峡东震旦系层型剖面沉积相研究  

Advances in the Study of Sedimentary Facies of the Sinian Candidate Stratotype in the Eastern Areas of the Three Gorges, Hubei

作　　者：柳永清[1,2] 尹崇玉[1,2] 高林志[1,2] 王自强 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质大学,北京100083

出　　处：《地质论评》2003年第2期187-194,T006,共9页Geological Review

基　　金：科技部基础工作项目(编号 G99-A-05a)

摘　　要：峡东震旦系为缓坡型台地碳酸盐岩沉积序列。陡山沱组从下至上发育内缓坡相的潮上带 潮间带含膏盐塞卜哈、环潮坪碳酸盐岩和陆源碎屑岩混积以及中外缓坡相潮间带—潮下带和盆地相沉积。灯影组发育内缓坡相带内的各种沉积亚微相序列,沉积亚微相型复杂多样,为碳酸盐海滩沉积,垂向序列上发育“对偶砂滩坝”微相,即下部蛤蟆井段为潮间下—潮下碳酸盐鲕滩,中下部石板滩段为向上变浅、变细的滩后潮间澙湖沉积,中上部白马坨段为滨岸带碳酸盐砂滩坝与环潮坪沉积。碳酸盐岩地球化学研究表明,Mn/Sr比值从浅滩相(2.0到0.1～0.5),内缓坡塞卜哈(1.0)至滩后(0.4～0.8)和中外缓坡(0.1～0.5)具有双峰式分布特点。δ^(18)O、δ^(13)C和稀土元素组成分析表明,白云岩以准同生成因为主。潮间带以下的微相稀土总量最为丰富,近岸的浅滩、潮汐流浅滩和滩后澙湖等最低,变浅、暴露以及干燥蒸发微相中普遍表现Eu的亏损,随着环境由深到浅的微旋回变化表现着δCe的明显减少和δEu的相对减低。The Sinian carbonates, which are further divided into the Doushantuo and Dengying formations from bottom to top in the eastern areas of the Three Gorges, Hubei, is characterized by the deposition of ramp-platform facies. The carbonates of the Doushantuo formation mainly consist, upwards, of supratidal-intertidal Sabkha with evaporates, peritidal, siliciclastics of the inner ramp subfacies and intertidal-subtidal and basin of outer ramp subfacies, while the Dengying formation, in which 3 members are recognized as the Hamojing, Shibantan and Baimatuo, is composed of inner ramp carbonate sequences which is called beach bar deposits, and vertically shows double sandy bars. The Hamojing member at the bottom is of oolitic carbonate bar from inter-subtidal subfacies, the Shibantan in the middle is of intertidal lagoon deposits with shallowing and thinning-upward sequences, and the Baimatuo on the top is mainly of beach oolitic and peritidal carbonates. Research on the Sinian carbonates indicate that the Mn/Sr ratio is 0. 1 - 0. 5 in shoals, 1. 0 in inner ramp sabkha, 0. 4 - 0. 8 in back shoal and 0. 1~0. 5 in outer-mid ramp, and the total ratio represents a symmetrical pattern vertically, and δ18O, δ13C and REE suggests that dolomites in the Sinian carbonates is syngenetic, and REE is rich below the intertidal subfacies and shoals while beach bar and back lagoon subfacies are poor in REE. The shallowing and exposed microfacies is characterized by the loss of Eu, and δCe and δEu decrease in the depositional cycles from deep to shallow.

关 键 词：震旦系 沉积相 碳酸盐岩 沉积序列 沉积环境 

分 类 号：P512.2[天文地球—地质学] P534.31