Nodules in carbonaceous sediments of the Southern Tunguska basin

Pioneer results of the comprehensive analysis of nodules from the Upper Paleozoic coaliferous association and the underlying Middle Paleozoic sequence in the southern Tunguska Basin (Siberian Craton) suggest the following: (1) sediments underlying the coaliferous association contain two (siliceous and carbonate) types of normal nodules and one type of allogenic nodules (redeposited chalcedony nodules in the kaolin-itechalcedony unit of the Beloyarsk Formation); (2) the coaliferous association includes four (calcite, siderite, pyrite, and goethite) types of nodules; (3) each nodule type is confined to a specific genetic type of sediment; e.g., siliceous nodules are confined to lagoonal sediments; calcite nodules, to lacustrine and lacustrine-boggy sediments; siderite nodules, to lacustrine-boggy and boggy sediments; pyrite nodules, to boggy sediments; and goethite nodules, to alluvial sediments; (4) the formation of goethite nodules is mainly related to the erosion and redeposition of siderite nodules; (5) the coefficient of carbon concentration shows a distinct positive correction with the coefficient of nodule content; (6) nodules appeared in the coaliferous association during diagenesis and epigenesis; the calcite and pyrite nodules are enriched in sandy material, as suggested by the high content of insoluble residue; (7) combustion of coal seams promoted the melting of the adjacent siderite nodules and the formation of magnetite ores; consequently, the thermally altered mudstones, siltstones, and sandstones were transformed into a high-quality building material that is used as road fill.