Study on the cause of the Earth's greatest mass extinction

地球最大规模灭绝原因研究

基本信息

批准号：
10041113
负责人：
ISOZAKI Yukio
金额：
$ 6.02万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

This project was aimed to reveal the cause of the Permo-Triassic boundary (ca. 250 million years ago) mass extinction which represents the greatest biospheric catastrophe in the Earth's history. We planned to collect a continuous sedimentary sequence that recorded the secular environmental change around the P-T boundary, particularly by deep-drilling, because it is critical for this study to obtain weathering -free fresh rock samples for geochemnical analyses. Out of 4 candidate sections in South China, the Chaotien section was chosen on the basis of preliminary field research in winter of 1998. We conducted an academic drilling at Chaotien in northern Sicuan province in summer of 1999 and recovered 260 m long drilled core samples. The section along the Jialingian river covers the entire Upper Permian series from top Maokoan to Changhsingian plus the lowest Griesbachian of Lower Triassic. Numerous samples including ammonoid, coral, brachiopod and fusulinid fossils collected from surfac … More e outcrops made the total sample weight ca. 5 tons.These samples were shipped to Tokyo in Fall of 1999 and are currently under geochemical analyses in various aspects including major element composition, carbon isotope ratio plus rare earth element composition. In Particular, the Scanning X-ray Analyzing Microscope of the Nagoya Univ. is used for recovering visualized images of chemical composition of the samples. As the geochemical analysis has just started, results will be summarized later on.According to the field research and preliminary indoor analyses, the following new observations were made ; 1) The Chaotien section covers fossiliferous Upper Maokoan, Wuchapingian and Canhsingian plus the lowest Griesbachian on the basis of index fossils, 2) the cored samples are quite fresh, much better than those from the outcrop, 3) This section has many tuff layers whose horizons often correspond to the disappearance horizon of particular fossils. This suggests the "Plume Winter" scenario (proposed by the project leader) that connects plume-induced extraodinarily violent volcanism with the Pangean supercontinent breakup, and with the global environmental change associated with mass extinction across the P-T boundary. Less

该项目旨在揭示二叠纪-三叠纪边界（约 2.5 亿年前）大规模灭绝的原因，这是地球历史上最大的生物圈灾难，我们计划收集记录周围长期环境变化的连续沉积序列。 P-T 边界，特别是通过深钻，因为对于本研究来说，获得无风化的新鲜岩石样本以进行地球化学分析至关重要，在华南的 4 个候选剖面中，我们选择了朝田剖面。 1998年冬天，我们在初步实地研究的基础上进行了研究。1999年夏天，我们在四川省北部的朝田进行了一次学术钻探，并回收了260 m长的钻取岩心样品，沿嘉陵江的剖面涵盖了从猫科安顶部开始的整个上二叠统。从地表采集到长兴阶以及下三叠统最低的格里斯巴阶化石，包括菊石、珊瑚、腕足动物和氟苏林化石。 … 更多 e 露头的样本总重量约为 5 吨。这些样本于 1999 年秋季运往东京，目前正在进行各方面的地球化学分析，包括主要元素成分、碳同位素比率以及稀土元素成分。名古屋大学的扫描X射线分析显微镜用于恢复样品化学成分的可视化图像，由于地球化学分析刚刚开始，结果将在稍后总结。通过现场研究和初步室内分析，得出以下新的观察结果；1）朝天剖面包括了猫口阶、五查坪阶和灿兴阶的化石，以及基于指标化石的最低的格里斯巴阶；2）岩心样品相当新鲜，比之前的要好得多。 3) 该部分有许多凝灰岩层，其地平线通常与特定化石的消失地平线相对应，这表明了“羽冬季”情景（由该项目提出）。领导者）将羽流引发的异常猛烈的火山活动与泛古大陆超大陆的分裂以及与 P-T 边界大规模灭绝相关的全球环境变化联系起来。