湘中地区中奥陶统烟溪组沉积相特征

Sedimentary facies characteristics of Middle Ordovician Yanxi Formation in central Hunan Province

陈广 刘辰生 郭建华 周瑶 吴诗情 李智宇

中南大学有色金属成矿预测与地质环境监测教育部重点实验室，湖南 长沙 410083 中南大学地球科学与信息物理学院，湖南 长沙 410083

Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, Ministry of Education, Central South University, Changsha 410083, China School of Geosciences and Info?鄄Physics, Central South University, Changsha 410083, China

通过分析岩性、沉积构造及岩心薄片观察等资料，在湘中地区烟溪组识别了4种沉积相类型，从盆地近源（NE侧）到盆地沉积中心（SW侧），依次为浊积扇相、浅海陆棚相、半深海相、深水盆地相。烟溪组沉积演化经历了4个阶段：SQ1上升半旋回快速海侵，发育浅海陆棚相、半深海相、深水盆地相；SQ1下降半旋回开始海退，区内半深海相和深水盆地相展布面积减小，浅海陆棚相面积增大，近物源的NE区开始发育浊积扇相，沉积相体系向SW迁移；SQ2上升半旋回海侵，海平面再次上升，沉积相体系与SQ1上升半旋回大体相似，但半深海相发育区域减小；SQ2下降半旋回快速海退，浊积扇相广泛发育，深水盆地相不再发育。

By analysis of lithology, sedimentary structure and thin section, four types of sedimentary facies had been identified in the Yanxi Formation of central Hunan. From the near-source area(NE side) to the sedimentary center(SW side), turbidity-fan facies, neritic shelf facies, hemi-deep sea facies and deep-water basin facies were developed in turn. The sedimentary evolution of the Yanxi Formation can be divided into four stages. SQ1 ascending semi-cycle experienced rapid transgression, in which neritic shelf facies, hemi-deep sea facies and deep-water basin facies were developed. SQ1 descending semi-cycle began to experience regression, with the distribution area of the hemi-deep sea facies and deep-water basin facies decreased and the area of the neritic shelf facies increased; the turbidity-fan facies developed in the NE area near the source, and the sedimentary facies system migrated to the SW. SQ2 ascending semi-cycle experienced transgression with the sea level rose again, and the sedimentary facies system was similar to the SQ1, but the distribution area of hemi-deep sea facies reduced. SQ2 descending semi-cycle experienced rapid regression, with the turbidity-fan facies developed extensively and the deep-water basin facies no longer developed.

10.6056/dkyqt202005004