Study of end-Paleozoic double-phased mass extinction : the G-L boundary and P-T boundary events

在4年的资助研究中，我们在中国四川北部、日本九州中部、克罗地亚Velebit山区进行了实地研究，并进行了地球化学分析。这些导致了以下结果和结论。1)在G-L界大灭绝前500万年的时间间隔内首次检测到异常高的碳同位素比值。我们将这一全球范围内的独特事件命名为“Kamura事件”，以九州的研究地区命名。这意味着超级海洋初级生产力的提高、大气中二氧化碳的大量消耗、温室效应的减弱以及由此导致的全球变冷。2)在特提斯和超大洋Panthalassa，瓜达卢普浅海区动物群同时灭绝，这些动物群由巨型双壳类（Alatoconchidae）、大型杂藻和绢珊瑚组成。这些“热带三重奏”在贫营养环境下与藻类/细菌有相同的光共生习惯，它们可能因光共生的崩溃而冷却而终止。3)确认了晚瓜达鲁普期显生界sr同位素比值最小。这显然与显生宙海平面最大幅度的下降相吻合。4)华南的P-T边界层段具有长英质（爆炸性）火山活动频繁的特征。地球化学和矿物学的证据表明，这次火山活动与地幔柱活动有关。上述结果在一定程度上支持了首席研究员10多年前提出的“羽流冬季”设想。由于结果包含了一些新的发现和第一个视角，我们已经在国际科学期刊上发表了29篇文章，出版了2本书，在国际会议上做了6次口头报告，其中包括3次主题演讲。少

During the 4 years of research under the support of this grant-in-aid, we conducted field studies in the northern Sichuan in China, central Kyushu in Japan, and the Velebit mountains in Croatia, and in door geochemical analyses. These led the following results and conclusions.1) An unusually high positive values of carbon isotope ratio was detected for the first time from a 5 million years interval immediately before the G-L boundary mass extinction. We named this unique event of a global context the "Kamura event" after the study area in Kyushu. This implies the increase in primary productivity in the superocean, mass consumption of atmospheric C02, decline in greenhouse effect, and resultant global cooling.2) The simultaneous extinction of the Guadalupian shallow marina fauna composed of gigantic bivalves (Alatoconchidae), large-tested fusulines and rugose corals was documented both in Tethys and the superocean Panthalassa. These "tropical trio" shared the same habit of photosymbiosi … More s with algae/bacteria under oligtrophic environments, and they were terminated probably by cooling through the collapse of photosymbiosis.3) We confirmed that the Sr-isotope ratio reached the minimum of the Phanerozoic in the late Guadalupian. This apparently coincided with the greatest sea-level drop in the Phanerozooic. These indicate the end-Guadalupian event was related to the initial Pangean breakup in the late Middle Permian.4) We found that the P-T boundary interval in South China is characterized by frequent activity of felsic (explosive) volcanism. Geochemical and mineralogical lines of evidence suggest that this volcanism was related to mantle plume activity.The above-listed results partly prove thus positively support the "Plume Winter" scenario that the head investigator proposed more than 10 years ago. As the results contain several new finds and the first perspectives, we already reported in 29 articles in international scientific journals, 2 books, and 6 oral presentations at international meetings including 3 keynote speeches. Less