Russian Regional Carboniferous Stratigraphy

Several existing schemes for Carboniferous stratigraphy officially adopted in regions of the Russian Federation are summarized and discussed. These regions with different geological histories and distinct depositional settings include the Moscow Basin, the Urals, North Timan, Siberia, the Kuznetsk Basin, the Mongol-Okhotsk Region, and the Verkhoyansk-Okhotsk Region, and Kolyma-Omolon Region. Region. Broad correlations based on macro- and microfossils are possible between the regions, while all regional schemes are correlated to the official Russian General Stratigraphic Scheme for the Carboniferous, using zonations based on orthostratigraphic fossils. The Russian General Stratigraphic Scheme is correlated to the International Stratigraphic Scale using ammonoids, conodonts, foraminifers and palynomorphs.

ON THE POSITION OF THE BOUNDARY BETWEEN THE MOSCOVIAN AND KASIMOVIAN GLOBAL STAGES OF THE CARBONIFEROUS IN THE DONETS BASIN

Detailed new data on paleontology and stratigraphy were obtained in the process of fulfilling the tasks of the International Carboniferous Subcommission on definition of the scopes of the Moscovian and Kasimovian global stages and the precise position of the boundary between them. The analysis of these data has shown that the position of this boundary in the type area and in the other regions needs the revision. Recently the investigation of the conodonts from the Moscovian–Kasimovian boundary deposits in the Donets Basin revealed that the boundary between the Moscovian and Kasimovian stages in the official Ukrainian Carboniferous Stratigraphic Scheme does not correspond to this boundary in the type area of these stages in the Moscow Basin. To correct this situation the lower boundary of the Kasimovian in the Ukrainian Scheme must be downgraded by two conodont zones — Swadelina subexcelsa and Sw. makhlinae. To update this boundary in the type area to fulfill the task of the Carboniferous Subcommission four conodont species were proposed as potential index-species for the definition of the boundary between the Moscovian and Kasimovian global stages. These conodont species are as follows Sw. subexcelsa, Idiognathodus sagittalis, I. turbatus and I. heckeli. One of these species, which is selected, will be used as a marker of the studied boundary. None of these species is officially selected as a marker. If Sw. subexcelsa will be selected, the position of the Moscovian–Kasimovian boundary will remain at the present position. In this case this boundary in the Donets Basin has to be downgraded by two conodont zones. If one of three Idiognathodus will be selected, this boundary in the type area will be upgraded by one and a half regional substage. In the Donets Basin it will be upgraded by less than a cycle. Keywords: Carboniferous, stratigraphy, conodonts, extinction event, index-­species.

Stratigraphic correlation of the Permian-Triassic red beds constrained by detrital zircon geochronology: Moscow basin, East European platform

<p>There's no doubt that nowadays detrital zircon U-Pb geochronology is actually required method of sedimentary basins analysis. Furthermore, this approach may have a lot of applications, such as a stratigraphic correlation. Here we present the first results of U–Pb LA–ICP–MS dating of detrital zircon from the Permian-Triassic red beds located within the Moscow Basin of the East European platform. Two outcrops have been studied: the Zhukov Ravine P/T boundary reference section and the Nedubrovo strata with uncertain stratigraphic position (uppermost Permian or lower Triassic?).</p><p>U–Pb ages of detrital zircon grains have been obtained for two samples – the Upper Permian and Lower Triassic age, which were taken in the proximity to the Permian–Triassic boundary in the Zhukov Ravine. Corresponding age distributions show contrasting provenance of the studied sedimentary rocks, pointing out that principal change in source of clastic material occurred on the Paleozoic-Mesozoic boundary. It means that detrital zircon U–Pb geochronology can be used as an additional independent tool for stratigraphic correlation of the Permian-Triassic red beds, at least within the Moscow Basin. We demonstrate this in the case of the Nedubrovo section with debated (Permian or Triassic?) stratigraphic position: the obtained data on detrital zircons persuasively suggests Early Triassic age of the Nedubrovo strata.</p><p>This study is supported by the Russian Foundation for Basic Research (project no. 18-05-00593).</p>

Geochemical alterations of forest soils in post-mining area (the Moscow brown coal basin, Russia)

