Structure and formation conditions of the ice complex in the lower reaches of the Vilyui River, Central Yakutia
M.R. Pavlova, A.A. Galanin, V.M. Lutkin, N.V. Torgovkin
Melnikov Permafrost Institute, Siberian Branch of the Russian Academy of Sciences, Yakutsk, Russia
Keywords: ice complex, ice wedge, chemical composition, isotope analysis, palynology, radiocarbon dating, grain size, Late Pleistocene, Central Yakutia
Abstract
This article presents the results of a comprehensive investigation of the ice complex discovered within the strath terrace in the lower course of the Vilyui River, Central Yakutia. On the basis of chemical, isotopic, granulometric, palynological, and radiocarbon data, it has been revealed that the formation of the ice complex took place from the end of the Kargin (MIS-3) and throughout the Sartan (MIS-2) epochs of the Late Pleistocene (between 29 and 11.7 ka BP) under cryoarid conditions with a predominance of dry cold xerophytic steppes and, locally, forb-grass meadows. Mineralization of syngenetic ice wedges is low (0.07-0.29 g/dm3), and a predominance of calcium bicarbonates suggests that winter precipitation - snowmelt water - was the main source of wedge ice. The increased content of heavy metals (Fe, Mn, Co, V, Sr) indicates that the formation of ice wedges also involved the water of shallow freezing lakes confined to the polygonal microrelief. The ice wedges have a relatively light isotopic composition (δ18О -(29.2 ± 0.3)‰ and -(27.2 ± 1.4)‰; δD -(226.6 ± 2.3)‰ and -(215.8 ± 8.5)‰, dexc (6.8±0.51)‰ and (1.7±3.1)‰), which is close to the composition of modern atmospheric precipitation of the cold season and spring snow storage in Yakutsk. These data attest to dry and cold conditions, thin snow cover, and moisture deficiency in cryogenic landscapes during the formation of the ice complex.
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