The earth surface setup, palaeogeography and geoheritage in Onuškis area

Valentinas Baltrūnas, Bronislavas Karmaza, Violeta Pukelytė

The land surface in the area of the former Onuškis Valsčius (a rural district) is notable for great variety in its geology and geomorphology, due to complicated palaeogeographical evolution of the Dzūkija Upland. The geological setup of the area and its geomorphology is related to the Baltic (Pomeranian) stages and Žiogeliai (Frankfurt) glacial retreat stages of the Last (Nemunas) glaciation. New data of the area studies enabled to define peculiar geological and gemorphological complexes (micro-regions) notable for specific geological setup and composition, hydrogeological, hydrological and geomorphological features. This caused also the spread of forests and location of bogs in the area, the potentials for agrarian expansion, urbanisation and mining, as well as a distinction of its landscapes. Small marginal areas of plain micro-regions (Rūdiškės–Senieji (Old) Trakai and Paluknys–Lieponiai) have been distinguished and described. The micro-regions of Žilinai and Vilkokšnis–Tolkiškės formed by the earlier stage (Žiogeliai) of the Last (Nemunas) glaciation and those of Onuškis–Dusmenys, Alaburdiškės–Pivašiūnai on the Dzūkija Upland left by the later stage (Baltic) of the glacier as well as a small margin of the Stakliškės micro-region have been also dealt. Now the area of Onuškis has only one valid geological nature monument, i.e., Nikronys Mythological Stone, there are also four landscape reserves and three more reserves: geomorphological, hydrographical and telmatological. From petrological and palaeogeographical viewpoints, the houses built of boulders, including the Onuškis Church, are interesting for onlookers; there are also some attraction sites, such as bog iron ore production and moulding places including the Dusmenys Estate foundry in the nearby village of Rudnia.