EUROPE/Permian Basins 97 resulting changes in climate, formation of substantial coal measures north of the Variscides had already ceased in the Westphalian D, whereas in the southern areas it continued until the end of the Stephanian The sediments and volcanic rocks accumulated during the syn-rift and subsequent thermal subsidence phases can locally reach total thicknesses of up to km However, it should be noted that the thicknesses presently observed are often only erosional remnants At least in parts of the Variscan orogen it can be shown that a substantial part of the sediments deposited during the Stephanian to Early Permian was already eroded prior to the Zechstein transgression In the Saar-Nahe Basin, for example, estimates based on shale compaction data and vitrinite reflectance modelling indicate removal of up to 3.7 km of sediments during this phase Between these basins, the basement was exposed or was directly overlain by younger deposits The geometry and structural style of the individual basins were strongly controlled by the interplay of pre-existing structural elements and new faults that formed in conjunction with the dextral translation of Gondwana relative to Laurussia A dextral strike–slip component is inferred from basin geometry and orientation, isopach maps of syn-rift deposits, migration direction of depocentres, the orientations and structural data from syn-sedimentary faults, simultaneous horst and basin formation, and the arrangement of volcanic centres and dykes Thus, some of the basins trend obliquely to the structural grain of the orogen and intersect the Variscan deformation front, whereas others owe their formation to transtensional reactivation of older, compression-related faults A prime example of the latter is the Saar-Nahe Basin in south-west Germany, which formed by oblique extensional reactivation of a crustal-scale fault structure, along which the internal zone of the Variscan orogen (Mid-German Crystalline Rise, part of the Saxothuringian Zone) was previously thrusted onto the external fold-and-thrust belt (Rhenohercynian Zone) Thus, the basins that were formed by transtensional reactivation of former thrusts frequently have half-graben structures In contrast, pull-apart basins that opened during dextral strike–slip movements tend to be located next to the dominant north-westto south-east-trending faults (continental-scale dextral shears parallel to the Tornquist–Teisseyre Line; e.g., the Elbe Line, Pays de Brays Fault, Bay of Biscay, Gibraltar-Minas, and Agadir fracture zones) Several of the faults that controlled PermoCarboniferous basin evolution were later reactivated, particularly in connection with the inversion of the Alpine foreland in the Late Cretaceous and Early Permian These later events can sometimes obscure the Permo-Carboniferous basin geometry and fault displacement Thus, identification of faults that were active in Permo-Carboniferous times requires careful analysis of indicators for syn-sedimentary tectonics, such as abrupt variations in thickness and facies architecture and syn-depositional deformation structures Magmatism Late Carboniferous to Early Permian volcanic and plutonic activity of varying style and composition was coeval with extension and basin formation in both foreland and the internal Variscides, and occurred in crustal domains of various ages (Figure 1) Reliable U–Pb and 40Ar/39Ar mineral ages show that most of the activity occurred in the period 305 to 290 Ma Magmatic rocks of mafic composition are common in the foreland, but are relatively rare in the internal Variscides Layers of strongly altered air-fall tuffs, known as bentonites or tonsteins, occur in nearly every basin, but most of these originated from distal volcanic sources Extensional faulting took place before, during, and after volcanic activity In the north-western part of the North German Basin, initial faulting caused the formation of horsts and grabens that strongly controlled the placement and thickness of the volcanic rocks Faulting in the central North Sea mainly postdates the volcanic activity, whereas in the Oslo Rift, the main east and west extension was coeval with the main phase of trachyandesitic volcanism In nearly all of the basins, lavas occur interbedded with sediments, showing that magmatic activity took place during subsidence and extension The volcanic rocks are interbedded and alternate with Stephanian coal measures and Early to Late Permian, Rotliegendfacies alluvial and fluviatile clastic sediments, and lacustrine marls deposited in semiarid environments Where not eroded, these are often followed by aeolian sandstones Foreland In the foreland, a variety of volcanic and plutonic rocks are present in the Oslo Rift in south Norway, and large volumes of rhyolitic and andesitic volcanic rocks occur in northern Germany below younger cover and are known only from deep boreholes More mafic magmatic activity resulted in the formation of dyke swarms and sills, such as the basaltic Whin Sill and the Midland Valley complexes in Great Britain, the basaltic dyke swarm in South Sweden, and the lamprophyre dyke swarms in the western Highlands of Scotland Smaller volumes of mafic and felsic volcanic rock have been drilled in the