References of "Cornet, Yohan"
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See detailPhototrophic green algae in Mid-Proterozoic oceans
Sforna, Marie-Catherine ULiege; Loron, Corentin ULiege; Demoulin, Catherine ULiege et al

Poster (2020, January)

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See detailNew insights on the paleobiology, biostratigraphy and paleogeography of the pre-Sturtian microfossil index taxon Cerebrosphaera
Cornet, Yohan ULiege; François, Camille; Compère, Philippe ULiege et al

in Precambrian Research (2019)

Important biological and geological events occurred during the early Neoproterozoic. Among diversifying eukaryotic assemblages, populations of the distinctive robust organic-walled vesicular microfossils ... [more ▼]

Important biological and geological events occurred during the early Neoproterozoic. Among diversifying eukaryotic assemblages, populations of the distinctive robust organic-walled vesicular microfossils (acritarchs) Cerebrosphaera occur as a short-lived taxon in several late Tonian to early Cryogenian worldwide successions. Here we report the first occurrence of this taxon in the Bouenza Subgroup (Republic of the Congo), enlarging its paleogeographic distribution and biostratigraphic significance. We also attempt to determine its biological affinities, using a combined analytical approach on specimens from the Kanpa and Hussar Formations, Australia, and from the Svanbergfjellet Formation, Spitsbergen. Morphological and quantitative analyses were performed using light microscopy and scanning electron microscopy, on more than 200 specimens and 9 specimens, respectively. The analyses show fine-scale morphological details and a morphological continuum between the former species Cerebrosphaera ananguae and Cerebrosphaera buickii, confirming their synonymy as proposed by a recently revised taxonomy. These observations also highlighted the presence of a previously mentioned envelope, formerly described and illustrated here for the first time. Ultrastructural analyses performed with TEM revealed two types of complex (bilayered and trilayered) wall ultrastructures. The molecular structure and thermal maturity of the organic walls estimated using Infrared and Raman microspectroscopies, reveal the highly aromatic composition of Cerebrosphaera’s wall biopolymer with short/highly branched aliphatic chains unlike known biopolymers. The complex morphology, ultrastructure and recalcitrant chemistry, combined with the large size of Cerebrosphaera confirm its eukaryotic nature. Comparison with possible modern analogues permits to suggest an affinity to stem metazoan eggs. This hypothesis is consistent with estimates from molecular clocks and, if confirmed, would provide an older evidence for stem metazoans than the Cryogenian biomarker and Ediacaran body fossil records. Our study reveals that Cerebrosphaera populations are important for the late Proterozoic biostratigraphy, but also participated to the Neoproterozoic diversification eukaryotes in connected oceans. [less ▲]

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See detailRaman microspectroscopy, bitumen reflectance and illite crystallinity scale: comparison of different geothermometry methods on fossiliferous Proterozoic sedimentary basins (DR Congo, Mauritania and Australia)
Kabamba Baludikay, Blaise ULiege; François, Camille ULiege; Sforna, Marie-Catherine ULiege et al

in International Journal of Coal Geology (2018)

Sedimentary rocks containing microfossils are crucial archives to reconstitute early life evolution on Earth. However, the preservation of microfossils within rocks depends on several physico-chemical ... [more ▼]

Sedimentary rocks containing microfossils are crucial archives to reconstitute early life evolution on Earth. However, the preservation of microfossils within rocks depends on several physico-chemical factors. Among these factors, the thermal evolution of the host rocks can be decisive. Here, we investigated carbonaceous shale samples containing exquisitely preserved organic-walled microfossils assemblages from three Proterozoic shallow marine sedimentary sequences: the Mbuji-Mayi Supergroup (Democratic Republic of Congo, Congo Basin), the Atar/El Mreïti Group (Mauritania, Taoudeni Basin) and the Kanpa Formation (Australia, Officer Basin). Thermal maturity of these rock samples is evaluated with Raman geothermometry, Raman reflectance, solid bitumen reflectance, illite crystallinity and Thermal Alteration Index. The comparison of results coming from these different techniques validates the use of Raman reflectance on Proterozoic carbonaceous material and especially for poorly-ordered carbonaceous material. We show that extracted kerogen (microfossils and amorphous organic material) is more accurate to estimate the thermal maturity of low-grade temperature Proterozoic sequences than kerogen in thin section. All techniques provide consistent range of temperatures except for Raman geothermometry, giving slightly higher estimates. Raman reflectance appears to be a fast, robust and non-destructive tool to evaluate the thermal maturity of poorly-organized carbonaceous material from Proterozoic rocks. [less ▲]

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See detailFTIR micro-spectroscopy: a tool to identify microfossils
Cornet, Yohan ULiege; Javaux, Emmanuelle ULiege

