The horizontal sedimentary layers forming the eastern third of the Kaiserstuhl date back to the Jurassic and the Tertiary long before the volcanic activity. Important stratigraphic outcrops include the Hauptrogenstein (local oolite) which is found mainly near the village of Riegel and the Pechelbronner Schichten (local Tertiary layers in the South German Scarplands) near Bötzingen. During the formation of the Upper Rhine Plain this part of the Kaiserstuhl sloped less in respect to its surrounding area - and thus appears as a so-called horst. In terms of its geological structure and the sequence of its escarpments, the Kaiserstuhl is comparable to the nearby Tuniberg, Nimberg and also to the Schönberg, which is situated south of the city of Freiburg.