Coniacian followed by Santonian
Stratigraphic definitions
The Coniacian is named after the city of Cognac in the French region of Saintonge. It was first defined by French geologist Henri Coquand in 1857.
The base of the Coniacian Stage is at the first appearance of the inoceramid bivalve species Cremnoceramus deformis erectus. The official reference profile for the base (a GSSP) is located in Salzgitter-Salder, Lower Saxony, Germany.
The top of the Coniacian (the base of the Santonian Stage) is defined by the appearance of the inoceramid bivalve Cladoceramus undulatoplicatus.
The Coniacian overlaps the regional Emscherian Stage of Germany, which is roughly coeval with the Coniacian and Santonian Stages. In magnetostratigraphy, the Coniacian is part of magnetic chronozone C34, the so-called Cretaceous Magnetic Quiet Zone, a relatively long period with normal polarity.