Toward a comprehensive paraglacial model: case studies from Iceland

International audienceFrom the end of the Weichselian period and during the early Holocene, the landscape in Iceland underwent major changes. During this short-time interval, while glaciers were retreating from the lowlands, an exacerbation of geomorphic activity is noticed, due to lowering of the relative sea level, large glacial rivers flooding from the retreating ice margins and hillslope debutressing. As a consequence, many of the major paraglacial landforms that carved the Icelandic landscape are still visible nowadays. Two kinds of early Holocene paraglacial landforms can be identified in Iceland: (i) paraglacial denudation landforms (some slope failure deposits such as sackungs, rock avalanches and various other landslide types...), and (ii) paraglacial deposition landforms (alluvial fans, terraces, valley-train deposits, outwash plains or "sandurs" with outburst floods or "jökulhlaups", coastal deposits...). By using the sediment cascade framework, several paraglacial sources and sinks are also identified. This classical geomorphological approach privileges forms, processes to typify their temporal evolution through the Holocene. Some post-little ice age analogues in Iceland are also clear examples of such paraglacial evolution. To those external paraglacial dynamics we also propose to couple the consequences of the deglaciation to the internal earth dynamics (such as seismicity and volcanism, i.e. internal paraglacial effects). All around Iceland, glacio-isostatic rebound can explain the formation of numerous raised beaches, deltas, and strandflats. Also, an intense volcanic activity phase occurred within the early Holocene in Iceland, highlighting a link with the ice pressure release on the magma transfer. Based on our own researches and on literature review, we develop a spatial analysis at different time and space scales and propose a comprehensive paraglacial model, including external and internal earth dynamic implications