Vaiguva Valsčius subsurface setup


Aleksandras Šliaupa


The area of the former Vaiguva Valsčius is sandwiched among the Central Žemaitija hill area and two plateaus: North-east Žemaitija and East Žemaitija. Therefore, the relief and the geological face of the surface are rather varying, as well as the subsurface setup that has been explored by core sampling and geophysical methods. Two stages are distinguished in the developmental history of the subsurface: a very long (billions of years) geological epoch, when the crystalline, magmatic and metamorphic rocks were forming, and the stage when the sedimentary cover was being settled. The latter stage lasted just about 700 million years, when the 1800–1900 metre thick layer of sedimentary deposits was formed. The crystalline rocks make more than 40 km thick Earth’s crust.

Magmatic and metamorphic rocks, due to their variety and structure conditions, are grouped into separate blocks or zones. Thus the environs of Vaiguva lie at the eastern margin of the West Lithuanian granulitic domain (block), where Tauragė–Ogrė, Telšiai, Mažeikiai–Vilnius and Jurbarkas zones are distinguished. The sedimentary cover consists of Cambrian, Ordovician, Silurian, Devonian, Upper Permian, Lower Triassic, Middle–Upper Jurassic, Lower Cretaceous and Quaternary deposits with the latter beds having received the most attention in the present paper. The Quaternary deposits form the recent relief. At the line separating the Prequaternary and the Quaternary rocks, there is a neotectonic structure closely related to the structure of the Prequaternary and the block setup of the crystalline basement.