The Ge/Si ratio as a tool to recognize biogenic silica in chert - 30/05/13
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Abstract |
Germanium and silicon, dissolved in seawater, are considered to be incorporated into biogenic opal with no or little fractionation, which permitted to use diatoms as reliable recorders of seawater Ge/Si. Does some fractionation occur during diagenesis, preventing the use of Ge/Si in ancient sediments? We examined the Ge/Si ratio of fossil sponges and flint nodules of the Cretaceous Chalk Formation of northern France. Though disputed, silica in this formation is considered to originate from sponges. No fractionation is observed between sponges and diagenetic flints, which allows us to observe whether Ge/Si bears a biogenic or detrital signature. We may thus confirm that sponges were the main silica supplier during the chalk deposition. The Ge/Si ratio may be used to identify a biogenic signature in cherts where the origin of silica is dubious.
Le texte complet de cet article est disponible en PDF.Keywords : Germanium, Flint, Biosilica, Sponges, Diagenesis, Chalk
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Vol 345 - N° 3
P. 160-165 - mars 2013 Retour au numéroBienvenue sur EM-consulte, la référence des professionnels de santé.
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