Permian (Upper Rotliegend) synsedimentary tectonics, basin development and palaeogeography of the southern North Sea

Abstract

Abstract Upper Rotliegend sedimentation in the southern North Sea Basin (SNSB) was a response to complex synsedimentary tectonics and cyclical climatic changes. During the early Upper Rotliegend, faulting (?dextral strike-slip) resulted in the formation of a number of isolated sub-basins e.g. the Sole Pit, Silverpit and the Broad Fourteens, which were gradually united as a consequence of the progressive collapse of the Inde-Cleaver Bank High. Basin-margin tectonics controlled the evolution of the basin and the nature and distribution of the various types of alluvial fan and fan delta systems that evolved during pluvial climatic phases. Many of the earlier Upper Rotliegend fans display a systematic lateral displacement along synsedimentary faults. Along the Dowsing Fault Zone, ‘dry-type’ alluvial fans display a progressive northwestward migration with time. Also, fan deltas, sourced from the Texel-Ijsselmeer High, young progressively to the SE along the trend of the main faults. These systematic lateral displacements have been tentatively explained by invoking dextral oblique transfer of the source area relative to the depositional basin, within the context of a strike-slip tectono-sedimentary model. Alternatively, in an extensional model, the distribution pattern could be explained by sourcing the fans from both the footwall scarps and the transfer zones of dip-slip faults. A rapid decline in synsedimentary faulting, and a gradual change to more pluvial climatic conditions, resulted in the development of larger ‘wet type’ fans during the later part of the Upper Rotliegend time interval.