藏北安多晚侏罗世古环境、古气候与地球化学元素关系研究  

The relationship of Late Jurassic paleoenvironment and paleoclimate with geochemical elements in Amdo Country of northern Tibet

作　　者：梁文君[1] 肖传桃[1] 肖凯[2] 林婉[1] 

机构地区：[1]长江大学油气资源与勘探技术教育部重点实验室,湖北武汉430100 [2]江西省地质矿产勘查开发局902地质大队,江西新余338000

出　　处：《中国地质》2015年第4期1079-1091,共13页Geology in China

基　　金：国家自然科学基金项目(40972019);湖北省教育厅计划类科技项目(03Z0105);国家大学生创新性试验计划联合资助

摘　　要：藏北安多地区毗邻羌塘盆地南界,属于藏北地层分区。研究区沙木罗组地层为一套稳定的浅海相碎屑岩和碳酸盐岩建造,依次发育风化壳沉积,潮坪相沉积以及混合台地相沉积,有大量生物礁产出。本文通过对沙木罗组地层中采集到的18件样品进行常量、微量元素及碳氧同位素测试,结合沉积相分析,旨在探索本区晚侏罗世古海平面升降、氧化还原条件以及古气候的演化规律。研究发现,Ni、Sr、Cu、V、Cr、Ni/Co及δ^(13)C等变化能反映氧化还原环境的变化,而Mn、Na、Sr/Cu、P、Ti及δ^(18)O和Z值的波动能指示古气候的变化。研究结果表明:研究区的古环境演化共经历了3个阶段:(1)风化壳阶段的强氧化环境;(2)潮坪阶段的半氧化半还原环境;(3)台地区与三期生物礁建造相对应的3次氧化与还原环境转换。古气候演化也经历了3个阶段:(1)风化壳区的干旱气候;(2)潮坪区的半干旱半湿润气候;(3)台地区3次干湿气候的频繁转换,分别与本区的3个造礁期相对应。Amdo Country of northern Tibet is close to south boundary of Qiangtang Basin and belongs to Qiangtang stratigraphic area. The late Jurassic Shamuluo Formation of the study area is mainly composed of a series of neritic clastic rock and carbonate deposits, which are in turn weathering crust sediments, tidal fiat facies sediments and mixed platform facies sediments, characterized especially by a lot of organic reefs. Based on analyzing 18 samples from Shamuluo Formation, combined with the sedimentary facies analysis, the authors investigated the ancient sea-level eustacy, oxidation-reduction conditions and paleoclimate of late Jurassic period in the study area. Specifically, the changes of Ni, Sr, Cu, V, Cr, Ni/Co and carbon isotopes were used to detect the changes of paleoenvironment, and the fluctuation of Mn, Na, Sr/Cu, P, Ti, oxygen isotopes and Z values were employed to deduce paleoclimate. The results show that paleoenvironment evolutions experienced three stages： （1） strong oxidation environment of weathering crust; （2） semi-oxidation-reduction environment of tidal flat; （3） three times of changes between oxidation and reduction environment in platform, corresponding to the three times of reef formation; paleoclimate evolutions also experienced three stages： （1） arid climate of weathering crust; （2） semi-arid and semi-humid climate of tidal flat; （3） three times of changes between arid and humid climate in platform, respectively corresponding to the three reef-forming periods.

关 键 词：沙木罗组 微量元素 碳氧同位素 古环境 古气候 

分 类 号：P534.52[天文地球—古生物学与地层学]