白垩纪至早第三纪的极端气候事件  被引量:20

EXTREME CLIMATES EVENTS IN THE CRETACEOUS AND PALEOGENE

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作  者:刘志飞[1] 胡修棉 

机构地区:[1]同济大学海洋地质教育部重点实验室,上海200092 [2]意大利安科纳大学海洋科学系,意大利安科纳60131

出  处:《地球科学进展》2003年第5期681-690,共10页Advances in Earth Science

基  金:国家自然科学基金项目"青藏高原可可西里地区早新生代古气候记录"(编号:40102010);国家重点基础研究发展规划项目"地球圈层相互作用中的深海过程和深海记录"(编号:G2000078500);上海市青年科技启明星计划"渐新世最早期全球最大冰盖事件及其对未来气候预测应用的研究"资助

摘  要:地球科学界正在将预测未来气候变化的研究重点放到地球过去突然发生的气候变暖事件。白垩纪至早第三纪发生的极端气候事件被认为是最接近于现今的地球系统,对其研究有利于理解现今地球系统过程在碳循环快速搅动时的响应。这些气候事件主要包括:古新世—始新世最热事件(PETM,~55MaBP)、早阿普第晚期和森诺曼—土仑界线的大洋缺氧事件(OAE1a,~120Ma;OAE2,~93.5MaBP)。PETM事件是中白垩世以来一次突然变暖事件,在10ka年以内深海温度增加~5℃,表层海水温度增加4~8℃,而δ13C至少发生3.0‰的负偏移。目前普遍认为PETM事件是由于海洋气水化合物(CH4)的巨量释放造成的。大洋缺氧事件(OAEs)记录了海洋环境下有机质的大量埋藏,代表了碳循环和海洋生物系统的重大搅动事件。综合大洋钻探计划(IODP)将极端气候确定为优先研究领域,将采取特定的钻探策略,在世界大洋范围内获取最低限度蚀变的新生代至白垩纪沉积物,研究精度要求达到米兰柯维奇的天文调谐时间尺度,其最终目标是定量描述过去全球气候变化,并为未来气候变化预测提供依据。Predictions for modern global warming resulting from increased CO2 levels have caused a heightened interest in the mechanics of ancient warm climates and especially of geologically abrupt warming events. Certain key intervals of the Cretaceous and Paleogene marked by rapid climate change are significant to current Earth science objectives because focused research has the potential to considerably improve our understanding of the general dynamics of the Earth during rapid perturbation of carbon cycle. These intervals mainly include: the PaleoceneEocene Thermal Maximum (PETM, ~55 Ma) and Oceanic Anoxic Events (OAEs) in the late early Aptian (OAE1a,Selli Level, ~120 Ma) and at the CenomanianTuronian Boundary (OAE2, Bonarelli Level, ~93.5 Ma). Known as one of the most extreme and abrupt warming episodes since the midCretaceous, the PETM is characterized by a rapid ~5℃ increase in deep ocean, about 4 to 8℃ increase in surface ocean, and a prominent negative carbon isotope excursion of at least 3.0‰ in less than 10 ka. One plausible explanation for the observed PETM δ13C excursion involves massive release of CH4 from gas hydrates in the ocean. The OAEs represent major perturbations of the ocean system defined by massive deposition of organic matter in marine environments. Integrated Ocean Drilling Program (IODP) includes the extreme climates as one of major scientific objectives. Worldwide oceans with the minimal diagenesis in Cretaceous and Cenozoic sediments will be drilled by special drilling strategies to yield critical information of our understanding of these climatic extremes under a Milankovitch astronomicallycalibrated time scale. The end is fundamental to a quantitative description of global change.

关 键 词:极端气候 古新世-始新世最热事(PETM) 大洋缺氧事件(OAEs) 白垩纪 早第三纪 大洋钻探计划(ODP) 综合大洋钻探计划(IODP) 

分 类 号:P71[天文地球—海洋科学]

 

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