Methane release into mine workings and the atmosphere poses a serious environmental and safety risks. This study examines the composition and stable isotope geochemistry of coalbed methane in a hard coal mine of the Upper Silesian Coal Basin (Poland), with emphasis on gas migration pathways from the coal seam through mine workings and ventilation shaft to the atmosphere. Methane concentrations decrease progressively with distance from the active excavation zone toward the exhaust shaft. In addition to CH4 and CO2, the coalbed gas contained notable amounts of nitrogen heterocyclic compounds, sulfur-bearing species, and chlorinated gases, depending on the sampling location and temporal window. Geochemical results reveal a strong link between gas migration and isotopic variability in the underground environment. Zones of methane accumulation, commonly associated with bends in return airways, showed enrichment in 13C, consistent with diffusive fractionation. Variations in CH4 and corresponding isotope effects during coal transport indicate multiple gas origins within the coal seam. Isotope signatures point to predominantly thermogenic CH4 at the active mining level, whereas 13C-depleted methane at the exploited and flooded levels suggests secondary microbial generation. The microbial contribution is likely promoted by infiltrating meteoric waters supplying nutrients for methanogenic archaea, as supported by delta 2H, delta 18O signatures of mine water, and measurable tritium activity. The absence of enriched delta 13C values in CO2 and dissolved inorganic carbon (DIC) further implies mixed thermogenic-microbial gas origin in abandoned mine workings. These findings highlight the combined influence of mining operations, diffusion-desorption processes, microbial activity, and gas mixing on the molecular and isotope composition of coalbed gases transported toward the exhaust shaft. Moreover, isotopic data from downwind emission plumes demonstrate the value of integrating underground measurements with atmospheric observations to trace and quantify methane emissions from coal mining operations.
Le site de Mibladen, situé près de Midelt dans la région de la Haute Moulouya (Maroc), constitue l’un des rares affleurements fossilifères ayant livré des empreintes de ptérosaures non seulement au Maroc, mais également à l’échelle du continent africain. Pour la première fois sur ce site, des pistes de ptèrosaures comportant à la fois des empreintes de mains et de pieds ont été découvertes. À l’instar d’Agadirichnus elegans Ambroggi et Lapparent, 1954, ces traces présentent une morphologie en forme de U et partagent plusieurs caractéristiques avec celles de l’ichnofamille Agadirichnidae. Toutefois, elles s’en distinguent par certains traits spécifiques, qui les différencient des deux ichnogenres actuellement reconnus au sein de cette famille: Haenamichnus et Agadirichnus. En raison de la qualité médiocre de certaines traces et de la perte d’une partie du matériel (vandalisme), la création d’un nouvel ichnogenre ne peut être justifiée. Ces empreintes sont donc provisoirement classées comme aff. Agadirichnus isp. Elles montrent de fortes similitudes morphométriques et stratigraphiques avec des ichnofossiles découverts en Asie de l’Est (Corée du Sud, Chine) et en Europe (Espagne), ce qui témoigne de la large distribution géographique et de la diversification des ptérosaures au Crétacé inférieur. L’auteur probable de ces empreintes appartient à la superfamille des Azhdarchoidea.
The 80th anniversary (1945–2025) of the Konin Lignite Mine (KLM) invites some summaries of the mine’s characteristics. Therefore, the current study is devoted to rocks/sediments and tectonic or sedimentary structures that were observed and examined in lignite opencasts in the vicinity of the town of Konin. Some of them can be considered wonders and/ or curiosities of nature, some are unique, and others are quite common. Hence, they were generally defined as geological peculiarities in this article. In stratigraphic order they are sandstones, cleats, crevasse splays, palaeochannels and palaeosols. They represent various lithostratigraphic units (formations and members) of the Neogene of central Poland, while their age ranges from the Early Miocene to the earliest Pliocene. Among the listed objects, quartzite sandstones (situated below and between the lignite beds) and palaeosols in the Poznań Clays are very common, known from other lignite opencasts in Poland. In the case of cleats and crevasse splays occurring within the lignite seam exploited by the KLM, they are among the most numerous and best developed of all lignite-bearing formations in the world. On the other hand, the presence of palaeochannels in fine-grained sediments, constituting the overburden of the exploited lignite seam, provides additional and convincing evidence for the fluvial origin of the Poznań Clays.
