张剪向左旋压剪的转化,盆地属于转换伸展性质。伸展及走滑两种机制共同控制了盆地的演化及各阶段的充填样式-沉积体系的三维配置。这一研究成果已作为预测储层和烃源岩分布及地层岩性圈闭的基础。

The Yitong Graben is located in the north eastern segment of the Tertiary rift system in East China.The graben is bounded by a steep dipping transform fault on the northwestern side and subparallel normal faults on the southeastern side, with very thick marginal fan complexes indicating syntectonic sedimentation. The graben is infilled with Tertiary sediments up to 6000 m thick, in which a series of different scaled hiatuses and tectonic inversion events have been discerned during hydrocarbon exploration. According to regional and local conformities, the basin infill may be divided into three tectonic sequences, among which the major sequence TS2 is further subdivided into three sequences sets and fourteen subsequences. Based on the sequence stratigraphic framework, depositional system tracts are reconstructed. Integrative analysis of the depositional structural features showed that the regional tectonic stress system experienced a transformation from dextral transfersional-shear through thermal subsidence to sinistral compressional-shear with a general extensional setting. Extension and wrenching dominated the graben evolution and affected the depositional style in different evolutionary stages and the spatial configuration of depositional system. The conclusions have been applied with some success to prospection of reservoir and hydrocarbon source-rock distribution and lithologic-stratigraphic traps in this basin.

地矿部重大基础项目《中国东部及邻区中、新生代盆地演化及地球动力学背景》资助(8502204)

https://doi.org/10.11781/sysydz199903232