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Microfossil (Diatoms, Tintinnids, and Testate Amoebae) Assemblages in the Holocene Sediments of the Laptev Sea Shelf off the Yana River as a Proxy for Paleoenvironments
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Maria S. Obrezkova, Lidiya N. Vasilenko, Ira B. Tsoy, Xuefa Shi, Limin Hu, Yaroslav V. Kuzmin, Aleksandr N. Kolesnik, Alexandr V. Alatortsev, Anna A. Mariash, Evgeniy A. Lopatnikov, Irina A. Yurtseva, Darya S. Khmel and Anatolii S. Astakhov
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Abstract
The paper presents the results of a microfossil study of Holocene sediments in the Yana River flow zone in the southeastern part of the Laptev Sea. A rich diatom flora (242 species and intraspecific taxa, of which 177 species are freshwater) was revealed;
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The paper presents the results of a microfossil study of Holocene sediments in the Yana River flow zone in the southeastern part of the Laptev Sea. A rich diatom flora (242 species and intraspecific taxa, of which 177 species are freshwater) was revealed; additionally, five species of marine tintinnids (planktonic ciliates) and 15 species of freshwater testate amoebae (testacean) were discovered for the first time in the sea sediments. Three assemblages of microfossils reflecting the phases of environmental changes during the Holocene transgression are distinguished in the studied sediments of core LV83-32. Assemblage 1 was formed under terrestrial conditions (assemblage of diatoms
Eunotia-Pinnularia and testacean
Difflugia-Cylindrifflugia-Centropyxis), assemblage 2 in the zone of mixing of sea and fresh waters (assemblages of diatoms
Cyclotella striata-Aulacoseira,
Thalassiosira hyperborea-Chaetoceros and
T. hyperborea-Aulacoseira, testacean
Cyclopyxis kahli, tintinnids
Tintinnopsis fimbriata), and assemblage 3 reflects modern conditions in the inner shelf of the Laptev Sea under the strong influence of river runoff (assemblage of diatoms
T. hyperborea-Aulacoseira-M. arctica and tintinnids
Tintinnopsis ventricosoides). Changes in the natural environment in the coastal part of the Laptev Sea shelf during the Holocene, established by microfossil assemblages, are confirmed by geochemical data.
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