The Late Proterozoic (late Riphean) sections of Varanger Peninsula, northern Norway, and the Rybachi Peninsula, Kola Peninsula. Russia, both show an overall progradational succession from deep-marine to slope environments, with the Varanger sections passing up into shallow-marine and then fluviatile deposits. The oldest exposed parts of both successions are correlated along-strike over a minimum distance of c. 75 km, and the turbidite systems are interpreted as fragments of the sedimentary infill of the same rift basin, defined here as the Varanger–Rybachi Basin, which fringed the Fennoscandian Shield in Late Proterozoic time. Sediment transport patterns show lateral input and axial deflection to more eastward-flowing currents. Proximal-to-distal and axial-to-lateral changes in the sedimentary facies associations are placed within deep-marine slope and basin-floor turbidite systems. In Arctic Russia. the basin-bounding Rybachi-Sredni Fault Zone probably broke the seafloor to shed breccias along a fault scarp, possibly even as a subaerial fault zone and associated with fan-deltas. In contrast, to the west in northern Norway, the Trollfjord–Komagelv Fault Zone probably acted as a concealed basin-margin fault zone which controlled the location and pattern of deep-water sedimentation, offshore from a major fluvially dominated delta system. The Late Proterozoic development and subsequent infilling of this basin is interpreted as having formed in response to the opening of the Iapetus Ocean. possibly associated with mantle plume activity farther west. The Late Proterozoic Barents Sea Basin may have been analogous to the late Jurassic and Palaeogene northern North Sea, in which sand-prone turbidite systems accumulated predominantly by deep-marine sediment transport away from a developing ocean basin (North Atlantic) associated initially with thermally induced lithospheric extension and uplift (late Jurassic), followed by mantle-plume activity centred over Iceland during Paleocene time causing the development of a thermal-sag basin and uplift over the plume.