| 中新生代海水锶同位素演化和古海洋事件 |
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| 引用本文： | 黄思静,吴素娟,孙治雷,裴昌蓉,胡作维.中新生代海水锶同位素演化和古海洋事件[J].地学前缘,2005,12(2):133-141. |
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| 作者姓名： | 黄思静 吴素娟 孙治雷 裴昌蓉 胡作维 |
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| 作者单位： | 油气藏地质及开发工程国家重点实验室,成都理工大学,地球科学学院,四川,成都,610059;油气藏地质及开发工程国家重点实验室,成都理工大学,地球科学学院,四川,成都,610059;油气藏地质及开发工程国家重点实验室,成都理工大学,地球科学学院,四川,成都,610059;油气藏地质及开发工程国家重点实验室,成都理工大学,地球科学学院,四川,成都,610059;油气藏地质及开发工程国家重点实验室,成都理工大学,地球科学学院,四川,成都,610059 |
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| 基金项目： | 中国科学院资助项目;国家重点基础研究发展计划(973计划) |
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| 摘 要： | 中新生代是地质历史中海水锶同位素组成变化最大的时期。晚白垩世以来海水N(87 Sr)/N(86Sr)值的持续上升与全球海平面的持续下降有关。喜马拉雅造山运动造成了40 Ma以来N(87 Sr)/N(86 Sr)值上升速度的显著加快;侏罗纪—早白垩世海水锶同位素的变化在很大程度上受泛大陆的解体控制,该地质事件使侏罗纪—早白垩世海水锶同位素总体上呈降低趋势;二叠/三叠纪界线的生物绝灭事件及界线后三叠纪初期的生态萧条控制了晚二叠世—早三叠世海水的锶同位素组成,早三叠世在全球海平面上升的背景下反而出现了锶同位素比值的急剧上升,单位时间的上升幅度居显生宙之首。与二叠/三叠纪界线生物绝灭有关的全球大陆植被的缺乏和风化速率加快是其主要控制因素;发生于中生代的海相红层事件记录了海水锶同位素比值的上升,显示风化作用的加剧可能诱发海相红层;但晚白垩世的大洋红层对应着全球海平面下降,其成因还与在全球变冷的背景下,温度较低且富氧的大洋表层水以及从两极向赤道方向运动的低温富氧海水与大洋深层水交换并造成大洋底层水富氧和沉积物的氧化有关。中生代的三次大洋缺氧事件均发生在锶同位素下降的时间间隔中,这与洋中脊洋壳生产和有关热液活动的增加有关,洋壳生产的增加导致了CO2 排气作用的增强和全球变暖,最
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| 关 键 词： | 海水锶同位素组成 古海洋事件 中生代 新生代 |
| 文章编号： | 1005-2321(2005)02-0133-09 |
| 修稿时间： | 2004年10月6日 |
Seawater strontium isotopes and paleo-oceanic events over the past 260 Ma |
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| HUANG Si-jing,WU Su-juan,SUN Zhi-lei,PEI Chang-rong,HU Zuo-wei.Seawater strontium isotopes and paleo-oceanic events over the past 260 Ma[J].Earth Science Frontiers,2005,12(2):133-141. |
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| Authors: | HUANG Si-jing WU Su-juan SUN Zhi-lei PEI Chang-rong HU Zuo-wei |
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| Abstract: | The Mesozoic and the Cenozoic are geological periods in which the greatest change in the composition of seawater strontium isotopes occurred. The continuous rise of (~(87)Sr/~(86)Sr) was controlled by a continuous global sea-level fall since the Late Cretaceous. The sharp rise in the (~(87)Sr/~(86)Sr) values during the last 40 million years was related to the effects of rapid exhumation and chemical weathering of Himalaya. The Jurassic and Cretaceous strontium isotope evolution is also a record of hydrothermal variations during the breakup of Pangaea. The sharp change in the (~(87)Sr/~(86)Sr) curve during the Late Permian/Early Triassic may have been due to the absence of a dense protective land plant cover following the mass extinction during the latest Permian, which led to a rapid continental silicate weathering. An increase of (~(87)Sr/~(86)Sr) values corresponds to the deposition of the marine red beds in the Mesozoic and shows that enhanced weathering could have been a possible cause to trigger the deposition of marine red beds. However, the late Cretaceous oceanic red beds (CORB) was also coincident with a sea-level fall, global cooling and oxic deep-water activity. The three Oceanic Anoxic Events (OAE) in the Mesozoic coincide with three negative seawater strontium isotope excursions (shift to lower (~(87)Sr/~(86)Sr) values). We propose that the reason was an increase in oceanic-crust production, which led to enhanced CO_2 outgassing and global warming, and in turn led to several processes that acted to make surface ocean waters more productive. |
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| Keywords: | seawater strontium isotopes paleo-oceanic events Mesozoic Cenozoic |
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