Chronology of Late Saalian and Middle Weichselian episodes of ice-free lacustrine sedimentation recorded in the Arumetsa section, southwestern Estonia

The information obtained from a 21 m thick open-pit section of silty-clayey sediments in the Arumetsa bedrock valley, southwestern Estonia, revealed that lacustrine to glaciolacustrine sedimentation at the site started prior to 151 ka ago and lasted to about the end of marine isotope stage 6 (MIS6) at 130 ka. Further down from the 151 ka age-level to the bottom of the buried valley there are ca 60 m of lacustrine fine-grained sediments, the age of which remains still unclear. The Late Saalian sediments at Arumetsa are discordantly overlain by Middle Weichselian clay, silt and sand, deposited between ca 44 and 37 ka ago. As testified by optically stimulated luminescence (OSL) ages, and pollen and diatom record, the Middle Weichselian fine-grained sediments contain redeposited Holsteinian but no Eemian pollen, and have not been fully bleached during deposition. Chronological, microfossil and sedimentological data show two hiatuses in the Arumetsa section. The first hiatus has left no sedimentary evidence for the period between ca 130 ka and 44 ka ago (MIS5 to older half of MIS3). The younger hiatus from ca 37 to 22 ka occurs between the Middle Weichselian lacustrine silt and the Late Weichselian till layer on top of the section

Late Glacial vegetation, sedimentation and ice recession chronology in the surroundings of Lake Prossa, central Estonia

Pollen records from Lake Prossa, located in the Saadjärv Drumlin Field, indicate rather homogeneous pollen spectra in the pre-Allerød period and a thick sediment sequence suggesting high input of mineral matter and erosion. This period is characterized by pioneer vegetation with dwarf-shrubs. At the beginning of the Allerød, Salix, Artemisia and redeposited temperate and thermophilous taxa prevailed in pollen spectra, referring to shrub tundra conditions, followed later by Betula and Pinus(?) arrival. Silt with organic debris deposited. Vegetational set-back and tundra plant species with scattered birches and silty deposits containing abundantly Drepanocladus fragments characterize the Younger Dryas stadial. The sedimentation rate decreased markedly and was followed by a hiatus at the beginning of the Holocene. The AMS 14C dates, and microfossil and sedimentological data show that the ice front receded and stratified sediments started to deposit about 14 200–14 300 cal yr BP, permitting specification of poorly constrained ice recession chronology in central Estonia

Ice-free interval corresponding to Marine Isotope Stages 4 and 3 at the Last Glacial Maximum position at Kileshino, Valdaj Upland, Russia

Radiocarbon and optically stimulated luminescence dates, together with bio- and lithostratigraphical data, revealed an interval of ice-free conditions between 72.2 OSL and 33.8 cal 14C ka BP at the Kileshino site (Valdaj Upland, Russia), corresponding to Marine Isotope Stages (MIS) 4 and 3. Limnic sedimentation conditions occurred at the Kileshino site between 57.5 OSL and 33.8 cal 14C ka BP, corresponding to MIS 3 ‘megainterstadial’ in European Russia (Oerel to Hengelo interstadials in Central Europe). During the last glaciation, a sedimentary unit of laminated silt and sand of fluvial origin was redeposited at that site due to expansion of the Scandinavian Ice Sheet (SIS). This unit expresses fluvial sedimentation conditions NW of Kileshino between 72.2 and 40.8 OSL ka. All dates together suggest that the Kileshino site was ice-free between 72.2 OSL and 33.8 cal 14C ka BP. The sedimentary unit of laminated silt and sand was redeposited at the Kileshino site during the last SIS not before 33.8 cal 14C ka BP, according to previous studies, possibly at its maximum extent between 19.1 cal 14C BP and 18 OSL ka. Only one till, younger than 72.2 ka, was found from the Kileshino outcrop. It can be concluded that the SIS reached this area only once during the last 72.2 ka – in the late Valdaj (Weichselian), after 33.8 cal 14C ka BP. The expansion of the SIS to the study area between 115 and 58 ka could be neither proved nor disproved as there is no chronological information about the time between 115 and 72.2 ka

Reading past landscapes : combining modern and historical records, maps, pollen-based vegetation reconstructions, and the socioeconomic background

Context: Anthropogenic and environmental changes are reshaping landscapes across the globe. In this context, understanding the patterns, drivers, and consequences of these changes is one of the central challenges of humankind. Purpose: We aim to test the possibilities of combining modern multidisciplinary approaches to reconstruct the land-cover and linking the changes in land-cover to socioeconomic shifts in southern Estonia over the last 200 years. Methods: The historical records from five, and maps from six time periods and 79 pollen-based land-cover reconstructions from four lakes are used to determine the land-cover structure and composition and are thereafter combined with the literature based analyses of socioeconomic changes. Results: All information sources recorded similar changes in the land-cover. The anthropogenic deforestation was comparable to today’s (approximately 50%) during the nineteenth century. Major political and socioeconomic changes led to the intensification of agriculture and maximal deforestation (60–85%) at the beginning of the twentieth century. The land nationalisation following the Soviet occupation led to the reforestation of the less productive agricultural lands. This trend continued until the implementation of European Union agrarian subsidies at the beginning of the twenty first century. Conclusions: Pollen-based reconstructions provide a trustworthy alternative to historical records and maps. Accounting for source specific biases is essential when dealing with any data source. The landscape’s response to socioeconomic changes was considerable in Estonia over the last 200 years. Changes in land ownership and the global agricultural market are major drivers in determining the strength and direction of the land-cover change

Long-term drivers of forest composition in a boreonemoral region: the relative importance of climate and human impact

Aim To assess statistically the relative importance of climate and human impact on forest composition in the late Holocene. Location Estonia, boreonemoral Europe. Methods Data on forest composition (10 most abundant tree and shrub taxa) for the late Holocene (5100-50 calibrated years before 1950) were derived from 18 pollen records and then transformed into land-cover estimates using the REVEALS vegetation reconstruction model. Human impact was quantified with palaeoecological estimates of openness, frequencies of hemerophilous pollen types (taxa growing in habitats influenced by human activities) and microscopic charcoal particles. Climate data generated with the ECBilt-CLIO-VECODE climate model provided summer and winter temperature data. The modelled data were supported by sedimentary stable oxygen isotope (O-18) records. Redundancy analysis (RDA), variation partitioning and linear mixed effects (LME) models were applied for statistical analyses. Results Both climate and human impact were statistically significant predictors of forest compositional change during the late Holocene. While climate exerted a dominant influence on forest composition in the beginning of the study period, human impact was the strongest driver of forest composition change in the middle of the study period, c.4000-2000years ago, when permanent agriculture became established and expanded. The late Holocene cooling negatively affected populations of nemoral deciduous taxa (Tilia, Corylus, Ulmus, Quercus, Alnus and Fraxinus), allowing boreal taxa (Betula, Salix, Picea and Pinus) to succeed. Whereas human impact has favoured populations of early-successional taxa that colonize abandoned agricultural fields (Betula, Salix, Alnus) or that can grow on less fertile soils (Pinus), it has limited taxa such as Picea that tend to grow on more mesic and fertile soils. Main conclusions Combining palaeoecological and palaeoclimatological data from multiple sources facilitates quantitative characterization of factors driving forest composition dynamics on millennial time-scales. Our results suggest that in addition to the climatic influence on forest composition, the relative abundance of individual forest taxa has been significantly influenced by human impact over the last four millennia