Tremadocian

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Tremadocian
485.4 ± 1.9 – 477.7 ± 1.4 Ma
Chronology
Rock from the Skiddaw Group, of Ordovician (Tremadocian) age, at Scawgill Bridge quarry in Cumbria, England, UK

The Tremadocian is the lowest stage of

Lower Ordovician Epoch. The Tremadocian lasted from 485.4 to 477.7 million years ago. The base of the Tremadocian is defined as the first appearance of the conodont species Iapetognathus fluctivagus at the Global Boundary Stratotype Section and Point (GSSP) section on Newfoundland.[7]

Naming

The Tremadocian is named after the village Tremadoc in Wales. The name was proposed by Adam Sedgwick in 1846 (as "Tremadoc group").

GSSP

The GSSP for the beginning of the Tremadocian is the Green Point section (49°40′58″N 57°57′55″W / 49.6829°N 57.9653°W / 49.6829; -57.9653)

graptolites appear 4.8 m above the first appearance of Iapetognathus fluctivagus at Greenpoint section.[5]

The Tremadocian ends with the beginning of the

Diabasbrottet quarry, Västergötland, Sweden.[9]

Regional stages

In North America the first stage of the Ordovician is the Gasconadian Stage.[10] In Baltic region the stages corresponding to Tremadocian are Pakerort stage (older) and Varangu stage (younger).[11][12]

Major events

The Cambrian-Tremadocian boundary is marked by the

Cambrian-Ordovician extinction event. Overall the amount of biodiversity of the Cambrian was maintained.[13] At the beginning of the Tremadocian, about 485.4 million years ago, biodiversity, which had been at a low level, began its long increase phase, known as the Great Ordovician Biodiversification Event.[14]

At the Furongian‒Tremadocian boundary, a mantle plume event occurred on the territory of the northwestern Gondwana, which is now the Iberian Peninsula. Ollo de Sapo magmatic event continued in this region further into Ordovician.[15]

The middle of the Tremadocian witnessed an extinction event known as the Mid-Tremadocian Extinction Event[16] or the Base Stairsian Mass Extinction Event,[17] which is particularly known to have affected Baltican conodonts.[16] This extinction event may have been caused by anoxia.[18][19]

Tremadocian life

Planktonic graptolites, an important

trilobites of the genus Platypeltoides in Belgium, Wales (both were parts of Avalonia) and Morocco (Gondwana).[21]

Ocean and climate

Further information: Ordovician § Climate_and_sea_level

The

Early Ordovician in general was a time of transgression. The climate was slowly cooling throughout the Ordovician.[22]

References

  1. PMID 10905606
    .
  2. doi:10.1111/j.1945-5100.2007.tb00221.x
    .
  3. PMID 28117834
    . It has been suggested that the Middle Ordovician meteorite bombardment played a crucial role in the Great Ordovician Biodiversification Event, but this study shows that the two phenomena were unrelated
  4. ^ "Chart/Time Scale". www.stratigraphy.org. International Commission on Stratigraphy.
  5. ^
    doi:10.18814/epiiugs/2001/v24i1/005. Archived
    (PDF) from the original on 2024-03-25. Retrieved 2024-04-15.
  6. doi:10.18814/epiiugs/2004/v27i4/005. Archived
    (PDF) from the original on 2023-06-20. Retrieved 2024-04-15.
  7. ^ a b "GSSP Table - Paleozoic Era". Archived from the original on 2023-10-08.
  8. ^ "GSSP for Tremadocian Stage". timescalefoundation.org. Archived from the original on 2024-04-04.
  9. ^ "GSSP for Floian Stage". timescalefoundation.org. Archived from the original on 2024-04-04.
  10. ^ "Kentucky Stratigraphy With Stage Correlations". University of Kentucky. Archived from the original on 2024-04-16.
  11. ISSN 1392-110X. Archived
    (PDF) from the original on 2024-04-16.
  12. ^ "Ordovician of the Baltic". Paleobiology Database. Archived from the original on 2024-04-16. Retrieved 2024-04-16.
  13. ^ Sepkoski, J. J. (1995). "The Ordovician Radiations: Diversification and Extinction Shown by Global Genus-Level Taxonomic Data". pp. 393–396. Archived from the original on 2022-10-04. Retrieved 2024-04-05.
  14. doi:10.1016/j.palaeo.2023.111492.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  15. doi:10.1080/00206814.2023.2263787.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  16. ^
    S2CID 146630424
    . Retrieved 2024-04-15.
  17. S2CID 254361718
    . Retrieved 2024-04-15.
  18. doi:10.1016/j.epsl.2017.10.002
    . Retrieved 2024-04-15.
  19. doi:10.1130/G36814.1
    . Retrieved 2024-04-15.
  20. doi:10.4202/app.01103.2023.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  21. doi:10.1016/j.geobios.2023.04.003.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  22. doi:10.1016/j.palaeo.2010.08.001
    .

External links
Retrieved from "https://en.wikipedia.org/w/index.php?title=Tremadocian&oldid=1219671262"