The Middle Pleistocene glaciolacustrine environment of an ice‐dammed mountain valley, Sudeten Mountains, Poland

Abstract

This article reports on an Early Saalian proglacial lake formed between the Scandinavian Ice Sheet and the front of the Sudeten Mountains, Poland. Sediments investigated at Mysłów point to a transition from glacifluvial to glaciolacustrine environments. The bulk of the sediments was deposited in deep‐water Gilbert‐type deltas (A–E complexes). A delta plain (topset) gradually passes into a subaerial plateau and then a clastic shoreline and the subaquatic slope of a prograding delta (foreset). The glaciolacustrine lithofacies represent a number of lake‐basin environments, from marginal subaqueous slopes to distal parts of a subaqueous fan. Glaciolacustrine and glaciodeltaic deposits locally reach ˜50–70 m in thickness. Analyses of A–E complexes indicate that the lake existed for more than 130 years and that its origin and evolution were closely connected with the ice front. This case study records lake sedimentation at an ice‐sheet margin with cohesionless gravity flows, turbidity currents, debris‐avalanching and, to a much lesser degree, parapelagic suspension fall‐out and ice‐raft dumping. In the initial stage, the lake extended more than 10 km to the south, and the deposition was relatively slow. In the second stage, recession of the ice sheet caused rapid growth of a delta. The third and ultimate stage coincided with the final glacial recession, with rapid deposition occurring only on the lake bottom. The model of the glaciolacustrine environment presented here may also be applicable to many other proglacial lakes in mountain areas.

An examination of the glaciomarginal fan of the Odranian glaciation at the Mokrzeszów site, Sudetic Foreland, SW Poland

“…The sedimentary record from this period was presented by Salamon et al (2013), showing the succession of a narrow, proglacial lake. A similar situation was described by Krzyszkowski et al (2019b). The ice sheet then crossed/overcame the SMF barrier (Fig.…”

“…16 -3a), when the ice sheet reached far to the south, the area was covered by the ice sheet to the line of the Sudetes Mountains (Czerwonka & Krzyszkowski 1992, Marks 2011, and there was a local break in the ice sheet continuity, and the formation of a lake took place at the study site. Based on lithopetrographic studies, the depositional sequence exposed in the Mokrzeszów pit can be interpreted as the upper part of deltaic sediments accumulated from the south-east to a small ice-dammed lake that formed between the advancing ice sheet and the edge of the Central Sudetes (Salamon et al 2013, Hanáček et al 2018, Krzyszkowski et al 2019b. A similar situation was described by Salamon (2009) for the Polish part of the Eastern Sudetes (see Fig.…”

“…During this stage, deposition on the top was predominantly in channels by migrating dunes (Sp) The deposition of Sp, Sh and Sr sands is a distinctive feature of a subaqueous fan, as described by Winsenann et al (2004Winsenann et al ( , 2007aWinsenann et al ( , 2007bWinsenann et al ( , 2009Winsenann et al ( , 2018 and Lang et al (2017). Such a stratification formation may be present in the glaciolacustrine succession (see : Cheel 1990, Gruszka 2001, 2007, Gruszka & Zieliński 2021 formed in the marginal part of a lake (see: Krzyszkowski 1993, Krzyszkowski et al 2019b). Similar facies are characteristic for the alluvial form, e.g.…”

“…The critical shear stress (Costa 1983) cannot be estimated due to the limited number of observations. It occurred immediately after flooding on the gentle delta slope (truncated by debris flow) and probably during a period of water scarcity in the glacial system , Krzyszkowski et al 2019b. During this stage, deposition on the top was predominantly in channels by migrating dunes (Sp) The deposition of Sp, Sh and Sr sands is a distinctive feature of a subaqueous fan, as described by Winsenann et al (2004Winsenann et al ( , 2007aWinsenann et al ( , 2007bWinsenann et al ( , 2009Winsenann et al ( , 2018 and Lang et al (2017).…”

Maximální rozšíření pleistocenního ledovcového štítu ve Vnějších Západních Karpatech a Východních Sudetech – současné znalosti a nový důkaz

“…Eratický materiál je ale součástí i terminoglaciálních až proglaciálních výplavových sedimentů. V říčních údolích vznikala terminoglaciální jezera, protože po zahrazení ledovcem se fluviální údolí měnila v glacilakustrinní vnitrohorské pánve, intenzivně vyplňované hrubými deltovými klastickými sedimenty (Salamon 2014;Hanáček et al 2018;Krzyszkowski 2013;Krzyszkowski et al 2019). V severních Čechách, Rejvízké hornatině a Porubské bráně progradovaly před nejexponovanějšími výběžky ledovce terminoglaciální kužely a údolní proglaciální řeky, transportující eratika do předpolí zaledněného území (Nývlt, Hoare 2000;Tyráček 2011;Hanáček 2011).…”