北部北上帯の遠洋成深海相ペルム紀/三畳紀境界層セクションにみられるペルム紀末の放散虫の減少と有機炭素量の増加  [in Japanese] High organic carbon content and a decrease in radiolarians at the end of the Permian in a newly discovered continuous pelagic section: a coincidence?  [in Japanese]