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Mapping of depositional zones within the Zechstein Supergroup using semi-regional 2D and 3Dseismic data constrains the geological evolution of the northwestern margin of the North Permian Basinin UK offshore Quadrants 14, 15, 19, 20 and 21. Four depositional zones are identified on the basis of mappable seismic facies, which are assumed to vary with halite content. Well control characterizes the most reflective seismic facies as an interbedded carbonate and anhydrite ‘shelf’ succession which grades laterally through clastic-rich sequences to the least reflective, a thick halite basinal equivalent. The trendsof the depositional zones illustrate the geometry of the North Permian Basin and may have been locally controlled by basement lineaments. Within the North Permian Basin a N–S-trending axis (Devil’s Hole High) characterized by thick reflective facies separates the Central North Sea from the Forth Approaches Basin. Basement fault blocks control facies type and thickness along the northwest margin of the North Permian Basin in the Moray Firth area. Permian tilt of the Zechstein shelf related to regional flexure played a role in precipitating gravity-driven tectonics within the seismically reflective facies on the east flank of the Devil’s Hole High. This Permian phase of salt tectonics resulted in numerous intra-Zechstein structures which can be interpreted as rafted and folded zones of interbedded halite, carbonate, sulphate and clastics. The ‘rafts’ initially slid downdip towards the main halite basin then their evolution became dominated by differential subsidence of the interbeds which forced salt layers into adjacent passive diapirs. This episode predates deposition of the Triassic Smith Bank shales which rest upon the Zechstein with local angular unconformity. The spatial distribution of Zechstein facies influenced the tectonostratigraphy of the Triassic, Jurassic and Cretaceous systems. Boundaries between Zechstein facies correspond to the limit of Triassic halokinesis on the West Central Shelf and the limit of detachment of Jurassic and lower Cretaceous thin-skinned tectonics in Moray Firth half graben.

The North Sea Basin contains a widespread Permian salt layer that reached a depositional thickness ofc.

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The Central North Sea lies within the North Permian evaporite Basin, which was largely flexural but with locally significant basement faults. While the main evaporite basin fill is halite, seismically reflective basin margin facies delineate the salt basin shape. The marginal Zechstein strata record Permian salt tectonics including listric faulting, slumping of kilometre-scale carbonate rafts and halite diapirism, all related to localized pre-Triassic gravity-driven collapse of the Zechstein basin margin. Triassic thickness in the Central North Sea (CNS) was directly influenced by salt, the most significant phase of salt tectonics in the history of the CNS in terms of volume of salt redistributed and dissolved. Lower–Middle Triassic ‘minibasins’ subsided into the salt over much of the CNS. Different initiating mechanisms operated around the basin–differential loading was important near sediment input points, and thin-skinned extension on the platforms balanced a pulse of basement extension in the Central Graben. Minibasin subsidence was accommodated by salt wall growth; salt was eroded during periods of base-level fall and redeposited locally and in the Southern North Sea. The minibasins touched down on basement progressively from the basin margins towards the Central Graben, the timing being a function of salt thickness. The diachronous halting of accommodation space generation combined with the effects of erosion led to a variety of field relationships between the Middle–Upper Triassic Skagerrak sands and the underlying salt–minibasin system. Regionally, the Skagerrak sands are thickest near input points and in the Central Graben, where accommodation space was supplemented by basement faulting.The platforms were subaerially exposed and eroded for much of the period between the late Triassic and late Jurassic. On these platforms, the distribution of the relatively thin Late Jurassic section was controlled by a combination of regional tilt and pre-existing topography created by differential erosion (including dissolution) of the salt walls versus grounded minibasins. The late Jurassic Fulmar shallow marine sands are thickest on the differentially eroded salt highs, which constituted several hundred foot-deep palaeovalleys. Rifting occurred in the Central Graben where tilts of detachments on top of major basement fault blocks caused thin-skinned extension in the overlying strata, either for the first time, or reactivating Triassic minibasin systems. The Fulmar sands are thickest where basement-controlled accommodation space was accentuated by detached fault systems (e.g. fallen diapirs) near sediment input points in the Central Graben.The Early Cretaceous was a time of tectonic stabilization following Late Jurassic basement rifting, although the perched detachment systems in the major basement graben continued to evolve. Accommodation space for Upper Jurassic and Lower Cretaceous turbidites was influenced by up-dip salt high collapse and down-dip ‘rim syncline’ growth. By the end of the Early Cretaceous these systems had stabilized and the surrounding basement highs were sufficiently blanketed to shut off salt dissolution. Chalk isopach variations pick out subtle regional tilts and local basement fault reactivations.Major flexural subsidence in the Tertiary tilted the basin again and precipitated local cover slip, e.g. extensional faults balanced by down-dip folds on the West Central Shelf and diapir rejuvenation on the graben margin.A variety of inversion structures are present in the CNS and are dominantly Cretaceous and Tertiary in age. Several styles of inversion structure occur including thin-skinned and thick-skinned compression, diapir rejuvenation, compaction and dissolution-related features. Salt governed the geometry of many of these structures and in turn the geometry of the Tertiary sand fairways.