Laboratory of Environmental Paleoarchives

The history of landscape and climate change in the center of the East European Plain suffers from in-completeness and insufficient specification over the last 25 ka. The most significant gaps are found in the Late Pleniglacial (25-15 ka) due to the rarity of continuous paleorecords of this interval. In the Late Glacial and Holocene, whence the availability of sedimentary records is relatively higher, the time resolution rarely reaches tens of years, and is usual-ly measured in centuries. This project aims at partially filling these gaps. We propose to obtain and study bottom sedimentary cores from lakes with high sedimentation rates (about 1 mm per year), which provide a detailed record of paleogeographic events. Cores from lakes Kasplya (Smolensk region), Petrovskoe (Tver re-gion), Somino and Pleshcheyevo (Yaroslavl region) will cover the Holocene and parts of the Late Glacial. Cores from the Sara and Solovey depressions (Yaro-slavl region), as well as the Chukhlomskoe Lake (Kostroma region) will cover the Late Pleniglacial interval. The presence of thick sedimentary strata in these lakes is confirmed by the results of reconnais-sance fieldwork and geological exploration carried out by the research team over the past 2 years. Lake basins and their watersheds will be surveyed by geological, geomorphological and geophysical methods in order to identify the structure and vol-ume of bottom sediments, areas preferable for drill-ing, and to determine the structure and age of lake terraces, and also to understand sedimentation drivers. For sedimentary cores, it is planned to carry out a complex of lithological, geochemical and paleobo-tanical studies with a high-frequency sampling, and acquire a chronosequence based on mass radiocar-bon dating and stratigraphic markers. It is planned to perform granulometric analysis, XRF determina-tion of the elemental content, determination of or-ganic matter and carbonate matter content, meas-urement of magnetic susceptibility, study of sedi-ment microstructure, hyperspectral scanning of cores, search for and geochemical studies of cryp-totephra, diatom and spore-pollen analyses, anal-yses of macro-charcoals and plant macro-remains. The implementation of the work planned will allow: 1. to create a reference network of high-resolution (first years to decades) paleoarchives of lacustrine deposits, covering the interval of the last 25 ka. 2. to specify regional and local paleoreconstructions of hydrological conditions, erosion and accumula-tion dynamics, vegetation and climate for the Late Pleniglacial, Late Glacial and Holocene. 3. to identify previously unknown extreme events in the history of geosystems: catastrophic floods, fires, extensive human development of the territory. The results obtained will be published in peer-reviewed international and Russian journals and will allow replenishing global and regional data-bases on paleolimnology and ecosystem history (NOAA, PBDB, Neotoma, Paleoecology Database, PaleoLake, Tephrabase, etc.), will contribute to the development of paleoclimatic models through the assimilation of paleodata.

