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| Bankole, Olabode M.; El Albani, Abderrazak; Meunier, Alain; Rouxel, Olivier; Gauthier-lafaye, Francois; Bekker, Andrey. |
| Red beds are extensively used as evidence for an oxygenated atmosphere in the Paleoproterozoic. Red beds in the unmetamorphosed, ca. 2.15 Ga FA Formation of the Franceville Basin, Gabon were geochemically, petrographically, and mineralogically characterized to constrain the process of their formation and their relationship to atmospheric oxygenation in the early Paleoproterozoic. Petrographic observations indicate that ferric oxides are dispersed in clay filling intergranular pores and along platy cleavage in altered phyllosilicates. Grain-coating hematite is generally rare to absent in most samples suggesting hematite precipitation after sediment deposition and during burial diagenesis. Textures and geochemical data suggest that iron was likely sourced... |
| Tipo: Text |
Palavras-chave: Red beds; Atmospheric oxygenation; Diagenesis; Iron isotopes; Franceville Basin; Oldest sandstone-type U deposit. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00358/46966/48278.pdf |
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| El Albani, Abderrazak; Bengtson, Stefan; Canfield, Donald E.; Riboulleau, Armelle; Bard, Claire Rollion; Macchiarelli, Roberto; Pemba, Lauriss Ngombi; Hammarlund, Emma; Meunier, Alain; Mouele, Idalina Moubiya; Benzerara, Karim; Bernard, Sylvain; Boulvais, Philippe; Chaussidon, Marc; Cesari, Christian; Fontaine, Claude; Chi-fru, Ernest; Garcia Ruiz, Juan Manuel; Gauthier-lafaye, Francois; Mazurier, Arnaud; Pierson-wickmann, Anne Catherine; Rouxel, Olivier; Trentesaux, Alain; Vecoli, Marco; Versteegh, Gerard J. M.; White, Lee; Whitehouse, Martin; Bekker, Andrey. |
| The Paleoproterozoic Era witnessed crucial steps in the evolution of Earth's surface environments following the first appreciable rise of free atmospheric oxygen concentrations similar to 2.3 to 2.1 Ga ago, and concomitant shallow ocean oxygenation. While most sedimentary successions deposited during this time interval have experienced thermal overprinting from burial diagenesis and metamorphism, the ca. 2.1 Ga black shales of the Francevillian B Formation (FB2) cropping out in southeastern Gabon have not. The Francevillian Formation contains centimeter-sized structures interpreted as organized and spatially discrete populations of colonial organisms living in an oxygenated marine ecosystem. Here, new material from the FB2 black shales is presented and... |
| Tipo: Text |
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| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00202/31356/29754.pdf |
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