(from the name of the city of Siegen, Federal Republic of Germany), second stage (from below) of the Devonian system. Identified by the Belgian geologist
J. de Dorlodot in 1900 in the Rhenish Slate Mountains and the Ardennes, where it is composed of sandstones and shales with Acrospirifer pimaevus and other fossils. The Siegenian stage is found in many countries of Western Europe and in North Africa. In the USSR rocks analogous to the Siegenian stage occur in the Urals, the northern part of the Balkhash Region, and the Salair Ridge.