湖北崇阳二叠纪—三叠纪之交生物灭绝和沉积微相演化  

Mass Extinction and Evolution of Sedimentary Microfacies Across the Permian-Triassic Boundary in Chongyang,Hubei Province

作　　者：单厚香[1] 王永标[1,2] 何磊[1] 余黎雪[1] 

机构地区：[1]中国地质大学地球科学学院 [2]中国地质大学地质过程与矿产资源国家重点实验室,武汉430074

出　　处：《地质科技情报》2012年第1期16-21,共6页Geological Science and Technology Information

基　　金：国家自然科学基金项目(40730209);国家大学生创新性实验计划项目(091049105);中国地质大学(武汉)教学实验室开放基金项目(SKJ2011005)

摘　　要：二叠纪—三叠纪之交,湖北崇阳地区处于浅水碳酸盐岩台地环境。二叠纪末的全球事件在该剖面的沉积微相和生物演化上均留下了清楚的记录。二叠纪末生物大灭绝之前,崇阳地区为典型的正常浅海台地环境,生物种类多样,数量丰富,主要生物化石有钙藻、有孔虫、腕足、棘皮类和海绵等。生物大灭绝之后,钙藻、类、棘皮类、海绵、绝大部分有孔虫开始消失,取而代之的是个体微小的腹足、介形虫和大量的蓝细菌化石。大灭绝界线之上,首先出现的是25cm厚的纹层状的微生物岩,含较丰富的种类单调的有孔虫化石。之后逐渐相变为花斑状微生物岩和穹隆状微生物岩,厚度分别为6.4,2.3m。不同类型微生物岩在结构构造和生物组成上存在差别。微生物岩沉积结束之后,则相变为浅滩相鲕粒灰岩。共划分出3种沉积相,即开阔台地相、潮坪相和浅滩相。崇阳剖面的生物灭绝和沉积微相变化是二叠纪—三叠纪之交浅水台地环境生物与环境过程的典型代表,为认识二叠纪末浅海沉积相演化和全球事件提供了新材料。Chongyang was located on shallow carbonate platform during the Permian-Triassic transition, where the end-Permian global event of biotic crisis was highly marked both on fossil record and sedimenta- ry facies. Before the end-Permian mass extinction, abundant and diverse species, such as fusulinds, calcar- eous alga, calcisponges, echinoderms, lived in a normal shallow marine environment. However, microgas- tropods, ostracods and abundant calcified cyanobacteria replaced these Permian species after the big crisis. A thickness of 25 cm laminated microbialites sharply overlaps on Permian packstone in Chongyang, and next are 6.4 m thrombolites and 2.3 m dome microbihlites. Different types of microbialites have different sedimentary structures and biological compositions. Oolitic limestones began to deposit after the termina- tion of microbialites. Three sedimentary facies are concluded according to the five sedimentary microfacies above, which are open platform facies, tidal-flat facies and platform edge shallow facies. The mass extinc- tion and change of sedimentary facies in Chongyang section typically stand for the interaction between crea- tures and environment on shallow carbonate platform across the Permian-Triassic boundary. Hence, this study offers new information for studying the end-Permian global event.

关 键 词：钙质微生物岩 生物灭绝 沉积微相 二叠纪-三叠纪 崇阳 

分 类 号：P53[天文地球—古生物学与地层学]