The paper deals with the origin of a large number of sand massifs concentrated in the South Minusa basin. The study of the sand deposits was based on field and laboratory work. Cross sections were selected in such a way as to penetrate the deposits of ridgy sands and the underlying surface at different hypsometric levels. Cross-section studies have demonstrated that the sands formed both under subaerial and subaqueous conditions. Analysis of the work of our predecessors has shown that the formation of a thick unit of subaqueous sand deposits, including those at high hypsometric levels, might be related to the removal of large amounts of sediments by catastrophic flooding along the Yenisei River caused by the failure of an ice dam in the Darhad basin at ~ 17 ka. The overlying sand deposits, which now occur as sand bars, are of eolian genesis. These bars formed in the Late Holocene owing to eolian transport and redeposition of the underlying sand members.