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Environmental drivers and trends of postglacial relief development in selected mountain regions in Iceland, Sweden and Norway

Beylich A. A., Laute K.

Studia Geomorphologica Carpatho-Balcanica

2017/2018

Vol. 51/52

7--23

The various mountainous landscapes of Iceland, Sweden and Norway are characterized by Pleistocene glaciations and, connected to this, a dominance of glacially sculpted landforms like U-shaped valley systems, cirques, lakes and hanging valleys. The thickness of glacigenic deposits from this period can vary significantly across different mountain landscapes. In consideration of such legacies, these formerly glaciated landscapes today can be considered at a unique stage of readjustment (recovery) with respect to spatial organization of currently active geomorphic process domains and the magnitude and patterns of sediment storage and sedimentary fluxes. Accordingly, the postglacial relief development in these landscapes is controlled by a wide range of environmental drivers. This study focuses on trends of postglacial relief development in five selected valley systems in formerly glaciated mountain landscapes in eastern Iceland, northern Sweden and western Norway. The selected valley systems Austdalur (23.0 km2) and Hrafndalur (7.0 km2) in eastern Iceland, Latnjavagge (9.0 km2) in northern Sweden, and Erdalen (79.5 km2) and Bødalen (60.1 km2) in western Norway are considered to be representative valley systems for the respective mountain regions they are situated in. Our investigations include a quantitative compilation of contemporary mass transfers in the five valley systems, the quantitative analysis of current Ho/Hi index values for the slope systems in the valleys as well as a semi-quantitative description of changes of valley cross-sectional and longitudinal profiles since deglaciation. As a result, all U-shaped valley systems are characterized by an ongoing valley widening due to the continuing retreat of the existing rock-walls. However, the different valley systems show significant variations in the intensity of slope-channel coupling, in their slope and valley-floor storage behavior, in the development of their longitudinal valley profiles, and in the general intensity of postglacial relief modification. Accordingly, trends of postglacial relief development appear to be rather complex in the different mountain landscapes. It is found that the specific characteristics of the glacially sculpted and inherited valley morphometries are the most important control of the detected differences in slope-channel coupling, storage behavior and longitudinal valley profile development. Lithology and the given weathering resistance of the predominant bedrock are most important for the general intensity of postglacial relief modification. A part from Hrafndalur which is characterized by rhyolites with particularly low weathering resistance, post-glacial modification of the inherited glacially sculpted valley morphometries is altogether little and the landforms have not yet adjusted to the geomorphic surface processes that have been operating under postglacial morphoclimates.