[3] The Coniacian is named after the city of Cognac in the French region of Saintonge.
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.
[citation needed] Beginning in the Middle Coniacian, an anoxic event (OAE-3) occurred in the Atlantic Ocean, causing large scale deposition of black shales in the Atlantic domain.