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Source-to-Sink Analysis of Marine Rift Basins Surrounding a Long-Lived Structural High: The Frøya High, Norwegian Continental Shelf


A key aspect of siliciclastic reservoirs deposited in marine rift basins is the importance of tectonics as a control on sediment supply. During rifting, existing pre-rift drainage basins may become compartmentalized, potentially with reversal of drainage. A better understanding the evolution of drainage catchments may reduce exploration risks regarding the presence and quality of reservoir. We present a source-to-sink-based seismic case study of the evolution of catchments on an exposed fault block and their associated sedimentary systems in the adjacent marine depocentres. The Frøya High is a prominent N-S-trending, 25 km wide horst located on the mid-Norwegian margin. At the onset of Late Jurassic rifting, the high became a semi-isolated promontory bounded by a deep-marine, fault-controlled hanging wall basin to the west and a relatively shallow-marine basin on the hanging wall dip-slope to the east. A series of fringing clastic wedges formed as the exposed part of the Frøya High was being eroded. Using well-calibrated 3D seismic reflection data we identify a series of Upper Jurassic and Lower Cretaceous clastic wedges on both sides of the high. We observe submarine gravity flow fans in the hanging wall basin to the west whereas the eastern margin is characterised by a series of adjacent deltaic clinoform packages. Updip of these depositional features, on the high itself, erosional surfaces can be mapped that look like E-W-trending canyons and valleys in map-view. These are interpreted to represent river catchments that delivered the sediment to the wedges. By restoring and backstripping the erosional surfaces we are able to analyse the catchments as they existed in Late Jurassic and Early Cretaceous times. The clastic wedges that formed along the high can be correlated to their associated drainage catchments, allowing a holistic, source-to-sink evaluation of an exposed horst block and its surrounding basins. We demonstrate how sedimentary systems evolved; sediment transport was initially predominantly directed towards the east during the Late Jurassic, followed by the development of incised canyons along the S-W margin which, in some cases, captured and redirected the older drainage catchments. We discuss the implications for sediment supply to marine basins that surround such exposed horst blocks, during and after rifting. This study contributes to a better understanding of generic reservoir distribution and quality in marine and lacustrine rift settings.