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Vol 10, No 4 (2017)
- Year: 2017
- Articles: 11
- URL: https://journals.rcsi.science/1995-4255/issue/view/12576
Article
Paleolimnological studies in Russian northern Eurasia: A review
Abstract
This article presents a review of the current data on the level of paleolimnological knowledge about lakes in the Russian part of the northern Eurasia. The results of investigation of the northwestern European part of Russia as the best paleolimnologically studied sector of the Russian north is presented in detail. The conditions of lacustrine sedimentation at the boundary between the Late Pleistocene and Holocene and the role of different external factors in formation of their chemical composition, including active volcanic activity and possible large meteorite impacts, are also discussed. The results of major paleoclimatic and paleoecological reconstructions in northern Siberia are presented. Particular attention is given to the databases of abiotic and biotic parameters of lake ecosystems as an important basis for quantitative reconstructions of climatic and ecological changes in the Late Pleistocene and Holocene. Keywords: paleolimnology, lakes, bottom sediments, northern
327-335
Macroentomology analysis: Methods, opportunities, and examples of reconstructions of paleoclimatic and paleoenvironmental conditions in the Quaternary of the northeastern Siberia
Abstract
Macroentomology analysis mainly studies terrestrial insect species with a hard exoskeleton (Coleoptera, some Hymenoptera, Homoptera, and sometimes other orders). The method has shown a great potential for environmental and climatic paleoreconstructions of the Quaternary worldwide. A large volume of the entomological material has also been collected in Siberia. However, an analysis of the published data demonstrates that the investigations of fossil insects are irregular in Siberia. The most studied sites are in Northwestern and Central Siberia and in northeastern Russia. The rest of Siberia is still almost unstudied. This work aims to present this method (sampling method, laboratory treatment, and examples of paleoreconstructions) to a wide group of researches. In some cases, the study of insects allows one to make more accurate reconstructions than traditional paleobotanical methods. The application of this method is effective for recognizing differences in herbaceous communities similar in appearance, which were typical for the cold periods in the Pleistocene.
336-349
Chironomid fauna of the lakes from the Pechora river basin (east of European part of Russian Arctic): Ecology and reconstruction of recent ecological changes in the region
Abstract
We investigated chironomid fauna of surface sediments and a short sediment core (Bol’shoy Kharbey Lake) from Pechora river basin, Northern Russia. Twenty three investigated lakes have thermokarst, glacial or floodplain origin and are characterised by low mineralization, mostly hydrocarbon-calcium type of water and low concentration of nutrients. Most of the lakes have circumneutral pH around ≤7 and only two lakes are slightly more acidic with pH ≤ 6. Ninety six chironomid taxa were identified in the surface sediments. Distribution of chironomids in the studied region is driven by continentality, mean TJuly and рН. Chironomid communities from the core of the B. Kharbei Lake demonstrate the highest similarity with the fauna of the deeper lakes of the glacial origin. The glacial lakes have the highest indices of continentality and the lowest winter temperatures within the investigated data set. The chironomid fauna of the glacial lakes is composed of the profundal, oligotrophic and cold-stenotherm taxa. The fauna of the floodplain and thermokarst lakes is more closely related to TJuly and is composed of littoral and phytophilic taxa of meso–or eutrophic waters and moderate temperature conditions. The fauna of the acidic thermokarst lakes considerably differs from the other lakes. Chironomid communities here are represented by tolerant to acidification taxa, and by the typically littoral and shallow water acid-tolerant taxa that apparently also can tolerate acidification. Studied sediment record covers ca last 200 years. The reconstructed TJuly during the entire period remain slightly below the modern temperatures. From 1970 reconstructed TJuly shows steady increase to the modern level. The reconstructed water depths (WDs) of the lake are higher than today till 1980. The highest WDs are reconstructed for ca 1970. After that the WDs gradually decrease to the modern level. Changes of the WDs are most probably related to changes in the precipitation rate.
350-362
Reconstruction of palaeoecological and palaeoclimatic conditions of the Holocene in the south of the Taimyr according to an analysis of lake sediments
Abstract
A sediment core from Khatanga-12 Lake (Taimyr Peninsula, Krasnoyarsk krai) has been studied. The 131.5-cm-long core covers ca. 7100 years of sedimentation. Chironomid analysis, a qualitative reconstruction of the paleoenvironment in the region, and a quantitative reconstruction of variations of the mean July air temperature and in the water depth of the lake have been performed using Northern Russia chironomid-inferred mean July temperature models (Nazarova et al., 2008, 2011, 2015). Khatanga-12 Lake was formed during the Middle Holocene warming as a result of thermokarst processes. The development of the lake ecosystem at different stages of its development was influenced by climatic and cryolithogenic factors. The Middle Holocene warming, which occurred around 7100–6250 cal. years BP, activated thermokarst processes and resulted in the formation of the lake basin. Later, between 6250 and 4500 cal. years BP, a period of cooling took place, as is proved by chironomid analysis. The bottom sediments of the lake during this period were formed by erosion processes on the lake shores. The reconstructed conditions were close to the modern after 2500 cal. years BP.
363-369
New data on age and conditions of buried organic-rich sediments formation in the сentral Ob River
Abstract
This article presents the results of a comprehensive geochronological study of gyttja deposits from a section of a terrace above a floodplain located on the right bank of the Ob River near the town of Kolpashevo. According to the 230Th/U dating, the age of the gyttja could be dated in the range of 110–95 kyr. The results of spore–pollen analysis suggest that the gyttja deposit was formed in the period of a wide distribution of middle taiga forest landscapes with the dominance of spruce; the climatic conditions were similar to modern ones. These events probably took place in the interstadial time during MIS-5c or at the end of Kazantsevo interglacial period.
