Analysis of paleoclimate during OAE2. with world-highest resolution

OAE2 期间的古气候分析。

• 批准号: 18340164
• 负责人: HASEGAWA Takashi
• 金额: $ 10.46万
• 依托单位: Kanazawa University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2006
• 资助国家: 日本
• 起止时间: 2006 至 2007
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18340164/
• 关键词: Carbon isotope; Cretaceous; Oceanic Anoxic Event; OAE; Cenomanian; Turonian; carbon circulation; Yezo Group; OAE2; 炭素同位体比曲線; バイオマーカー; 高時間解像度; 気候変動

Cretaceous Oceanic Anoxic Event 2 (OAE2) is one of the most well studied oceanic anoxic event through the geologic history. Objective of this study is to decode paleoenvirorment in northwestern Pacific during the OAE2 with world-highest resolution.We firstly establish carbon isotope (δ^<13>C) stratigraphy in a resolution of several kyr through the Yezo Group sequence in the Tappu area (Tappu section) and compared it with world reference section in UK. All phases of δ^<13>C event through OAE2 observed in the reference section was found in the Tappu section. Based on this result, the interval that records strongest oxygen deficiency and associated cooling derived from CO_2 withdrawal from ocean-atmosphere system recognized in European sections was correlated and identified in the Tappu section. Then we performed detailed sampling through the interval (about 70m thick). Nearly continuous samples were cut out from river floor using engine cutter and full-scaled sketches were taken from the … More m, then 1/5 geologic column was compiled. Such description enables us to exclude material of re-deposition or considerable bioturbation when collecting sub-samples for analyses. Ultra-high resolution sampling was then successfully performed with time interval of several hundreds years.Carbon isotope stratigraphy of the Tappu section shows generally comparable pattern with that of the reference section in UK ; however, conspicuous 2.7‰ negative excursion that was peculiar to our section was observed and named as NEMO event. The sequence below the NEMO showsδ^<13>C pattern with little sample-to-sample variation whereas theδ^<13>C pattern above the NEMO apparently have larger variation within several adjacent samples. This potentially suggests re-establishment of surface earth carbon circulation (appearance of kyr-order fluctuation). NEMO may be a key event to elucidate such re-establishment of carbon circulation.Based on the resolution and the accuracy of correlation with the reference section, we analyzed plankton microfossils and biomarkers for paleoenvironmental reconstruction. Twice disappearance of entire planktonic foraminifera from sediments was observed associated with the early phase of OAE2. These biotic events were not resulted from secondary effect such as dissolution, for identical events were also observed in the Oyubari area, more than 100km away from the Tappu section. Biomarkers show a remarkable change in relative abundance of terrestrial molecules. It may suggest floral turnover over the provenance of the Yezo Group. At this moment, time-stratigraphic resolution of these paleoenvirormertal analyses has not caught up with the world-highest resolution ofδ^<13>C stratigraphy. We keep working through a strategy of zooming-in (selecting several inportant intervals as NEMO and perform concentrated analyses) to achieve ultra-high resolution analyses of the paleoenvironment during OAE2. Less

白垩纪海洋缺氧事件 2 (OAE2) 是地质史上研究最深入的海洋缺氧事件之一。本研究的目的是以世界最高的分辨率解码 OAE2 期间西北太平洋的古环境。我们首先建立了碳同位素 (δ)。 ^<13>C) 通过 Tappu 地区（Tappu 剖面）的 Yezo 群层序以数 kyr 的分辨率进行地层学研究，并将其与世界参考资料进行比较在英国的Tappu剖面中观察到的通过OAE2观测到的δ^ 13 C事件的所有阶段均在Tappu剖面中发现，记录了来自海洋的CO_2提取的最强缺氧和相关冷却的区间。然后，我们在 Tappu 剖面中对欧洲剖面中识别出的大气系统进行了关联和识别，然后使用发动机切割机从河底切取了几乎连续的样本，并从该剖面中绘制了全尺寸草图。 … 更多的m，然后编制了1/5地质柱。这样的描述使我们能够在收集子样本进行分析时排除再沉积或相当大的生物扰动的物质，然后成功地以数百年的时间间隔进行了超高分辨率采样。 Tappu剖面的碳同位素地层学显示出与英国参考剖面大致相似的模式；然而，观察到了我们剖面特有的显着的2.7‰负偏移，并将其命名为NEMO事件。 NEMO 下方的 δ^13C 模式显示样本间差异很小，而 NEMO 上方的 δ^13C 模式在几个相邻样本中显然有较大变化，这可能表明地球表面碳循环的重建。 kyr级波动的出现）可能是阐明碳循环重建的关键事件。基于与参考部分相关的分辨率和准确性，我们分析了浮游生物微化石和生物标志物。在OAE2的早期阶段，观察到整个浮游有孔虫从沉积物中消失，这些生物事件不是由溶解等二次效应引起的，因为在100多公里外的大夕张地区也观察到了相同的事件。来自 Tappu 部分的生物标记显示陆地分子的相对丰度发生了显着变化，这可能表明此时叶佐群的起源发生了变化。这些古环境分析的时间地层分辨率还没有赶上δ^<13>C地层学的世界最高分辨率，我们不断通过放大策略（选择几个重要层段作为NEMO进行集中分析）来实现。 OAE2 期间古环境的超高分辨率分析。

项目成果

Coniacian-Santonian stratigraphy in Japan : a review.

日本的康尼亚阶-桑托阶地层学：综述。

• 发表时间: 2007
• 作者: Toshimitsu; S.; Hasegawa; T.; Tsuchiya; K.
• 通讯作者: K.

Terrestrial response to the rapid greenhouse warming across the Paleoc ene/Eocene thermal maximum.

陆地对古新世/始新世热最大值期间温室气体快速变暖的反应。

• 发表时间: 2007
• 作者: Hasegawa; T.; Pratt; L. M.; Kro on; D.; Sluijs; A.; Ikehara; M.; Mori; T.; Yamamoto; S.; Zac hos; J. C.
• 通讯作者: J. C.

古生物情報の高度利用による温室期の深層水循環の解明

通过古生物学信息的先进利用来阐明温室期间的深层水循环

• 发表时间: 2007
• 作者: 長谷川卓; 棚部一成; 西弘嗣
• 通讯作者: 西弘嗣

白亜紀中期・セノマニアン/チューロニアン境界の絶滅事変時における有孔虫化石群組成の超高解像度解析

中白垩世塞诺曼阶/土伦阶边界灭绝事件期间有孔虫化石群落组成的超高分辨率分析

• 发表时间: 2008
• 作者: 守屋和佳; 長谷川 卓; 成瀬貴洋; 瀬尾草平; 根本俊文; 鈴木崇章; 森本このみ
• 通讯作者: 森本このみ

温室地球期の海洋鉛直隔環の解読 : OAE堆積物を利用する新視点. 特集 : 温室地球における生命と環境の共進化-

破译温室地球时期的海洋垂直隔膜：利用 OAE 沉积物的新视角特色：温室地球上生命与环境的共同进化。

• 发表时间: 2008
• 作者: 長谷川 卓; 棚部一成; 西 弘嗣
• 通讯作者: 西 弘嗣