贵州册亨中三叠统坡段组巨鲕特征及其环境指示意义  

The Characteristics of Giant Ooids from the Poduan Formation during the Early Middle Triassic and Its Environmental Significance at Poduan Section,Ceheng,Guizhou Province

作　　者：赵俊杰 黄云飞[1] 田力[2] 黄子航 王延达 吉霞 张世岩 童金南[2,3] Zhao Junjie;Huang Yunfei;Tian Li;Huang Zihang;Wang Yanda;Ji Xia;Zhang Shiyan;Tong Jinnan(School of Geosciences,Yangtze University,Wuhan 430100,China;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Wuhan 430074,China;School of Earth Sciences,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]长江大学地球科学学院,湖北武汉430100 [2]中国地质大学生物地质与环境地质国家重点实验室,湖北武汉430074 [3]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地球科学》2023年第8期2822-2836,共15页Earth Science

基　　金：国家自然科学基金项目(Nos.42030513,42272361)。

摘　　要：二叠纪末期生物大灭绝之后的早三叠世,巨鲕作为一种异常碳酸盐沉积物,在全球范围内广泛发育,代表了不利于后生动物生存的极端温室气候条件,在中三叠世早期环境稳定后,异常碳酸盐沉积物变得十分罕见.然而,贵州册亨坡短剖面中三叠世初巨鲕的发现,是否意味着该时期古海洋环境条件仍然没有恢复正常呢?对册亨坡短剖面坡段组底部碳酸盐岩进行了沉积微相和沉积组构分析,从鲕粒特征、鲕粒含量、生屑含量、沉积微相等角度综合分析鲕粒富集层位的沉积环境.册亨坡短地区坡段组共发现了4种不同的鲕粒,包括普通同心鲕粒、巨型同心鲕粒、多晶鲕粒和泥晶鲕粒,可认为有两个鲕粒富集时期.根据岩石结构和碳酸盐颗粒特征等识别出4种微相类型,包括鲕粒颗粒灰岩、泥晶灰岩、生物碎屑颗粒灰岩和双壳类砾状灰岩微相.沉积微相分析表明册亨坡短地区在中三叠世早期为台地边缘的台缘鲕粒滩与生物碎屑滩交互沉积.这一地区坡段组所发育的巨鲕可能指示海水碳酸盐饱和度仍然十分高,表明该地区中三叠世初仍处于异常海洋环境,暗示着中三叠世全球海洋环境存在明显的区域性差异,这可能是中三叠世生物复苏辐射模式复杂的重要原因.Giant ooids have been considered as abnormal sediment and distributed globally in the aftermath of the end-Permian mass extinction,and represent a marine carbonate supersaturated state which is unfavourable to the survival of metazoans.The marine environment returned to normal in the early Middle Triassic when abnormal sediments became rare.However,the discovery of giant ooids in the early Middle Triassic at the Poduan section,Ceheng,Guizhou Province,could give us more insights into the marine environmental conditions during that time.In this study,the sedimentary microfacies and fabrics of the carbonate rocks at the bottom of the Poduan section were analyzed.The sedimentary environments of the giant ooid-bearing beds were comprehensively studied based on the oolitic characteristics,oolitic content,bioclastic content and sedimentary microfacies.It can be considered that there are two oolitic enrichment periods.Four kinds of oolitic grains have been found at the Poduan section,including common concentric oolitic grains,giant concentric oolitic grains,polycrystalline oolitic grains and mud crystal oolitic grains.Four sedimentary microfacies were identified based on rock structure and carbonate particle characteristics and could represent the interbedded deposition of platform margin oolitic shoal and bioclastic shoal.The development of giant ooids in this area indicated that the marine carbonate saturation is still very high and the abnormal marine environment occurred in this area during the early Middle Triassic.It suggests that there were obvious regional differences in the global marine environment during the Middle Triassic,which is an important reason for the complexity of the model of biotic recovery and radiation.

关 键 词：中三叠世 巨鲕 生物复苏 沉积微相 碳酸盐超饱和 沉积学 

分 类 号：P53[天文地球—古生物学与地层学]