Regional variability of onset and cessation of salt tectonics in the Mesozoic and Cenozoic Southern North Sea subbasins

Abstract

Early post-Permian salt mobilization of the Zechstein Supergroup was a major controlling factor of the post-Permian basin evolution and complex Mesozoic–Cenozoic architecture of different subbasins across the Southern North Sea. Supraregional merged seismic data sets enable the basin-scale systematic analysis of salt tectonic processes and their regional tectonic and local paleodepositional controls.This study uses the Southern North Sea MegaSurvey basin-scale three-dimensional seismic data set for the systematic identification and classification of salt structures, with a particular focus on the onset and cessation of individual salt structures across different subbasins. Regional analysis of high-resolution isochron maps demonstrates the basin-wide onset of salt mobilization occurred in the Triassic in most of the subbasins. The exceptions are the Silverpit Basin and the Cleaver Bank high, where the onset of salt mobilization was delayed until the Jurassic and the Cretaceous. Jurassic mobilization was restricted to major depocenters such as the Broad Fourteens Basin, Silverpit Basin, and Southern Central Graben. Basin-wide pulses of mobilization occurred throughout the Cretaceous and, apart from the Sole Pit and Silverpit Basins, continued during the Paleogene. The cessation of salt mobilization occurred mainly throughout the Paleogene, with only a few isolated structures active until the Neogene in areas such as the Central Graben and the Broad Fourteens Basin.Improved understanding of these early salt tectonic processes will provide new insights into fundamental salt basin–forming processes and mechanisms while developing new exploration strategies in the suprasalt overburden in the mature Southern North Sea Basin.