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Holocene paleoevironmental changes of Laptev See region -evidence from pollen records of the El'gene-Kyuele lake

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Savelieva, L. , Bolshiyanov, D. , Vakhrameeva, P. , Titova, D. , Herzschuh, U. , Biskaborn, B. and Funk, C. (2010): Holocene paleoevironmental changes of Laptev See region -evidence from pollen records of the El'gene-Kyuele lake , Joint Russian-German Workshop on Research in the Laptev Sea Region, November 8-11, 2010, St. Petersburg, Russia .
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Abstract:

Vegetation changes reflected in fossil pollen spectra are a primary source ofinformation about climatic fluctuation in the past. Pollen data is widely used inpalaegeographical reconstructions. Still there is only a small number of dataincluding spore-pollen results to allow a general view on Holocenepalaeoclimatic events particularly within the Laptev Sea region. Really, up tonow there are only several publications devoted to pollen investigations of lake sediments of the region [Andreev et al., 2002, 2004; Pisaric et al., 2001;Schirrmeister et al., 2003]. Therefore, the similar studies were initiated in theframeworks of Russian-German collaborations in this region and the first results obtained are presented in this work.The sedimentary core 135 cm thickness was collected during the Lena-2009expedition from the Elgene-Kuele lake (PG1975: coordinates: N 71° 017 39,7,E 125° 33 01,7). The main goals of our study were to carry out pollen analyses of the sedimentary in order to obtain new data for reconstruction ofpalaeoclimatic history of the Laptev Sea region during the Holocene.Pollen data indicate that 4 main taxa Betula, Alnus fruticosa, Poaceae,Cyperaceae dominate from top to bottom of the section. Percentage content ofmain components of spore-pollen spectra varies insignificantly. Curve ofdistribution of content of Larix pollen allowed us to distinguish 4 zones along the sedimentary core.Zone 1 (135-71 cm): The portion of trees and shrubs pollen fluctuates between 60-70%. The zone is dominated by the pollen Betula and Alnus fruticosa, with Cyperaceae and Poaceae. Pollen of Salix and Larix are present. The spectra show relatively high percentages of Larix pollen (5%). This can indicate to larch forest tundra conditions. Zone 2 (71-23 cm): The percentage ration of tree and herb pollen is likelyprevious zone 1. But decrease in larch pollen suggests insignificant climatecooling relatively of zone 1. Zone 3 (23-7 cm): Low percentages of Larix (less 1%), and increase of herbs pollen (up to 55%) may reflect shrub tundra conditions. This change might be associated with climate deterioration during the Little Ice Age.Zones 4 (7-0 cm): The final zone marked by negligible increases in Larix (about 1%) and is dominated by Betula and Alnus fruticosa. This zone is interpreted as the establishment of the modern forest tundra with birch, alder and larch.Pollen data from the sedimentary core of the Elgene-Kyuele Lake (PG1975-1,lake 05) showed insignificant variability of spectra along the section.Nevertheless, the most favorable climatic conditions formed duringaccumulation of Zone 1 when the forest-tundra vegetation was expanded withdomination of birch, alder and larch. Spore-pollen spectra of Zone 2 reflectinsignificant cooling during which the forest-tundra vegetation becomes morethinned out. Lack of larch pollen in spore-pollen composition provides evidence of even greater deterioration of climatic conditions in Zone 3. Probably, this time can be belonged to the Little Ice Age. Domination of forest-tundra vegetation is fixed in Zone 4 and it reflect contemporary vegetation. Carrying out of radiocarbon dating of the sedimentary cores is required for recognition of sequence and duration of paleoclimatic events in time.Up to now we have not so much statistical data to make a completed (final)conclusions concerning the palaeoclimatic changes in Holocene within theLaptev Sea region. Hence, we are continuing our palaeoclimatic investigations including comprehensive spore-pollen and geochemical analyses of sedimentary cores from other lakes of the region.The work was carried out in frames of the OSL project № OSL-10-22.

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