Effects of adjacent fault systems on drainage patterns and evolution of uplifted rift shoulders: The Lower Cretaceous in the Loppa High, southwestern Barents Sea

Sedimentological models for rift shoulders have poorly documented the effect of adjacent fault systems on drainage patterns. In this study we investigate the Loppa High, an ancient tilted rift shoulder located in the southwestern Barents Sea. We use seismic and well data, sedimentological log descriptions, and biostratigraphic information to understand the drainage patterns and the Early Cretaceous geological history of the Loppa High. This study provides an example of how the drainage systems in low-gradient flanks of a rift shoulder can be modified and confined by normal faults occurring almost orthogonal to the main fault system. These orthogonal faults might have acted as preferential sediment routes. Thus, potential deposits of the main drainage systems directed to the low gradient flank are found almost exclusively associated with grabens formed due to these orthogonal faults. The Early Cretaceous evolution of the Loppa High is summarized as follow: 1) during the Boreal Berriasian/Volgian to early Barremian, the Asterias and the Bjørnøyrenna fault complexes were active. Diachronous shallow to eventually deep-marine fans and incised valleys were developed along the southern and western flanks of the Loppa High; 2) late Barremian–Aptian fault activity is interpreted along the Ringvassøy Loppa Fault Complex. A second generation of incised valleys and their related shallow-marine fans were formed in the western flank of the Loppa High; and 3) during late Aptian–early Albian the Loppa High and the Hammerfest Basin were tilted eastwards. The latter event triggered a switch in depocenter location and development of shelf-margin clinoforms downlapping in close proximity to the eastern flank of the high.