Valanginian
| Valanginian | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Chronology | |||||||||
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| Etymology | |||||||||
| Name formality | Formal | ||||||||
| Usage information | |||||||||
| Celestial body | Earth | ||||||||
| Regional usage | Global (ICS) | ||||||||
| Time scale(s) used | ICS Time Scale | ||||||||
| Definition | |||||||||
| Chronological unit | Age | ||||||||
| Stratigraphic unit | Stage | ||||||||
| Time span formality | Formal | ||||||||
| Lower boundary definition | Not formally defined | ||||||||
| Lower boundary definition candidates | FAD of the Calpionellid Calpionellites darderi | ||||||||
| Lower boundary GSSP candidate section(s) | |||||||||
| Upper boundary definition | FAD of the Ammonite genus Acanthodiscus | ||||||||
| Upper boundary GSSP | La Charce, Drôme, France 44°28′10″N 5°26′37″E / 44.4694°N 5.4437°E | ||||||||
| Upper GSSP ratified | December 2019[2] | ||||||||
In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 139.8 ± 3.0 Ma and 132.6 ± 2.0 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretaceous and precedes the Hauterivian Stage of the Lower Cretaceous.[3]
Stratigraphic definitions
[edit]The Valanginian was first described and named by Édouard Desor in 1853. It is named after Valangin, a small town north of Neuchâtel in the Jura Mountains of Switzerland.
The base of the Valanginian is at the first appearance of calpionellid species Calpionellites darderi in the stratigraphic column. A global reference section (a GSSP) had in 2009 not yet been appointed.
The top of the Valanginian (the base of the Hauterivian) is at the first appearance of the ammonite genus Acanthodiscus.[citation needed]
Subdivision
[edit]The Valanginian is often subdivided in Lower and Upper substages. The Upper substage begins at the first appearance of ammonite species Saynoceras verrucosum and the major marine transgression Va3.
In the Tethys domain, the Valanginian stage contains five ammonite biozones:
- zone of Criosarasinella furcillata
- zone of Neocomites peregrinus
- zone of Saynoceras verrucosum
- zone of Busnardoites campylotoxus
- zone of Tirnovella pertransiens [citation needed]
Flora
[edit]The oldest fossils that can definitely be attributed to the clade Angiospermae (flowering plants) are dated to the Late Valanginian.[4]
References
[edit]Notes
[edit]- ^ International Commission on Stratigraphy. "ICS - Chart/Time Scale". www.stratigraphy.org.
- ^ Mutterlose, Jörg; Rawson, Peter; Reboulet, Stéphane; Baudin, François; Bulot, Luc; Emmanuel, Laurent; Gardin, Silvia; Martinez, Mathieu; Renard, Maurice (September 2020). "The Global Boundary Stratotype Section and Point (GSSP) for the base of the Hauterivian Stage (Lower Cretaceous), La Charce, southeast France". Episodes. 44 (2): 129–150. doi:10.18814/epiiugs/2020/020072. Retrieved 24 December 2020.
- ^ See Gradstein et al. (2004) for a detailed geologic timescale
- ^ Coiro M, Doyle JA, Hilton J (July 2019). "How deep is the conflict between molecular and fossil evidence on the age of angiosperms?". The New Phytologist. 223 (1): 83–99. doi:10.1111/nph.15708. PMID 30681148.
Literature
[edit]- Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; (2004): A Geologic Time Scale 2004, Cambridge University Press.
External links
[edit]- GeoWhen Database - Valanginian
- Mid-Cretaceous timescale and ühttp://stratigraphy.science.purdue.edu/charts/Timeslices/5_JurCret.pdf 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
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