Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original Paper

Rojík

New stratigraphic subdivision of the Tertiary in the Sokolov Basin in Northwestern Bohemia

Journal of the Czech Geological Society, volume 49 (2004), issue 3-4, 173 - 185

An updated stratigraphic division of the Tertiary fill in the Sokolov Basin is proposed. Lithostratigraphic units are defined, in principle, by lithological criteria. The lithostratigraphic scale is fixed to time points established by means of biostratigraphic and magnetostratigraphic data. A great number of marker beds, composite marker beds and marker horizons enhanced correlation among heteropic units. The Tertiary volcani-sedimentary succession of the Sokolov Basin, up to nearly 400 m thick, is divided into four formations: The Staré Sedlo Formation (Eocene/Oligocene boundary, ca. 35 Ma) represents the initial, fluvial stage of the basin development. The Nové Sedlo Formation (Oligocene to Early Miocene, ca. 24-23 Ma) reflects the first dynamic stage of the area extension, accompanied by intensive volcanism and tectonic subsidence. The Nové Sedlo Formation is subdivided into three heteropically interfering members: the Davidov Member, the Josef Member and the Chodov Member. The Sokolov Formation (Early Miocene, ca. 23-21 Ma), separated from the previous formation by a disconformity, represents the second stage of extension, subsidence and volcanism. It is subdivided into four heteropically interfering members: the Habartov Member, the Těšovice Member, the Anežka Member and the Antonín Member. The Cypris Formation (Early Miocene, ca. 21-17 Ma) with member of the Čankov Sand is characterized by a stepwise cessation of endogenic processes. The Staré Sedlo, Nové Sedlo and Sokolov formations are separated by disconformities. The Sokolov Formation underlies the Cypris Formation with a conformity indicating an abrupt regional change of the environment.