[B-PT27] 原生代末／顕生代生物多様性変遷：絶滅と多様化

[BPT27-03] GSSPセクションに記録された後期デボン紀大量絶滅時の土壌浸食事件

*三浦 真実¹、海保 邦夫¹、カジエ ジャンジョルジュ² (1.東北大学、2.ベルギー王立自然史博物館)

キーワード：大量絶滅, デボン紀, 土壌浸食

The Late Devonian mass extinction occurred in a stepwise manner and culminated close to the Frasnian-Famennian (F-F) boundary (372 million years ago). Organic-molecular indices from marine sedimentary rocks at the GSSP section at Coumiac, France, indicate that the sequence of soil erosion and euxinia occurred close to this boundary. The increased concentrations of organic molecules indicating combustion and soil erosion measured in the Coumiac section suggest that terrigenous organic matter flowed into the ocean at this time, leading to reduction of the ocean that caused marine extinctions. Since this soil erosion event simultaneously occurred at the Sinsin section in Belgium (Kaiho et al., 2013), expansion of the reducing environment of the ocean due to soil inflow is thought to have occurred in a wide area. The study of sedimentary organic molecules presents several lines of evidence to link reduction of the ocean due to soil erosion to the Late Devonian mass extinction.

Kaiho, K., Yatsu, S., Oba, M., Gorjan, P., Casier, J.-G., Ikeda, M., 2013. A forest fire and soil erosion event during the Late Devonianmass extinction. Palaeogeogr. Palaeoclimatol. Palaeoecol. 392, 272-280.