09:15 〜 09:30
[SGL22-02] 後期三畳紀の絶滅事変：最近の研究動向
★招待講演
キーワード：後期三畳紀、絶滅、レーティアン
We focus on environmental changes during the Rhaetian (Late Triassic) and review the nature of the extinctions that occurred during this period. Extinctions within major marine groups occurred during the last 10 Myr of the Triassic. Most of these extinctions were long conflated as a single mass extinction at the end of the Triassic, the so-called end-Triassic extinction (ETE). However, recent developments in marine biostratigraphy and magnetostratigraphy allow a more detailed sequence of extinction events during the Norian/Rhaetian boundary (NRB) and Triassic/Jurassic boundary (TJB). The NRB and TJB episodes are characterized by negative organic carbon isotope excursions, which are thought to result from perturbations in the carbon cycle caused by the eruption of the Angayucham flood basalt and CAMP volcanism, respectively. By studying the geochemical and isotopic composition of different latitudinal and hemispheric sections on both sides of the Pangaea continent, we found that chemical weathering accelerated with global warming in both the NRB and TJB. Increased chemical weathering resulted in accelerated nutrient discharge to the ocean, which led to a significant increase in biological productivity, which in turn led to ocean anoxia. Severe extinctions of several fossil groups, including ammonoids, bivalves, conodonts, and radiolarians, have been documented globally in the NRB and TJB as a biological consequence of these climatic and environmental changes.