The Permian to Cretaceous structural evolution of the Western Approaches Basin (Melville sub-basin), UK

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Abstract
Summary: The tectonic-sedimentary evolution of the western part of the Western Approaches Basin (Melville sub-basin) was initiated during early Permian times when synrift clastic sedimentation and volcanism commenced within an ENE trending half-graben. This sequence thickened to the south and onlapped a high to the north. During the Permian an early NNW-SSE basin extension was accommodated on an array of ENE-WSW trending normal faults linked by NNW-SSE orientated transfer faults. This was followed by a period of ENE-WSW extension along the basin axis when the normal and transfer faults of the previous faulting episode swapped roles. This was possibly related to early rifting in the Bay of Biscay. Both sets of faults appear to be controlled to some extent by Variscan thrusts and strike-slip faults within the basement. During the Upper Triassic the ridge in the north subsided allowing a thick sequence of salt to be deposited where there had previously been a topographic high. During Jurassic times sedimentation extended across the Permian-Triassic half-graben into the French sector. This was followed by an episode of rifting and wrench deformation (and inversion?) during which the Permian to Jurassic basin was domed and uplifted. The Cretaceous to Tertiary sedimentation which followed probably resulted from postrift thermal subsidence related to cooling of the continental platform adjacent to the opening Atlantic Ocean. Steep normal and/or strike—slip faults data from the earliest part of this postrifting stage.