Geochemical composition of Holocene and Late Pleistocene ice wedges in the yedoma of Stanchikovsky Yar and near the Chersky town, Northern Yakutia

Abstract

The subject of this research is the Late Pleistocene and Holocene ice wedges exposed near Chersky settlement, lower Kolyma River, and in the yedoma strata of the Stanchikovsky Yar on the Maly Anyuy River. In the yedoma of the Stanchikovsky Yar, multi-tiered syngenetic ice wedges were exposed at different levels – from 10 to 35 m above river level. Ice wedge in the lower tier was sampled in detail. In the yedoma strata near Chersky relatively small fragments of ice wedges up to 1.5 m wide and up to 2 m high were exposed. 1.5-2 km from Chersky within the lacusrtine-paludal depression Holocene ice wedges were exposed. Ice wedges in these three sections was sampled to clarify the geochemical conditions of their formation. It is shown that concentration of Na+, K+, Mg2+, Cl- and SO42- in Holocene and Late Pleistocene ice wedges is very low and mean values do not exceed 5 mg/L. The highest values were obtained for Ca2+, which corresponds to the predominance of this ion in the modern snow of Yakutia and indicates that ice wedges were formed mainly from melted snow. Rather high values of NO3-, reaching 14-27 mg/L, are quite likely due to the swampy environment within polygonal landscapes, where organic matter of both plant and animal origin is decomposed. For comparison, in the water of the Kolyma and Maly Anyu rivers, concentration of nitrates is quite low and does not exceed 0.3 mg/L.