Mineral dust aerosol is correlated with the climate's condition on the Earth in general and specific planet's regions. The dust accumulation in environmental paleoarchives (loess, lacustrine, glacial) reflects the intensity of aeolian processes and the climate's humidity. In the south of European Russia, in the Ciscaucasia, there are vast areas of loess deposits that continuously cover the territory from the Sea of Azov to the Caspian Lowland. The Ciscaucasian loess formation generated by the mineral dust sedimentation over the past 500-800 thousand years. The total thickness of these deposits can reach 150-200 meters, and the thickness of the Upper Pleistocene loess in the east of the region reaches 50 meters, which is a record for European loess. Such high sedimentation rates make it possible to provide highly detailed paleoreconstructions based on serial luminescence dating and lithological and geochemical analyses complex use. But the composition of loess and its thickness is heterogeneous across the territory. This heterogeneity is the key to understanding the sources of dust (areas of deflation). It can be sandy alluvial massifs of large rivers' lower reaches (Volga, Don, Terek and Kuma) and sea terraces. The scientific significance of the project is determined by the international scientific community's broad interest in the sources and volumes of mineral dust entering the atmosphere during the end of the Quaternary period. Quantitative regional assessment of the rate of mineral dust intake is an essential link in the chain of paleoclimatic reconstructions. It serves as an indicator of the climate aridization extent. Much attention in the scientific literature of the last two decades is paid to the atmospheric circulation reconstruction, the direction and strength of paleowind based on studies of mineral dust transport routes. Regarding regional paleogeography, it seems to be of great interest to extract the following information of significant changes in the hydro-climatic characteristics of the East European plain out of the loess-paleosol series: the area of the glacier cover, the river flow volume, the average annual precipitation and evaporation, the Caspian and Black Seas' levels. Stratigraphically, the loess-paleosol series of the Ciscaucasia (especially the central and eastern territories) can claim the role of regional stratotype sections for the Middle and Late Pleistocene. The high risks to agriculture, life and health of people in densely populated areas of the south of Russia, associated with soil erosion and dust accumulation processes, determine the project's practical significance. The study of the mechanisms of these processes' reaction to global and regional climate changes will allow us to make more reasonable long-term forecasts of the rate of deflation and aeolian accumulation, the deflation areas localization, and dust storms intensity and frequency. Besides, reliable paleoreconstructions based on the sedimentary paleoarchives study will verify existing paleoclimatic models, contributing to their qualitative improvement. During the project realization, we plan to study the structure, material composition and precise age of the loess-paleosol series in the interval of the last 250 thousand years at seven key sites on the west, central, and east parts of the region. Luminescent dating of the samples (at least 7 per site) and a series of lithological and geochemical studies of samples taken at least every 10 cm are supposed to get done. For Holocene loess in the east of the region, the detail of testing in cores suppose to be every 2 cm. The study of lake-marsh paleoarchives will support the identification of extreme Holocene aeolian events. As a result of the study, we suppose to calculate the dynamics of loess accumulation rates at different stages, determine the sources of dust, identify regional litho-geochemical markers, clarify and detail the scheme of loess-paleosol stratigraphy, link the history of loess accumulation with paleogeographic events in marine basins, correlate with global scales, and verify existing paleoclimatic models.

Identification of natural and climatic events of the past corresponds to modern trends in disciplines dealing with the Earth's past, towards detailed reconstructions, the desire to move from average estimates to the event level of research. These trends are dictated by the needs for a more reliable linking of all the diverse results into a single picture of the past, which, in turn, serves as a basis for understanding modern changes in the natural environment, making long-term forecasts, and assessing the risks of extreme and catastrophic processes. Success in achieving these goals is based, first of all, on the study of geological and other natural formations formed in the epoch of interest in the past - paleoarchives of the natural environment, containing "records" of information about natural settings and events. Sedimentary paleoarchives of the Pleistocene and Holocene of the continental regions of Russia are represented mainly by lake-bog, loess, alluvial and slope deposits. The wide distribution of these paleoarchives makes it possible, on the one hand, to check the reliability of paleorecords through the reproducibility of results, and on the other hand, to identify zonal differences in synchronous paleorecords remote from each other. For the territory of Russia, two problems in this research area remain significant: 1) low coverage of the network of reference points where reliable paleoreconstructions were obtained; 2) low temporal resolution of paleoreconstructions beyond the late Holocene. The solution to the first problem is associated with an increase in the number of objects studied by modern analytical methods and reliable age reference. The solution to the second problem is associated with the search for rare high-resolution paleoarchives, in which the temporal resolution is measured in years or the first decades of life. Such paleoarchives include some types of lake deposits formed at high sedimentation rates and low bioturbation intensity. These conditions sometimes allow seasonal pairs of layers - varves - to be preserved. The study of such highly detailed lake-sedimentary records yields breakthrough results in detailing events and understanding cause-and-effect relationships in geosystems. The purpose of the study: diagnostics of natural and climatic events of the Pleistocene and Holocene in Russia through a detailed analysis of sedimentary records of various types. To achieve this goal, the following tasks were set: 1) Improving the methods of sampling and analyzing high-resolution sedimentary records; 2) Identifying chronostratigraphic markers of abrupt changes in the natural environment in sediment; 3) Diagnostics of traces of volcanic paleoevents; 4) Identifying and assessing the recurrence of hydrometeorological extremes in the European territory of Russia.