Inversion tectonics of the Variscan foreland of the British Isles

Abstract

Abstrart: 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.

Miocene fault-controlled sedimentation and thrust propagation in the previously faulted external zones of the Umbria-Marche Apennines, Italy

“…Elsewhere however, basement involvement has been postulated by several authors (e.g. Lavecchia et al, 1987;Menichetti et al, 1991;Sage et al, 1991;Coward et al, 1999) and appears to be confirmed by the interpretation of the CROP 03 deep seismic reflection profile (Barchi et al, 1998).…”

“…This occurs also in a more external area of the thrust belt, in the coastal structures of the Pesaro area (Fig. 1), where the Messinian evaporites mark again the onset of contraction and there is evidence for synchronous growth of different anticlinal structures during the late Messinian (De Donatis et al, 1998;Coward et al, 1999). Marine seismic data from the northern Adriatic (Argnani and Gamberi, 1995) suggest that similar features occurred in even more external areas of the thrust belt.…”

“…1), upper Messinian-Pliocene strata are disconformable upon Messinian units that form particular strong, characteristic reflectors (which can be ascribed to the Gessoso-solfifera Fm (e.g. Calamita et al, 1990;Coward et al, 1999)). As shown in Fig.…”

“…In the UmbriaMarche Apennines, as in most fold and thrust belt around the world, the fundamental role played by pre-orogenic structures related to rifting and subsequent passive margin development is now well established (e.g. Tavarnelli, 1996a;Coward et al, 1999;Marchegiani et al, 1999). On the other hand, the occurrence of synsedimentary normal faults which developed during continental collision ahead of the advancing thrust front has also been demonstrated by several workers (e.g.…”

Warwickshire Group (Pennsylvanian) red-beds of the Canonbie Coalfield, England–Scotland border, and their regional palaeogeographical implications

“…In several parts of northern England and in the southern North Sea, it has been suggested that deposition of the latest part of the basin-fill was contemporary with the early phases of the Variscan Orogeny and that many of the folds are in part syndepositional (e.g. Leeder & Hardman, 1990;Chadwick et al 1995, p. 36;Corfield et al 1996). Within the study area, Chadwick et al (1995, fig.…”