Lithostratigraphy and age estimations of the Pleistocene erosional remnants near the centre of the Scandinavian glaciations in western Finland

Extensive, 20–100 m thick Quaternary sediment accumulations, deposited before the latest Weichselian stage, were discovered in the Suupohja region in western Finland, near the centre of the Scandinavian glaciations. Fourteen lithofacies have been identified and interpreted in the accumulations. Geomorphologically and lithostratigraphically these accumulations occur in two forms: (1) till-covered beaded gravelly ridges that have occasional fine-grained sediments and paleosols between the gravel and the overlying till, and (2) irregularly shaped broad multilayer accumulations that include up to seven till units, three silt/clay units and three sand units. These sediments have been deposited in glacial, glaciofluvial, glaciomarine/-lacustrine and possibly in littoral and eolian environments during up to six glacial–deglacial cycles. The units are divided into five formations, which are proposed to form the Suupohja Group. According to the luminescence datings, lithostratigraphy and sedimentary structures, the sediments below the uppermost till are interpreted to have been deposited before the latest Weichselian glaciation, which occurred during the Middle or Late Weichselian Substage. This article clarifies the multiple lithostratigraphy of the Suupohja region and introduces potential type sections for further stratigraphic studies. The rich diversity of the sediments and their large extent makes this region one of the key areas in the Pleistocene research of the glaciated areas of northern Europe.