APPLICATION PALEOGEOGRAPHIC DATABASE OF "Q-KOLA" IN THE STUDY OF THE PLEISTOCENE-HOLOCENE BOUNDARY

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STUDY OF PALEOGEOGRAPHIC FEATURES OF THE NORTHERN PART OF THE KARELIAN ISTHMUS DURING THE HOLOCENE

112-11

Paleoecological and paleoclimatic reconstructions for the Karelian Isthmus based on the study of subfossil cladocerans from Lake Medvedevskoe (Northwest Russia)

The purpose of our study is to reconstruct the climatic and environmental changes that took place over the Holocene in Northwest Russia. The results of the palaeobiological analysis of cladoceran community of Lake Medvedevskoe (Karelian Isthmus, located between the Gulf of Finland of the Baltic Sea and Lake Ladoga, Northwest Russia) have been discussed. In the sediments of Lake Medvedevskoe, we have identified 38 cladoceran taxa that belong to 7 families: Bosminidae, Holopedidae, Chydoridae, Daphnidae, Polyphemidae, Macrotricidae, and Sididae. It has been revealed that Bosmina (Eubosmina) longispina and Alonella nana are the most common for subfossil Cladocera community of the lake. Palearctic and Holarctic species are dominant. Both pelagic and littoral taxa are well represented in the lake. The down-core changes in cladoceran community allowed to identify five statistically significant zones. It has been discovered that the taxonomic richness of biological communities is low at the bottom of the core with the dominance of typical northern species and increases towards the sediment surface alongside with the rise of organic content in sediments. Based on the shifts in the taxonomic composition of cladoceran community, we have concluded upon the trophic status of the lake and climate changes. The obtained data have been compared with the results of the chironomid analysis that was performed earlier

Palaeoecological and palaeoclimatic conditions on the Karelian Isthmus (northwestern Russia) during the Holocene

© 2020 University of Washington. Published by Cambridge University Press. The Holocene evolution of climate in easternmost Fennoscandia and adjoining regions is poorly known, compared with regions to the west. To address this, a 224-cm-long sediment core from Lake Medvedevskoe, situated on the Central Upland of the Karelian Isthmus, northwestern Russia, was examined to investigate variations in the Holocene climate. Analyses indicate that the dry and cold late Pleistocene climate was replaced by the warmer and more humid early Holocene climate after ca. 10.5 cal ka BP. During the early Holocene, the lake transitioned from an oligotrophic to a mesotrophic state, characterized by a Corynocera ambigua/Microtendipes pedellus-type phase, which has been found in other lakes across Fennoscandia. Taxonomic shifts in the chironomid and cladoceran communities associated with climatic amelioration were identified at ca. 10.6 and 9.17 cal ka BP using breakpoint analysis. Reconstructed July temperatures indicate climatic patterns comparable to those seen in eastern Fennoscandia. The warm period between ca. 9.5 and 5.5 cal ka BP (T July 14.5-15°C) was interrupted by a slight cooling between ca. 8.5 and 8.1 cal ka BP, possibly relating to the 8.2 event, with peak temperature reached at ca. 7.8 cal ka BP. Neoglacial cooling started after ca. 5.5 cal ka BP, the median reconstructed July temperature dropped to 2-3°C cooler than present (mean T July 13.5°C) before recovering in recent time

STUDY OF PALEOGEOGRAPHIC FEATURES OF THE NORTHERN PART OF THE KARELIAN ISTHMUS DURING THE HOLOCENE

112-11

APPLICATION PALEOGEOGRAPHIC DATABASE OF "Q-KOLA" IN THE STUDY OF THE PLEISTOCENE-HOLOCENE BOUNDARY

38-3

Recent shift in biological communities: A case study from the Eastern European Russian Arctic (Bol`shezemelskaya Tundra)

