Geology December 2001 Vol 50/4 []

CONTENTS & ABSTRACTS

InEnglish. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.

Geology



Volume 50 No. 4December 2001



Jubilee thoughts; 211–213

(full article in PDF format)

Anto RAUKAS

Advances inthe luminescencedating: the optically stimulated luminescence based procedures and their physical background;214–232

(full article in PDF format)

GalinaHÜTT and Ivar JAEK

Abstract. A review of theachievements made during the last decade in the study of the energyaccumulation and transformation processes in quartz and alkali feldspars, usedas natural palaeo­dosimeters, is given. Itis shown how the obtained results have contributed to the application ofoptical dating through the use of alkali feldspars, finding moreeffective spectral regions of stimulation, and choice of optimal powers andduration of the stimulating impulses. The strong and weak points of themeasuring procedures used in optical dating are analysed and the correspondingnew high-sensitivity apparatus isintroduced. It appears that, in the case of a reasonable choice of theparameters of stimulating impulses,the presently used multiple-aliquots method is in every way competitive withthe new methods.

Key words: naturalpalaeodosimeters, optically stimulated luminescence, dating procedure.

New data on the distributionand stratigraphy of the bottom deposits of Lake Peipsi, eastern Estonia; 233–253

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Tiit HANG, Avo MIIDEL, Volli KALM, and KaiKIMMEL

Abstract. The bottom sediments of Lake Peipsi, eastern Estonia, wereinvestigated. Earlier obtained continuousseismic reflection profiling data is compared with the coring data. Generallygood accordance is found, with minor discrepancies in the southern partof the investigated area. A map of the distribution and thickness of Holoceneorganic lake deposits is presented. Water level during the Lake Small Peipsistage at the end of the Younger Dryas was at least 10 m lower than atpresent (30 m a.s.l.), as recorded from the sediment record and pollenanalyses. The Preboreal Lake Peipsi is characterized by the accumulation of calcareousdeposits, ostracod evidence in which point to a shallow and cold body of waterwith a slow lake level rise.

Key words: Late Weichselian, Lake Peipsi, lakelevel changes, lithology, Pandivere–Neva ice marginal formations,pollen stratigraphy.

Podzolizationin aeolian sands, underlain by Gleysol formation, during nine millenniain southwestern Estonia; 254–281

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LoitREINTAM, Anto RAUKAS, Anne KLEESMENT,

Tanel MOORA, and Raja KÄHRIK

Abstract. An outcropof Carbic Podzol on aeolian sand, underlain by Molli-Histic Gleysol oncalcareous till of the last glaciation, was studied on the bank of theLemmejõgi River, SW Estonia. Molli-HisticGleysol at depths of 342–380 cm formed as a result of pedogenesis withinthe Younger Dryas–Pre-Boreal duringabout 1500–3200 years at an average accumulation rate of organic carbonof 5.3–2.5 g m–2 yr–1. The histic horizonformed during about 1000 years at a rate of 12–13 g m–2 yr–1of organic carbon. Gleying of underlying till has led to slight texturalchanges but to some essential changes in mineral and chemical status. Gleysolwas buried under the sediments of the Ancylus transgression about 9200–9000years ago. Within the uppermost stratum, stratified sands have been reshaped bycoastal 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 unitaryCarbic Podzol with the A–E–Bhs–Bs–BC–C sequence was formed. Organic C hasaccumulated at an average rate of8.1 mg m–2 yr–1 cm–1 in theA–E–Bhs sequence, while the A- and Bhs-horizons were humus-accumulativeand humus-illuvial in origin, respectively. Under the influence of R2O3-and/or Ca-fulvic humus, total cheluviation and formation of the albic horizonhas proceeded at a rate of 55 µm yr–1. The solum of180 cm, formed during about 9000 years, represents the result of theweathering and podzolization of the initial sand column of 171 cm, whilethe upward expansion in the uppermost 75 cm progressed at a rate of6–7 µm m–2 yr–1. As a consequence ofinterfraction changes, 5.6 g m–2 yr–1of fine particles and 2.9 g m–2 yr–1 ofchemical constituents have accumulated in the solum, although the A–Esequence is eluvial. Quartz and feldspars have mostly concentrated in finesand. The increase in ore minerals and/or their eluvio-illuvial distributionhas been induced by the weathering of pyroxenes and amphiboles. Against thebackground of total accumulativeness, the relationships of nonsiliceoussubstances are characterized by podzolic distribution. Due to human and someevident natural agents, a decrease in acidity and an increase in base exchangecapacity and base saturation have taken place in the A–E–Bhs sequence of CarbicPodzol.

Key words: aeoliansands, Holocene pedogenesis, podzolization, Carbic Podzol, soil composition,soil properties, changes in pools.



Instructionsto authors; 282–284

Copyright Transfer Agreement; 285

Contentsof volume 50; 286–287