Oceanic change of Northwest Paleo-Pacific during Jurassic based on radiolarian research

本课题研究的课题是侏罗纪时期古太平洋西北部的海洋环境变化。基于侏罗纪放射虫动物群的数据来自日本西南部Tanba-Mino和Chihibu地体的侏罗纪增生杂岩。放射虫的研究主要集中在动物区系的分析上，通过对每个样品的整体物种进行鉴定，明确了放射虫动物群的具体数量在三叠系/侏罗系界线附近呈减少趋势。这一现象被认为是受三叠系/侏罗系界线大灭绝事件的影响。以海洋缺氧为代表的托尔西亚事件也影响了放射虫动物群的具体数量。虽然放射虫的动物群变化在托阿尔西中期至阿勒尼亚早期较慢，但在阿勒尼亚晚期至巴约西晚期变化较快。这一现象可能与中大西洋海道的发展引起的海洋环境变化有关。

This project had a subject to consider the change of oceanic environment in the northwestern Paleo-Pacific during Jurassic time. The data based on Jurassic radiolarian faunas were gotten from the Jurassic accretionary complexes of the Tanba-Mino and Chichibu terranes in southwest Japan. The radiolarian research was focused on the faunal analysis by means of identification of whole species occurred from each samples.It was clarified that the specific number of radiolarian fauna was decreased around the Triassic/Jurassic boundary. This phenomenon is considered to be affected by the mass extinction event of Triassic/Jurassic boundary. The Toarcian event, which was represented by the oceanic anoxia, also affected the specific number of radiolarian fauna. Although the faunal change of radiolarians was slow from middle Toarcian to early Aalenian time, it was fast from late Aalenian to Bajocian time. This phenomenon may be related to the change of oceanic environment caused by the development of Central Atlantic Seaway.