The red sandstone overburden with striking steps rises above the crystalline base (basement) in the northern Black Forest and in the adjacent parts of the Central Black Forest. The most resistant surface layer on the stepped surface of the Grindenhöhen, which is strongly dissolved by the Murg tributaries and the closed Enzhöhen, is the silicified main conglomerate (Middle Buntsandstein). To the east and north are the slabs of the Upper Buntsandstein (slab sandstone and red clay). South of the Kinzig, the red sandstone narrows to a border in the east of the mountains.
Ice Age and Shaping
It is proven that the Black Forest was heavily glaciated during the peak phases of at least the Riss and Würme Ice Ages (up to around 10.000 years ago). The glacial treasure trove of forms shapes almost the entire High Black Forest and the main ridge of the Northern Black Forest. Otherwise it is only noticeable in a large number of cirques, mostly facing northeast. Especially in this exposure, accumulations of snow on the slopes of the summit plateaus facing away from the sun and wind led to the formation of short cirque glaciers that carved out these funnel-shaped hollows. There are still a few in them, partly due to re-accumulation Karseen preserved like Mummelsee, Wildsee, Schurmsee, Glaswaldsee etc.
Gneiss rocks predominate in the basement. Several large granite bodies penetrated in the course of older mountain formations. These can be found, for example, between the Kinzig and the Middle Murgtal. The formation of ore deposits was associated with igneous phenomena, some of which man used for mining. Also worth mentioning are the depressions in Rotliegend, for example the Baden-Baden depression, with partly thick quartz porphyry and tuff ceilings (exposed on the Battert rock massif, in the urban district of Baden Baden).
The Black Forest, which emerged in the Late Tertiary - Paleocene - was bulged up to varying degrees, as if in a huge wave movement. The southern Black Forest with the Feldberg as the highest center (1493 m) was hit most intensively, but the area around the area was less affected Hornisgrind (1164 m). In between lie wide, tectonic hollows like the river valleys of Kinzig and Murg. The Black Forest consists of two geological units: an older crystalline base, also known as the basement, and the overlying cap rock made of red sandstone.