Pleistocene permafrost of West Siberia as a deformable glacier bed

Subglacial permafrost is usually referred to as a factor impeding basal glacial processes, and the deformation of soft substrata in particular. In West Siberian, widespread glacial disturbances present in permafrost of Pleistocene age suggest that frozen sediments, if clayey and/or icy, can readily deform, thus translating basal glacial stress into sliding of the entire glacier/sediment complex along subglacial shear zones. Ductile deformations such as folds and diapirs are also widespread. The mode of deformation of frozen subglacial sediments is dependent on their lithology, ice content and temperature conditions. Signatures of former subglacial permafrost in currently thawed sediments are deduced from contrasting deformation behaviours of lithologically different sedimentary formations.