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| Hoshino, Yosuke; Poshibaeva, Aleksandra; Meredith, William; Snape, Colin; Poshibaev, Vladimir; Versteegh, Gerard J. M.; Kuznetsov, Nikolay; Leider, Arne; Van Maldegem, Lennart; Neumann, Mareike; Naeher, Sebastian; Moczydlowska, Malgorzata; Brocks, Jochen J.; Jarrett, Amber J. M.; Tang, Qing; Xiao, Shuhai; Mckirdy, David; Das, Supriyo Kumar; Alvaro, Jose Javier; Sansjofre, Pierre; Hallmann, Christian. |
| Sedimentary hydrocarbon remnants of eukaryotic C-26-C-30 sterols can be used to reconstruct early algal evolution. Enhanced C-29 sterol abundances provide algal cellmembranes a density advantage in large temperature fluctuations. Here, we combined a literature review with new analyses to generate a comprehensive inventory of unambiguously syngenetic steranes in Neoproterozoic rocks. Our results show that the capacity for C-29 24ethyl- sterol biosynthesis emerged in the Cryogenian, that is, between 720 and 635 million years ago during the Neoproterozoic Snowball Earth glaciations, which were an evolutionary stimulant, not a bottleneck. This biochemical innovation heralded the rise of green algae to global dominance of marine ecosystems and highlights the... |
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| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00638/75021/75667.pdf |
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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... |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00637/74951/76030.pdf |
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| Pasquier, Virgil; Toucanne, Samuel; Sansjofre, Pierre; Dixit, Yama; Revillon, Sidonie; Mokeddem, Zohra; Rabineau, Marina. |
| In this study we use bulk sediment organic matter stable isotopes (δ13Corg and δ15N) to examine the nature and timing of preserved organic matter in borehole PRGL1-4 from Northwestern Mediterranean Sea. This region is known as a transitional zone between the North Atlantic atmospheric circulation and the North African monsoon system. In the Gulf of Lion (SE France), increased inputs of organic matter from sediment-laden rivers occurred during warm substages of the last 200 kyr (MIS 5e, 5c, and 5a; MIS 6d, and 6b). Increased terrestrial organic matter are inferred from organic carbon isotopic composition (δ13Corg), and are interpreted as resulting from enhanced rainfall over the Rhone river catchment area. Such increase in terrestrial organic carbon induced... |
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Palavras-chave: Mediterranean; Rainfall; North Atlantic oscillation; Organic matter; North Mediterranean borderland; Sapropel. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00473/58421/61116.pdf |
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| Wilmeth, Dylan T.; Nabhan, Sami; Myers, Kimberly D.; Slagter, Silvina; Lalonde, Stefan; Sansjofre, Pierre; Homann, Martin; Konhauser, Kurt O.; Munoz-saez, Carolina; Van Zuilen, Mark A.. |
| Siliceous sinter deposits from El Tatio, Chile, preserve a wide variety of depositional environments and biosignatures, from high-temperature (~85 °C) vent-proximal facies to distal deposits dominated by silicified microbial mats. Four cores were drilled into an El Tatio sinster mound and associated distal apron to investigate changes in hydrothermal environments over geologic timescales. Sedimentary and geochemical analysis of multiple sinter cores records the initiation and accretion of diverse depositional features still observed today in El Tatio. Facies adjacent to hydrothermal vents are dominated by laminated sinter crusts on the steep margins of a high-temperature pool, with sparse microbial preservation. Outer margins of the same pool contain... |
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Palavras-chave: Siliceous sinter; Hot springs; El Tatio; Microbialites; Microfossils. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00641/75332/75994.pdf |
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| Eickenbusch, Philip; Takai, Ken; Sissman, Olivier; Suzuki, Shino; Menzies, Catriona; Sakai, Sanae; Sansjofre, Pierre; Tasumi, Eiji; Bernasconi, Stefano M.; Glombitza, Clemens; Jorgensen, Bo Barker; Morono, Yuki; Lever, Mark Alexander. |
| Serpentinitic systems are potential habitats for microbial life due to frequently high concentrations of microbial energy substrates, such as hydrogen (H-2), methane (CH4), and short-chain organic acids (SCOAs). Yet, many serpentinitic systems are also physiologically challenging environments due to highly alkaline conditions (pH > 10) and elevated temperatures (>80 degrees C). To elucidate the possibility of microbial life in deep serpentinitic crustal environments, International Ocean Discovery Program (IODP) Expedition 366 drilled into the Yinazao, Fantangisfia, and Asut Tesoru serpentinite mud volcanoes on the Mariana Forearc. These mud volcanoes differ in temperature (80, 150, 250 degrees C, respectively) of the underlying subducting slab, and... |
