In the Ruhla anticline the basement rocks, folded in the Variscan era, are exposed. They are named Ruhlaer Kristallin after the location and are according to Franz Kossmat considered part of the Central German Crystalline Zone, of which Odenwald and Spessart are also constituents. In the Rotliegend era the region formed the crest of a mountain range where the debris originated that was deposited in the Eisenach trough and the northwestern part of the Oberhof trough.