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| Van Maldegem, Lennart M.; Sansjofre, Pierre; Weijers, Johan W. H.; Wolkenstein, Klaus; Strother, Paul K.; Woermer, Lars; Hefter, Jens; Nettersheim, Benjamin J.; Hoshino, Yosuke; Schouten, Stefan; Damste, Jaap S. Sinninghe; Nath, Nilamoni; Griesinger, Christian; Kuznetsov, Nikolay B.; Elie, Marcel; Elvert, Marcus; Tegelaar, Erik; Gleixner, Gerd; Hallmann, Christian. |
| Eukaryotic algae rose to ecological relevance after the Neoproterozoic Snowball Earth glaciations, but the causes for this consequential evolutionary transition remain enigmatic. Cap carbonates were globally deposited directly after these glaciations, but they are usually organic barren or thermally overprinted. Here we show that uniquely-preserved cap dolostones of the Araras Group contain exceptional abundances of a newly identified biomarker: 25,28-bisnorgammacerane. Its secular occurrence, carbon isotope systematics and co-occurrence with other demethylated terpenoids suggest a mechanistic connection to extensive microbial degradation of ciliate-derived biomass in bacterially dominated ecosystems. Declining 25,28-bisnorgammacerane concentrations, and a... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00637/74951/76030.pdf |
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| Hensen, Christian; Duarte, Joao C.; Vannucchi, Paola; Mazzini, Adriano; Lever, Mark A.; Terrinha, Pedro; Géli, Louis; Henry, Pierre; Villinger, Heinrich; Morgan, Jason; Schmidt, Mark; Gutscher, Marc-andre; Bartolome, Rafael; Tomonaga, Yama; Polonia, Alina; Gràcia, Eulàlia; Tinivella, Umberta; Lupi, Matteo; Çağatay, M. Namık; Elvert, Marcus; Sakellariou, Dimitris; Matias, Luis; Kipfer, Rolf; Karageorgis, Aristomenis P.; Ruffine, Livio; Liebetrau, Volker; Pierre, Catherine; Schmidt, Christopher; Batista, Luis; Gasperini, Luca; Burwicz, Ewa; Neres, Marta; Nuzzo, Marianne. |
| Marine transform faults and associated fracture zones (MTFFZs) cover vast stretches of the ocean floor, where they play a key role in plate tectonics, accommodating the lateral movement of tectonic plates and allowing connections between ridges and trenches. Together with the continental counterparts of MTFFZs, these structures also pose a risk to human societies as they can generate high magnitude earthquakes and trigger tsunamis. Historical examples are the Sumatra-Wharton Basin Earthquake in 2012 (M8.6) and the Atlantic Gloria Fault Earthquake in 1941 (M8.4). Earthquakes at MTFFZs furthermore open and sustain pathways for fluid flow triggering reactions with the host rocks that may permanently change the rheological properties of the oceanic... |
| Tipo: Text |
Palavras-chave: Transform faults; Fractures zones; Coupling of seismicity and fluid flow; Microbial life; Heat flow; Fluid geochemistry; Seafloor observation systems; Seismic precursors. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00489/60085/63422.pdf |
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| Lever, Mark A.; Rouxel, Olivier; Alt, Jeffrey C.; Shimizu, Nobumichi; Ono, Shuhei; Coggon, Rosalind M.; Shanks, Wayne C., Iii; Lapham, Laura; Elvert, Marcus; Prieto-mollar, Xavier; Hinrichs, Kai-uwe; Inagaki, Fumio; Teske, Andreas. |
| Sediment-covered basalt on the flanks of mid-ocean ridges constitutes most of Earth's oceanic crust, but the composition and metabolic function of its microbial ecosystem are largely unknown. By drilling into 3.5-million-year-old subseafloor basalt, we demonstrated the presence of methane-and sulfur-cycling microbes on the eastern flank of the Juan de Fuca Ridge. Depth horizons with functional genes indicative of methane-cycling and sulfate-reducing microorganisms are enriched in solid-phase sulfur and total organic carbon, host delta C-13- and delta S-34-isotopic values with a biological imprint, and show clear signs of microbial activity when incubated in the laboratory. Downcore changes in carbon and sulfur cycling show discrete geochemical intervals... |
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| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00176/28767/32146.pdf |
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