神农架成冰纪宋洛生物群的赋存层位厘定  

Stratigraphic Position of Cryogenian Songluo Biota in Shennongjia Area

作　　者：安志辉 叶琴[3] 胡军[4] 童金南[3,4] 田力[4] An Zhihui;Ye Qin;Hu Jun;Tong Jinnan;Tian Li(Hubei Key Laboratory of Paleontology and Geological Environment Evolution,Wuhan 430205,China;Wuhan Center of China Geological Survey,Wuhan 430205,China;School of Earth Sciences,China University of Geosciences,Wuhan 430074,China;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Wuhan 430078,China)

机构地区：[1]古生物与地质环境演化湖北省重点实验室,湖北武汉430205 [2]中国地质调查局武汉地质调查中心,湖北武汉430205 [3]中国地质大学地球科学学院,湖北武汉430074 [4]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430078

出　　处：《地球科学》2023年第10期3799-3811,共13页Earth Science

基　　金：中国地质调查局项目(Nos.DD20230218,DD20190811);国家自然科学基金(Nos.41702200,41802206,41825019,41902004);古生物与地质环境演化湖北省重点实验室(Nos.PEL-202002,PEL-202003);中国博士后科学基金面上项目(No.2021M692980);生物地质与环境地质国家重点实验室(No.GBL201709);中国地质大学(武汉)“地学长江计划”(No.CUGCJ1816).

摘　　要：新元古代成冰纪末期“雪球地球”中的宏体化石是认识早期生命演化与极端环境变化的关键.神农架的宋洛生物群是华南成冰纪地层中唯一有详细报道的宏体藻类化石记录.然而,对这套宏体藻类化石赋存层位的认识存在归属南沱组还是大塘坡组两种不同的观点,因此其地层序列和宏体化石赋存层位亟需进一步厘定.笔者通过大量野外地质工作,对神农架宋洛地区宋洛生物群的赋存层位及空间分布开展调查研究.宋洛剖面沿公路出露时发育3个正断层,造成部分地层(如第9~11层)多次重复出现,易引起混淆,产生不同的认识.厘定后的宋洛剖面具有24层,其中第1~19层归属南沱组,而第20~24层为陡山沱组.基于南沱组中发育多个黑色页岩层、黑色页岩夹层上下岩性特征相似、不同黑色页岩夹层内化石面貌不同、神农架地区大塘坡组只分布在神农架西侧、以及黑色页岩具有极低的锰含量等5个原因,认为宋洛生物群的赋存层位为南沱组,而非大塘坡组.Macrofossils in Late Neoproterozoic“Snowball Earth”are significant to the coevolution of early life and environment.Songluo biota of Nantuo Formation in Shennongjia area is the unique macroalgae record during the Cryogenian“Snowball Earth”.However,because of lacking precise dating data,the stratigraphic position of fossil-bearing shale is controversial.One viewpoint correlates to Nantuo Formation,and the other correlates to Datangpo Formation.Stratigraphic correlation of Songluo biota is in need of restudy.The stratigraphic position and spatial distribution of Songluo biota were investigated under numerous field work.Three normal faults recorded in the Songluo Section along the roadside,leading to recurring problems for some layers(e.g.layers 9-11).Totally,24 layers have been divided in the Songluo Section,of which the Nantuo Formation contains layers 1-19 and the Doushantuo Formation covers layers 20-24.Based on multiple black shales documented in Nantuo Formation,black shales sandwiched in similar calcareous diamictite,the fossil assemblages changed in different shales,the Datangpo Formation only recorded in western Shennongjia area,and extremely low concentration of Mn in black shales,the Songluo biota and hence the fossiliferous black shale at Songluo Section is part of the Nantuo Formation rather than the Datangpo Formation.

关 键 词：成冰纪 南沱组 宋洛生物群 宏体藻类 神农架 生物地层 环境地质学 

分 类 号：P535[天文地球—古生物学与地层学]