Late Pliocene and early Pleistocene environments of the north-eastern Russian Arctic inferred from the Lake El'gygytgyn pollen record (original) (raw)

2013, Climate of the Past Discussions

The 318 m thick lacustrine sediment record in Lake El'gygytgyn, northeastern Russian Arctic cored by the international El'gygytgyn Drilling Project provides unique opportunities allowing the time-continuous reconstruction of the regional paleoenvironmental history for the past 3.6 Myr. Pollen studies of the lower 216 m of the lacustrine sed-5 iments show their value as an excellent archive of vegetation and climate changes during the Late Pliocene and Early Pleistocene. About 3.50-3.35 Myr BP the vegetation at Lake El'gygytgyn, in nowadays tundra area, was dominated by spruce-larchfir-hemlock forests. After ca. 3.4 Myr BP dark coniferous taxa gradually disappeared. A very pronounced environmental changes took place at ca. 3.305-3.275 Myr BP, cor-10 responding with the Marine Isotope Stage (MIS) M2, when treeless tundra-and steppelike habitats became dominant in the regional vegetation. Climate conditions were similar to those of Late Pleistocene cold intervals. Numerous coprophilous fungi spores identified in the pollen samples suggest the presence of grazing animals around the lake. Following the MIS M2 event, larch-pine forests with some spruce mostly dom-15 inated in the area until ca. 2.6 Myr BP, interrupted by colder and drier intervals ca. 3.04-3.02, 2.93-2.91, and 2.725-2.695 Myr BP. At the beginning of the Pleistocene, ca. 2.6 Myr BP, noticeable climatic deterioration occurred. Forested habitats changed to predominantly treeless and shrubby environments, which reflect a relatively cold and dry climate. Revealed peaks in green algae colonies (Botryococcus) around 2.53, 20 2.45, 2.320-2.305 and 2.175-2.150 Myr BP suggest a spread of shallow water environments. Few intervals (i.e. 2.55-2.53, ca. 2.37, and 2.35-2.32 Myr BP) with a higher presence of coniferous taxa (mostly pine and larch) document some relatively shortterm climate ameliorations. 4601 10 are the highest within the studied interval. Rather high contents of Abies pollen and permanent presence of pollen of some relatively thermophilic taxa, like Tsuga, Carpinus, Corylus, Quercus, Pterocarya, and Carya are also characteristic for PZ-2. Percentages of tree pollen, especially the more thermophilic ones like Picea, Tsuga and Abies decreased in the lower part of PZ-3 (ca. 3.48-3.45 Myr BP), while amounts of Poaceae 15 and Cyperaceae pollen significantly increase. Higher presence spores of Sphagnum, Lycopodium, Polypodiaceae, Sporormiella, and Sordaria is also notable. PZ-4 (ca. 3.45-3.42 Myr BP) is characterized by a further decrease in Picea and Abies pollen percentages and higher contents of Sphagnum, Sordaria and Sporormiella spores. Percentages of Picea and Abies increase again in PZ-5 (ca. 3.42-3.38 Myr BP), while 20 amounts of Poaceae, and Cyperaceae pollen, as well as Sphagnum, Sporormiella, and Sordaria spores are significantly decreased. In PZ-6 (ca. 3.380-3.352 Myr BP) percentages of Picea and Abies decrease, while amounts of Betula sect. Nanae, Artemisia, Poaceae and Cyperaceae pollen significantly increase. Spores of Selaginella rupestris also become an important component of the pollen assemblages in this zone. PZ-7 (ca. 25 3.352-3.310 Myr BP) is distinguishable by disappearance of Artemisia pollen from the pollen assemblages and a further gradual decrease in coniferous pollen percentages. PZ-8 (ca. 3.310-3.283 Myr BP) is remarkable by a distinct decrease in coniferous pollen percentages, while amounts of Poaceae, Cyperaceae, Artemisia,