Middle and Late Weichselian stratigraphy and palaeoenvironments in central Poland

Abstract

The moraine plateau near Beichatow (central Poland) was incised at the beginning of the Middle Weichselian. Valleys 2&35 m deep were formed and then infilled with silts, sands, gravels, organic sediments and slope diamictons of the Piaski Formation, which is characterized by highly varying sedimentary environments. Initially -40,00&30,000 BPlacustrine sediments with an obvious eolian supply (re-worked loess) and locally fluvial suites were deposited in depressions. Slope sediments were simultaneously deposited at the valley margins. The Middle Weichselian was relatively mild and dry, but the milder interstadial periods have not been precisely established. Semi-anastomosing, stable-channel, highly aggrading and ephemeral streams of a semi-arid climate (subpolar desert) formed c. 3 0 , m 22,ooO BP. Continuous permafrost is implied from cyclic sedimentary processes reflecting summer melting and from periglacial structures. This was succeeded by a highly aggrading, high-energy and ephemeral braided fluvial system in an arid climate (polar desert), reflecting a complete lack of vegetation and increased eolian activity. These braided rivers formed during a period which may be directly correlated with the time of the maximum extent of the last ice sheet (22,00&14,350 BP), characterized by the most severe climatic conditions with strong periglacial activity. Finally -(14,35&12,700 BP) -eolian sediments were deposited, reflecting milder climatic conditions at the time of the abrupt ice sheet decay.

Cechy uziarnienia vistuliańskich aluwiów w dolinie Warty, Kotlina Kolska

“…Niejednokrotnie w osadach środkowego plenivistulianu, deponowanych w dolinach rzecznych, stwierdzano obecność poziomów organicznych, które ułatwiały lokowanie kolejnych etapów rozwoju dolin rzecznych w czasie, szczególnie w przypadkach, kiedy wiek poziomów organicznych mieścił się w zasięgu metody 14 C (Pazdur i in. 1980;Krzyszkowski 1990;Manikowska 1996;Petera 2002;Forysiak 2005). Z kolei za powszechną cechę aluwiów górnego plenivistulianu uważa się brak materii organicznej (Krzyszkowski 1990;Goździk 1995;Goździk, Zieliński 1999).…”

Czynniki determinujące zróżnicowanie inwolucji późnovistuliańskich w północno-zachodniej części regionu łódzkiego

“…Nieliczną grupę stanowią inwolucje, których czas powstania określono na późny vistulian, a udokumentowano je w następujących stanowiskach: Witów (Chmielewski 1970), Sąsieczno (Goździk 1973), Wola Grzymalina (Krzyszkowski 1990), Folwark (Kasse i in., 1998) oraz Sobień (Twardy 2008). W tych przypadkach nie zawsze jednoznacznie wiązano formowanie inwolucji z funkcjonowaniem wieloletniej zmarzliny, podając jako czynnik wystarczający głębokie sezonowe przemarzanie gruntu.…”

Heavy minerals as a tool to reconstruct river activity during the Weichselian glaciation (Toruń Basin, Poland)

“…The fluvial reworking caused a decrease in the amount of minerals that are less resistant to mechanical abrasion, as well as an increase in the garnet percentage (cf. Clemens & Komar, 1988;Krzyszkowski, 1990Krzyszkowski, , 1998Komar, 2007). It follows that the cyclical increases in the total amounts of amphibole, pyroxene, chlorite and biotite in the channel-lag deposits of the ephemeral, sandy, meandering rivers (Lower Member of the Rzęczkowo Formation) was caused by seasonally increased fluvial erosion rates and denudation of the catchment area built of glacial deposits, which is characteristic of nival flood regime rivers (Fig.…”

“…The decreased amount of amphibole and the increased amount of garnet in the younger deposits might indicate increasing transport distances from the ice-sheet front to the sedimentary basin (cf. Krzyszkowski, 1990;Wysota, 2002). Such a relationship was found at the Paterek site (Figs 8 and 10).…”

“…Besides, the type of the river-channel pattern controlled the efficiency of fluvial transport and the transport mode; it also influenced the type of channel macroforms and river erosion. The nature of fluvial processes controlled by climatic factors consequently reflect the fluvial architecture and the petrographic composition of fluvial deposits as an effect of physical sorting and mechanical abrasion of heavy-mineral grains during transport (Lowright et al, 1972;Krzyszkowski, 1990Krzyszkowski, , 1995Krzyszkowski, , 1996Fletcher et al, 1992;Morton & Hallsworth, 1999;Busschers et al, 2007;Komar, 2007;Ludwikowska-Kędzia, 2013;Wachecka-Kotkowska & Ludwikowska-Kędzia, 2013;Woronko et al, 2013).…”