Aptian

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Aptian
~121.4 – ~113.0 Ma
Chronology
Palaeogeography of the Earth in Aptian.

The Aptian is an

Ma to 113.0 ± 1.0 Ma (million years ago), approximately. The Aptian succeeds the Barremian and precedes the Albian, all part of the Lower/Early Cretaceous.[3]

The Aptian partly overlaps the upper part of the Western European Urgonian Stage.

The Selli Event, also known as OAE1a, was one of two oceanic

silicate weathering,[7] as well as ocean acidification.[8] The Aptian extinction was a minor extinction event hypothesized to have occurred around 116 to 117 Ma.[9]

Stratigraphic definitions

The Aptian was named after the small city of Apt in the Provence region of France, which is also known for its crystallized fruits. The original type locality is in the vicinity of Apt. The Aptian was introduced in scientific literature by French palaeontologist Alcide d'Orbigny in 1840.

The base of the Aptian Stage is laid at

GSSP) had in 2009 not yet been appointed. The top of the Aptian (the base of the Albian) is at the first appearance of coccolithophore species Praediscosphaera columnata in the stratigraphic record.[citation needed
]

Subdivision

In the

ammonite biozones
:

  • zone of Hypacanthoplites jacobi
  • zone of Nolaniceras nolani
  • zone of Parahoplites melchioris
  • zone of Epicheloniceras subnodosocostatum
  • zone of Duffrenoyia furcata
  • zone of Deshayesites deshayesi
  • zone of Deshayesites weissi
  • zone of Deshayesites oglanlensis

Sometimes the Aptian is subdivided in three substages or subages: Bedoulian (early or lower), Gargasian (middle) and Clansayesian (late or upper). In modern formal chronostratigraphy the Aptian is divided into Lower and Upper sub-stages. The Lower Aptian is equivalent to the Bedoulian, and it includes the oglanensis to furcata Tethyan ammonite zones. The Upper Aptian is equivalent to the Gargasian and Clansayesian, it includes the subnodosocostatum to jacobi Tethyan ammonite zones (Gradstein et al. 2004).[citation needed]

Lithostratigraphic units

Examples of rock units formed during the Aptian are:

Santana Formation, Twin Mountains Formation, Xinminbao Group and Yixian Formation
.

See also

References

Notes

  1. ^ International Commission on Stratigraphy. "ICS - Chart/Time Scale". www.stratigraphy.org.
  2. doi:10.18814/epiiugs/2017/v40i3/017021
    .
  3. ^ Gradstein et al. (2004)
  4. S2CID 249328937
    .
  5. doi:10.1016/j.epsl.2008.03.055
    .
  6. doi:10.1029/2001pa000623
    .
  7. doi:10.1016/j.epsl.2015.09.052
    . Retrieved 30 September 2022.
  8. S2CID 19498439
    . Retrieved 24 January 2023.
  9. ^ Archangelsky, Sergio. "The Ticó Flora (Patagonia) and the Aptian Extinction Event." Acta Paleobotanica 41(2), 2001, pp. 115-22.

Literature

  • Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.
  • d'Orbigny, A.C.V.M.; 1842: Paléontologie française: Terrains crétacés, vol. ii. (in French)

External links

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