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

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 photosymbiosis 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.