The Slyngfjellet Conglomerate which occurs at the base of the Upper Proterozoic Sofiebogen Group in South Spitsbergen had formed predominantly as a debris-flow deposit, with subordinate contribution by fluvial and probably lacustrine sediments. There is no evidence for glacial conditions at the time of formation of the conglomerate, the latter being much older than the latest Proterozoic Varangian glaciation tillites elsewhere in Svalbard. The Slyngfjellet Conglomerate originally filled buried valleys eroded by rivers in block-faulted and uplifted western margin of the Mid-Proterozoic Torellian Basin.