In the geological timescale, the Berriasian is an age or stage of the Early or Lower Creteceous. It is the oldest or lowest subdivision in the entire Cretaceous. It spanned between 145.5 ± 4.0 Ma and 140.2 ± 3.0 Ma (million years ago). The Berriasian succeeds the Tithonian (part of the Jurassic) and precedes the Valanginian.[1]
[edit] Stratigraphic definitions
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 of Berriasian age and in the past the names Purbeck and Wealden were also used to address rocks of the lowest Cretaceous.
The base of the Berriasian (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 Cretaceous International Subcommission (ISCS) of IUGS. A range of contender GSSP localities are currently being studied by the ISCS's Berriasian Working Group. Several markers are being employed to refine correlations and to work towards definition of a stage base. These include calcareous nannofossils, such as Nannoconus steinmannii, calpionellids, ammonites, palynological datums and magnetostratigraphy, notably the base of chron m18r.
In the Tethyan Realm, the Berriasian consists four ammonite biozones, from top to bottom:
The top of the Berriasian stage (the base of the Valanginian) is at the first appearance of calpionellid species Calpionellites darderi in the stratigraphic column. This is just a little below the first appearance of ammonite species Thurmanniceras pertransiens.
[edit] Palaeontology
| Birds of the Berriasian |
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[edit] Crocodylomorphs
| Crocodylomorphs of the Berriasian |
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[edit] Mammalia
| Mammals of the Berriasian |
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Durlston Bay, Dorset, England |
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Durlston Bay, Dorset, England; Spain |
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Portugal |
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Durlston Bay, Dorset, England |
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Portugal |
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[edit] †Ornithischians
| Ornithischians of the Berriasian |
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Description |
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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. |
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Kirkwood Formation, Cape Province, South Africa |
A 4 meters long, 1.8 meters high stegosaurid with a skull similar to Kentrosaurus |
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Isle of Wight, England; Niger, Africa |
A dryosaurid |
[edit] †Pterosaurs
| Pterosaurs of the Berriasian |
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[edit] †Sauropods
| Sauropods of the Berriasian |
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[edit] †Thalattosuchia
| †Thalattosuchians of the Berriasian |
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Description |
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From Kimmeridgian to Valanginian |
Austria, England, Germany, Portugal and Switzerland |
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Attested since Toarcian |
England, France, Germany, Switzerland and Morocco |
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[edit] †Theropods (non-avian)
[edit] References
- ^ See Gradstein et al. (2004) for a detailed geologic timescale
- ^ a b Only known from this stage.
- ^ a b c d e f g h i Dating uncertain.
[edit] Literature
[edit] External links
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In horizontal bars are eras; in left column are periods; right column: bold are epochs; not bold not italic are ages; italic are chrons:
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kya = thousands years ago. Mya = millions years ago. * Not officially recognized by the I.C.S.
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