THE CONTRIBUTION OF GEOMORPHOLOGIC MAPPING IN UNDERSTANDING THE EVOLUTION OF RECENTLY DEGLACIATED TERRAIN. THE EXAMPLE OF KONGSFJORDEN (SVALBARD, NORWAY)

Ice retreat since the last glaciation has triggered drastic changes in high latitude environments where periglacial processes, as well as landslides and slope and fluvial processes are overprinting pre-existing glacial landforms.

Our study focuses on the understanding of the role of bedrock geology, climate, local conditions on the development of landforms with special focus on slope evolution. The study is part of a project on the analysis of geomorphological effects induced by glacier retreat in high geomorphological sensitivity glacial, periglacial or mountain environment and of a broader project aimed to analyze the Holocene environmental history in Kongsfjorden (Svalbard, Norway) since deglaciation.

We present the preliminary results of two seasons of geomorphologic survey on selected areas along the fjord, Ny Ålesund area and Blomstrand Island, which differ for bedrock geology and local relief.

The first area, in the vicinity of Ny Ålesund, is characterized by rugged non-vegetated mountains which host numerous valley glaciers. Valleys have steep, rocky flanks carved on a deformed metamorphic bedrock of Late Proterozoic thrusted over a heterogeneous Paleozoic sedimentary sequence. Predominant landforms in the low land are outwash and alluvial fans that cut and overlay glacial depositional complexes, slopes are characterizes by talus of debris from both periglacial processes and rock fall.

The second area, on the island of Blomstrand, is characterized by monotonous outcrop of Middle Proterozoic marbles, arranged in an imbricate stack of thin thrust sheets. The island appears as a low relief, broad, smooth dome, incised by small valley, which for the most part parallel tectonic elements. Rock fall and slope deposits are observed only in presence of structurally controlled scarps along the western and northern shore.

The data emerging from the two study areas show a strong control of bedrock geology over the evolution of first order glacial landforms with areas of steep valley sides and areas of broad, subdued relief. After the ice retreat, slope processes affect the landscape according to both local relief energy and bedrock geology.