Weichselian sediment succession at Ruunaa, Finland, indicating a Mid-Weichselian ice-free interval in eastern Fennoscandia

Abstract

Core material obtained from three boreholes was studied from the Ruunaa area, Finnish northern Karelia, in order to reveal the Late Pleistocene environmental history of eastern Finland. Conventional litho- and biostratigraphical methods were used and suitable sediment samples were dated using quartz optically stimulated luminescence. The results indicate that two till units were deposited by two separate Weichselian ice advances into the area. The first advance took place prior to 52 kyr ago, most likely during the early Middle Weichselian, while the second is thought to have taken place during the Late Weichselian after 25 kyr ago. The sediment succession at Ruunaa therefore indicates a Middle Weichselian ice-free period around 50-25 kyr ago in the eastern part of Fennoscandia. © 2007 The Authors, Journal compilation © 2007 The Boreas Collegium.