Geonvironmental change from Post Glacial to present – the Baltic region example
by
Satkunas, Jonas
IUGS Geoindicators Initiative & Geological Survey of Lithuania

Climate is the main factor of the geographic sphere in the bigger part of the Earth surface – it determines processes of landscape formation and specific its compounds, affects all exogenic geological processes, aquatic and terrestrial organic life and social conditions of human communities as well as economic development (Bukantis et al., 2001).

The Baltic Sea region is located in the periphery of the area of extension of the Fenoscandinavian Ice sheet during the Last Interglacial – Glacial climatic cycle period (127–10 kyr BP). A composite sequence of stratigraphic events of Upper Pleistocene in Lithuania has been compiled on the basis of all available stratigraphic data and correlation of climatostratigraphic events in the area of Last Fennoscandian ice sheet and outside it. The results of the studies show the presence of nonglacial (periglacial and interstadial) palaeoenvironments in Lithuania during Early and Middle Weichselian, since the end of the Eemian Interglacial (Satkunas, 1999; Satkunas et al., 2003).

During this period continental ice sheet margin was fluctuating over vast area due to climatic changes with the periodicity of thermomers (interstadial) and cryomers (stadials) of some 8–12 kyr as recorded in the continental sections by the climatostratigraphic evidence (Fig. 1–2.).

Palaeogeographical and palaeoenvironmental conditions were changing respectively. Arctic desert environments were prevailing during cryomers (stadials) and rather mild climate conditions with taiga type forests were prevailing during thermomers (Fig. 2).

The conditions for human occupation in the Eastern Baltic Region have been formed in the Post Glacial period that started some 16 kyr BP. The open and forest – tundra landscapes of Bölling and Older Dryas and light pine-birch forest landscape during Alleröd were present in the Lithuania (Stancikaite, 2000).

The South Baltic area was occupied by the Baltic tribes (present Lithuanians and Latvians) and Finougrian (present Estonians and Fins) tribes that settled here since the Palaeolithic period. Due to settlement of the first humans and practically absence of migration in later periods it is supposed that the features of particular environment of the retreating ice sheet margin are reflected by the topographic names of localities, landforms, rivers and lakes, given by first humans (Seibutis, 1988). For example, in Lithuania topographic names meaning, “end” (galas) most often are related with marginal moraines and kames. Names meaning islands (sala) are proper for islands of glaciolacustrine basins dammed by ice margin. Some hydrographic names can be related with glaciofluvial processes along the ice margin.

Another palaeoenvironmental record could be found in the folkloric heritage – tales, legends, songs (glass (ice?) hills, big flows and seas (glaciolacustrine phenomena?) etc.). The thermokarstic phenomena, that occurred most intensively in Alleröd (11 900–10 900 yr BP) and Atlantic (8 000–5 000 yr BP) periods (Stancikaite, 2000) and maybe even later, according to the geoscientific data, especially clearly is reflected in tales (e.g. castles, churches suddenly fallen into the earth). This phenomenon as well is indicated by relevant topographical names of thermokarstic kettle holes meaning collapse of ground.

It can be assumed that the formation of meteoritic impact craters as catastrophic phenomena has reflection in Estonian legends (Motuza and Motuza, 1999).

At present days the karst process is intensively developing in the North Lithuania (Fig. 3) and partly in South Latvia and is related with Upper Devonian gypsum and dolomites that occur beneath the Quaternary sediments (Narbutas et al., 2001).

Sinkholes appear frequently where the Quaternary is particularly thin and underlain by gypsum. Active karst landscapes are highly vulnerable and complicate the regional economic development and the protection of nature. This phenomenon is rather hazardous and severely impacts constructions, crops, pipelines etc by suddenly collapsing ground and opening karstic sinkholes. Therefore the special engineering means for constructions, special geotechnical investigations before construction must be undertaken in the karstic region. This in turn makes constructions much more expensive. Besides that, the karstic system increases the vulnerability of aquifers to pollution. The area under consideration is intensively used for agriculture. In order to protect aquifers from the pollution through karstic system the special fund and programme of ecological agriculture has been established in Lithuania. The specific karstic landscape is under protection by establishing protected areas and zones of sinkholes protection. In order understand the karstic phenomena and the prevent its hazardous consequences the mapping and monitoring projects are under implementation, however to available knowledge and methods so far are not sufficient do predict and localize concrete potential karstic sinkholes that are opening permanently. Therefore, local people of the karst area (as they call “where the thunder goes underground”) so far are facing to this “dark nature” phenomenon and are not able to predict or escape it.

The monitoring of the karst denudation has revealed that during the last two decades of the XXth century the appearance of the sinkholes became more active (Fig. 4) (Taminskas and Marcinkevičius, 2002). Hazardous sinkholes are forming even more often. The most feasible explanation of intensification of forming of sinkholes is the influence of the climate change for the karstic process. At present there is no reason enough to state that anthropogenic activities were not significant for the intensity of karstic process, however the forming of sinkholes, that became more active during the last two decades of the XXth century, mainly was determined by the climate warming.

References: Bukantis A., Gulbinas Z., Kazakevicius S., Kilkus K., Mikelinskiene A., Morkunaite R., Rimkus E., Samuila M., Stankunavicius G., Valiuskevicius G. and Zaromskis R., 2001. The influence of climatic variations on physical geographical processes in Lithuania. Institute of Geography and Vilnius University, p. 280 Motuza G. and Motuza V. 1999. Tracking Kalevipoeg. Geologijos Akiraciai, No. 2. Vilnius. pp.35-41.

Narbutas V., Lincius A. and Marcinkevicius V., 2001. Karst of the Devonian rocks and the problems of Environment protection in North Lithuania. Vilnius, Agora. 191p.

Satkunas J., 1999. The Upper Pleistocene stratigraphy and geochronology in Lithuania. Litosfera. Vilnius, No.3, pp. 43-57.

Satkunas J., Grigiene A., Velichkevich F., Robertsson A.-M. and Sandgreen, P., 2003. Upper Pleistocene stratigraphy at the Medininkai site, eastern Lithuania: a continuous record of the Eemian- Weichselian sequence. Boreas, Vol. 32, pp. 627-641, Oslo.

Taminskas J. and Marcinkevicius V., 2002 Karst geoindicators of environmental change: the case of Lithuania. Environmental geology, Springer Verlag, pp. 765-766.

Stancikaite M., 2000. Natural and human initiated environmental changes throughout the Late Glacial and Holocen in Lithuania territory. Abstract of doctoral dissertation. Physical sciences, geology (05 P). Vilnius University. Vilnius, 33p.

Seibutis A, 1988. Paleogeographical method in toponymics and its application prospects. The Geographical Yearbook Vol. 24, pp.190-197.

Date received: January 27, 2004

Copyright © 2004 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # camu-36.