Recent studies in the Middle Jurassic Bryne and Sandnes formations, primary reservoirs in several fields across the Norwegian and Danish North Sea, show the widespread occurrence of tidal-influenced and tide-dominated deposits. Aalenian–Bajocian Bryne cores reflect deposition by a shoal water, tidally influenced delta onto a low wave energy tidal platform (both supratidal and intertidal) that probably occupied the majority of the Søgne Basin, a narrow rift system connected to the Central and Danish graben and transgressed from an open-marine basin, possibly located to the south. At the Bathonian–Callovian boundary, a new phase of rifting and progressive salt movements led to the deposition of the upper Bryne and Sandnes formations within an 80–100 km long composite estuarine valley. Basin tilting to the south and continued transgression resulted in tidal deltas that offlap the northern margin of the basin. The basin was fully transgressed by the end of the Callovian. From the Late Bathonian onwards, differential tectonic movements along the broadly interconnected Middle Jurassic rift basins led to a change in the transgression direction from south to north, with an open-marine basin located in the Central and Viking graben.

A B S T R A C TUnderstanding the factors controlling the development of accommodation above collapsing salt diapirs and their influence on reservoir distribution is critical in reducing exploration risk in salt-influenced sedimentary basins. In this study, we use an integrated subsurface data set (three-dimensional and twodimensional seismic reflection, wire-line-log, core, and biostratigraphic data) from the Upper Jurassic of the Cod terrace, Norwegian North Sea, to understand the influence of rifting on accommodation creation and shallow-marine deposition during the initial-stage collapse of salt diapirs. We demonstrate that rifting resulted in the rise and fall of salt diapirs, and the formation of supra-diapir minibasin-style depocenters that became sites for deposition and preservation of up to 500 m (1640 ft) thick nettransgressive shallow-marine sandstone reservoirs. Maximum thickness is recorded in the axis of minibasins with a reduction in thickness of up to 65% noted on their flanks. The stratigraphic architecture of individual minibasins is variable. Proximal-todistal facies variations from shoreface to offshore shelf and commensurate changes in reservoir quality occur over scales larger than individual minibasins. These deposits contain large sand volumes, and are not confined to areas of localized sandstone subcrop. In combination, these features suggest that the minibasins

16 17 18 19 20 21 22 23 24 25 42 the net-transgressive, predominantly shallow-marine, Middle-to-Upper Jurassic syn-rift 43 succession. The resulting facies architecture reflects a delicate balance between fault-and 44 salt flow-driven accommodation creation and intra-and extra-basinal sediment supply. 45 Where sediment supply and accumulation rate exceeded accommodation, little or no 46 change in facies is observed across syn-depositional structures. In contrast, where 47 accommodation outpaced sediment supply and accumulation rate, footwall-attached 48 shorelines locally developed adjacent to large, thick-skinned normal faults, with deeper 49 water conditions persisting in the adjacent hanging wall. Flooding of individual structural 50 elements was strongly diachronous and influenced by the underlying rift-related 51 topography, which was characterised by intra-basinal horst and graben. This paper 52highlights the key role that salt plays in modifying the tectono-stratigraphic evolution of 53 rift basins, suggesting that existing models, based on salt-free structural templates, need to 54 be modified. 55 56

In this study, we integrate 3D seismic reflection, wireline log, biostratigraphic and core data from the Egersund Basin, Norwegian North Sea to determine the impact of syn-depositional salt movement and associated growth faulting on the sedimentology and stratigraphic architecture of the Middle-to-Upper Jurassic, net-transgressive, syn-rift succession. Borehole data indicate that Middle-toUpper Jurassic strata consist of low-energy, wave-dominated offshore and shoreface deposits and coal-bearing coastal-plain deposits. These deposits are arranged in four parasequences that are aggradationally to retrogradationally stacked to form a net-transgressive succession that is up to 150-m thick, at least 20 km in depositional strike (SW-NE) extent, and >70 km in depositional dip (NW-SE) extent. In this rift-margin location, changes in thickness but not facies are noted across active salt structures. Abrupt facies changes, from shoreface sandstones to offshore mudstones, only occur across large displacement, basement-involved normal faults. Comparisons to other tectonically active salt-influenced basins suggest that facies changes across syn-depositional salt structures are observed only where expansion indices are >2. Subsidence between salt walls resulted in local preservation of coastal-plain deposits that cap shoreface parasequences, which were locally removed by transgressive erosion in adjacent areas of lower subsidence. The depositional dip that characterizes the Egersund Basin is unusual and likely resulted from its marginal location within the evolving North Sea rift and an extra-basinal sediment supply from the Norwegian mainland.