Late Quaternary environmental and landscape dynamics revealed by a pingo sequence on the northern Seward Peninsula, Alaska

QUATERNARY SCIENCE REVIEWS

卷:39

Article

Wetterich, Sebastian¹  Grosse, Guido²  Schirrmeister, Lutz¹  Andreev, Andrei A.³  Bobrov, Anatoly A.⁴  Kienast, Frank^5,6  Bigelow, Nancy H.⁷  Edwards, Mary E.^7,8 

[1] Alfred Wegener Inst Polar & Marine Res, Dept Periglacial Res, Potsdam, Germany

[2] Univ Alaska Fairbanks, Inst Geophys, Fairbanks, AK USA

[3] Univ Cologne, Inst Geol & Mineral, Cologne, Germany

[4] Moscow MV Lomonosov State Univ, Fac Soil Sci, Moscow, Russia

[5] Senckenberg Res Inst, Weimar, Germany

[6] Nat Hist Museum, Res Stn Quaternary Palaeontol, Weimar, Germany

[7] Univ Alaska Fairbanks, Alaska Quaternary Ctr, Fairbanks, AK USA

[8] Univ Southampton, Southampton SO9 5NH, Hants, England

关键词: Holocene Thermal Maximum;    Central Beringia;    Thermokarst;    Pingo;    Spruce;    Picea sp.;   

DOI  :  10.1016/j.quascirev.2012.01.027

来源: Elsevier

【 摘 要 】

A terrestrial sediment sequence exposed in an eroding pingo provides insights into the late-Quaternary environmental history of the northern Seward Peninsula, Alaska. We have obtained the first radiocarbon-dated evidence for a mid-Wisconsin thermokarst lake, demonstrating that complex landscape dynamics involving cyclic permafrost aggradation and thermokarst lake formation occurred over stadial-interstadial as well as glacial-interglacial time periods. High values of Picea pollen and the presence of Larix pollen in sediments dated to 50-40 ka BP strongly suggest the presence of forest or woodland early in MIS 3: the trees grew within a vegetation matrix dominated by grass and sedge, and there is indirect evidence of grazing animals. Thus the interstadial ecosystem was different in structure and composition from the Holocene or from the preceding Last Interglacial period. An early Holocene warm period is indicated by renewed thermokarst lake formation and a range of fossil taxa. Multiple extralimital plant taxa suggest mean July temperatures above modern values. The local presence of spruce during the early Holocene warm interval is evident from a radiocarbon-dated spruce macrofossil remain and indicates significant range extension far beyond the modern tree line. The first direct evidence of spruce in Northwest Alaska during the early Holocene has implications for the presence of forest refugia in Central Beringia and previously assumed routes and timing of post-glacial forest expansion in Alaska. (c) 2012 Elsevier Ltd. All rights reserved.

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