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Biological pump and material flux in the hot-house Earth

温室地球中的生物泵和物质通量

基本信息

批准号：
11691113
负责人：
OKADA Hisatake
金额：
$ 7.49万
依托单位：
HOKKAIDO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11691113/
关键词：
Cretaceous OAE Balck Shale Paleoceanography

项目摘要

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.

我们已经研究了地质和采样的海洋南极事件序列在法国东南部的Goguel（OAE 1a）和基利安Paquir（OAE 1b）间隔。此外，我们从OAE 1b沉积物的最上层回收了三个8米长的岩心。通过对该岩心内石细菌遗迹的遗传分析，发现δ-变形菌门中存在大量海洋硫酸盐还原菌（SRB）的rDNA克隆。该岩芯中的富磷酸盐层很可能沉积在冷渗漏发育的海底。在Killian和Paquir水平，钙质超微化石的丰度显着下降，Nannoconus突然主导的物种组合。Nannoconus被假定为低透光区居民。由于溶球石不是一个重要的因素，在研究序列，这些意见清楚地表明，在OAE 1b黑色页岩沉积过程中的主要生产社会的重大变化。根据超微化石生物地层学，估计Paquir层存款所需的时间约为2000年。50千X射线分析的泥质层揭示了交替的细薄层有孔虫丰富的层和粘土丰富的层。后者的特点也是有机物浓度较高。一个高分辨率（1厘米的间隔）分析的钙质超微化石组合在Paquir水平显示了普遍的优势Nannoconus和重复发生的非常短的间隔，其中的类群大大减少其丰度。这些证据表明，1）在OAE 1b黑色页岩沉积期间，水柱的垂直混合普遍减少，2）但在Paquir沉积期间的几个短时间内，环境已恢复正常模式。