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Reconstruction of the sedimentary environment of phytogenic deposits in the Tomisławice opencast mine (Konin Region, central Poland)

Słodkowska Barbara, Widera Marek

Geological Quarterly

2022

Vol. 66, No. 4

art. no. 34

Palynological analysis of the Tomisławice opencast mine deposits has allowed reconstruction of the plant communities and investigation of the evolution of sedimentary environments at various stages of lignite-forming marsh development, recorded in the composition of pollen assemblages from deposits of the 1st Mid-Polish lignite seam (MPLS-1). Rich pollen communities from an ~9 m thick section has enabled study of the succession of plant communities and of the evolution of phytogenic sedimentation. The pollen succession indicates that the assemblages in the whole lignite seam represent the VIII Celtipollenites verus pollen Zone. Slight differences in the composition of the communities reflect different stages of basin development, depending more on the variable water dynamics than on climatic oscillations. Lignite of the MPLS-1 developed in a continental regime on alluvial plains. Changes in the succession of plant communities in the Tomisławice section record flooding-drainage cycles caused by groundwater level oscillations. Peat bog accumulation took place in river basins, in which the lack of siliciclastic intercalations within the massive lignite seams points to weak fluvial dynamics. A rise in groundwater level and/or surface water resulted in flooding of the marshes and the formation of an extensive shallow lake basin, as shown by the presence of freshwater algae and pollen of aquatic plants. The section as a whole does not record an increased contribution of thermophilic plant taxa. The flora was generally dominated by warm-temperate and thermophilic species, without the participation of strongly thermophilic vegetation, which indicates that the lignite seam in the Tomis³awice opencast mine was formed in the generally stable conditions of a warm temperate climate.

Vegetation response to environmental changes based on palynological research on the Middle Miocene lignite at the Jóźwin IIB open-cast mine (Konin region, central Poland)

Słodkowska Barbara, Widera Marek

Annales Societatis Geologorum Poloniae

2021

Vol. 91, No. 2

149--166

Palynological research was performed on the first Mid-Polish lignite seam (MPLS-1) at the Jóźwin IIB open-cast mine. The extremely rich pollen assemblages allowed investigation of the development of phytogenic sedimentation and the succession of plant communities. The vegetation cover, representing peat accumulation and adjacent areas, was reconstructed in the homogeneous lignite seam. Despite the lack of clear macroscopic differences in the lignite lithology and a similar floristic composition, a similar succession of plant communities was observed in three repetitions in the profile. The plant communities described were grouped into five cycles. Changes in the succession resulted mainly from oscillations of the groundwater level. On the basis of the vegetation composition, the climatic conditions predominant during the peat-forming sedimentation were reconstructed. Climate changes are most precisely recorded in the mixed mesophilous forest community. Its floristic composition shows that the climate was warm-temperate and humid at that time. The lower part of the profile contains more taxa with high thermal requirements: Araliaceae, Mastixiaceae, Anacardiaceae, Hammamelidaceae, Cornaceae, Symplocaceae, Ilex, Itea, Engelhardia, etc. It is related to the Middle Miocene Climatic Optimum (MMCO). In the upper part of the profile, the vegetation composition reflects the beginning of a cooling trend. This is indicated by the reduced number of highly thermophilous taxa and the decreased taxonomic diversity of forest communities. The changing climatic and environmental conditions interrupted peat-bog sedimentation and caused termination of the development of thicker lignite seams.