Biological pump and material flux in the hot-house Earth

我们研究了法国东南部Goguel(OAE1a)和Killian-Paquir(OAE1b)段的地质和取样的海洋缺氧事件序列。此外，我们还从OAE1b沉积物的最上层找到了三个8米长的岩芯。对该岩心石器时代细菌遗迹的遗传分析表明，δ-变形杆菌中含有高浓度的海洋硫酸盐还原细菌rDNA克隆。该岩心富含磷酸盐岩层很可能沉积在冷渗漏发育的海底。在基利安和帕奎尔两个层级，钙质超微化石的丰度显著下降，而纳米锥突然占据了物种组合的主导地位。Nannoconus被认为是低光区的居民。由于球石的溶解在所研究的层序中不是一个重要因素，这些观察清楚地表明，在OAE1b黑色页岩沉积期间，主要生产群落发生了重大变化。根据超微化石生物地层学，沉积帕奎尔层所需的时间估计约为50年。对泥质岩层的X射线分析揭示了由富有孔虫地层和富含粘土地层组成的细微纹层的交替。后者的特点也是有机质浓度较高。对帕奎尔层钙质超微化石组合的高分辨率(间隔1厘米)分析表明，超微锥化石总体上占优势，并反复出现极短的间隔，其中分类群显著减少其丰度。这些证据表明，1)在OAE1b黑色页岩沉积过程中，水柱的垂直混合作用普遍减少；2)在帕奎尔沉积时间内，环境在几个短的时间间隔内恢复到正常模式。

We have studied the geology and sampled Ocean Anoxic Event sequences in SE France from the Goguel (OAE1a) and Killian to Paquir (OAE1b) intervals. In addition, we recovered three 8m long cores from the upper-most level of OAE1b sediment. The genetic analysis of endolithic bacterial relics for this core has revealed a high concentration of rDNA clones of oceanic sulfate-reducing bacteria (SRB) within δ-Proteobacteria predominated. The phosphate rich bed in this core is likely to be deposited at the sea floor where cold seepage developed. At the Killian and Paquir levels, the abundance of calcareous nannofossils decreased significantly and Nannoconus suddenly dominated the species assemblage. Nannoconus is postulated as a lower-photic zone dweller. Because the dissolution of coccolith is not a significant factor in the studied sequence, these observations clearly indicate a major change in the primary producing community during the deposition of OAE1b black shales. From the nannofossil biostratigraphy, the time needed to deposit the Paquir level was estimated as ca. 50 Kyrs. A X-ray analysis of the shaly beds revealed an alternation of fine lamina consisting foraminifera-rich layers and clay-rich layers. The latter is also characterized by a higher concentration of organic matter. A high-resolution (1 cm interval) analysis of calcareous nannofossil assemblage in the Paquir level shows a general dominance of Nannoconus and repeated occurrence of very short intervals where the taxa decreased its abundance dramatically. These evidences indicate, 1) vertical mixing of water column was generally reduced during the deposition of OAE1b black shales, 2) but the environment had returned to normal mode during several short intervals within the time of Paquir deposaition.