Evolution of Early Pleistocene fluvial systems in central Poland prior to the first ice sheet advance – a case study from the Bełchatów lignite mine
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Date
2017-08
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Instytut Geologii UAM
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Abstract
Deposits formed between the Neogene/Pleistocene transition and into the Early Pleistocene have been studied, mainly
on the basis of drillings and at rare, small outcrops in the lowland part of Polish territory. At the Bełchatów lignite mine
(Kleszczów Graben, central Poland), one of the largest opencast pits in Europe, strata of this age have long been exposed
in extensive outcrops. The present paper is based on our field studies and laboratory analyses, as well as on research
data presented by other authors. For that reason, it can be seen as an overview of current knowledge of lowermost Pleistocene
deposits at Bełchatów, where exploitation of the Quaternary overburden has just been completed. The results
of cartographic work, sedimentological, mineralogical and palynological analyses as well as assessment of sand grain
morphology have been considered. All of these studies have allowed the distinction of three Lower Pleistocene series,
i.e., the Łękińsko, Faustynów and Krzaki series. These were laid down in fluvial environments between the end of the
Pliocene up to the advance of the first Scandinavian ice sheet on central Poland. The following environmental features
have been interpreted: phases of river incision and aggradation, changes of river channel patterns, source sediments for
alluvia, rates of aeolian supply to rivers and roles of fluvial systems in morphological and geological development of
the area. The two older series studied, i.e., Łękińsko and Faustynów, share common characteristics. They were formed
by sinuous rivers in boreal forest and open forest environments. The Neogene substratum was the source of the alluvium.
The younger series (Krzaki) formed mainly in a braided river setting, under conditions of progressive climatic
cooling. Over time, a gradual increase of aeolian supply to the fluvial system can be noted; initially, silt and sand were
laid down, followed by sand only during cold desert conditions. These fluvio-periglacial conditions are identified in the
foreground of the advance of the oldest ice sheet into this part of central Poland. The series studied have been compared
with other fluvial successions which accumulated in the Kleszczów Graben during subsequent glaciations so as to document
general changes in fluvial systems as reactions to climatic evolution. Thus, a palaeoenvironmental scenario has
emerged which could be considered to be characteristic of central Poland during the Early Pleistocene.
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Quaternary, preglacial, fluvial-aeolian interaction, heavy minerals, quartz grain morphology, sedimentology, palaeoclimate
Citation
Geologos, 2017, 23, 2, pp. 89-107
ISBN
978-83-232187-4-6