CONTENTS & ABSTRACTS
In English. Summaries in Estonian
Proceedings of the Estonian Academy of Sciences.
Volume 54 No. 1 March 2005
Anto Raukas – an encyclopaedist in Estonian Quaternary geology; 3–4
Dimitri Kaljo, Avo Miidel, Leili Saarse, and Alvar Soesoo
Chronological data from Estonian Pleistocene; 5–25
Abstract. Pleistocene chronostratigraphy in Estonia is based on 60 radiocarbon (14C, 14C AMS), 63 TL/OSL, and 17 10Be datings from 57 studied sites/sections that cover a time span from approximately 200 000 yr BP to the Pleistocene–Holocene chronostratigraphic boundary. For the first time all scattered data from 40 years of chronological study into Estonian Pleistocene are presented together and critically analysed in regard to validity of obtained ages. Half of the relatively abundant but scattered chronological data cover only the youngest 5000–6000 year part of the Late Weichselian. New OSL datings, together with the results of earlier palynological, carpological, and diatom studies, have invalidated almost one-third of the available 14C dates, obtained mostly in the late 1960s and 1970s. Thermoluminescence ages from tills, available from the early 1980s, are very inconsistent within the studied sections and are considered to be unreliable because of questionable bleaching of the TL signal. The results of the 10Be method, recently applied to the study of deglaciation chronology of the Estonian territory, do not contradict the earlier age estimations. However, due to relatively large uncertainties of the method, the results were not able to refine the existing Late-Glacial chronology in Estonia.
Key words: geochronology, Late Weichselian, deglaciation, Estonia, dating methods.
Eskers in the periphery of their distribution in North Estonia; 26–39
Abstract. Eskers are frequent landforms in the palaeo-glacial erosional zone. A channelized network of subglacial water conduits above the nonpermeable surface is an obligatory precondition for esker genesis. The current study supports the results of the investigations of modern high-arctic esker formation. The structure and stratification of the esker deposits indicate fast changes and alternation of erosion–transport–accumulation processes. The extent of esker systems over tens or hundreds of kilometres indicates their time-transgressive inherited genesis.
The territory of Estonia lies in the periphery of the esker distribution area of the Scandinavian glaciation. Radial eskers in Estonia consist mainly of coarse-grained deposits of local Palaeozoic bedrock. The combination of eskers and glaciokarst kettle holes or glaciofluvial plateaus and kame fields is frequent. The ridge-like glaciofluvial topography, morphologically similar to eskers but formed in stagnant ice is specified as crevasse fillings, and is genetically related to kames.
Key words: eskers, Scandinavian glaciation, glacial topography, lithology, Late Weichselian.
Grain size of the bottom sediments of Lake Väike Juusa (southern Estonia) as the indicator of water-level fluctuations; 40–51
Jaan-Mati Punning, Jaanus Terasmaa, and Ene Kadastik
Abstract. Surface sediments and sediment cores from Lake Väike Juusa were studied in order to examine the dependence of the sedimentation regime on the topography and development of the lake. Close relationship was established between the grain size of the surface samples and depth of water at the sampling site. The data obtained show that in the lake the accumulation area is situated deeper than 4.0 m. The grain size data for three sediment cores allowed reconstruction of lake-level fluctuations and their amplitude.
Key words: lithology, lake sediments, lake-level fluctuations, palaeolimnology, Estonia.
Palynostratigraphy of Holocene lake sediments on the Otepää Heights, southern Estonia; 52–68
Abstract. The pollen diagram with accelerator mass spectrometer (AMS) radiocarbon dates covering Holocene sediments from the Otepää Heights gives a general overview of the vegetation history of the area. The pollen assemblage zones (PAZs) defined on the pollen diagram of the Lake Väike Juusa core in general correspond to the PAZs on the stratigraphic chart of Holocene sediments in Estonia. Comparison of the pollen profile of Lake Väike Juusa with other pollen diagrams from the same area enables us to distinguish differences in the vegetation history induced by local factors. The most characteristic differences occur in the Picea pollen content. Picea migrated to the Otepää Heights in small patches already at the end of the Boreal Chronozone and started to spread at the end of the Atlantic Chronozone. This is about 1000 years earlier than shown in the Holocene stratigraphic chart of Estonia. Also human activity and forest fires in the areas surrounding the study sites have affected the vegetation dynamics on a local scale during the last two millennia.
Key words: pollen, palynostratigraphy, vegetation history, forest fires, southern Estonia.
Instructions to authors; 69–71
Copyright Transfer Agreement; 72