Deglaciation pattern indicated by the ice‐margin formations in Northern Karelia, eastern Finland

Abstract

A map has been reconstructed representing the large‐scale glacial and glaciofluvial morphology of Northern Karelia and the adjacent area of Soviet Karelia. Observations have been made on the directions of glacial striae and on the distribution of sub‐aquatic and supra‐aquatic terrain in order to obtain a consistent picture of the course of deglaciation in the area and the factors affecting it. The map indicates that the behaviour of the glacier during the deglaciation was largely governed by the distribution of sub‐aquatic and supra‐aquatic areas. The marginal zone of the ice sheet was divided into two large lobes in this area. The Finnish Lake District Lobe terminated mostly in water, giving rise to massive glaciofluvial accumulations, while the North Karelian Lobe flowed on the land above the highest shore levels, pushing up several more or less discontinuous narrow end‐moraine ridges. Relatively large glaciofluvial deposits were also formed in the supra‐aquatic area in places where the ice margin terminated in a local ice‐dammed lake. It is evident that the Salpausselkä I and II end‐moraines extend as continuous formations only to the zone where the former ice margin rose onto dry land during the deglaciation phase. The spatial and temporal differences in the glacial dynamics and differing depositional environments gave rise to the complex glacial morphology of Northern Karelia.

Sedimentary record of a Pleistocene ice-sheet interlobate zone (NE Poland)

“…Sedimentation in interlobate zones is commonly dominated by glaciofluvial processes, but embraces a complex pattern of sedimentary environments, from subglacial tunnels through ice-walled channels and alluvial fans to subaqueous fans and glacial lakes. Allocation of the aforesaid environments is largely governed by the distribution of subaqueous and supraaqueous areas (Eronen & Vesajoki, 1988). The type of glaciomarginal forms and sedimentation is also related with the type of crevasse system in the marginal part of the ice lobes.…”

A comment on the deglaciation of Northern Karelia

“…In their consideration of the course of deglaciation in eastern Finland, Eronen & Vesajoki (1988) conclude that the ice margin retreated from the Salpausselka I marginal formation to the Salpausselka IIposition earlierin the east than furtherwest, whereas the present author has previously put forward the contrary suggestion that the eastern parts of the Salpausselka complexes are in fact younger than the western parts (Forsstrom 1984). Eronen & Vesajoki (1988) base their interpretation on the relatively highlevelsof the glaciofluvialdeltas in the eastern parts of Salpausselka I1 (Figs. 1,2), which are regarded as having been deposited at the stage preceding the formation of the main part of Ss I1 (Saarnisto 1970).…”

Deglaciation dynamics of the Scandinavian Ice Sheet in the Salpausselkä zone, southern Finland

“…However, the major re-advance took place only in the area covered by the Finnish Lake District Ice Lobe but not in the area covered by the Baltic Sea Ice Lobe. Based on glacial landform (eskers) studies in the Ilomantsi area, in the eastern part of Finnish Karelia, Eronen & Vesajoki (1988) also suggested that the so-called Heinola deglaciation took place in the area covered by the Finnish Lake District Ice Lobe. The till stratigraphical results in North Karelia in the northeastern part of the Finnish Lake District Ice Lobe also support the re-advance evidence reported here.…”