The Oberhof trough is by far the largest of the main geologic parts of the Thuringian Forest. It consists of the uplifted part of the so-called Thuringian Forest Basin whose contents can be further subdivided into several formations. Their relative ages have not been fully resolved yet, partly because the Oberhof trough had been a rift zone with intense tectonics and continual changes of the internal relief and of the main areas of deposition. The tectonic processes were accompanied by an intense felsitic volcanism which was the origin of many volcanic rock formations, predominantly rhyolites of porphyric structure with accompanying tuff deposits. These volcanic rocks alternate in sequence with the typical reddish molasse sediments (conglomerates, sandstones, siltstones, and claystones) of the Rotliegend.