CONTENTS & ABSTRACTS
InEnglish. Summaries in Estonian
Proceedings of the Estonian Academy of Sciences.
Geology
Volume 51 No. 3September 2002
New species of Estlandia (Clitambonitidina, Brachiopoda) in theUpper Ordovician of the East Baltic; 135–142
Michael Zuykov and Linda Hints
Abstract. A new species of the gonambonitid genus Estlandia, E. hispida, is described from the lower part of the Upper Ordovician inEstonia and northwestern Russia (Ingria). The new species differs clearly from the most similar species E. marginata (Pahlen) in theexternal sculpture, in having less convex valves, and in the stratigraphicaldistribution.
Key words: Brachiopoda,Rhynchonelliformea, Gonambonitidae, Upper Ordovician, Estonia, northwestern Russia.
Correlation of Telychiansections from shallow to deep sea facies in Estonia and Latvia based on thesanidine composition of bentonites;143–156
Tarmo Kiipli and Toivo Kallaste
Abstract. Sanidine composition of 130 samples of bentonites from 12 sectionsof Telychian (some possibly Sheinwoodian) age was analysed by X-raydiffractometry for correlation purposes. Solid solution of magmatic sanidinecontained 20–47% NaAlSi3O8 molecules. The sanidinecomposition is very individual for many beds and can be used successfully for correlations.
Key words: sanidine, bentonites, correlation, Silurian.
Geological history of LakeVõrtsjärv; 157–179
Tanel Moora, Anto Raukas, and Elvi Tavast
Abstract. LakeVõrtsjärv, with a surface area of 270 km2, has a verycomplicated geological history. Proglacial lakes ofdifferent shape and size were formed in the Võrtsjärv Lowland. Due to thetectonic uplift outflows to the west closed in the Early Holocene. At thebeginning of the Middle Holocene, about 7500 BP, an outflow to the eastdeveloped and little by little the lake acquired its present contours. Likemany lakes in Europe, Võrtsjärv has an open eastern (leeward) and a more swampyand overgrown western (windward) bank. The bottom sediments consist mostly ofsapropel (gyttja), fine sand and silt. The sediments are thicker in thesouthern part of the elongated lake basin where the up to 9 m thick layerof sapropel is usually underlain by 8 m of lacustrine lime. Gradual riseof water level in the southern portion of the basin is caused by land uplift,the rate of which increases towards the northwest.
Key words: glaciallakes, neotectonic uplift, outflows, sapropel, lake marl, floods.
Stableisotope and pollen stratigraphy in marl sediments from Lake Ilmjärv (centralEstonia); 180–192
Jaan-Mati Punning, Tiiu Koff, Tõnu Martma,and Göran Possnert
Abstract. Theaim of the present research was to reconstruct trends in the environmentalchanges and estimate the importance of the rapid change of d13C in the Boreal as a stratigraphic marker by comprehensive study ofstable carbon and oxygen isotopes and pollen from the lake marl section of LakeIlmjärv (c. 2.5 ha closed lake situated in the Vooremaa drumlinarea). The d13C and the d18O values reached their maxima near the end of theBoreal, then dropped and were practically constant up to the top of the marl sequence c. 3000 BP. These changeswere accompanied by a remarkable improvement of climatic conditions andshifts in the vegetation.
Key words: lakemarl, carbon and oxygen isotopes, pollen analysis, isotope stratigraphy,Estonia.
Instructions toauthors; 193–195
Copyright TransferAgreement; 196
