滇东南晚寒武世-早奥陶世唐家坝组-博菜田组碳酸盐岩碳氧同位素特征及意义  

δ^13C andδ^18O Values and Their Significances for the Upper Cambrian-Lower Ordovician Tangjiaba Formation-Bocaitian Formation in Southeast Yunnan

作　　者：王春林 李小军 WANG Chun-lin;LI Xiao-jun(No.403 Geological Team,BGEEMRSP,Emeishan,Sichuan 614200;Yunnan Institute of Geological Survey,Kunming 650216)

机构地区：[1]四川省地质矿产勘查开发局四〇三地质队,四川峨眉山614200 [2]云南省地质调查院,昆明650216

出　　处：《四川地质学报》2020年第4期680-685,共6页Acta Geologica Sichuan

基　　金：中国地质调查局项目(12120114072701,12120100000150008-04)。

摘　　要：滇东南晚寒武世-早奥陶世为一套碳酸盐岩夹陆源碎屑岩沉积建造,沉积相为开阔台地相向浅海陆棚相过渡特征,沉积水体从早到晚表现出动荡变深特征,岩石组合表现出多个下粗上细沉积韵律特征,为退积型沉积序列。笔者对该套地层碳氧同位素研究工作,结果显示:δ13C测试值介于-0.96‰~3.21‰,平均0.41‰;δ18O测试值介于-11.48‰^-9.35‰,平均-10.12‰。碳酸盐岩样品δ13C、δ18O值受后期成岩作用影响较小,基本保留了原始沉积环境碳氧同位素组成特征。碳同位素值总体呈现下降趋势,局部有波动特征,共出现2次正漂移事件和2次负漂移事件。其中P1正漂移事件与寒武纪全球性正漂移事件SPICE基本相符,与寒武纪生物多样性恢复有关;其余碳同位素漂移事件可能是因沉积环境(岩相古地理、古盐度和古温度)局部变化引起。利用碳氧同位素数据对古环境恢复结果表明:晚寒武世-早奥陶世研究区处于海相沉积环境,古海洋盐度值从早到晚呈现逐渐降低趋势,古海水温度介于21.55℃~31.41℃,平均25.02℃。说明当时处于温暖或炎热的亚热带气候。The UpperCambrian-LowerOrdovician in southeast Yunnan is a set of sedimentary formation of carbonate rocks intercalated with terrigenous clastic rocks.The sedimentary facies is open platform facies transitioning to shallow sea shelf facies.The Rock associationis characterized by multiple lower coarse to upper fine sedimentary rhythms characteristic of retrograding sequence.δ13C values of carbonate rock samples range from-0.96‰to3.21‰with theaverage of 0.41‰andδ18O values change from-11.48‰to-9.35‰with the average of-10.12‰which indicates thatthe characteristics of carbon and oxygen isotopic composition in the original sedimentary environment are basically preserved.Theδ13C valuesindicate a general decreasing trend with local fluctuation,showing two positive drift events and two negative drift events.Results ofpaleoenvironment restoration byδ13Candδ18O valuesindicate that the research area during Late Cambrian-Early Ordovician was in a marine sedimentary environment with agradually decreased paleo-ocean salinity and palaeo-sea temperature of 21.55-31.41℃,representing a warm or hot subtropical climate.

关 键 词：碳氧同位素 古盐度 晚寒武世 早奥陶世 碳酸盐岩 滇东南 

分 类 号：P597.2[天文地球—地球化学]