Ferruginous microbialite blooms of the Miaolingian (Cambrian) in the southern North China Craton: a response to the volcanic event?
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[1] Henan Polytechnic University
Henan Polytechnic University
China
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[2] Nanjing Institute of Geology and Paleontology
Nanjing Institute of Geology and Paleontology
China
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- Localización: Carbonates and Evaporites, ISSN 0891-2556, Vol. 35, Nº. 4, 2020
- Idioma: inglés
- Enlaces
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Resumen
Ferruginous microbialites of the Mantou Formation (Miaolingian, Cambrian) in the southern North China Craton are available for investigation of their formation mechanisms. The ferruginous microbial structures are existing in a deepening upwards sequence with occurrences of the oolitic limestone, oncolite, stromatolite, and thrombolite in ascending order. The ooids larger than 2 mm in diameter are made up of repeated alternations of bright coarse-grained calcites and homogeneously ferruginous fine-grained calcites. Oncoids and stromatolites comprise alternations of coarse-grained calcite and Girvanella-laminae. Thrombolites consist of massive Girvanella-clots and micritic interstitial sediments. Several filaments with ferruginous sheathes in the laminae/clots are interpreted as the remains of iron-oxidizing bacteria. Mineral components of ferruginous microbialites are mainly calcite, quartz, plagioclase, microcline, clay minerals, and some iron minerals. The sharp increases of ferruginous volcanogenic materials in the strata are ascribed to the contemporaneous ash fall. The elevated nutrient concentration dramatically spurred the cyanobacterial bloom and then caused an extensive eutrophication. Microaerophilic iron-oxidizing bacteria then thrived therein promoting oxidize ferrous solution into iron oxide/oxyhydroxide. The widespread Miaolingian ferruginous microbialites indicated the proliferation of microbial communities in the aftermath of contemporaneous volcanism in the southern North China Craton.
