Aptian
Aptian | |||||||||
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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 |
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Lower boundary GSSP candidate section(s) | , Piobbico, Central Apennines, Italy | ||||||||
Upper boundary definition | FAD of the Planktonic Foraminifer Microhedbergella renilaevis | ||||||||
Upper boundary GSSP | , Arnayon, Drôme, France 44°29′47″N 5°18′41″E / 44.4964°N 5.3114°E | ||||||||
GSSP ratified | April 2016[2] |
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 125.0 ± 1.0 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 Stage.
The , also known as OAE1a, was one of two oceanic anoxic events in the Cretaceous Period, which occurred around 120 Ma and lasted approximately 1 to 1.3 million years.[4][5] The Aptian extinction was a minor extinction event hypothesized to have occurred around 116 to 117 Ma.[6]
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 . A global reference profile for the base (a 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 in the stratigraphic record.
Subdivision[]
In the Tethys domain, the Aptian contains eight ammonite biozones:
- zone of
- zone of
- zone of
- zone of
- zone of
- zone of
- zone of Deshayesites weissi
- zone of Deshayesites oglanlensis
Sometimes the Aptian is subdivided in three substages or subages: (early or lower), (middle) and (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).
Lithostratigraphic units[]
Examples of rock units formed during the Aptian are: Antlers Formation, Cedar Mountain Formation, Cloverly Formation, Elrhaz Formation, Jiufotang Formation, Little Atherfield, Mazong Shan, Potomac Formation, Santana Formation, Twin Mountains Formation, Xinminbao Group and Yixian Formation.
See also[]
References[]
Notes[]
- ^ International Commission on Stratigraphy. "ICS - Chart/Time Scale". www.stratigraphy.org.
- ^ Kennedy, J.W.; Gale, A.S.; Huber, B.T.; Petrizzo, M.R.; Bown, P.; Jenkyns, H.C. (2017). "The Global Boundary Stratotype Section and Point (GSSP) for the base of the Albian Stage, of the Cretaceous, the Col de Pré-Guittard section, Arnayon, Drôme, France" (PDF). Episodes. 40 (3): 177–188. doi:10.18814/epiiugs/2017/v40i3/017021.
- ^ Gradstein et al. (2004)
- ^ Li, Yong-Xiang; Bralower, Timothy J.; Montañez, Isabel P.; Osleger, David A.; Arthur, Michael A.; Bice, David M.; Herbert, Timothy D.; Erba, Elisabetta; Premoli Silva, Isabella (2008-07-15). "Toward an orbital chronology for the early Aptian Oceanic Anoxic Event (OAE1a, ~ 120 Ma)". Earth and Planetary Science Letters. 271 (1–4): 88–100. Bibcode:2008E&PSL.271...88L. doi:10.1016/j.epsl.2008.03.055.
- ^ Leckie, R.; Bralower, T.; Cashman, R. (2002). "Oceanic anoxic events and plankton evolution: Biotic response to tectonic forcing during the mid-Cretaceous" (PDF). Paleoceanography. 17 (3): 1–29. Bibcode:2002PalOc..17.1041L. doi:10.1029/2001pa000623.
- ^ 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[]
- GeoWhen Database - Aptian
- Mid-Cretaceous timescale, at the website of the subcommission for stratigraphic information of the ICS
- Stratigraphic charts of the Lower Cretaceous: [1] and [2], at the website of Norges Network of offshore records of geology and stratigraphy
- Aptian
- Early Cretaceous
- Geological ages
- Cretaceous geochronology