Weichselian stratigraphy, geomorphology and glacial dynamics in southern Finnish Lapland

Abstract

Quaternary stratigraphy and geomorphology were investigated by using aerial photo interpretation, digital elevation models and stratigraphical studies in southern Finnish Lapland. The development of glacial morphology was examined by reconstructing glacial flow patterns and subglacial conditions with emphasis on glacial dynamics. By comparing the climate history and available chronological data the ice-sheet development during the Weichselian was modelled in the area. Also, the Quaternary lithostratigraphy with descriptions, formal names and type sections of the Peräpohja Group was proposed. Glacial morphology with clear indication of glacial flow directions represents two Weichselian glacial advances in the area of southern Finnish Lapland. The older, northwest-southeast oriented glacial movement was seen as a drumlin field and was preserved under a later cold-based ice sheet. A west-east oriented landform assemblage of ribbed moraines, drumlins and flutings mainly indicated the younger glacial phase. Of the age of ice sheet development during the Weichselian two alternative interpretations have been presented: In the first model, the first glacial advance occurred during the Early Weichselian and was followed by interstadial about 85-74 ka ago. The Middle and Late Weichselian glaciation was continuously covering southern Finnish Lapland after that. The second model includes a new interpretation, in which the first glacial advance that reached the area is connected to the beginning of the Middle Weichselian. Ice-free interstadial occurred about 50-30 ka ago before the Late Weichselian glacial advance, when the Weichselian maximum was reached.

Glaciotectonic deformation of till-covered glaciofluvial deposits in Oulu region, Finland

“…The drumlin field with the same orientation occurs also in the South-western Lapland (Mäkinen, 1985;Sutinen, 1992;Sarala, 2005). Gibbard (1979) found a similar direction from till clast-fabric measurements from the last deglaciation Pohjola Till in the Montanlampi section 10 km south-east of the Hangaskangas study area.…”

Evolution of the eastern part of the Kuusamo Ice Lobe, based on geomorphological interpretation of high-resolution LiDAR data

“…11). Sarala (2005a) reported lineations and erosional marks with the same orientation from the western KIL area and interpreted these as representing Middle Weichselian glaciation (MIS 4). One aim with the new glaciogenic morphology identification and classification is re-interpretation of glacial dynamics and subglacial conditions Figure 10.…”

“…The geomorphological interpretation process was supported by reference to the old mapping data revision, including old Quaternary geological maps, and GTK's surficial morphology database, RukaOulanka outdoor map (Räisänen et al, 2012) and earlier literature (e.g. Kurimo, 1974;Aario, 1977;Aario & Forsström, 1979;Sutinen, 1992;Johansson & Kujansuu, 2005a;Sarala, 2005a).…”

“…After the margin of that ice stream reached the Pääjärvi area in Russian Karelia, it was reoriented to form KIL, which created a drumlin field over the Tuoppajärvi drumlin field (Aario, 1990). The most favourable conditions for the Kuusamo drumlin field occurred after the Younger Dryas stage, when the glacier melted rapidly and active ice lobes were a surging type (Sarala, 2005a). Johansson & Kujansuu (2005b) have estimated that the margin of KIL was in the eastern Kuusamo area about 10 500 years ago.…”

“…In Finland, in the central part of the Scandinavian Ice Sheet (SIS), ice lobe identification until now has been based on morphological reconstruction of moraine and glaciofluvial formations using satellite and aerial image interpretation, as well as field mapping (e.g. Aario & Forsström, 1979;Kurimo, 1982;Punkari, 1997;Johansson & Kujansuu, 2005a;Sarala, 2005a).…”