DEEP-WATER FAULT-CONTROLLED SEDIMENTATION, ARCTIC NORWAY AND RUSSIA -RESPONSE TO LATE PROTEROZOIC RIFTING AND THE OPENING OF THE IAPETUS OCEAN

The Late Proterozoic (late Riphean) sections of Varanger Peninsula, no rthern Norway, and the Rybachi Peninsula, Kola Peninsula, Russia, both show an overall progradational succession from deep-marine to slope e nvironments, with the Varanger sections passing up into shallow-marine and then fluviatile deposits. The oldest exposed parts of both succes sions are correlated along-strike over a minimum distance of c. 75 km, and the turbidite systems are interpreted as fragments of the sedimen tary infill of the same rift basin. defined here as the Varanger-Rybac hi Basin, which fringed the Fennoscandian Shield in Late Proterozoic t ime. Sediment transport patterns show lateral input and axial deflecti on to more eastward-flowing currents. Proximal-to-distal and axial-to- lateral changes in the sedimentary facies associations are placed with in deep-marine slope and basin-floor turbidite systems. In Arctic Russ ia. the basin-bounding Rybachi-Sredni Fault Zone probably broke the se afloor to shed breccias along a fault scarp, possibly even as a subaer ial fault zone and associated with fan-deltas. In contrast, to the wes t in northern Norway, the Trollfjord-Komagelv Fault Zone probably acte d as a concealed basin-margin fault zone which controlled the location and pattern of deep-water sedimentation. offshore from a major fluvia lly dominated delta system. The Late Proterozoic development and subse quent infilling of this basin is interpreted as having formed in respo nse to the opening of the Iapetus Ocean, possibly associated with mant le 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 predomina ntly by deep-marine sediment transport away from a developing ocean ba sin (North Atlantic) associated initially with thermally induced litho spheric extension and uplift (late Jurassic), followed by mantle-plume activity centred over Iceland during Paleocene time causing the devel opment of a thermal-sag basin and uplift over the plume.