Santonian

The Santonian (also Santon ) is a chronostratigraphic stage of the Upper Cretaceous. It includes in absolute terms ( geochronological ) the period from about 86.3 to about 83.6 million years. It follows the Coniacian and is detached from the Campanian.

Naming and history

The rock series, which typify this stage, are the Saintonge area near the French city of Saintes. The Latin name " Santonum " for this landscape was the stage name. Henri Coquand in 1857 suggested the name and level.

Definition and GSSP

The beginning of the stage is defined by the first appearance of inoceramids Type Cladoceramus undulatoplicatus. The stage ends with the extinction of the crinoid type Marsupites testudinarius. A GSSP (global type locality and type profile) for the Santonian has not yet been ratified concluded.

Subdivision

The Santonian can be divided into sub- steps lower, middle and Obersantonium.

In Tethysbereich the Santonian has only one ammonite biozone:

• Placenticeras polyopsis

A finer breakdown can be achieved with inoceramids, foraminifera and nannoplankton.