M id‐ W eichselian interstadial in K olari, western F innish L apland

F innish L apland is known as an area where numerous sites with sediments from P leistocene glacial and interglacial periods occur. Recent sedimentological observations and dating call for reinterpretation of the record, which shows a complicated M id‐ W eichselian ice‐sheet evolution within the ice‐divide zone. Here, a large, previously unstudied section from a former H annukainen 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 M id‐ or L ate W eichselian/ H olocene 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 M id‐ W eichselian 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 K olari area when unravelling the complex L ate P leistocene glacial history of northern F inland and adjacent regions.