A geological setup of subsurface in Žarėnai area
The Žarėnai Valsčius (a rural district) lies on that part of the Žemaitija Upland, where the recent relief variety has been created by two ice lobes of the last glaciation moving from the Gulf of Riga and the Baltic Sea depression area. Overall, from the very start, the formation of the Žemaitija Upland has been caused by the neotectonic structure being formed during the Quaternary and by a repeating impact of continental ice. The dynamics of the last continental glaciers (their advances and retreats), accompanied by formation of deposits and relief shapes, has been determined by such neotectonic structures as the Šiauliai elevation, West Lithuanian monocline with the Rietavas depression, Jelgava depression, Panevėžys saddle and Kaunas structural terrace. The structural base of the all Žemaitija Upland was the West Žemaitija structural terrace.
According to the deep geological setup, the area of Žarėnai lies in a greatly complex Telšiai deformation zone of crystalline basement and sedimentary cover. Active formation of this zone started in the Proterozoic 1.8 billion years ago and lasted as long as the Early Proterozoic. A calmer palaeogeographic environment, although rather changeable (with alterations of sedimentation and denudation processes) started in Lower Devonian Viešvilė time and takes place up to now.