Conference (2018, March 20)

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See detailUse of different geothermometry methods on fossiliferous Proterozoic sediments to constrain thermal maturity of microfossils and sedimentary basins (DRCongo, Mauritania & Australia)
Kabamba Baludikay, Blaise ULiege; François, Camille ULiege; Sforna, Marie-Catherine ULiege et al

Poster (2018, March)

Evaluate the thermal maturity of old sedimentary basins containing microfossils is crucial to reconstruct early life evolution on Earth. Here, we investigate carbonaceous shale samples containing ... [more ▼]

Evaluate the thermal maturity of old sedimentary basins containing microfossils is crucial to reconstruct early life evolution on Earth. Here, we investigate carbonaceous shale samples containing exquisitely preserved organic-walled microfossil assemblages from three Proterozoic shallow marine sedimentary sequences: the Mbuji-Mayi Supergroup (Democratic Republic of Congo, Congo Basin), the Atar/El Mreïti Group (Mauritania, Taoudeni Basin) and the Kanpa Formation (Australia, Officer Basin). By comparison with Raman geothermometry, solid bitumen reflectance, illite crystallinity and Thermal Alteration Index, we evaluate and validate the use of Raman reflectance on Proterozoic carbonaceous material and especially for poorly-ordered carbonaceous material. We show that extracted kerogen (microfossils and amorphous organic material) is more accurate to estimate the thermal maturity of low-grade temperature Proterozoic sequences than kerogen in thin section. All the techniques provide consistent range of temperatures except for Raman geothermometry, giving slightly higher estimates. Raman reflectance appears to be a fast and robust tool to evaluate the thermal maturity of poorly-organized carbonaceous material from Proterozoic rocks and by extension could be used to assess the thermal evolution of a sedimentary successions. This work was supported by the ERC StG ELITE FP7/308074; BELSPO IAP PLANET TOPERS, and the Marie-Curie Cofund program. [less ▲]

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See detailEarly eukaryotes: insights from microanalyses of proterozoic microfossils
Cornet, Yohan ULiege; Beghin, Jérémie ULiege; Kabamba Baludikay, Blaise ULiege et al

in Goldschmidt Abstracts, 2017 (2017, August)

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See detailPLANET TOPERS: Planets, Tracing the Transfer, Origin, Preservation, and Evolution of their ReservoirS
Dehant, Véronique ULiege; Kabamba Baludikay, Blaise ULiege; Beghin, Jérémie ULiege et al

in Origins of Life and Evolution of the Biosphere (2016), DOI 10.1007/s11084-016-9488

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See detailMicroanalyzes of remarkable microfossils of the Late Mesoproterozoic–Early Neoproterozoic
Cornet, Yohan ULiege; Beghin, Jérémie ULiege; Kabamba Baludikay, Blaise ULiege et al

in European Geosciences Union General Assembly 2016 Vienna, Austria, 2016 (2016)

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See detailEtude de faisabilité : Détection de sites archéologiques et cartographie géomorphologique en Syrie par l'exploitation d'images des satellites ERS1 et SPOT2 intégrées dans un système d'information géographique
Closson, Damien; Ozer, André ULiege; Tunca, Önhan ULiege et al

in Actualité scientifique (1999, June 14)

Dans cette étude, on a pour objectifs de mesurer la contribution de la télédétection à la connaissance du système paléogéographique et de cibler la ou les partie(s) du spectre électromagnétique ... [more ▼]

Dans cette étude, on a pour objectifs de mesurer la contribution de la télédétection à la connaissance du système paléogéographique et de cibler la ou les partie(s) du spectre électromagnétique susceptible(s) de convenir le mieux en prospection archéologique. Une base de données cartographiques est réalisée sur une zone-témoin syrienne centrée sur les sites de Terqa (3e/2e millénaire av. J.-C.) et Doura Europos (Haut-Empire Romain). On montre que la connaissance de l'affectation du sol participe à la mise en évidence d'éléments géomorphologiques remarquables ainsi qu'à la découverte des relations entre tous les éléments du paysage. Le croisement des images avec des données thématiques permet d'ajuster et de compléter des informations et d'effectuer des prévisions. Les images satellitaires sont rarement d'une utilité directe dans les travaux de terrain à cause de leur échelle. Elles fournissent cependant des spatiocartes qui donnent un autre point de vue que les cartes topographiques généralement utilisées. En fournissant des données originales, elles contribuent à améliorer la réflexion sur le problème de la localisation de sites à prospecter. Des deux capteurs analysés (RSO de ERS-1, HRV de SPOT-2), celui du satellite SPOT-2 fournit les images qui conviennent le mieux pour cet usage. L'étude est cependant beaucoup trop limitée pour diminuer la valeur des images radars. [less ▲]

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