The Berriasian Stage was introduced in scientific literature by
Henri Coquand in 1869. It is named after the village of
Berrias in the
Ardèche department of
France. The largely non-marine English
Purbeck Formation is in part of Berriasian age. The first rocks to be described of this age were the beds of the English Purbeck Formation, named as the Purbeckian by
Alexandre Brongniart in 1829 following description by
Henry De la Beche,
William Buckland,
Thomas Webster and
William Henry Fitton. The base of the Berriasian, which is also the base of the Cretaceous
System, has traditionally been placed at the first appearance of fossils of the
ammonite species
Berriasella jacobi. But this is a species that has a stratigraphically problematic and geographically limited distribution. A global reference profile (a
GSSP) for the Berriasian has been under active consideration by the Berriasian Working Group (ISCS) of
IUGS since 2010. A range of contender GSSP localities has been studied in detail by the Working Group including localities as far apart as Mexico, Ukraine, Tunisia, Iraq and the Russian Far East. Several markers have been employed to refine correlations and to work towards defining a base for the Berriasian Stage. These include calcareous
microfossils, such as
Nannoconus,
calpionellids,
ammonites, palynological data and
magnetostratigraphy, notably magnetozone M19n. The calibration of these markers, especially
Nannoconus steinmannii minor,
N. kamptneri minor, and
Calpionella alpina, within precisely fixed magnetozones give greater precision in trying to identify the best position for a boundary. In 2016, the Berriasian Working Group voted to adopt
Calpionella alpina as the primary marker for the base of the Berriasian Stage. In 2019, a GSSP for the Berriasian was nominated by a vote of the Berriasian Working Group of the Cretaceous Subcommission (ISCS): it is the profile of Tré Maroua in the Vocontian Basin (Hautes Alpes, France). The GSSP was defined at the base of the Alpina Subzone in the middle of magnetozone M19n.2n. This site proposal, of Tré Maroua, was subsequently unsuccessful in a vote of the ISCS (8 votes for and 8 against: 4 not voting); a new working group was formed in 2021. In the western part of the
ocean of Tethys, the Berriasian consists of four ammonite
biozones, from top to bottom (latest to earliest): •
Thurmanniceras otopeta •
Subthurmannia boissieri •
Tirnovella occitanica •
Berriasella jacobi/Pseudosubplanites grandis The top of the Berriasian stage is defined by the base of the Valanginian, which is fixed at the first appearance of
ammonite species
Thurmanniceras pertransiens. Regional terms used in Russia include "Volgian"(which spans perhaps the latest
Kimmeridgian, all the Tithonian and an uncertain amount of the lower Berriasian) and the "Ryazanian" (?upper Berriasian) . == Climate ==