<p>Long-term coal mining in the Moscow basin has a complex negative impact on soils of natural ecosystems. Due to underground mining operations at coal deposits in the Moscow basin spoil heaps with a high content of iron sulfides and aluminosilicates were formed. Active oxidation of sulfides in waste dumps results in the producing of toxic sulfuric acid and iron sulfates (Nordstrom and Alpers 1999). Acid mine drainage (AMD) of sulfuric acid, Al and Fe sulfates as well as pyritized material, entering from eroded spoil heaps, results in physico-chemical and morphological changes in soil properties. On foreslopes around spoil heaps technogenically transformed soils are common. Our study aimed at evaluation of post-mining geochemical transformation of soil properties, which is adjacent to spoil heaps.</p><p>We observed two key sites within abandoned coal mines in the western part of Moscow basin (the Tula region, Russia). Prevailing natural soils are Umbric Albeluvisols and Umbric Podzols (sod-podzolic soils and sod-podzols in Russian classification). Soils with transformed water regime are formed in mine subsidence.</p><p>Soil samples and displaced soil solutions (by ethanol) were analysed for acid-base properties, content and composition of readily soluble salts, content of Fe<sup>2+</sup> and Fe<sup>3+</sup>, H<sup>+</sup> and Al<sup>3+</sup>, composition of exchangeable cations, total content of S, Al, Fe, heavy metals (HM) and organic carbon).</p><p>Properties of newly formed soils differ significantly from natural soils. We identified the transformation of the composition of soil solutions. The basic geochemical processes in contaminated soils are as follows: the acidification and changes in the composition of ions in soil solutions from bicarbonate-sulfate-calcium to sulfate-iron-aluminum-calcium; cation exchange, leading to the replacement of Cа<sup>2+ </sup>and Mg<sup>2+</sup> ions by Al<sup>3+</sup> and H<sup>+</sup> ions, and, probably, by Fe<sup>2+</sup> and Fe<sup>3+</sup> in soil ion-exchange complex. Transformed soils were characterized by a very low degree of base saturation (less than 20%). Estimation of the saturation degree of liquid phases of transformed soils with poorly soluble compounds revealed a high oversaturation of soil solutions with Fe<sup>3+</sup> and Al<sup>3+</sup> hydroxides. The total content of HM in transformed soil profiles were lower than background values due to the removal of soil reserves of elements in highly acidic conditions (pH<4.5). Among the morphological features of transformed forest soils intensification of podzolization process (acid hydrolysis of fine clay fractions of aluminosilicates) as well as; ferrugination (segregation of ferric iron, mainly in amorphous or poorly crystallized forms) and carbon enrichment of coal origin can be noted. Due to AMD impact that had destroyed fine clay minerals, numerous clarified areas were formed, composed of quartz and feldspar. Semi-hydromorphic soils with signs of gleying and peat accumulation were formed in subsidence areas.</p><p> </p>

Changes in soils of Central Russian forest-steppe under the impact of sulfur coal mining (the Moscow basin)

<p>In mining areas of the Moscow brown coal basin, soils are impacted by acid mine drainage (AMD), solid sulfide-bearing mine wastes and carbonaceous particles. Spoil heaps of overburden rocks and subsidence areas over the mined space are formed at abandoned mine fields. Most of the spoil heaps have not been remediated and erode intensively due to physical and chemical properties of waste rocks. AMD of sulfuric acid, Al and Fe sulfates as well as pyritized material, entering from the eroded spoil heaps, results in morphological changes in soil properties. Other environmental concern is the formation of subsidence areas over the mined space due to the dewatering of abandoned сoal mines. It results in alteration of the soil water regime. On deluvial and proluvial dump tailings around spoil heaps technogenically transformed soils are common.</p><p>The aim of the study was to examine the post-mining evolution of natural soils under the impact of supply of tecnhogenic material from the spoil heaps and changes of the terrain in abandoned sulfur coal mining areas.</p><p>We investigated two key sites within abandoned coal mine fields in the central part of the Moscow basin (the Tula region, Russia). Prevailing natural soils are Greyic Phaeozems and Haplic Chernozems (WRB 2014) (Grey forest and Leached Chernozems in Russian classification).</p><p>Soil samples and soil solutions were analysed for (acid-base properties, content and composition of readily soluble salts, content of Fe<sup>2+</sup> and Fe<sup>3+</sup>, H<sup>+</sup> and Al<sup>3+</sup>, carbonates, composition of exchangeable cations, particle size content, total content of S, Al, Fe and organic carbon). Soil solutions were displaced by ethanol (Ishcherekov-Komarova method, Russia) (Snakin et al. 2001). The level of saturation of soil solutions by gypsum, iron and aluminum hydroxides was evaluated.</p><p>Properties of newly formed soils differ significantly from natural soils. We identified the transformation of the composition of soil solutions. Key geochemical processes at mine sites in soils were:  (1) acidification and Fe-Al-SO<sub>4</sub> salinization of soil profile along with the increment in H<sup>+</sup> and Al<sup>3+</sup> ions content; (2) cation exchange, leading to displacement of Cа<sup>2+ </sup>and Mg<sup>2+</sup> ions by Al<sup>3+</sup>, H<sup>+</sup>, Fe<sup>2+ </sup>and, perhaps, by Fe<sup>3+ </sup>in soil ion-exchange complex; (3) alteration of radial differentiation of organic carbon and carbonates in soils; (4) mineral transformations.</p><p>  Semi-hydromorphic soils with signs of gleying and peat accumulation were formed in subsidence areas. In Greyic Phaeozems the intensification of podzolization process could be noted. In Haplic Chernozems gypsum neoformations (neogypsans) were observed. Post-technogenic soils have no analogues in natural forest-steppe landscapes of the Russian Plain.</p><p> </p><p> </p>

New data on the mineral composition of unique rhenium U-Mo-Re ores of the Briketno-Zheltukhinskoe deposit in the Moscow Basin

Data on the mineral composition of Re-rich U-Mo-Re ores from the Briketno-Zheltukhinskoe deposit that were obtained using state-of-the art analytical equipment are presented for the first time. The deposit is confined to Lower Carboniferous (Missisipian) coal-bearing strata in the Moscow Basin. The found mineral association of Re ores has made it possible to identify the most likely rhenium carrier minerals. They are Mo-containing minerals: wulfenite, ilsemannit, ferrimolybdite, and kamiokite. Re is hosted by them and partly replaces Mo in the structure. The association of Re with U, Mo, Se, Ag, V, Tl, As, Ni, Co, and dispersed organic matter is recorded.