In the northeast part of Bolshezemelskaya tundra within Eletsky palsa mire, peat accumulation began in the early Holocene between 11 and 8 cal ka BP, and between 8 and 5 cal ka BP, frost heaving and palsa growth were most active. The largest palsas reached 3–5 m in height. Later, some palsas partially thawed; some of them completely collapsed and sank. A new stage of heaving was recorded at about 2 cal ka BP, when new mounds began to grow and older palsas continued their growth. Precipitation-fed surface and supra-permafrost waters are assumed to be the main sources for ice core formation. Significantly lower isotope values of the initial water for palsa ice core relatively modern surface waters may be explained by a larger proportion of isotopically depleted precipitation of the cold period in the water source during palsa growth, while the proportion of isotopically enriched summer precipitation decreased and evaporation had a minor influence. Climate cooling related to the Holocene "8.2 cal ka event" could lead to the elongation of the winter season and lower winter air temperatures, which, in turn, led to an increased proportion of isotopically depleted precipitation throughout the year. Segregated ice in the ice cores of the studied palsas was formed during the freezing of water in semi-closed conditions. The upper part of the palsa ice core experienced deep thawing and could be saturated with meteoric water; repeated freezing of this part of the ice core likely occurred in closed system conditions.

Data was submitted and proofread by Yurij K Vasil'chuk and Lyubov Bludushkina at the faculty of Geography, department of Geochemistry of Landscapes and Geography of Soils, Lomonosov Moscow State University.