Appearance of the Cenozoic-type chemosynthetic communities and its paleoecological factors

在半深海上层和高度多样化的类囊藻群落中，出现了泡囊藻类和深海藻类，它们是孢子虫化学合成群落的特征类群。尽管在北美始新世中期出现，但在始新世晚期和渐新世早期，它们在地理上传播到日本。古新世落木群落是在Hokakido东部Katsuhira组中首次发现的，不包括任何Bathy-Modelolins。古新世Katsuhira组也首次发现了产于日本新生代的Aporrhaid气足类。在此基础上，在PETM灭绝事件之后出现了新生代类型的化学合成群落。

Vesicomyids and bathymodiolins which are characteristic taxa of the Cenozoicchemosynthetic communities appeared in the upper bathyal and highly diversified communities withthyasirids. The bathymodiolins spread geographycally to Japan during the late Eocene and the early Oligo- cene despite they appeared in the middle Eocene of North America. The Paleocene wood-fall commnunities have been fisrt discovered from the Katsuhira Formation, eastern Hokakido and do not include any bathy- modiolins. Aporrhaid gasrtopods flourished in the Creataceous in Japan have also been first found from thePaleocene Katsuhira Formation. From these, the Cenozoic-type chemosynthetic communities appeared after theextinction event at PETM.