Special Issue. Pathways of evolutionary geography 2. Part 1. Palaeogeography of the Quaternary. Editorial

The Ivantsevo section is located in a gravel pit at an outskirt of Dmitrow town, Moscow region. The section consists of sand, peat, gyttia, and silt; cryogenic structures including ice wedge casts are well developed. Repeatedly lake-bog sedimentation changes were observed there. The lake-boggy unit has been formed during MIS 5 since MIS 5e, it includes 3–4 warm intervals. The peat yields fossil insects (mainly beetles), small freshwater invertebrates, and plant macrofossils. Carpological remains include some typical for Mikulino interglaciation species. Pollen record allow recognizing the vegetation changes from mixed pine-birch with single broad-leaved trees to coniferous forests and open communities dominated by birch, shrubs, light-demanding grasses, and Artemisia. The section allows to reconstruct the history of the climate and environment from the Middle Pleistocene (Moscovian Dnieper glaciation) to the early stages of the Late Pleistocene.

High-resolution multi-proxy studies of lake sediments, including AMS 14C dating, lithology, loss-on-ignition measurements, pollen analysis and identification of plant macrofossils, of Lake Seliger (57°17'N, 33°04'Е) and five other lacustrine records from the adjacent areas used for comparison, make it possible to reconstruct the main changes in the productivity of lakes and vegetation development in response to the short-term climatic oscillations during the Late Glacial and early Holocene. The analysis showed that lacustrine sedimentation at all these sites began 13–14.5 cal kyr BP, in the Allerød Interstadial, when spruce, birch and pine began to spread in the northwest of European Russia forming the open woodlands. A substantial cooling in the Younger Dryas caused a rapid decline of forest communities and a re-advance of the tundra-steppe vegetation with scattered groups of trees in the protected habitats. The composition of lake sediments changed everywhere in a similar way – from predominantly mineral deposits in the Late Glacial to those with high organic contents (gyttja) in the early Holocene. Following the rapid warming at the Late Glacial/Holocene transition, woodlands formed by birch and, later, pine expanded again over the area. A short-term cooling 11.4–11.2 cal kyr BP, coeval with the Preboreal Oscillation observed in the Greenland ice-core records, most clearly manifested itself by a decrease in the proportion of organic matter in lake sediments. It also interrupted or slowed down the expansion of birch and pine forests and caused a new spread of open grassland vegetation. However, the impact of this cooling on the vegetation development and lake ecosystems in the northwest of European Russia was probably weaker than in western and central Europe. At the beginning of the late Preboreal, there was a new rapid shift to a warmer and more humid climate, when birch forests expanded again, followed later by pine. Further warming during the Boreal brought about the introduction of broadleaved tree species into forest communities and a decrease in the landscape role of birch forests. At this time, some lakes were filled, and lacustrine sedimentation was replaced by the formation of peat.

The sediment sequence from Lake Kanozero in the Kola Peninsula was studied for pollen, diatoms and lithology in order to investigate responses of the lake ecosystem to environmental changes. Our first results show that development of the Lake Kanozero was complex and included a Late Glacial lake phase and subsequent drainage, a history of fluvial input affected by nearby wetland expansion, and formation of the shallow lake. Organic matter began to accumulate in the lake at about 9100–9200 cal. kyr BP, which provides a minimum age for the deglaciation of the basin. This period is distinguished by the all reconstructed indicators. The climate is getting warmer and drier. The vegetation acquires a northern taiga type with Pinus and Betula forests spread. The diatom record suggests environmental changes that apparently related to the water-level lowering, as indicated by disappearance of Aulacoseira taxa and general increase in benthic species. This transitional horizon of very strong shallowing corresponds to the initial stage of the formation of the modern Lake Kanozero. The active movements of ancient people were possible at about the end of the Atlantic and the beginning of the Subboreal periods.

