|
|
|
|
|
| Galbraith, Ed; Kienast, M; Pedersen, Tf; Calvert, Se. |
| An analysis of sedimentary nitrogen isotope records compiled from widely distributed marine environments emphasizes the global synchrony of denitrification changes and provides evidence for a strong temporal coupling of these variations to changes in nitrogen fixation as previously inferred. We explain the global coherence of these records by a simple physical control on the flux of dissolved oxygen to suboxic zones and the coupling to fixation via the supply of phosphorus to diazotrophs in suitable environments. According to our hypothesis, lower glacial-stage sea surface temperature increased oxygen solubility, while stronger winds in high-latitude regions enhanced the rate of thermocline ventilation. The resultant colder, rapidly flushed thermocline... |
| Tipo: Text |
Palavras-chave: Isotopes; Fixation; Denitrification. |
| Ano: 2004 |
URL: https://archimer.ifremer.fr/doc/00229/34026/32421.pdf |
| |
|
|
| Bertrand, P; Pedersen, Tf; Schneider, R; Shimmield, G; Lallier-verges, E; Disnar, Jr; Massias, D; Villanueva, J; Tribovillard, N; Huc, Ay; Giraud, X; Pierre, C; Venec-peyre, Mt. |
| Sediments on the Namibian Margin in the SE Atlantic between water depths of similar to1000 and similar to3600 m are highly enriched in hydrocarbon-prone organic matter. Such sedimentation has occurred for more than 2 million years and is geographically distributed over hundreds of kilometers along the margin, so that the sediments of this region contain a huge concentrated stock of organic carbon. It is shown here that most of the variability in organic content is due to relative dilution by buried carbonates. This reflects both export productivity and diagenetic dissolution, not differences in either water column or bottom water anoxia and related enhanced preservation of organic matter. These observations offer a new mechanism for the formation of... |
| Tipo: Text |
Palavras-chave: Petroleum source rocks; Coastal upwelling; Deep-sea sediments; Quaternary climate; Southwestern African Margin. |
| Ano: 2003 |
URL: https://archimer.ifremer.fr/doc/00224/33553/31977.pdf |
| |
|
|
|
