塔西台地寒武纪沉积环境演化与海陆耦合  

Evolution of Cambrian Sedimentary Environment and Ocean-Land Coupling of the Western Tarim Carbonate Platfrom

作　　者：刘沛显 关平[1] 冯帆[1] 贾文博[1] 张巍[1] 邓世彪[1] 金亦秋 

机构地区：[1]北京大学造山带与地壳演化教育部重点实验室北京大学地球与空间科学学院,北京100871 [2]中国石油天然气股份有限公司勘探开发研究院,北京100083

出　　处：《沉积学报》2016年第6期1092-1107,共16页Acta Sedimentologica Sinica

基　　金：国家重点基础研究发展计划(973计划)项目(2012CB214801);国家科技重大专项(2011ZX05009-002-403;2011ZX05004-004-005)~~

摘　　要：碳酸盐岩台地作为陆地与深海间的过渡带,其沉积记录了海洋和邻近陆地的演化。结合已有的沉积学工作,对塔里木盆地西部台地寒武系碳酸盐岩进行全岩及酸不溶物地球化学研究。塔西台地寒武纪主要发育局限台地、局限—蒸发台地或蒸发台地相沉积。碳酸盐岩的地球化学特征主要受沉积环境和成岩作用影响,对研究区寒武系白云岩来说,其元素组成极易受沉积微相的控制,氧同位素组成则很可能已被成岩作用改造,仅原生、准同生白云岩的Sr/Ba、Fe/Mn和C同位素可反映沉积相演化对应的古盐度、离岸距离等沉积环境特征的变化,酸不溶物化学蚀变指数(CIA值)则指示邻近陆地的化学风化强度与气候特征。寒武纪时期,塔西台地在相对海平面较高时发育局限台地相沉积,以水体盐度较低、沉积环境离岸较远和生物活动相对较弱为特征,陆地化学风化强度适中,气候温暖湿润;在相对海平面较低时发育蒸发台地相沉积,具有水体盐度较高、沉积环境离岸较近和生物活动相对较强等特点,陆地化学风化强烈,气候炎热极端;在相对海平面适中时发育局限—蒸发台地,沉积环境和邻近陆地的特征介于前述二者之间。沉积相演化对应的较长周期的海陆演化可能主要受全球海平面升降及宏观气候变化控制,具体表现为相对海平面升降所导致的海相沉积环境的变化,以及气候变化引起的陆地化学风化强度的变化。寒武纪塔西台地所处区域的海洋—陆地演化具有高度耦合的特征。As the transition zone between terrestrial and marine environment,carbonate platform sediments record information both from ocean and land. Some geochemical research are carried on Cambrian carbonates and their acid-insoluble residua based on sedimentary facies analysis,focused on development of sedimentary environment,change of paleosalinity,sea level fluctuations,evolution of terrestrial chemical weathering intensity and climate change. Lithological and sedimentological research show that sedimentary facies of the Western Tarim Carbonate Platform in Cambrian was mainly restricted platform,restricted-evaporite platform or evaporite platform. Geochemical characteristics of carbonates is usually generated by sedimentation and reformed by diagenesis. The elemental composition and O isotope of our samples are respectively affected by sedimentary micro-facies and water-rock interaction,only Sr / Ba,Fe / Mn and C isotope of primary or penecontemporaneous dolomite can be used to indicate paleosalinity,offshore distance and other characteristics of sedimentary environment. Evolution of terrestrial chemical weathering intensity and climate change can be reflected by CIA（ chemical index of alteration） of the carbonates＇ acid-insoluble residua. In Cambrian,restricted platform was developed in western Tarim when the RSL（ relative sea level） is at high position,sedimentary environment was characterized by relatively low salinity,far offshore distance and weak biological activity,with moderate terrestrial chemical weathering and mild climate. On the contrary,when the RSL is relatively low,evaporite platform is developed and with sedimentary environment characterized by high salinity,near offshore distance and strong biological activity,the terrestrial chemical weathering is intense,indicating hot or possibly humid climate. The situation when restricted-evaporite platform developed is between the two forementioned. Relatively long-period evolution of the Western Tarim Carbonate Platform corresponding to facies＇ dev

关 键 词：塔西台地 寒武系白云岩 沉积环境 酸不溶物CIA 海陆耦合 

分 类 号：P534.41[天文地球—古生物学与地层学]