Biogeochemical formation of calyx-shaped carbonate crystal fans in the subsurface of the Early Triassic seafloor

Détails

ID Serval
serval:BIB_D8B0273CF067
Type
Article: article d'un périodique ou d'un magazine.
Sous-type
Etude de cas (case report): rapporte une observation et la commente brièvement.
Collection
Publications
Titre
Biogeochemical formation of calyx-shaped carbonate crystal fans in the subsurface of the Early Triassic seafloor
Périodique
Gondwana Research
Auteur(s)
Heindel Katrin, Richoz Sylvain, Birgel Daniel, Brandner Rainer, Klügel Andreas, Krystyn Leopold, Baud Aymon, Horacek Micha, Mohtat Tayebeh, Peckmann Jörn
ISSN
1342-937X
Statut éditorial
Publié
Date de publication
2015
Volume
27
Numéro
2
Pages
840-861
Langue
anglais
Résumé
The Kuh e Dena sedimentary section in Iran developed on the southwestern margin of the Neotethys Ocean. The fossil- and bioturbation-lean Early Triassic section (Late Dienerian to Early Smithian) is typified by finely laminated calcareous shales that are interbedded with laterally extending carbonate beds, which are mostly composed of calyx-shaped carbonate crystal fans. The calyxes consist of fibrous crystals that apparently formed within the subseafloor in soft, water-saturated sediment by displacive growth. Rare earth element and yttrium patterns indicate that calyx-shaped crystals precipitated from anoxic pore waters. Biomarker patterns of the carbonate beds reveal major input of lipids from prokaryotes that typically occur within layered benthic microbial mats (i.e., cyanobacteria, anoxygenic phototrophic bacteria, sulphate-reducing bacteria, and methanogenic archaea). Along their length, the fibrous crystals of the calyxes reveal a trend of increasing δ13Ccarb values (from 2.7 to 3.3‰), suggesting that archaeal methanogenesis affected the carbonate pool. Apart from the putative benthic prokaryotes, molecular fossils of halophilic, most likely planktic, archaea were detected in the carbonate beds. Low pristane to phytane ratios (≤0.8) and the presence of halophilic archaea are in accord with the lack of bioclasts and bioturbation, which likely reflects increased salinities. The former presence of a benthic microbial mat with cyanobacteria underlain by anoxygenic phototrophic bacteria, sulphate-reducing bacteria, and methanogenic archaea is in accordance with studies on living microbial mats in hypersaline, low-oxygen marine environments. The Early Triassic subseafloor seems to have been a sink for carbon, driven by biologically-induced formation of secondary, diagenetic carbonate.
Mots-clé
Diagenetic carbonate, Subseafloor, Lipid biomarkers, Rare earth elements, End-Permian extinction
Création de la notice
30/10/2019 18:17
Dernière modification de la notice
31/10/2019 18:09
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