Organic geochemical study on the relationship between primary productivity of palaeocean and evolution of marine invertebrates

在日本西南部的坦巴和Chichibu地块，出露的二叠纪/三叠纪（P/T）界线上嵌有富有机质的黑色页岩。考虑到它们的成熟度，初始有机碳浓度估计约为3%（平均）。干酪根不含任何高等植物起源的碎屑，而主要由无结构的无定形组成。生物标志物表明，黑色页岩的有机质主要来源于浮游生物，另外还有与细菌活性有关的有机质。黑色页岩形成时期的古海洋相对活跃。在P/T转换时期，构造和气候诱导的活跃洋流系统间歇性地破坏了具有丰富营养物质的氧最低层发育良好的分层海洋，导致了高初级产量的上升流。晚二叠纪氧最小层的扩张及其突然破坏可能是海洋无脊椎动物大灭绝及其进化的重要原因之一。

Outcrops containing the Permian/Triassic (P/T) boundary exposed in the Tanba and Chichibu terranes, Southwest Japan, have intercalated organic rich black shales. The initial organic carbon concentration was evaluated to be about 3% (average), considering their maturity levels. Kerogens do not contain any debris of higher plant origins, but are mostly composed of structureless amorphous ones. Biomarkers show that black shales comprise organic matter derived mainly from plankton with the additional organic matter related tothe bacterial activity. Palaeocean at the time of black shale formation was comparatively active. The stratified ocean with well developed oxygen minimum layr rich in nutrients was intermittently destroyed due to the tectonically and climatically induced active ocean current systems in the P/T transition time, resulting in upwelling for the remarkably high primary production. Expanding oxygen minimum layr in the Late Permian and its abrupt destruction can be one of crucial causes for the mass extinction of marine invertebrates and their evolution.