Development and evolution of the Flamborough Head Disturbance

Abstract

Previous models on the formation of the Flamborough Head Disturbance have been hindered by a lack of data integration, especially between onshore and offshore subsurface datasets. This project resolves the problem and long-standing controversies through the interpretation of an extensive, seismic and borehole dataset that spans the coastline and delivers a unified geological model for the Flamborough Head Disturbance. The model consists of a W-E striking array of planar basement faults, throwing to the north and controlled by the presence of the granite cored Market Weighton Block to the south, marking an onshore extension of the Dowsing Fault Zone. Above this and striking in the same orientation is a Late Triassic-Early Jurassic to Lower Cretaceous aged listric fault controlled Mesozoic graben system that is decoupled from the basement by thick Permian evaporites. Migration of Permian salt in the Lower Cretaceous has resulted in the syn-halokinetic but post-rift deposition of the Cromer Knoll Group marine strata. The model recognises two episodes of major basin reconfiguration during the Cenozoic: regional tilting to the south-east and basin inversion through the reactivation of basement faults. Basement fault reactivation was focussed in the hanging wall of the fault system due to buttressing against the Market Weighton Block buried granite during compression. Fault reactivation did not propagate through the Zechstein salt, with shortening being taken up by buckling of the post-salt section in the hanging wall of the fault system. This preserved the extensional geometries of the detached listric faults of the detached graben system and resulted in the deformation structures observed in outcrop. Cenozoic tilt and structural inversion has resulted in hydrocarbon trap breaching in the hanging wall of the Flamborough Head fault system and the depressurisation of Carboniferous source rocks. This study complements existing research on Cenozoic uplift and intraplate deformation in the UK and emphasises the importance that buried Caledonian granites and mobile salt have on the creation and inversion of Mesozoic sedimentary basins in the UK.