摘要
对四川省兴文县上奥陶统宝塔组底部含鲕绿泥石灰岩开展成因研究,有助于了解扬子台地西南部同时期的沉积环境演化过程.通过沉积学分析,并辅助以电子探针和扫描电镜等矿物学研究方法,发现富鲕绿泥石鲕粒及球粒为同生期沉积物,共生的生物碎屑组合指示海水为氧化性水体.丰富的微生物相关组构表明同期微生物席发育,且其代谢活动可致使水岩界面附近形成还原性水体,这是同生鲕绿泥石形成的必要条件,鲕绿泥石形成所需的Fe、Al元素来自早期风化壳在海侵阶段的大规模输入.宝塔组底部富鲕绿泥石灰岩是同期全球海平面演化在扬子台地的具体表现,佐证了早桑比期的海平面下降,是晚桑比期扬子台地快速海侵的重要标志.
A set of the chamosite-ooidal limestones was discovered at the bottom of the Pagoda Formation(Upper Ordovician)in Xingwen County,Sichuan Province,and its genesis can facilitate the understanding the evolution of the depositional environment in the southwestern Yangtze platform during the same period.Based on a detailed sedimentological analysis,this paper presents a study on the genesis of the chamosite-ooidal limestones,combined with mineralogical characterization via electron microprobe and scanning electron microscope studies.It is found that chamosite-rich ooids and peloids are syngenetic sediments,and symbiotic bioclastic assemblages indicate that the seawater was oxidizing.The abundant microbial-related fabric indicates that microbial mats develop during the same period,and their metabolic activities can lead to the formation of reducing water bodies near the water-sediment interface,which is a necessary condition for the formation of syngenetic chamosite.The Fe and Al elements needed for chamosite formation are derived from large-scale inputs of the early weathering crust during the transgression stage.The chamosite-ooidal limestones at the bottom of the Pagoda Formation are the concrete manifestation of global sea-level evolution in the Yangtze platform at same time.It is an important indicator of sea level fall in the Early Sandbian and rapid transgression in the Late Sandbian in the Yangtze platform.
作者
陈思
曾敏
田景春
任科法
靳晓雨
李晨伟
Chen Si;Zeng Min;Tian Jingchun;Ren Kefa;Jin Xiaoyu;Li Chenwei(College of Earth Sciences,Chengdu University of Technology,Chengdu 610059,China;Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2021年第9期3107-3122,共16页
Earth Science
基金
国家自然科学基金项目(No.41872110)
中国博士后基金项目(No.2018M633331).
关键词
扬子台地
宝塔组
鲕绿泥石
微生物
海平面升降
沉积学
Yangtze platform
Pagoda Formation
chamosite ooids
microbial
sea⁃level change
sedimentology
