Inversion tectonics of the Variscan foreland of the British Isles

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Late Westphalian inversion structures on the Variscan foreland display wide variations in orientation that are the product of the underlying basement grain. The orientation of the major basement lineaments in relation to the direction of maximum shortening also determined the severity of deformation of the inverted basins. NE–SW-trending faults were oriented roughly perpendicular to the NW–SE to NNW–SSE direction of maximum shortening determined from thrust transport directions in the Variscan orogen to the south. As a consequence, NE–SW-trending basins in the Variscan foreland have been strongly inverted, the Silesian post-rift fill has commonly been expelled from the basins and the syn-rift sediments have been deformed by chevron folds (Dublin and Bowland Basins). In contrast, the N–S- and NW–SE-trending faults were oriented more obliquely to the direction of maximum shortening and, as a consequence, display a significant component of oblique slip. This oblique slip component is manifested as en-echelon periclines and flower structures. In general, the N–S- and NW–SE-trending basins were less strongly inverted and the Silesian post-rift fill has been retained.