Palaeosols preserved within the Mudstone Series of the Upper Silesian Basin offer a potential archive of Pennsylvanian environmental conditions, yet they remain largely uncharacterized. The aim of this study was to evaluate whether these mineral palaeosol horizons can reliably record palaeoenvironmental and palaeoclimatic signals, despite their fluvial depositional setting and subsequent diagenetic overprint. Palaeosols from selected intervals of six cores were described macroscopically and investigated, using micromorphological analysis, X-ray diffraction, scanning electron microscopy (SEM), and bulk-rock geochemistry. The palaeosol profiles are thin and weakly developed. Most consist of a massive or weakly structured C horizon and a single mineral B horizon, overlain by a coal seam (H horizon). They were classified as gleyed Protosols. Micromorphology evealed frequent preservation of primary lamination, limited pedogenic aggregation, and rare other pedogenic features, such as slickensides and clay skins. SEM analyses documented in situ pedogenic and early diagenetic siderite, as well as accessory minerals (galena, pyrite, sphalerite, barite), commonly associated with organic matter. Mineralogically, the palaeosols are dominated by phyllosilicates (kaolinite, illite-smectite, and muscovite) and quartz, with a smaller content of feldspars, chlorite, and carbonates. The mineralogical variability between boreholes was low. Geochemical proxies (CIW > 90, high CALMAG, elevated Rb/Sr and low Sr/Cu ratios; ω–ψ and RW indices) consistently indicate strong weathering and a predominantly felsic provenance, with most samples plotting as highly weathered, relative to reference profiles. However, these indices contradict the weak pedogenic development observed microscopically, implying that the chemical signatures predominantly reflect pre-depositional weathering in the broader catchment, rather than in situ soil-forming processes. Frequent flooding strongly prohibited the development of highly mature and differentiated soil profiles, which effectively limits the utility of the material investigated as a direct palaeoclimate archive.
