Controls on deposition of shallow marine carbonates and evaporites – lower Permian Gipshuken Formation, central Spitsbergen, Arctic Norway

The interbedded shallow marine carbonates and evaporites of the 95 to 105 m thick lower Permian Vengeberget member in central Spitsbergen form a lowstand to possibly early transgressive wedge sandwiched between open marine highstand carbonates along the northern margin of Pangea. Deposition took place on a wide (much greater than 40 000 km²) evaporitic platform separated from the open marine environments to the east by an inferred shelf margin barrier. Based on detailed description of facies in unique mountain-scale outcrops, five CaSO₄ and nine carbonate facies have been identified, all reflecting deposition in shallow evaporitic environments. The gypsum beds represent subaqueous deposition in broad hypersaline lagoons whereas the carbonates were deposited in protected shallow marine to peritidal environments and ooid-dominated grainstone shoals. Cyclicity is expressed both as lithological shifts from carbonate to CaSO₄ deposition and in the stacking of facies during CaSO₄ and carbonate deposition. The number of carbonate–evaporite cycles varies from 12 to 28, but the overall thickness of the succession varies only slightly as a result of variations in cycle thickness, from 0·5 to 13·0 m. Two basic types of carbonate units can be recognized and reflect a combination of allocyclic and autocyclic controls. In addition, differential subsidence along older north–south orientated lineaments added to the complexity of cyclicity. The study provides insight into the complexity of the controls on deposition, architecture and dynamics of large-scale mixed carbonate–evaporite successions formed in the shallow inner part of an epeiric sea or platform.