Simulation of the shorelines of glacial Lake Peipsi in Eastern Estonia during the Late Weichselian

Digital reconstruction of the evolution of glacial Lake Peipsi, Eastern Estonia, was based on a geographic information system (GIS) method that removed isostatically deformed palaeowater planes fromthe current digital terrain model. A reconstruction of the proglacial water levels was performed with respect to geomorphological correlation of river terraces, raised shorelines and eroded surfaces of various aqueoglacial landforms. The configuration of shorelines, main outlets and water depths of glacial Lake Peipsi, corresponding to the Otepää, Piirissaar, Kaiu and Pandivere–Neva stades during the deglaciation of the Lake Peipsi depression, was simulated. The two approaches used, reflecting the geomorphological correlation of Raukas and Rähni (1969) and Hang (2001), are discussed

Ancient buried valleys in the city of Tallinn and adjacent area

The distribution, morphology, fillings, and origin of buried valleys are discussed. The direction of the valleys varies from NW to NE. Within the Viru-Harju Plateau the valleys have a more or less symmetric profile, but asymmetric profiles are dominating in the pre-klint area. They are mainly filled with glacial (till), glaciofluvial (sand, gravel, and pebbles), glacio­lacustrine (varved clay), and marine (fine-grained sand) deposits. The Tallinn valley with its tributary valleys (Saku and Sausti) and fore-klint branches (Harku, Lilleküla, and Kadriorg) looks like a river system. The fore-klint branches extend over 20 km in the Gulf of Finland. They are probably tributaries of the ancient river Pra-Neva. Most likely, the formation of valleys was continuous, starting from pre-Quaternary river erosion, and was sculptured by variable processes during the ice ages and influenced by flowing water during the interglacial periods

Proglacial lake shorelines of Estonia and adjoining areas

A uniform database of the proglacial lake coastal landforms of Estonia, Latvia and NW Russia was created and used to reconstruct the spatial distribution of proglacial lakes using the kriging point interpolation and GIS approaches. Correlation of the Late Glacial coastal landforms confirms that the proglacial lake stage A1 in Estonia is synchronous with the BglI level in Latvia and with one level in NW Russia of undefined index. Proglacial lake A1 was formed concurrently with the Pandivere-Neva ice-margin about 13,300 cal. yrs BP. Proglacial lake A2 level formed probably about 12,800 cal. yrs BP and correlates with the level of BglII in Latvia and GIII in NW Russia. Simulated isobases of proglacial lake water-levels show a relatively regular pattern of the land uplift along the eastern coast of the Baltic and in the northern part of the Lake Peipsi basin, with a steeper tilt towards the northwest. Isobases in the southern part of the Lake Peipsi basin are curving towards SE and are up to 14 m higher than expected from the regional trend. This phenomenon can reflect the forebulge effect during the deglaciation and its later collapse. Shoreline reconstruction suggests that proglacial lakes in the Peipsi and Baltic basins were connected via strait-like systems and had identical water levels. Our reconstructions also show that after the glacier halted at the Pandivere-Neva ice margin about 13,300 cal. yrs BP, there was a connection with the initial Baltic Ice Lake in the west of the Gulf of Riga

Simulation of proglacial lake shore displacement in Estonia

The Late Glacial shoreline database compiled for Estonia covers 149 sites on the proglacial lakes A1 (Voose) and A2 (Kemba). Eighty-two sites were used in further simulations. Point kriging interpolation with a linear trend approach was applied to create interpolated surfaces of water levels for checking the spatial correctness of data. The sites with altitudes visually not matching with sites nearby were discarded, as well as those with residuals of more than 1 mand 0.7 mrespectively. The final surfaces were analysed geostatistically by simulating isobases, direction of tilting, and shoreline gradient. The simulated isobases suggest that both proglacial lakes A1 and A2 were connected with the glacial lake in the Lake Peipsi basin. The interpolated surface aspect shows that the direction of tilting varies between 320° and 340°. The surface gradient of lake A1 is highest in the NW and SE parts of the study area (50 and 25 cm km-1, respectively), and that of lake A2 is highest in the NWand SE parts (40 and 20 cm km-1, respectively). Using the modelling data, the shoreline correlation between the two proglacial lakes has been revised

Conodont biostratigraphy and sedimentary history in the upper Tremadoc at Uuga, Cape Pakri, NW Estonia

The upper Tremadocian boundary beds at Cape Pakri, NW Estonia, consist of an extremely friable glauconitic sandstone, which presents a challenge to detailed biostratigraphy. A combination of sedimentological and biostratigraphical criteria has served to clarify the tempo and mode of the processes that formed the sandstone and explain its relationships to strata immediately below and above it. Apatitic conodont elements, which abound in all these sediments, are particularly well suited to tracing the geological history of the surrounding sediment, since they can be repeatedly included in the sediment, eroded and redeposited, often leaving telltale marks on the elements which are nevertheless identifiable. By separating the indigenous elements from those that had been redeposited, we could place the local upper boundary of the Tremadocian at slightly more than 1 m above the base of the c. 4 m-thick sandy deposit. We showed that the sandstone, where 58-97% of the conodont elements have been redeposited, had been formed during four successive phases of sand deposition. The entire sandstone unit belongs to the Paroistodus proteus Zone. In the sandy and clayey Varanguan beds of the Paltodus deltifer Zone that underlie the sandstone, less than 50% of the conodont elements had been redeposited. The upper part of the section consists of limestone beds belonging to the Oepikodus evae Zone, where the redeposited portion of the conodont elements decreases upwards