CONTENTS &
ABSTRACTS
In
English. Summaries in Estonian
Proceedings of the Estonian Academy of Sciences.
Geology
Volume 50 No. 4
December 2001
Jubilee thoughts; 211–213
Anto RAUKAS
Advances in
the luminescence
dating: the optically stimulated luminescence based procedures and their physical background;
214–232
Galina
HÜTT
and Ivar JAEK
Abstract. A review of the achievements made during the last decade in the study of the energy accumulation and transformation processes in quartz and alkali feldspars, used as natural palaeodosimeters, is given. It is shown how the obtained results have contributed to the application of optical dating through the use of alkali feldspars, finding more effective spectral regions of stimulation, and choice of optimal powers and duration of the stimulating impulses. The strong and weak points of the measuring procedures used in optical dating are analysed and the corresponding new high-sensitivity apparatus is introduced. It appears that, in the case of a reasonable choice of the parameters of stimulating impulses, the presently used multiple-aliquots method is in every way competitive with the new methods.
Key words: natural
palaeodosimeters, optically stimulated luminescence, dating procedure.
New data on the distribution
and stratigraphy of the bottom deposits of Lake Peipsi, eastern Estonia; 233–253
Tiit HANG, Avo MIIDEL, Volli KALM, and Kai
KIMMEL
Abstract. The bottom sediments of Lake Peipsi, eastern Estonia, were investigated. Earlier obtained continuous seismic reflection profiling data is compared with the coring data. Generally good accordance is found, with minor discrepancies in the southern part of the investigated area. A map of the distribution and thickness of Holocene organic lake deposits is presented. Water level during the Lake Small Peipsi stage at the end of the Younger Dryas was at least 10 m lower than at present (30 m a.s.l.), as recorded from the sediment record and pollen analyses. The Preboreal Lake Peipsi is characterized by the accumulation of calcareous deposits, ostracod evidence in which point to a shallow and cold body of water with a slow lake level rise.
Key words: Late Weichselian, Lake Peipsi, lake level changes, lithology, Pandivere–Neva ice marginal formations, pollen stratigraphy.
Podzolization
in aeolian sands, underlain by Gleysol formation, during nine millennia
in southwestern Estonia; 254–281
Loit
REINTAM, Anto RAUKAS, Anne KLEESMENT,
Tanel MOORA, and Raja KÄHRIK
Abstract. An outcrop of Carbic Podzol on aeolian sand, underlain by Molli-Histic Gleysol on calcareous till of the last glaciation, was studied on the bank of the Lemmejõgi River, SW Estonia. Molli-Histic Gleysol at depths of 342–380 cm formed as a result of pedogenesis within the Younger Dryas–Pre-Boreal during about 1500–3200 years at an average accumulation rate of organic carbon of 5.3–2.5 g m–2 yr–1. The histic horizon formed during about 1000 years at a rate of 12–13 g m–2 yr–1 of organic carbon. Gleying of underlying till has led to slight textural changes but to some essential changes in mineral and chemical status. Gleysol was buried under the sediments of the Ancylus transgression about 9200–9000 years ago. Within the uppermost stratum, stratified sands have been reshaped by coastal winds after the retreat of the shoreline. Simultaneously with the development of the forest vegetation, pedogenesis started a little later than 9000 BP, and a unitary Carbic Podzol with the A–E–Bhs–Bs–BC–C sequence was formed. Organic C has accumulated at an average rate of 8.1 mg m–2 yr–1 cm–1 in the A–E–Bhs sequence, while the A- and Bhs-horizons were humus-accumulative and humus-illuvial in origin, respectively. Under the influence of R2O3- and/or Ca-fulvic humus, total cheluviation and formation of the albic horizon has proceeded at a rate of 55 µm yr–1. The solum of 180 cm, formed during about 9000 years, represents the result of the weathering and podzolization of the initial sand column of 171 cm, while the upward expansion in the uppermost 75 cm progressed at a rate of 6–7 µm m–2 yr–1. As a consequence of interfraction changes, 5.6 g m–2 yr–1 of fine particles and 2.9 g m–2 yr–1 of chemical constituents have accumulated in the solum, although the A–E sequence is eluvial. Quartz and feldspars have mostly concentrated in fine sand. The increase in ore minerals and/or their eluvio-illuvial distribution has been induced by the weathering of pyroxenes and amphiboles. Against the background of total accumulativeness, the relationships of nonsiliceous substances are characterized by podzolic distribution. Due to human and some evident natural agents, a decrease in acidity and an increase in base exchange capacity and base saturation have taken place in the A–E–Bhs sequence of Carbic Podzol.
Key words: aeolian sands, Holocene pedogenesis, podzolization, Carbic Podzol, soil composition, soil properties, changes in pools.
Instructions
to authors; 282–284
Copyright Transfer Agreement; 285
Contents of volume 50; 286–287