The SE sector of the Middle Weichselian Eurasian Ice Sheet was much smaller than assumed.

Quaternary climatic and glacial history must be known in order to understand future environments. Reconstructions of the last Weichselian glacial cycle 117,000–11,700 years (kyr) ago propose that S Finland, adjacent Russia and the Baltic countries in the SE sector of the Eurasian Ice Sheet (EIS), were glaciated during the Middle Weichselian time [marine isotope stage (MIS) 4, 71–57 kyr ago] and that this glaciation was preceded in S Finland by an Early Weichselian interstadial (MIS 5c, 105–93 kyr ago) with pine forest. We apply glacial sequence stratigraphy to isolated Late Pleistocene onshore outcrop sections and show, that these events did not take place. The one Late Weichselian glaciation (MIS 2, 29–11 kyr ago) was preceded in S Finland by a nearly 90 kyr non-glacial period, featuring tundra with permafrost and probably birch forest. Our new Middle Weichselian paleoenvironmental scenario revises the configuration and hydrology of the S part of EIS and gives new setting for the evolution of Scandinavian biota. If future development during the coming glacial cycle proves to be similar, the high-level nuclear waste stored in the bedrock of SW Finland should be located deeper than currently planned, i.e. below any possible future permafrost. [ABSTRACT FROM AUTHOR]