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See detailIron microbial mats in Modern and Phanerozoic environments
Baele, J. M.; Boulvain, Frédéric ULg; De Jong, J. et al

in Instruments, Methods and Missions for Astrobioçlogy- Proc. of SPIE (2008), 7097

The recognition of iron microbial mats in terrestrial environments is of great relevance for the search for extraterrestrial life, especially on mars where significant iron minerals were identified in the ... [more ▼]

The recognition of iron microbial mats in terrestrial environments is of great relevance for the search for extraterrestrial life, especially on mars where significant iron minerals were identified in the subsurface. Most researches focused on very ancient microbial mats (e.g. BIFs) since they formed on Earth at a time where similar conditions are supposed to have prevailed on Mars too. However, environmental proxies are often difficult to use for these deposits on Earth which, in addition, may be heavily transformed due to diagenesis or even metamorphism. Here we present modern and phanerozoic iron microbial mats occurrences illustrating the wide variety of environments in which they form, including many marine settings, ponds, creeks, caves, volcanoes, etc. Contrarily to their Precambrian counterparts, Modern and Phanerozoic deposits are usually less affected by diagenesis and the environmental conditions likely to be better constrained. Therefore, their investigation may help for the search for morphological and geochemical biosignatures (e.g. iron isotopes) in ancient iron microbial occurrences on Earth but also on other Planets. In particular, many of the case studies presented here show that microstromatolithe-like morphologies may be valuable targets for screening potential biosignatures in various rock types. [less ▲]

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See detailRecognition and implication of tectonic loading-induced reheating in the northern Variscan front (Belgium and northern France), based on an illite Kubler index and oxygen isotope study
Han, G.; Yans, J.; Goudalier, M. et al

in International Journal of Earth Sciences (2003), 92(3), 348-363

Illite Kubler index (KI) and oxygen isotope (brachiopods and micrites) investigations have been performed on more than 300 Frasnian limestones sampled in one borehole and numerous outcrops in the Dinant ... [more ▼]

Illite Kubler index (KI) and oxygen isotope (brachiopods and micrites) investigations have been performed on more than 300 Frasnian limestones sampled in one borehole and numerous outcrops in the Dinant Synclinorium (Belgium, northern France) of the northern Variscan front. The illite Kubler index and delta(18)O data of a 3-km-thick, tectonically repeated Frasnian series from the Focant borehole are compared with their surrounding surface correspondents and document in-situ reheating induced by Variscan tectonic loading, which post-dated sedimentary burial alteration. The boundary between these two thermal processes (sedimentary burial and tectonic loading) on the Focant profile corresponds to an important location where the heat induced by the tectonic loading was equivalent to that Frasnian strata suffered during maximum sedimentary burial. Mainly based on this knowledge and on a former conodont colour alteration index study, the thickness of the eroded thrust sheet in the Focant area is estimated to be around 3,000 m. Oxygen isotopic exchange in these Frasnian closed carbonate systems, occurring under highest-grade diagenesis and anchimetamorphism, records two events. Brachiopods present a quite different and more homogeneous pattern, due to their higher resistance to heat alteration. These thermal events caused both delta(18)O records to become increasingly lighter than the presumed original seawater signature. The comparison between KI and delta(18)O profiles indicates that illite KI analysis is more appropriate than delta(18)O in highlighting the temperature variations in the burial metamorphism at the periphery of orogenic belts. [less ▲]

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See detailIron microbial communities in Belgian Frasnian carbonate mounds
Boulvain, Frédéric ULg; De Ridder, C.; Mamet, B. et al

in Facies (2001), 44

The Belgian Frasnian carbonate mounds occur in three stratigraphic levels in an overall backstepping succession. Petit-Mont and Arche Members form the famous red and grey “marble” exploited for ornamental ... [more ▼]

The Belgian Frasnian carbonate mounds occur in three stratigraphic levels in an overall backstepping succession. Petit-Mont and Arche Members form the famous red and grey “marble” exploited for ornamental stone since Roman times. The evolution and distribution of the facies in the mounds is thought to be associated with ecologic evolution and relative sea-level fluctuations. Iron oxides exist in five forms in the Frasnian mounds; four are undoubtedly endobiotic organized structures: (1) microstromatolites and associated forms (blisters, veils...), possibly organized in “endostromatolites”; (2) hematitic coccoids and (3) non dichotomic filaments. The filaments resemble iron bacteria of the Sphaerotilus- Leptothrix "group"; (4) networks of dichotomic filaments ascribable to fungi; (5) a red ferruginous pigment dispersed in the calcareous matrix whose distribution is related to the mound facies type. The endobiotic forms developed during the edification of the mounds, before cementation by fibrous calcite. The microbial precipitation of iron took place as long as the developing mounds were bathed by water impoverished in oxygen. [less ▲]

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See detailIron Oxidation and Deposition in the Biofilm Covering Montacuta ferruginosa (Mollusca, Bivalvia).
Gillan, D.; Warnau, M.; De Vrind-De Jong, E. W. et al

in Geomicrobiology Journal (2000), 17(2), 141-150

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See detailThe stratigraphy of the Middle Devonian in Belgium
Bultynck, P; Coen-Aubert, M; Godefroid, J et al

in Memoirs of the Geological Survey of Belgium (1991), 30

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See detailLes calcaires laminaires du Givétien Inférieur du Bassin de Dinant : témoins paléogéographiques et paléoclimatiques
Préat, A.; Boulvain, Frédéric ULg

in Annales de la Société Géologique du Nord (1987), CVI

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See detailEtude sédimentologique des calcaires du Givétien Inférieur d'Olloy-sur-Viroin (bord Sud du Bassin de Dinant, Belgique)
Préat, A.; Ceuleneer, G.; Boulvain, Frédéric ULg

in Annales de la Société Géologique du Nord (1987), CVI

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See detailLes calcaires laminaires du Givétien Supérieur du bord Sud du Bassin de Dinant (Belgique, France. témoins d'une évolution paléoclimatique
Boulvain, Frédéric ULg; Préat, A.

in Annales de la Société Géologique de Belgique (1986), 109

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See detailEtude sédimentologique des calcaires givétiens à Vaucelles (Bord Sud du Synclinorium de Dinant)
Préat, A.; Boulvain, Frédéric ULg

in Annales de la Société Géologique de Belgique (1982), 105

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See detailSur la structure des Labyrinthoconidae (Algues problématiques, Givétien)
Mamet, B.; Préat, A.; Boulvain, Frédéric ULg

in Annales de la Société Géologique de Belgique (1982), 105

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