Paleontological records indicate the occurrence of open woodlands in a dry inland climate at the present-day Arctic coast in western Beringia during the Last Interglacial

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Article

Kienast, Frank^1,2  Wetterich, Sebastian³  Kuzmina, Svetlana^4,8  Schirrmeister, Lutz³  Andreev, Andrei A.^3,9  Tarasov, Pavel⁵  Nazarova, Larisa³  Kossler, Annette⁵  Frolova, Larisa⁶  Kunitsky, Viktor V.⁷ 

[1] Senckenberg, Res Inst, D-99423 Weimar, Germany

[2] Nat Hist Museum, Res Stn Quaternary Palaeontol, D-99423 Weimar, Germany

[3] Alfred Wegener Inst Polar & Marine Res, Dept Periglacial Res, D-14473 Potsdam, Germany

[4] Univ Alberta, Dept Earth & Atmospher Sci, Edmonton, AB T6G 2E3, Canada

[5] Free Univ Berlin, Inst Geol Sci, D-12249 Berlin, Germany

[6] Kazan VI Lenin State Univ, Fac Biol & Soil, Kazan 420008, Russia

[7] Russian Acad Sci, Permafrost Inst, Siberian Branch, Yakutsk 677010, Russia

[8] Russian Acad Sci, Inst Paleontol, Moscow 117868, Russia

[9] Univ Cologne, Inst Geol & Mineral, D-50674 Cologne, Germany

关键词: Last Interglacial;    Northern tree line;    Tundra;    Bioindicators;    Thermokarst;    Continentality;    Permafrost;    Plant macrofossils;    Ostracods;    Chironomids;    Fossil insects;    Cladocerans;    Molluscs;   

DOI  :  10.1016/j.quascirev.2010.11.024

来源: Elsevier

【 摘 要 】

Permafrost records, accessible at outcrops along the coast of Oyogos Yar at the Dmitry Laptev Strait, NE-Siberia, provide unique insights into the environmental history of Western Beringia during the Last Interglacial. The remains of terrestrial and freshwater organisms, including plants, coleopterans, chironomids, cladocerans, ostracods and molluscs, have been preserved in the frozen deposits of a shallow paleolake and indicate a boreal climate at the present-day arctic mainland coast during the Last Interglacial. Terrestrial beetle and plant remains suggest the former existence of open forest-tundra with larch (Larix dahurica), tree alder (Alnus incana), birch and alder shrubs (Duschekia fruticosa, Betula fruticosa, Betula divaricata, Betula nana), interspersed with patches of steppe and meadows. Consequently, the tree line was shifted to at least 270 km north of its current position. Aquatic organisms, such as chironomids, cladocerans, ostracods, molluscs and hydrophytes, indicate the formation of a shallow lake as the result of thermokarst processes. Steppe plants and beetles suggest low net precipitation. Littoral pioneer plants and chironomids indicate intense lake level fluctuations due to high evaporation. Many of the organisms are thermophilous, indicating a mean air temperature of the warmest month that was greater than 13 degrees C, which is above the minimum requirements for tree growth. These temperatures are in contrast to the modern values of less than 4 degrees C in the study area. The terrestrial and freshwater organism remains were found at a coastal exposure that was only 3.5 m above sea level and in a position where they should have been under sea during the last Interglacial when the global sea level was 6-10 m higher than the current levels. The results suggest that during the last warm stage, the site was inland, and its modern coastal situation is the result of tectonic subsidence. (C) 2010 Elsevier Ltd. All rights reserved.

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