Berriasian

The Berriasian ( in German language, also shortened to Berriasian, more rarely, Berri Asia ) is in the earth's oldest chronostratigraphic stage of the Lower Cretaceous. The level corresponds to the geochronological time scale of the period of about 145 to 139.3 million years. The Berriasian follows the Tithonian ( latest stage of the Jurassic) and is detached from the Valanginian.

Naming and history

The stage is named after the place Berriasian in French Ardèche. Stage and name were introduced in 1869 by Henry Coquand in the scientific literature. Previously, the stage in the transition from Jurassic to Lower Cretaceous in northern Germany was also called Wealden.

Definition and GSSP

The beginning of the stage is (presumably ) defined by the first appearance of ammonite species Berriasella jacobi. A GSSP (global type locality and type profile ) has not yet been determined. The end of the stage is also determined only provisionally by the first appearance of calpionellids Type Calpionellites darderi. Also, for the base of Valanginiums is not yet a GSSP has been defined. Only slightly above the targeted limit Berriasian / Valanginian also uses the ammonite species Thurmanniceras pertransiens.

Subdivision of the Berriasian

The Berriasian is subdivided in the Tethyan region in four ammonite biozones:

• Thurmanniceras otopeta
• Subthurmannia boissieri
• Subthurmannia occitanica
• Berriasella jacobi