羌塘中生代盆地大洋缺氧事件及全球对比  

Oceanic anoxic events in the Mesozoic Qiangtang Basin and global comparison

作　　者：付修根 王剑 曾玉红 宋春彦[4] 曾胜强[4] FU Xiugen;WANG Jian;ZENG Yuhong;SONG Chunyan;ZENG Shengqiang(Qiangtang Institute of Sedimentary Basin,Southwest Petroleum University Chengdu,610050;School of Geoscience and Technology,Southwest Petroleum University,Chengdu,610050;State Key Laboratory of oil and Gas Reservior Geology and Exploitation(Southwest Petroleum University),Chengdu,610050;Chengdu Center,China Geological Survey,Chengdu,610081)

机构地区：[1]西南石油大学羌塘盆地研究院,成都610050 [2]西南石油大学地球科学与技术学院,成都610050 [3]油气藏地质及开发工程国家重点实验室(西南石油大学),成都610050 [4]中国地质调查局成都地质调查中心,成都610081

出　　处：《地质论评》2020年第5期1130-1142,共13页Geological Review

基　　金：国家自然科学基金资助项目(编号:91955204);第二次青藏高原科学考察研究计划(STEP)(编号:2019QZKK080301)的成果。

摘　　要：位于藏北高原的羌塘盆地保存了我国最大面积的侏罗纪海相盆地,记录了较为完整的中生代海相序列。在羌塘中生代(T3—K1)盆地演化过程中,发生了多次水体缺氧事件,这些缺氧事件是全球大洋缺氧事件在羌塘盆地的反映。本文对这些缺氧事件的最新研究成果进行了介绍。羌塘盆地海相T—J界线剖面的碳同位素表现为两次明显的负偏异常,对应于全球T—J典型界线剖面碳同位素的"初始负偏移"和"主要负偏移",T—J之交水体由氧化环境变为缺氧环境。在盆地演化早期,在毕洛错地区识别出早侏罗世托儿期碳同位素负偏异常,可与全球早侏罗世托尔期大洋缺氧事件的碳同位素负偏进行精确地对比,揭示了早侏罗世托儿期全球缺氧事件在羌塘盆地的普遍性。在盆地演化晚期,海水逐渐从北羌塘拗陷西北部退出盆地,广泛沉积了一套黑色页岩、油页岩、泥岩及泥灰岩的岩石组合,碳同位素特征可与南特提斯、北特提斯及西北特提斯对应时期的碳同位素相对比,是早白垩世巴雷姆期全球大洋缺氧事件在羌塘盆地的反映。Qiangtang Basin is the largest Jurassic marine basin in China,located in the northern part of the Qinghai—Tibet Plateau,and thus,the Mesozoic marine succession has been well documented in this basin.A series of ocean anoxic events occurred during the sedimentary evolution of the Mesozoic Qiangtang Basin.This paper summarized the major achievements of these ocean anoxic events.The carbonate carbon-isotope record contains two different excursions across the marine T—J transition in the Qiangtang Basin.These are consistent with the"initial"and"main"negative carbon-isotope excursions(CIE)found in the global stratotype section and point(GSSP)of the T—J boundary.The depositional environments change from oxic to anoxic conditions across the T—J boundary.During the early evolution of basin,the carbon-isotope profile exhibits a distinct negative excursion in the Bilong Lake area.This excursion is similar to negative CIE found in GSSP of the Early Toarcian ocean anoxic event,suggesting that the Early Toarcian ocean anoxic event is extensive in the Qiangtang Basin.A large-scale regression occurred during the late evolution of the Qiangtang Basin.In this interval,the sediments only deposited in the Northern Qiangtang Depression consisting shale,oil shale,mudstone,and marl.A high-resolution carbon-isotope record from these strata revealed a characteristic and well-correlatable Barremian—Lower Aptian pattern.This result is consistent with well-preserved patterns observed in the southern,northern,and northwestern Tethys,suggesting that the Barremian ocean anoxic event was recorded in the Qiangtang Basin.

关 键 词：海相T—J界线(海相J/T界线) 托儿期缺氧事件 巴雷姆期缺氧事件 羌塘盆地 

分 类 号：P618.13[天文地球—矿床学]