Late Quaternary glaciation of the northern Urals: a review and new observations

Abstract

This is a synthesis of the glacial history of the northern Urals undertaken using published works and the results of geological surveys as well as recent geochronometric and remote sensing data. The conclusions differ from the classical model that considers the Urals as an important source of glacial ice and partly from the modern reconstructions. The principal supporting evidence for the conventional model – Uralian erratics found on the adjacent plains – is ambiguous because Uralian clasts were also delivered by a thick external ice sheet overriding the mountains during the Middle Pleistocene. Alternative evidence presented in this paper indicates that in the late Quaternary the Ural mountains produced only valley glaciers that partly coalesced in the western piedmont to form large piedmont lobes. The last maximum glaciation occurred in the Early Valdaian time at c. 70–90 ka when glacial ice from the Kara shelf invaded the lowlands and some montane valleys but an icecap over the mountains was not formed. The moraines of the alpine glaciation are preserved only beyond the limits of the Kara ice sheet and therefore cannot be younger than MIS 4. More limited glaciation during MIS 2 generated small alpine moraines around the cirques of the western Urals (Mangerud et al. 2008: Quaternary Science Reviews 27, 1047). The largest moraines of Transuralia were probably produced by the outlet glaciers of a Middle Pleistocene ice sheet that formed on the western plains and discharged across the Polar Urals. The resultant scheme of limited mountain glaciation is possibly also applicable as a model for older glacial cycles.

Glacial and environmental changes over the last 60 000 years in the Polar Ural Mountains, Arctic Russia, inferred from a high‐resolution lake record and other observations from adjacent areas

“…at the western side of the valley to 560 m a.s.l. However, we also find it very unlikely that the Barents-Kara Ice Sheet reached the Ural Mountains as late as during MIS 2 Astakhov 2018). The ridge has an asymmetrical cross-profile with the steepest slope facing north.…”

“…1; Astakhov et al 1999;Astakhov 2018). Kara Valley starts at the watershed of the Pyryantan€ e River and descends westwards to the flat lowland along the flank of the mountain chain (Figs 2, 11).…”

“…1). It is controversial as to whether large icecaps formed over the Polar Ural Mountains during the last Ice Age (Astakhov 2013(Astakhov , 2014(Astakhov , 2016(Astakhov , 2018. However, it is clear that outlet glaciers from the mountain range reached the foothills during MIS 4 (Svendsen et al 2014).…”

“…It is correlated with the Halmer Moraine on the lowland to the west and is assumed to have been deposited by the last shelf-centred ice sheet that reached the Polar Urals from the Kara Sea region ( Fig. 1; Astakhov Astakhov 2018).…”

“…During an early stage of the last Ice Age (MIS 5d-4) large ice sheets formed over the Barents-Kara Sea region, but their form and dimension varied from time to time, and each of the major glaciations were separated by longlasting ice-free periods (Mangerud et al 2008b;M€ oller et al 2015). It is controversial as to whether large icecaps formed over the Polar Ural Mountains during the last Ice Age (Astakhov 2013(Astakhov , 2014(Astakhov , 2016(Astakhov , 2018. 1).…”