Biological pump and material flux in the hot-house Earth

对法国东南部Goguel （OAE1a）、Killian至Paquir （OAE1b）段的海洋缺氧事件序列进行了地质研究和采样。此外，我们还从OAE1b沉积物的最上层恢复了3个8m长的岩心。对该岩心的内生细菌遗物进行遗传分析，发现δ-变形菌门中存在高浓度的海洋硫酸盐还原菌（SRB） rDNA克隆。该岩心中的富磷酸盐层可能沉积在冷渗流发育的海底。在Killian和Paquir水平，钙质纳米化石丰度显著下降，纳米圆锥类突然占据物种组合的主导地位。纳米锥体被假定为低光区居民。由于球粒岩的溶解作用在研究层序中不是一个重要的因素，这些观察结果清楚地表明，在OAE1b黑色页岩沉积过程中，初级生产群落发生了重大变化。根据纳米化石生物地层学，估计Paquir水平沉积所需的时间约为50万年。对泥质层的x射线分析显示，细层由富有孔虫层和富粘土层组成。后者的另一个特点是有机质浓度较高。对Paquir水平钙质纳米化石组合的高分辨率（1 cm间隔）分析表明，纳米圆锥化石普遍占主导地位，并且在很短的间隔内重复出现，其丰度急剧下降。这些证据表明，1)OAE1b黑色页岩沉积期间水体垂直混合普遍减少，2)在Paquir沉积期间，环境在几个短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.