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Glaciotectonic deformation patterns in Estonia

100%

Rattas M. , Kalm V.

2004

tom Vol. 48, No 1

15-22

Field and archival data have been used in compiling the Glaciotectonic Map of Estonia. Two principal types of glaciotectonic deformations shown on this are discussed here: dislocations of rigid bedrock, and soft bed deformations associated with unconsolidated drift masses. Most bedrock disturbances occur in the narrow zone south of the Baltic Klint and in the tectonically crushed zone where the fractured bedrock was easy to break, displace and deform by the moving glacier. Some of the bedrock dislocations are related to ice-marginal deposits of the Late Weichselian Glaciation (Palivere and Pandivere Phases). Most subglacial deformations of soft sediments are simple in style, namely: shear and ductile deformations within a thin layer. The spatial organisation and efficiency of drainage beneath the local ice streams determined the deformational behaviour of sediments at the ice/bed interface. Ice-marginal deposits of the Late Weichselian deglaciation have not been subjected to large-scale compressive deformation. This suggests that most marginal deposits were formed as the result of brief standstills of the ice margin which caused sediment deformation either at the ice margin or beneath the ice sole.

Classification and areal distribution of glaciotectonic features in Estonia

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Rattas M. , Kalm V.

tom Vol. 43, Nr 2

177-182

Known glaciotectonic phenomena in Estonia were subjected to systematic analysis and mapping for the Estonian Glaciotectonic Database and Map Project. The available data allow classification of such features into five main categories. Ridges, hills and composite massifs composed of the Quaternary sediments appear to be the most common glaciotectonic landforms in Estonia. Glaciotectonic ridges and hills, composite massifs and sites in which the buried disturbed Quaternary sediments were estimated, are located mainly in southern and southeastern Estonia where a thickness of the Pleistocene cover varies between 50-200 m, or at the sites where they denote ice margin positions of different stadials (oscillations). Large glacial rafts of the pre-Quaternary bedrock as well as point samples of the disturbed pre-Quaternary bedrock were mapped near the North Estonian limestone escarpment and in northeastern Estonia.

Wszystkie dotychczas rozpoznane formy glacitektoniczne w Estonii zostały poddane systematycznej analizie i kartowaniu w trakcie opracowania "Glacitektonicznej Bazy danych i Mapy Estonii". Uzyskane materiały umożliwiły klasyfikację tych form w 5 głównych kategoriach. Najczęstszymi glacitektonicznymi formami rzeźby w Estonii są grzbiety, wzgórza i masywy z utworów podłoża czwartorzędu. Grzbiety i wzgórza glacitektoniczne oraz masywy i stanowiska, w których stwierdzono zdeformowane osady czwartorzędu, występują głównie w S i SE Estonii, gdzie miąższność pokrywy plejstoceńskiej wynosi 50-200 m. Stwierdzono je również w strefach marginalnych lądolądu podczas różnych stadiałów (oscylacji). Duże kry lodowcowe skał podłoża oraz stanowiska zdeformowanych utworów podłoża czwartorzędu stwierdzono w pobliżu NE kuesty wapiennej oraz NE Estonii.

Remote sensing of eskers from Vormsi and Väinameri vicinity, northwestern Estonia

100%

Aber J. S. , Kalm V.

2001

tom Vol. 45, No 4

365-372

We have utilised techniques of remote sensing in combination with ground observations in order to investigate eskers of the Vormsi and Väinameri region of northwestern Estonia. Landsat Thematic Mapper (TM) images were the basis for recognition and regional interpretation of esker systems, and kite aerial photography was employed for detailed, low-height views of selected eskers. A special Landsat TM composite was developed to enhance the display of shallow sea floor features. On this basis, we have extended known, land-based eskers across the sea floor, and we have identified additional probable eskers marked by shallow shoals and tiny islands. The known and suspected eskers of Vormsi and surroundings demonstrate a regular pattern in their distribution, which we suggest represents a subglacial drainage network that was anastomosing in character. The esker network is located along the central pathway of the Väinameri ice lobe, and the overall direction of drainage was toward the Palivere glacial limit. We interpret eskers of the Vormsi-Väinameri vicinity as evidence for substantial meltwater discharge beneath the Väinameri ice lobe, which terminated in a proglacial lake.