RECONSTRUCTION OF THE POST-GLACIAL ENVIRONMENTAL VARIATIONS BASED ON THE MULTI-PROXY APPROACH: DŪKŠTELIS LAKE, EASTERN LITHUANIA

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Regional variations of carbonates in postglacial sediments and response of physical sediment properties to climatic events and vegetation

Despite an increasing number of geochemical and palynological data representing the Lateglacial and Holocene sediment sequences that are used to evaluate long-term and short-term interactions between soil and vegetation, the main environmental drivers of these processes are not fully understood so far. Soil composition, vegetation and lake evolution are diverse in all sites analysed in this study. The work was aimed to provide a comparison of the evolution of conifer and broad-leafed plant taxa spread with sediment geochemical data, including organic carbon and CaCO3 changes during the same sedimentation period. Problems addressed here analyze the increased carbonate mobility initiated by the invasion of conifers and a subsequent drop in soil pH. Together with this, the influence of organic material on accumulation of carbonates and sensitivity of Mn and Fe to redox conditions was evaluated. In general, chronologically defined changes in sediment composition revealed the intervals of more stable environmental conditions during which biotic factors were of greater importance in altering vegetation structure and the periods during which scarce vegetation had a negative impact on soil development leading to its progressive deterioration. Related changes occurred in sediments from different lakes; however, due to geographical position, responses to warming or cold events were a bit asynchronous

Regional variations of carbonates in postglacial sediments and response of physical sediment properties to climatic events and vegetation

Despite an increasing number of geochemical and palynological data representing the Lateglacial and Holocene sediment sequences that are used to evaluate long-term and short-term interactions between soil and vegetation, the main environmental drivers of these processes are not fully understood so far. Soil composition, vegetation and lake evolution are diverse in all sites analysed in this study. The work was aimed to provide a comparison of the evolution of conifer and broad-leafed plant taxa spread with sediment geochemical data, including organic carbon and CaCO3 changes during the same sedimentation period. Problems addressed here analyze the increased carbonate mobility initiated by the invasion of conifers and a subsequent drop in soil pH. Together with this, the influence of organic material on accumulation of carbonates and sensitivity of Mn and Fe to redox conditions was evaluated. In general, chronologically defined changes in sediment composition revealed the intervals of more stable environmental conditions during which biotic factors were of greater importance in altering vegetation structure and the periods during which scarce vegetation had a negative impact on soil development leading to its progressive deterioration. Related changes occurred in sediments from different lakes; however, due to geographical position, responses to warming or cold events were a bit asynchronous

RECONSTRUCTION OF THE POST-GLACIAL ENVIRONMENTAL VARIATIONS BASED ON THE MULTI-PROXY APPROACH: DŪKŠTELIS LAKE, EASTERN LITHUANIA

33-3

The Late Pleistocene–Early Holocene palaeoenvironmental evolution in the SE Baltic region: a new approach based on chironomid, geochemical and isotopic data from Kamyshovoye Lake, Russia

© 2020 Collegium Boreas. Published by John Wiley & Sons Ltd The Kamyshovoye Lake sedimentary record in the southeastern Baltic Sea region was studied to reconstruct climatic fluctuations and the abiotic responses to them during the Lateglacial and Early Holocene. New results from chironomid, isotopic, palaeomagnetic and geochemical data analyses were correlated with earlier evidence of lithological and palynological changes in the Kamyshovoye Lake record. The section of the record that was studied covered the interval between 15 200 and 6500 cal. a BP. Palaeoclimatic reconstructions showed that during the Younger Dryas there was a two-step decrease in the mean July temperature. The temperature dropped by 3 °C in the period from ̃12 650 to 12 300 cal. a BP, and then it dropped by another 0.5 °C to a minimum of 11.5 °C at 11 900 cal. a BP. During the Younger Dryas–Holocene transition, a temperature increase of 3 °C can be seen over a period of several centuries, inferred from the chironomid data. Further, the temperature curve showed that significant fluctuations continued until ̃9500 cal. a BP. During the coolings, the average July temperature dropped to values that were typical for the Younger Dryas, while values characteristic for the Allerød were only reached at around 9700 cal. a BP. After 9500 cal. a BP, a more stable, gradual increase in temperature was recorded. The short-term Early Holocene climatic oscillations are clearly traced in the Kamyshovoye sequence, although the responses of the natural components are sometimes asynchronous. In the case of the Kamyshovoye study, the geochemical data seem to be a sensitive indicator of the climatic and environmental changes despite the absence of an evident response to the Holocene onset at ̃11 700 cal. a BP. Considerable changes in the geochemical pattern are recorded later, at ̃11 500 cal. a BP, coinciding with noticeable changes in the development of vegetation. The results obtained in this study contribute to a deeper understanding of how global climatic trends are manifested on a local scale