Recent Arctic warming has major influences on biological communities, especially in freshwater environments. There is substantial evidence that lake ecosystems in the Canadian Arctic and Fennoscandia are undergoing changes that have been linked to human-induced climate warming during the past 150–100 years. However, only few data linking recent climatic changes with the changes in biological communities are available from the Russian Arctic. We investigated a short sediment core (bottom of the core dates to 1830 CE) from Lake Bolshoy Kharbey, the biggest lake of the Bol`shezemelskaya Tundra, western Russian Arctic, using chironomid, cladocera, diatom and palynological analyses. Variations in biological proxy were linked to regional meteorological data and compared with the available sub-recent palaeoecological and hydrobiological studies from the region. The overall change in species composition was the smallest for terrestrial vegetation (0.485 SD) followed by cladoceran communities (0.966 SD). Chironomid taxonomic turnover was 1.331 SD, and the greatest rate of change was observed in diatom assemblages (1.701 SD). Changes in biological communities demonstrated a correlation with meteorologically recorded climatic parameters (air temperature and precipitation). The strongest taxonomic shifts in biological communities took place in 1880 and 1980. Both dates can be linked with prominent and recent climatic events: 1880 can be related to the end of the Little Ice Age in the region and 1980 is the beginning of the modern accelerating warming

The Holocene environmental changes revealed from the sediments of the Yarkov sub-basin of Lake Chany, south-western Siberia

Lake Chany is the largest endorheic lake in Siberia whose catchment is entirely on the territory of Russia. Its geographical location on the climate-sensitive boundary of wet and dry landscapes provides an opportunity to gain more knowledge about environmental changes in the West Siberian interior during the Holocene and about the evolution of the lake itself. Sediment cores obtained from the Yarkov sub-basin of the lake in 2008 have been comprehensively studied by a number of approaches including sedimentology and AMS dating, pollen, diatom and chironomid analyses (with statistical interpretation of the results), mineralogy of authigenic minerals and geochemistry of plant lipids (biomarker analysis.). Synthesis of new results presented here and published data provides a good justification for our hypothesis that Lake Chany is very young, no older than 3.6 ka BP. Before that, between 9 and 3.6 ka BP, the Chany basin was a swampy landscape with a very low sedimentation rate; it could not be identified as a water body. In the early lake phase, between 3.6 and 1.5 ka BP, the lake was shallow, 1.2–3.5 m in depth, and it rose to its modern size, up to 6.5 m in depth, during the last millennium. Our data reveal important changes in the understanding of the history of this large endorheic lake, as before it was envisioned as a large lake with significant changes in water level since ca. 14 ka BP. In addition to hydrology, our proxies provide updates and details of the regional vegetation and climate change since ca. 4 ka BP in the West-Siberian forest-steppe and steppe. As evolution of the Chany basin is dependent on hydroclimatic changes in a large region of southern West Siberia, we compare lake-level change and climate-change proxies from the other recently and most comprehensively studied lakes of the region

Climate, glacial and vegetation history of the polar Ural Mountains since c. 27 cal ka bp, inferred from a 54 m long sediment core from Lake Bolshoye Shchuchye

Because continuous and high-resolution records are scarce in the polar Urals, a multiproxy study was carried out on a 54 m long sediment succession (Co1321) from Lake Bolshoye Shchuchye. The sedimentological, geochemical, pollen and chironomid data suggest that glaciers occupied the lake's catchment during the cold and dry MIS 2 and document a change in ice extent around 23.5–18 cal ka bp. Subsequently, meltwater input, sediment supply and erosional activity decreased as local glaciers progressively melted. The vegetation around the lake comprised open, herb and grass-dominated tundra-steppe until the Bølling-Allerød, but shows a distinct change to probably moister conditions around 17–16 cal ka bp. Local glaciers completely disappeared during the Bølling-Allerød, when summer air temperatures were similar to today and low shrub tundra became established. The Younger Dryas is confined by distinct shifts in the pollen and chironomid records pointing to drier conditions. The Holocene is characterised by a denser vegetation cover, stabilised soil conditions and decreased minerogenic input, especially during the local thermal maximum between c. 10 and 5 cal ka bp. Subsequently, present-day vegetation developed and summer air temperatures decreased to modern, except for two intervals, which may represent the Little Ice Age and Medieval Warm Period