摘要
根据贵州火铺茅口组剖面的实际材料 ,采用聚类分析等方法对该地茅口组的沉积环境进行了详细研究。综合分析结果表明 ,火铺茅口组存在 8种微相类型 ,它们分别代表浪基面以下静水、盐度正常的浅海、高能浅滩、水循环受阻的泻湖等环境的沉积。微相组合及其在剖面的纵向分布规律显示 ,剖面中、下部以开阔台地沉积环境为主 ,上部为开阔台地到局限台地过渡带的沉积 ,其环境经历了由开阔浅海逐渐变浅的过程。在此变化过程中 ,茅口早期处于海侵高峰阶段 ,海水相对较深 ,海底水动能条件较弱、氧含量偏低 ,底栖生物含量相应较低 ;茅口中期海水以较浅—中等深度为主 ,水体清洁 ,循环良好、盐度正常、营养充分、生物丰富 ,总体反映了开阔台地浅海为主的环境特征 ;茅口晚期 ,海水变浅、循环受阻、盐度不稳定以及藻类的繁荣产生耗氧等导致海洋环境中主要因子发生恶化 ,生物含量显著下降。
Comprehensive studies have been conducted to investigate sedimentary environment of the Maokou Formation in Huopu section, Panxian, Guizhou province. The results of this study revealed that there are 8 microfacies in the Maokouan of Huopu area, which represent respectively the sedimentations of low energy environment below the wave base, epeiric sea with normal salinity, beach with high energy and lagoon with restricted circulation, etc. The assemblages and distribution pattern of the microfacies in the Huopu section demonstrated that the Maokouan sedimentation is dominated by open platform facies in the most time, but the late Maokouan is characterized by a transitional facies from the open platform to restricted platform. A further analysis on the shoaling upward sequence has suggested that the major environmental features changed remarkably during the Maokouan period. In the early Maokouan, transgression reached its climax in this area and the sea level was relatively high. The bottom of the sea in this stage was characterized by low energy and low content of oxygen. Therefore, the fossil benthos was of low abundance. The middle Maokouan deposits are typical open platform sedimentation formed in shallow medium depth. The marine environment in this stage was characterized by clean water with normal salinity, abundant nutrition and high abundance of organisms. In the late Maokouan, the seawater became shallower and circulation was restricted. High salinity and depletion of oxygen caused by diversification of algae further suggested deterioration of a series of factors in marine environment, which consequently lead to the significant decrease in abundance of marine organisms.
出处
《高校地质学报》
CAS
CSCD
1999年第4期448-458,共11页
Geological Journal of China Universities
基金
国家自然科学基金!(批准号 :4 95 72 0 75 )
国家教委博士点基金!(批准号 :95 2 84 17)资助项目
关键词
沉积环境
微相组合
茅口组
贵州
盘县
二叠纪
sedimentary environment, assemblage of microfacies, Maokou Formation, Guizhou
