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RESEARCH ON PERMIAN AND TRIASSIC BOUNDARY IN PELAGIC SEDIMENTS

远洋沉积物二叠系和三叠系边界研究

基本信息

批准号：
05304001
负责人：
IMOTO Nobuhiro
金额：
$ 1.28万
依托单位：
KYOTO UNIVERSITY OF EDUCATION
依托单位国家：
日本
项目类别：
Grant-in-Aid for Co-operative Research (A)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

This work has focused on an investigation of the Permian and Triassic boundary in bedded chert sequences of Southwest Japan. Bedded cherts are typical pelagic deep marine sediments which were regarded to be a continuous and seamless recorder. This is because they were rather exempted from an erosion than those of the shallow marine sediments where an invasion of the local flux of terrigenous materials were contaminated. Biostratigraphical, sedimentologic, geochemical and stable isotopic examinations have been carried out which resulted in an evaluation of the oceanic condition across this boundary.Even in a pelagic condition, siliceous planktons mostly extinct at the boundary, and ecologic system was wholly innovated. This bio-event followed Late Permian radiolarian blooming of which dominant supply of organic materials might be a trigger of shifting from oxic basin to anoxic one and change of ecological system. Organic black mudstones occurred above the boundary is an important key bed to elucidate change of oceanic condition ; namely this indicated high primary production and oxic depositional environment indicated by sulfur stable isotopic examination. This organic black mudstone also indicated enrichment in Ti, Th and Zr in comparison with standard continental shales which suggested possible effect from the activity of continental flood basalts. Co-operative research on the Permian and Triassic boundary produced some new ideas on bio-geo-system of the earth surface which will be examined in next project.

本文对日本西南部层状硅质岩序列中的二叠系和三叠系界线进行了研究。层状硅质岩是典型的远洋深海沉积物，被认为是一种连续、无缝的记录器。这是因为它们比浅海沉积物更不受侵蚀，因为在浅海沉积物中，当地陆源物质的入侵受到了污染。通过生物地层学、沉积学、地球化学和稳定同位素的研究，对该界线的海洋状况进行了评价。即使在远洋条件下，硅质浮游生物也大多在该界线上灭绝，生态系统得到了彻底的创新。这一生物事件发生在晚二叠世放射虫盛期之后，有机质的主要供应可能是从缺氧盆地向缺氧盆地转变和生态系统变化的触发因素。边界以上的有机黑色泥岩是阐明大洋条件变化的重要关键层，即硫稳定同位素研究表明其具有较高的原生油和氧的沉积环境。与标准陆相页岩相比，这种有机黑色泥岩还显示了钛、钍和锆的富集性，这可能是陆相溢流玄武岩活动的影响。对二叠系和三叠系界线的合作研究对地球表面的生物地球系统产生了一些新的想法，将在下一个项目中进行研究。