Large-scale bedrock displacement by cirque glaciers

Three moraine complexes containing large rafts of fractured-bedrock formed by small cirque glaciers occur in Reindalen, Svalbard. Glaciotectonic landf orms cored by rock rafts have been described from mid-latitude ice sheets o f Pleistocene age in the past, but we believe this to be the first time lar ge-scale bedrock rafts have been reported from moraines formed by small cir que glaciers. These moraine complexes consist of an imbricate stack of thru st slabs composed of fractured-bedrock and diamicton. Although the exact me chanism are unclear, we suggest that these moraines form by the displacemen t of subhorizontal strata within the cirque floor to form an initial stack of rock-cored thrust slabs, which subsequently confine the cirque glacier. Subsequent glacier advances, against this "barrier," establishes a strong c ompressive regime within the glacier snout, which leads to erosion and mora ine development. Estimates of the thickness of the rock rafts are used to d erive erosion rates, which are an order of magnitude greater than those pre viously reported for arctic regions.