从中下三叠统膏盐特征看中下扬子早印支运动  

Early Indosinian movement character in the Lower-Middle Yangtze region from gypsum-salt characters in Lower-Middle Triassic

作　　者：胡光明[1] 张亚金[2] 周雁[3] 

机构地区：[1]长江大学地球科学学院,湖北荆州434023 [2]大庆油田勘探开发研究院,黑龙江大庆163712 [3]中国石化石油勘探开发研究院,北京100083

出　　处：《地质科学》2010年第3期734-744,共11页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：长江大学科研发展基金项目(编号:CJDX2007004)资助

摘　　要：中下扬子早-中三叠世膏盐层是对早印支运动的沉积响应,本文从膏盐的成因、中下扬子膏盐层位的差异、沉积环境的变迁、膏盐的厚度变化和产状特征、沉积中心和沉降中心的分布等方面,分析早印支运动的表现形式。中下扬子早-中三叠世依次出现陆棚台地(碳酸盐岩)、潟湖—潮坪(白云岩与膏盐)和滨海(碎屑岩),这种大规模海退,正是早印支运动表现为构造抬升的结果。抬升过程中,残留海水在炎热干燥的气候条件下蒸发形成膏盐层,而中扬子的膏盐层位比下扬子低,据此推测中扬子先于下扬子与华北板块碰撞而抬升。平面上,现今构造格局(主要由中印支—早燕山运动形成复向斜、复背斜和推覆构造)的坳陷区主要为白云岩与(硬)石膏互层或石膏夹少量白云岩或云质石膏,膏盐层厚度大,现今构造的隆坳过渡区主要为石膏假晶、含膏云岩、石膏质白云岩、白云岩夹石膏等,膏盐层厚度小,而膏盐的厚度和产状与沉积时的水深和地势直接相关;另外,地层等厚图显示膏盐层主要分布于当时的沉降中心。这些沉积特征显示膏盐沉积时的地势与现今隆坳相间的构造地貌存在一定程度的吻合,说明膏盐沉积时的地层已经发生了轻微的褶皱变形(未见角度不整合和地层缺失)。The gypsum-sah deposition is the sedimentary response to early Indosinian movement. The author analyses the characters of early Indosinian movement from origin of gypsum-salt, the gypsum-salt vertical layer difference in Lower and Middle Yangtze region, the gypsum-salt characters in thickness and attitude, the distribution of sediment center and subsidence center. Shelf and platform （ carbonatite ）, lagoon-tidal fiat （ dolomite and gypsum-salt） and coast （ clastic rock） appear one by one,which indicates large-scale regressive from the tectonic uplift of early Indosinian movement. During the tectonic uplifting,the rudimental sea water in Lower-Middle Yangtze region is being evaporated to form gypsum-salt layers by the hot dry climate. And the gypsum-sah layers in Middle Yangtze are lower than that ones in Lower Yangtze. So,the author deduces that the collision between Middle Yangtze and Huabei Block was earlier than that between Lower Yangtze and Huabei Block. The current tectonic framework comes from the middle Indosinian movement and early Yanshan movement. But the thick gypsum-sah layers that are mainly dolomite-gypsum interbed, gypsum containing dolomite, dolomitic gypsum and so on, are distributing in current depression, and the thin gypsum-salt layers that are mainly pseudocrystals of gypsum, gypsum dolomite, dolomite containing gypsum and so on, are distributing in transition zone between current depression and uplift. And the gypsum-sah thickness and attitude is relating to the deep of water and topography. In addition, the stratum contour maps show that the gypsum-salt mainly distributes at the subsidence center. All those plane characters of gypsum-salt show that the topography during gypsum-salt depositing is in line with the current tectonic framework, and that slight fold deformation （no angular uncomformity or lostrecord）occurred during gypsum-sah depositing.

关 键 词：中下扬子 中下三叠统 膏盐 早印支运动 

分 类 号：P542[天文地球—构造地质学]