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

Abstract

In this article, we present new glacial geomorphological data from the eastern part of the Kuusamo Ice Lobe (KIL) in eastern Finland. The focus is on glacial lineations (about 9000 individual features) and interpretation of ice lobe evolution based on streamlined erosional and depositional formations, hummocky and ribbed moraines and glaciofluvial formations. Glacial geomorphological mapping was performed based on interpretation and classification of LiDAR data according to the Geological Survey of Finland’s new Glacier Dynamic database. The results revealed that modern surficial deposits were formed during three different ice flow phases. The oldest remains are seen as occasional NW-SE megalineations and unclassified glacially lineated terrains and erosional valleys representing the Middle Weichselian glaciation. The younger morphologies were formed from the two overlapping drumlin fields of the Tuoppajärvi and Kuusamo ice flow phases, with origins in the Late Weichselian deglaciation. Analysis of different erosional and depositional formation patterns was used to separate ice flow phases and estimate the evolution, subglacial conditions and mass balance of KIL during the last deglaciation. The morphological interpretation revealed that the Tuoppajärvi ice flow stage was large and homogeneous, while the later Kuusamo ice flow stage was more concentrated, narrower and heterogeneous, following a fan-type pattern that is also emphasised by the meltwater channel systems, including both erosional and depositional features. Furthermore, on both margins (northern and southern), part of the ice masses formed stagnant areas. The length of the lineations also indicates both glacier flow velocity and transport distances, which in the case of megalineations and drumlins are longer than in the fluted terrain. Ribbed moraines in the western (core part) of KIL indicate a very different depositional environment relating to strong quarrying and short transport distances under cold-based subglacial conditions, near the core area and the late ice divide zone of the Scandinavian Ice Sheet.