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Complex modern micro- and spectroscopic methods for study of siderite concretions in the Lower Carboniferous terrigenous strata on the Kozhym River (Subpolar Urals) have shown that its formation was caused by destruction of clay minerals due to the activity of bacterial communities. The abundance of these bacteria was caused by gas–fluid seeps and bacterial methanogenesis processes in bottom deposits. In basins with normal marine fauna, this led to local desalination, hydrogen sulfide contamination, mass collapse of primary organisms, and the development of element-specific bacteria. The occurrence of these bacteria caused the formation of specific authigenic mineralization in the concretion of sideritic bacteriolites: the framboidal pyrite, sphalerite, galenite, barite, sulfoselenides, and tellurides. 相似文献
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The article is dedicated to the lithological-paleoecological analysis of Upper Devonian fenestral limestones from different areas of the Timan-northern Ural region, which reflect paleogeographic settings from the coastal zone to the marginal part of the shelf. It is established that their main structural elements are represented by fenestrae, peloids, calcispheres, and occasional microzoo- and phytobenthos remains. The presence of a dark micritic envelope on calcispheres is their specific textural feature. The envelope of calcispheres represents mineralized vegetable mucus, which reflects their planktonic type of dwelling. These structures include representatives of radiolarian skeletons, Charophyceae and Chlorophyceae algae, and foraminiferal tests. The trophic system consists of five levels. Carbonate sediments accumulated in relatively shallowwater and lagoonal settings occupied mostly by tidal and shallow-water subtidal microbial mats. In these lagoons, intermittently limited circulation stimulated the formation of anoxic conditions in bottom waters. Development of anoxic conditions in the bottom water layer, sulfate reduction, and freshwater influence determined the formation of a specific paleocoenosis of fenestral limestones, which could not form biogenic frameworks. 相似文献
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A. I. Antoshkina N. N. Ryabinkina O. V. Valyaeva 《Lithology and Mineral Resources》2017,52(2):111-124
The paper presents the lithological, mineralogical, and geochemical characteristics of the composition, structure, and organic matter of siderite nodules and host mudstones in the Lower Carboniferous (Tournaisian–Visean) siderite-bearing sequence exposed along the Kozhym River on the western slope of the Subpolar Urals. The obtained results revealed that organic matter in the mudstones is dominated by C16 and C18 n-alkanes, suggesting a significant microbial activity in the sedimentation environment. The formation of nodules was promoted by the activity of diverse bacterial communities, the abundance of which was related to processes of methanogenesis in bottom sediments owing to gaseous fluid seepages that promote the saturation of sediments with methane and the flourishment of bacterial colonies. Such processes in a marine basin led to the local freshening or some salinization of water and the development of euxinic setting and specific bacteria. Consequently, siderite nodules therein are marked by bacteriomorphic textures and specific authigenic mineralization (framboidal pyrite, sphalerite, galena, sulfoselenides, and tellurides). Bacteria utilized the substrate of the redeposited weathered crust, resulting in a large-scale formation of the nodular siderite. 相似文献
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Doklady Earth Sciences - The complex of modern physical methods for studying authigenic carbonate crusts in the Miocene bryozoan bioherms of the Kazantip Cape (Kerch Peninsula) has made it possible... 相似文献
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