370-379
Modern and fossil diatom assemblages from Bol’shoy Lyakhovsky Island (New Siberian Archipelago, Arctic Siberia)
Abstract
This article discusses the results of a taxonomic and ecological investigation of diatoms from polygonal ponds and Quaternary permafrost deposits of Bol’shoy Lyakhovsky Island (New Siberian Archipelago) and the reconstruction of climatic changes on the Island during late Pleistocene/Holocene transition using fossil diatom assemblages from the permafrost deposits. The taxonomic list of diatoms includes 159 diatom species. The main ecological factors that determine the distribution of diatoms in the investigated data set are mean July air temperature, рН, electrical conductivity, water depth, and concentrations of Si4+ and Al3+. An increase in water depth and stable lacustrine conditions in the Lateglacial–Holocene in the ancient thermokarst lake relate to Lateglacial warming before 11860 ± 160 years BP and during the early Holocene between 11210 ± 160 and 7095 ± 60 years BP.
380-394
Subrecent spore–pollen spectra and modern vegetation from the Lena River Delta, Russian Arctic
Abstract
This paper presents the results of a pollen analysis of 40 surface samples collected from various geomorphological levels such as low and high floodplains, surfaces and slopes of terraces, tops of island remnants, etc., in different parts of the Lena River Delta. The obtained spore–pollen spectra (SPS) were compared with the modern vegetation composition. The role of long-distance transported pollen and the pollen of local plant biocenoses in the subrecent SPS formation is shown. Modern vegetation is most adequately reflected in the spectra of samples from a height range from 11 to 52 m above river level. SPS of other samples contain up to 40% of long-distance transported pollen, mostly Pinus s/g Haploxylon. This results in a significant decrease in the percentage of local pollen. The data offer the possibility of improving the reliability of palaeoclimatic reconstructions based on palaeopalynological data for Arctic regions.
395-410
Structure and evolution of dune massifs in the Vilyui River Basin over the Late Quaternary Period (by the example of the Makhatta and Kysyl-Syr Tukulans)
Abstract
The data of the comprehensive study of deposits of dune sand massifs—the Makhatta and Kysyl-Syr Tukulans—in the Vilyui River Basin (Central Yakutia) are given. We have revealed the structure and preliminarily reconstructed the evolution of tukulans in the Vilyui River basin and the environmental conditions of the surrounding area in the Late Pleistocene–Holocene period (the chronological period of the formation of tukulans) on the basis of lithological and palynological data and 17 radiocarbon datings. It has been revealed that the tukulans should be assigned to eolian deposits formed on sediments of complicated facial structure. We have distinguished four stages in the vegetation evolution within the last 40000-year period and three chronostratigraphical phases in the development of dune massifs.
411-422
Reconstruction of the history of a thermokarst lake in the Mid-Holocene based on an analysis of subfossil Cladocera (Siberia, Central Yakutia)
Abstract
This paper presents the results of a cladoceran analysis of a sediment core with a lenght of 382 cm collected from a pingo in alas Khara Bulgunnyakh located in Central Yakutia. Based on the Cladocera analysis results, the formation of the lake had started during the Holocene climatic optimum ~6600 cal. yrs. BP. The analysis of changes in the species composition of subfossil cladoceran communities made it possible to identify, on the basis of cluster analysis, four statistically significant ecological zones. The period of optimal conditions for the Cladocera community is defined by a complex evened community structure and numerous cladoceran remains in the sediments accumulated between 6500 and 6000 cal. yrs. BP. The history of the thermokarst water body development and existence reconstructed on the basis of the subfossil cladoceran analysis was rapid and short.
423-430
Environmental changes in the northeast of the Buryat Republic during the Holocene post-Optimum: First results
Abstract
The results of a high-temporal-resolution geochemical and pollen analysis of bottom sediments in Lake Baunt (55°11′15″ N and 113°01′45″ E), located within the continuous permafrost zone, have made it possible to reconstruct the environmental and climate changes in northern Buryatia during the Holocene post-Optimum for the first time. Over the last almost 7000 years, the natural and climatic conditions in the northeast of Buryatia have not remained homogeneous. A relatively warm and dry climate occurred here at the end of the Holocene Optimum between 6900 and 6000 BP. Later, about 6000–1500/1000 BP, the climate became colder, long-term permafrost activated, and chemical weathering attenuated. The climate over the last 1500–1000 years was colder in general than the modern climate. The environmental indices have different values in sediments with respect to warm and cold intervals and reflect the sedimentation conditions what were controlled by climate changes.
431-440
Environmental changes recorded in deposits of the Izyubrinye Salontsi Lake, Sikhote-Alin
Abstract
Paleoecological changes during the development of Lake Izyubrinye Solontsi from the Solontsovskie (Shanduyskie) Lakes located in the midlands of the Eastern Sikhote-Alin have been reconstructed. Lake formation is related to landslides on the paleovolcano slopes. A complex study of the peat-bog section (botanical, diatom, spore-pollen, and radiocarbon analysis) allows reconstructing paleoenvironmental changes with high resolution. A considerable variability of lake and swamp environments highly responsive to climate changes in the late Holocene has been revealed. Peat accumulation began about 400014С BP. The main peat-forming plants were Sphagnum mosses and herbs, except for the period 2330‒1530 14C BP (2360‒1480 cal. BP), when a swamp overgrown by larch forests and predominantly woody peat accumulated. Forest ecosystems on the lake coasts were quite stable. The role of fir and broadleaved species increased in the composition of dark coniferous forests with Korean pine during the warm phases and the role of birch, in the cold phases; secondary forests occupied the low slopes during the last 1000 years. The age of paleofires has been determined.
441-453