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Palavras-chave: Limits of life; Deep biosphere; Serpentinization; Abiotic synthesis; Formate; Acetate; Methane; International Ocean Discovery Program. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00637/74919/75981.pdf |
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| Pasquier, Virgil; Sansjofre, Pierre; Lebeau, Oanez; Liorzou, Celine; Rabineau, Marina. |
| Rationale Natural stable isotopes ratios (d13Corg and 15N vales) and associated elemental concentrations (i.e. total organic carbon and total nitrogen contents) preserved in marine sediments are frequently used for the determination of paleoenvironmental processes such as the origin of organic matter. Previous studies highlighted biases in the determination of such geochemical proxies due to pre-analysis acid treatment methods. This study is the first systematic comparison of the effect of acid treatment methods on bulk organic matter using a unique sedimentary system, under two contrasting climatic contexts (i.e. glacial vs interglacial). Methods We used the most common method for pre-treatment analysis, which consists of the acidification of bulk... |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00407/51830/52429.pdf |
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| Sansjofre, Pierre; Cartigny, Pierre; Trindade, Ricardo I. F.; Nogueira, Afonso C. R.; Agrinier, Pierre; Ader, Magali. |
| The terminal Neoproterozoic Era (850-542 Ma) is characterized by the most pronounced positive sulfur isotope (S-34/S-32) excursions in Earth's history, with strong variability and maximum values averaging delta S-34 similar to+38 parts per thousand. These excursions have been mostly interpreted in the framework of steady-state models, in which ocean sulfate concentrations do not fluctuate (that is, sulfate input equals sulfate output). Such models imply a large pyrite burial increase together with a dramatic fluctuation in the isotope composition of marine sulfate inputs, and/or a change in microbial sulfur metabolisms. Here, using multiple sulfur isotopes (S-33/S-32, S-34/S-32 and S-36/S-32 ratios) of carbonate-associated sulfate, we demonstrate that the... |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00639/75075/75603.pdf |
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| Pace, Aurelie; Bourillot, Raphael; Bouton, Anthony; Vennin, Emmanuelle; Galaup, Serge; Bundeleva, Irina; Patrier, Patricia; Dupraz, Christophe; Thomazo, Christophe; Sansjofre, Pierre; Yokoyama, Yusuke; Franceschi, Michel; Anguy, Yannick; Pigot, Lea; Virgone, Aurelien; Visscher, Pieter T.. |
| Microbialites are widespread in modern and fossil hypersaline environments, where they provide a unique sedimentary archive. Authigenic mineral precipitation in modern microbialites results from a complex interplay between microbial metabolisms, organic matrices and environmental parameters. Here, we combined mineralogical and microscopic analyses with measurements of metabolic activity in order to characterise the mineralisation of microbial mats forming microbialites in the Great Salt Lake (Utah, USA). Our results show that the mineralisation process takes place in three steps progressing along geochemical gradients produced through microbial activity. First, a poorly crystallized Mg-Si phase precipitates on alveolar extracellular organic matrix due to a... |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00347/45852/45517.pdf |
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| Cox, Grant M.; Sansjofre, Pierre; Blades, Morgan L.; Farkas, Juraj; Collins, Alan S.. |
| Precambrian hydrocarbons and their corresponding source rocks are distinctly different from their Phanerozoic counterparts, having been deposited in persistently anoxic environments in ecosystems dominated by bacteria. Here, we show that cyclic enrichment of organic matter in the world's oldest hydrocarbon play (ca. 1.38 Ga), is not associated with flooding surfaces and is unrelated to variations in mineralogy or changes in the relative rate of clastic to biogenic sedimentation-factors typically attributed to organic enrichment in Phanerozoic shales. Instead, the cyclic covariation of total organic carbon, delta N-15, delta C-13 and molybdenum are explained by the feedback between high levels of primary productivity, basin redox and the biogeochemical... |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00637/74942/75766.pdf |
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