(named after the Silurian king Cara-doc), the fifth stage (of six) from the bottom of the Ordovician system. Established by the British scientist R. Murchison in Wales (1839).
The Caradocian stage is represented by sandstones and argil-lites with limestone lenses. According to present-day divisioning, the Caradocian stage includes five graptolite zones from Nema-graptus gracilis to Pleurograptus linearis, which constitute themiddle and upper divisions of the Ordovician system. The depos-its of the Caradocian stage are widely distributed in the north-western part of the Eastern European Platform, in Kazakhstan, Middle Siberia, and the northeastern part of the USSR. Theyhave been found everywhere in the countries of Western Europe, in Burma, the Chinese People’s Republic, Australia, NorthAfrica, and America. In the Estonian SSR and LeningradOblast, oil shale deposits are found in the lower part of theCaradocian stage.