PALEOSTRESS FIELDS IN THE VARISCAN FORELAND DURING THE CARBONIFEROUS FROM MICROSTRUCTURAL ANALYSIS IN THE BRITISH-ISLES

North of the Variscan front the Carboniferous series of the British Isles is affected by mainly N-S trending folds which are almost perpendicular to this E-W oriented front. Flat and unconformable overlying Permian strata demonstrate a Variscan age for the deformation. A microtectonic survey made in Dinantian (and to a lesser extent Namurian) calcareous layers has revealed two successive events. According to chronological criteria, the first event (maximum stress E-W trending) led to the formation of N-S folds with local reorientation in the vicinity of major pre-existing faults. This compression may have been active since the Namurian. It pre-dates a second compressional event orientated N-S which is related to the final emplacement of the Variscan nappes. © 1990.