Land subsurface development and setup in the environs of Žagarė

Aleksandras Šliaupa

The environs of Žagarė are notable for the Devonian dolomite of Žagarė formation already from mid-19th century, when investigations on general geological setup had begun. The research that lasted about 150 years showed that the base of the sedimentary deposits, so-called crystalline basement, had been forming for several billion years. The sedimentary beds were laid during a period of 550–510 million years in the marine or continental environments. The youngest deposits observed closer to the land surface or on it are mostly related to the continental glaciers. The beds of sedimentary deposits play an important role as useful minerals being a raw material for construction works. The Upper Devonian beds are often filled with fresh water used for drinking.

The setup of the crystalline basement and sedimentary cover and their development history showed that very intricate processes took place in the environs of Žagarė, as well as in all Lithuania, often caused by the movements of Earth’s crust plates. Global geodynamical processes also were and are forming even the least structures of crystalline basement and the sedimentary cover. First of all, large or small blocks confined by faults should be mentioned. The sedimentary beds were being pulled or pressed, lifted or sunk, bent or torn. All this is seen well in the geological profiles presented. The faults in the crystalline basement and the sedimentary cover are still active during the current geological period, as the neotectonically active linear zones confirm. The dynamics of the Quaternary tectonic structures affected the dynamics of continental glaciers, formation of deposits and their survival, formation of relief and hydrographical network and other geological processes (earthquakes, erosion, denudation and hydrodynamics).