Berriasian

In the geological timescale, the Berriasian is an age or stage of the Early Cretaceous. It is the oldest or lowest subdivision in the entire Cretaceous. It spanned the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years ago). The Berriasian succeeds the Tithonian (part of the Jurassic) and precedes the Valanginian.^[1]

Stratigraphic definition

The Berriasian Stage was introduced in scientific literature by Henri Coquand in 1869. It is named after the village of Berrias in the Ardèche region of France. The largely non-marine English Purbeck Formation is in part of Berriasian age. In fact, 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. A global reference profile (a GSSP) for the Berriasian is under active consideration by the International Subcommission on Cretaceous Stratigraphy (ISCS) of IUGS. A range of contender GSSP localities currently being studied in detail by the ISCS's Berriasian Working Group include localities as far apart as Mexico, Ukraine, Tunisia, Iraq and the Russian Far East. Several markers are being employed to refine correlations and to work towards definition of a base for the Berriasian Stage. These include calcareous nanofossils, such as Nannoconus, calpionellids, ammonites, palynological data and magnetostratigraphy, notably the base of chron M18r. The calibration of these markers, especially Nannoconus steinmannii minor, N. kamptneri minor, and Calpionella alpina, within precisely fixed magnetozones gives greater precision in trying to identify the best position for a boundary.

In the Tethys Ocean, the Berriasian consists of four ammonite biozones, from top to bottom (latest to earliest):

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

The top of the Berriasian stage (the base of the Valanginian) is fixed at the first appearance of calpionellid species Calpionellites darderi in the stratigraphic column. This is just a little below the first appearance of the ammonite species Thurmanniceras pertransiens.

Palaeontology

Birds (avian theropods)

Crocodylomorphs (Non-Thalattosuchian)

Non-Thalattosuchian Crocodylomorphs of the Berriasian
Taxa	Presence	Location	Description	Images
Dakosaurus andiniensis				Dakosaurus andiniensis Geosaurus Goniopholis Steneosaurus
Geosaurus
Goniopholis
Lisboasaurus
Steneosaurus

Mammalia

†Ornithischians

Ornithischians of the Berriasian
Taxa	Presence	Location	Description	Images
Echinodon[3]		Swanage, England	A bipedal herbivore, it was around 0.6 meters (2 ft) long. Unlike most ornithischians, Echinodon had one or two caniniform teeth in each maxilla.	Echinodon Hylaeosaurus Owenodon Valdosaurus
Hylaeosaurus
Owenodon[3]
Paranthodon		Kirkwood Formation, Cape Province, South Africa	A 4 meters long, 1.8 meters high stegosaurid with a skull similar to Kentrosaurus
Valdosaurus		Isle of Wight, England; Niger, Africa	A dryosaurid

†Pterosaurs

†Sauropods

Sauropods of the Berriasian
Taxa	Presence	Location	Description	Images
Algoasaurus[3]				Pelorosaurus
Galveosaurus[3]
Turiasaurus[3]
Xenoposeidon[3]
Pelorosaurus[3]

†Thalattosuchia

†Theropods (non-avian)

†Non-avian theropods of the Berriasian
Taxa	Presence	Location	Description	Images
Dromaeosauroides				Dromaeosauroides
Embasaurus
Nuthetes

References

Notes

Literature

• Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; (2004): A Geologic Time Scale 2004, Cambridge University Press.

External links

• GeoWhen Database - Berriasian
• Jurassic-Cretaceous timescale, at the website of the subcommission for stratigraphic information of the ICS
• Stratigraphic chart of the Lower Cretaceous, at the website of Norges Network of offshore records of geology and stratigraphy