This paper presents the first reconstruction of the paludification process and vegetation history during the last 8000 cal years BP in the western part of the Tersky Coast (south Kola Peninsula); in the River Varzuga mouth; based on multi-proxy studies of the Kuzomen Mokh peatland including high resolution pollen and plant macroremains analyses; loss on ignition measurements; AMS radiocarbon dating of the peat; and quartz grain morphoscopy analysis for sandy deposits underlying the peat sequences. The obtained data revealed that the paludification stage was preceded by aeolian processes occurred in the study area during the Late Glacial and Early Holocene. Analysis of quartz sand grain morphoscopy revealed that glacial and fluvioglacial sands underlying peat deposits in Kuzomen Mokh peatland were partly affected by aeolian processes that are indicated by specific textures on the surface of quartz sand grains typical for air transport. Peat accumulation started not later than 7865 ± 45 cal yr. BP assuming a decline of aeolian processes in the study area. Analysis of plant macroremains showed an evolution of mire from the poor fen to ombrotrophic rised bog. Local vegetation successions were obviously influenced by fire in the period between 7800 and 2700 cal yr. BP. According to pollen data vegetation history in the Tersky coast of the White Sea during the last 8000 cal yr. BP included a series of successive phases of birch; birch-pine and pine forests caused probably by climatic changes and fire activity. Picea appeared in the study area around 7000 cal yr. BP and reduced in abundance during the last 200 years due to human impact and fires.

The paper deals with new palaeoecological reconstructions for the last ca. 4700 years based on detailed AMS-radiocarbon dating, pollen, plant macrofossils and macroscopic charcoal records from peat sequence, obtained from the mire near Igarka (Yenisei Siberia). The data obtained testify to the widespread of middle taiga larch forests with a high proportion of Abies sibirica, Picea obovata and Pinus sibirica over the study area between 4700 and 3600 cal. years BP. Сlimate warming caused the northward shift of the boundaries of the vegetation zones in the Yenisei Siberia and the expansion of Abies sibirica range by 200 km to the north compared to the modern one. Starting from ca. 3600 cal. years BP the forest cover began to gradually decrease, and the middle taiga vegetation gave way to sparse larch and birch-larch forests with the participation of spruce and Siberian pine and treeless vegetation characteristic of the northern taiga. The vegetation pattern of the region became close to the modern one around 2600 cal. years BP. Macroscopic charcoal analysis revealed that biomass burning was low until the last 500 cal. years, with the exception of an episode of a strong fire 3600–3500 cal. years BP. Fire activity intensified in the late 14th and early 15th centuries AD, obviously due to anthropogenic impact.

A new pollen record and biome reconstructions from the Lake Khikushka provide insights into environmental and climate changes of the so far unstudied area of the Oka Plateau in the East Sayan Mountains, south East Siberia over the last 13490 cal. yr BP. The tundra biome predominates ca. 13490–12600 cal. yr BP, closely followed by taiga and steppe suggesting cold continental climate where the permafrost layer was close to the surface. The reconstruction demonstrates significant participation of boreal trees such as Picea obovata and Larix sibirica in the vegetation at this time. Later, ca. 12600–11200 cal. yr. BP. the reconstruction suggests a reduction of the steppe and tundra biomes due to a further spread of Picea and Larix. A short interval ca. 11200–10500 cal. yr BP is marked by maximum distribution of Abies and the strengthening of the taiga biome. The interval between ca. 10500 and 6500 cal. yr. BP reveals progressive expansion of the pine-dominated taiga biome that is in line with many other pollen records from Eurasia. The taiga biome was dominant in the study area for the last 6500 cal. yr BP. Since ca. 5000 cal. yr BP the Larix stands were close to the lake. Vegetation became similar to the modern after ~5000 cal. yr BP.

Stable carbon isotopes in tree rings may serve as an important proxy of past climatic and environmental changes. However, the climatic signal that is expressed in this proxy vary across regions and species. European Russia is still an understudied region, where a few studies on climatic signal in isotopic composition of wood were undertaken. Here we provide the first results of such study for living Scots pines in the city of Yaroslavl. We measured the ratio of stable carbon isotopes (δC13) in wood cellulose of individual tree rings extracted from five trees, and calculated correlation coefficients of δC13 with meteorological parameters. The period analyzed is 2010–2020. We showed that δC13 in wood cellulose has a significant relationship with May-September temperature (r = 0.63, p = 0.037), May-September precipitation (r = –0.77, p = 0.0051), and May-September Palmer Drought Severity Index (r = –0.65, p = 0.032). These results are the first direct evidence that δC13 in wood cellulose of Scots pine in Yaroslavl may serve as a proxy for the warm period moisture variations. Additional measurements are required to make conclusions about the stability of climatic signal in this proxy throughout the 20th century. We also describe two new tree-ring chronologies based on archaeological and architectural materials from the Yaroslavl (AD 1438–2019) and Kostroma (AD 1283–2012) regions. According to the obtained results on the climatic sensitivity of δC13 in wood cellulose, these chronologies may serve as a material base for annually resolved moisture reconstructions in the region.

