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Evolution of Early Pleistocene fluvial systems in central Poland prior to the first ice sheet advance – a case study from the Bełchatów lignite mine

Goździk J., Zieliński T.

Geologos

2017

Vol. 23, No. 2

89--107

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.

Budowa geologiczna i stratygrafia formacji preglacjalnej południowego Mazowsza nad dolną Pilicą

Makowska A.

Prace Państwowego Instytutu Geologicznego

2015

T. 202

7--52

W pracy przedstawiono wyniki opracowania profili osadów z 10 kartograficzno-badawczych otworów wiertniczych, wykonanych na południowym Mazowszu, w rejonie Nowego Miasta n. Pilicą. Odwierty o maksymalnej głębokości 80 m przebiły kompleks osadów czwartorzędowych i dotarły do podłoża neogeńsko-paleogeńskiego i mezozoicznego. W dolnej części tego kompleksu występuje formacja preglacjalna, zajmująca ponad połowę jego miąższości. Osady tej formacji poddano badaniom litologiczno-mineralogicznym, palinologicznym i paleomagnetycznym. W wyniku badań określono litologiczny i stratygraficzny skład formacji preglacjalnej, jej wiek oraz paleogeografię analizowanego obszaru w czasie sedymentacji jej osadów. Z badań wynika, że formacja powstawała przez długi okres – od pliocenu po dolną część plejstocenu środkowego, znacznie dłużej niż młodsza glacjalna i postglacjalna część osadów czwartorzędowych.

The paper presents the results of studies of deposits from 10 exploration-mapping boreholes drilled in the southern Mazovia region near Nowe Miasto nad Pilicą. The boreholes, with a maximum depth of 80 m, pierced a complex of Quaternary deposits and reached the Neogene-Paleogene and Mesozoic basement. The lower part of the complex hosts the preglacial formation constituting more than half of its thickness. The deposits were subjected to lithological-mineralogical, palynological and palaeomagnetic investigations. The research enabled identification of the lithology and stratigraphy of the formation, its age and palaeogeography of the study area during the deposition. The research also shows that the formation was being deposited over a long period, starting from the lower Pliocene to the early middle Pleistocene, much longer than the period of deposition of the younger “glacial” and post-glacial parts of the Quaternary sediments.