The transition level (German: ) includes all unfolded sedimentary and volcanic rocks of late Carboniferous (Stephanian) to mid-Permian (Guadalupian) age. Transition level refers, in part, to the stratigraphic position of these rocks: they are younger than the folded Variscides but older than the layers of the Mesozoic platform. In addition, they stem from a geological transition phase, which is characterised by the flattening of the Variscan mountains and by post-Variscan volcanism, which was accompanied by crustal extension in the Variscan Orogen. The rocks of the transition level differ from the younger platform sediments in that they are often relatively coarse-grained (conglomeratic) Molasse sedimentary rocks and acidic to intermediate volcanic rocks (especially rhyolite), whereas the Mesozoic platform has few conglomerates and no volcanic rocks. The transition level is divided lithostratigraphically into Stephanian and Permian (Rotliegend) sequences. Rocks of the transition level are found today mainly in the Saar-Nahe Basin, the Halle-Leipzig area (e.g. Halle Porphyry Complex), the Ore Mountain Basin and the Thuringian Forest.