Lake sediments of the northern Mologa-Sheksna Lowland were for the first time studied using high-resolution x-ray fluorescence scanning and AMS dating, supplemented with x-ray diffraction, total organic carbon, grain-size and magnetic susceptibility measurements. The combined results revealed sedimentation type changes during the Late Glacial and Early Holocene, which were associated with the proportions of allogenic and authigenic material in the deposits. Short-lived periods of low allogenic activity were registered ~14.0 cal. ka BP and ~13.0 cal. ka BP, interrupted by episodes of enhanced minerogenic input and low organic accumulation ~13.7, ~13.1 and ~11.5 cal. ka BP. The outlined intervals correspond with the Late-Glacial climatostratigraphic units of the North Atlantic region. The beginning of the organic sedimentation ~11.7 cal. ka BP indicates climatic warming of the Early Holocene. During the Younger Dryas and Early Holocene, until ~11.0 cal. ka BP, the sedimentation was furthermore influenced by the lake-level changes.

Chocolate clays are polyfacial marine sediments of disputable genesis, widely distributed in the Lower Volga region. We present the results of detailed analysis of microstructure features, granulometric (42 samples) and mineralogical (24 samples) compositions of different layers in the thickness of the Lower Khvalynian chocolate clays of the Srednyaya Akhtuba and Raygorod sections. The sections are located on opposite sides of the Volga-Akhtuba floodplain. Based on the data obtained with a laser diffractometer, lithological coefficients were calculated. This allowed us to distinguish seven lithotypes common to the two sections, each of which also has specific mineralogical and micromorphological characteristics. The mineralogical structural features of minerals in the <1 μm fraction in each lithotype and the quantitative ratios of clay minerals were determined by X-ray diffractometry. It was revealed that the most clayey lithotypes are characterized by the predominance of trioctahedral illite over smectite. The opposite situation was observed in the silty lithotypes, where smectite predominated over dioctahedral illite. The swelling components were represented by highly charged beidellite in the Srednyaya Akhtuba section and highly charged montmorillonite in the Raygorod section. Such differences in the ratio and structure of clay minerals may be caused by different sources of drift or by their different synsedimentation or diagenetic transformations. Micromorphological data allowed us to establish biogenic textures in the clay lithotypes of the Lower Khvalynian Chocolate clays. In silty lithotypes, oblique layering and carbonaceous organic matter were determined, which suggests the proximity of their sedimentation zone to the coastline. The obtained materials made it possible to show the complex composition of individual layers of the chocolate clay sequence and determine new directions in the study of their genetic features. Studies of individual lithotypes of the Lower Khvalynian chocolate clays with a detailed reference to the depths were carried out for the first time.

The problem of the source of mineral dust, which makes up the loess-paleosol sequence of Ciscaucasia, remains relevant. One of the main approaches to solving the problem is the spatial analysis of the structure and composition of the loess. Based on the core analysis of three boreholes, a sublatitudinal cross-section of the loess-paleosol sequence of the Upper Pleistocene and Holocene was constructed. A gradual decrease in the thickness of loess-paleosol sequence and grain size from east to west was found out. The total thickness of the Upper Pleistocene and Holocene deposits in the OT-20 section (eastern part) is 22.6 m, SB-1 (central part) – 9.7 m, YS-1 (western part) – 5.3 m. The average content of the sand fraction decreases in the same direction: OT-20 – 17.1%, SB-1 – 6.1%, YS-1 – 1.9%. The results indicate that the main direction of the aeolian transport during the Late Pleistocene and Holocene was from east to west. Sand deserts of the Caspian low-land are probably the main source of the material. Secondary sources of mineral dust are local sandy massifs spread on the terraces of large rivers like Don and Kuban. Compositional variations of loess in depth show that the intensity of eolian processes was higher during cold periods and lower during warm ones. The loess sequences in the east of Ciscaucasia have higher temporal resolution and more responsive paleoclimatic indicators than the western ones.

