Salonen, Veli-Pekka2; Moreau, Julien3; Hyttinen, Outi2; Eskola, Kari O.2
1 Geology, Department of Geosciences and Natural Resource Management, Faculty of Science, Københavns Universitet2 University of Helsinki3 Geology, Department of Geosciences and Natural Resource Management, Faculty of Science, Københavns Universitet
Finnish Lapland is known as an area where numerous sites with sediments from Pleistocene glacial and interglacial periods occur. Recent sedimentological observations and dating call for reinterpretation of the record, which shows a complicated Mid-Weichselian ice-sheet evolution within the ice-divide zone. Here, a large, previously unstudied section from a former Hannukainen iron mine was investigated sedimentologically and dated with optically stimulated luminescence (OSL). Ten sedimentary units were identified displaying a variety of depositional environments (glacial, glaciolacustrine, fluvial and aeolian). They are all – except for the lowermost, deeply weathered till – interpreted to be of Mid- or Late Weichselian/Holocene age. Five OSL samples from fluvial sediments give ages ranging from 55 to 35 ka, indicating two MIS 3 ice-free intervals of unknown duration. The Mid-Weichselian interstadial was interrupted by a re-advance event, which occurred later than 35 ka and caused glaciotectonic deformation, folding and stacking of older sediments. This new evidence emphasizes the importance of the Kolari area when unravelling the complex Late Pleistocene glacial history of northern Finland and adjacent regions.