The paper presents the results of quartz grains surface textures study in order to reconstruct the sedimentary history and deposition environments of the crest strata formation in the Kareglazova section (southern part of the West Siberian Plain, Russian Federation). Using a scanning electron microscope (SEM), quartz grains of the medium sand fraction (0.25–0.5 mm) from 19 samples were studied. The crest is composed mainly of fine low-sorted sand with a large proportion of clay and silt components. The studied samples from the Kareglazova section contains four main types of quartz grains with different morphology and complexes of surface textures, which bear signs of transportation and accumulation in various environments. The roundness ratio of grains of the medium sand fraction (according to A.V. Khabakov) varies across the section from 54 to 65%. Semi-rounded quartz grains predominate (up to 57%), the share of well-rounded grains averages 39%. Vast majority of grains bear traces of post-sedimentary transformations, which are expressed in the presence of amorphous silica films and traces of etching of previously formed textures. Alluvial-lacustrine sediments of different age, common in the study area, are likely to be the primary sources for the crest deposits. The quartz grains surface features have traces of eolian processing and overlay of aeolian surface textures (upturned plates) on the surface textures typical for subaqueous environments (V-shaped pits, curved grooves, smooth surface). The occurrence of specific aeolian surface textures mainly on convex areas of quartz grains and the presence of cryogenic processing traces indicate the accumulative nature of crest with the predominance of local terrigenous provenances in cold and arid conditions of the periglacial climate. The upper part of the crest section was probably formed in a relatively moderate humid climate, when the migration of colloidal solutions was possible.

Specific landscapes defined as chalky polygons can be found formed on chalky rocks under a continental climate across the south-east of the East European Plain. Theses landscapes are characterized by polygonal microrelief and spotting, outwardly resembling tundra medallions. Such landscape complexes are unique and practically not investigated. Our investigation showed a number of relict cryogenic features: polygonal relief with the polygon side averaging 5 m; ground wedges associated with hollow-like depressions between polygons; cryoturbation of soil profiles, and paleocryotextures. The results suggested the paleofrost genesis of chalky polygons. Chalky polygons were found to be a kind of relict cryogenic relief formed in the Valdai Cryochron in conditions of cryoarid climate, permafrost, frost cracking of soils and the growth of polygonalvein ice.

The most active relief changes in the Northwest of European Russia during the last millennia were due to the geomorphological activity of rivers. Reconstruction of these changes is of great importance for the studies of the Late Holocene archaeological sites, many of which are located in the bottoms of river valleys. The studies performed at two key sites – Shnitkino (Toropa River valley, Western Dvina River basin) and Gnezdovo (upper Dnieper valley) – allowed to reconstruct the appearance of local landscapes in the Early Middle Ages. The geological and geomorphological structure of the valley sections was studied, and radiocarbon dating of the deposits was performed. The studied Early Medieval settlements were founded on the shores of lakes of non-oxbow type, quite numerous in the river valleys of the Dnieper-Dvina region. The mechanism of lake formation differed due to differences in the post-glacial history of the river valleys: in the glacial zone these could be residual lakes originating from larger post-glacial lakes (lake Shnitkino in the Toropa river valley), outside the boundary of the last glaciation – lakes associated with river activity (lakes Kamyshi and Bezdonka in the upper Dnieper valley). It has been found that during the Medieval Climate Warming (VIII–XII centuries) the magnitude of floods was lower than now, which allowed the settling of floodplains of rivers normally inundated by spring floods. The dynamics of river valleys in the Late Holocene was reconstructed. The development of river valleys was generally dominated by accumulation processes. Sediment accumulation on the river floodplains was interrupted when flood levels decreased, as during the Medieval Climate Warming, and resumed when the hydrological regime changed towards an increase in floods (the Little Ice Age in the 14th–19th centuries).

The features of the Volga water flow changes in the last interglacial climatic optimum (~125 ka BP), Holocene optimum, modern (starting from 1981), and scenario (2006–2039) global warming have been revealed. Paleoclimatic reconstructions based on data of spore and pollen analysis of fossil plants and results of calculations carried out on the ensemble of global climate models of PMIP-II program, as well as scenarios of climate warming, performed on an ensemble of global climate models of CMIP3 program, have been used. Hydrological changes have been evaluated on the basis of the monthly water balance model). The most notable hydroclimatic changes took place in the warm epoch of the last interglacial climatic optimum, when the annual river runoff was 25% less than its modern value. Scenario air temperature in the Volga basin for the first third of the current century was close to the temperature of the Holocene optimum, reconstructed on the basis of palynological data. At the same time, the simulated annual flow was lower than the modern one. At projected and the Holocene Optimum climatic conditions reconstructed within PMIP-II, it appears above modern. The most noticeable differences in the Volga flow in warm climate of the Holocene optimum, modern and scenario periods are manifested in changes in the intra-annual distribution of their water flow.