Aptian
| Aptian | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| 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 |
| ||||||||
| Lower boundary GSSP candidate section(s) | Gorgo a Cerbara, Piobbico, Central Apennines, Italy | ||||||||
| Upper boundary definition | FAD of the Planktonic Foraminifer Microhedbergella renilaevis | ||||||||
| Upper boundary GSSP | Col de Pré-Guittard section, Arnayon, Drôme, France 44°29′47″N 5°18′41″E / 44.4964°N 5.3114°E | ||||||||
| Upper 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 121.4 ± 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 Urgonian Stage.
The Selli Event, 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][6] being marked by enhanced 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
[edit]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 magnetic anomaly M0r. 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 Praediscosphaera columnata in the stratigraphic record.[citation needed]
Subdivision
[edit]In the Tethys domain, the Aptian contains eight 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
[edit]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.
Climate
[edit]A cold episode occurred at the start of the Aptian, as evidenced by the migration of the dinoflagellates Cepadinium variabilis and Pseudoceratium nohrhansenii into lower latitudes.[10] A decline in global pCO2 occurred from about 1,000 ppm to 800 ppm from the start of the Aptian to the C10 positive carbon isotope excursion.[11] During the late Aptian, pCO2 was between 515 ± 79 and 1029.8 ± 158 ppm as evidenced by the stomatal density of Pseudofrenelopsis capillata.[12]
See also
[edit]References
[edit]Notes
[edit]- ^ "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy. September 2023. Retrieved December 16, 2024.
- ^ 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)
- ^ Blok, C. N.; Ineson, J.; Anderskouv, K.; Fantasia, A.; Sheldon, E.; Thibault, N.; Jelby, M. E.; Adatte, T.; Bodin, S. (1 September 2022). "Latitude-dependant climate changes across the Aptian Oceanic Anoxic Event 1a". Palaeogeography, Palaeoclimatology, Palaeoecology. 601: 111085. Bibcode:2022PPP...60111085B. doi:10.1016/j.palaeo.2022.111085. S2CID 249328937.
- ^ 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 (15 July 2008). "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, Timothy J.; Cashman, R. (2002). "Oceanic anoxic events and plankton evolution: Biotic response to tectonic forcing during the mid-Cretaceous" (PDF). Paleoceanography and Paleoclimatology. 17 (3): 1–29. Bibcode:2002PalOc..17.1041L. doi:10.1029/2001pa000623.
- ^ Lechler, Maria; Von Strandmann, Philip A. E. Pogge; Jenkyns, Hugh C.; Prosser, Giacomo; Parente, Mariano (15 December 2015). "Lithium-isotope evidence for enhanced silicate weathering during OAE 1a (Early Aptian Selli event)". Earth and Planetary Science Letters. 432: 210–222. Bibcode:2015E&PSL.432..210L. doi:10.1016/j.epsl.2015.09.052. Retrieved 30 September 2022.
- ^ Erba, Elisabetta; Bottini, Cinzia; Weissert, Helmut J.; Keller, Christina E. (23 July 2010). "Calcareous Nannoplankton Response to Surface-Water Acidification Around Oceanic Anoxic Event 1a". Science. 329 (5990): 428–432. Bibcode:2010Sci...329..428E. doi:10.1126/science.1188886. PMID 20651148. S2CID 19498439. Retrieved 24 January 2023.
- ^ Archangelsky, Sergio. "The Ticó Flora (Patagonia) and the Aptian Extinction Event." Acta Paleobotanica 41(2), 2001, pp. 115-22.
- ^ Boukhamsin, Hani; Peyrot, Daniel; Lang, Simon; Vecoli, Marco (January 2022). "Low-latitude ?upper Barremian–lower Aptian palynoflora and paleovegetation of the Biyadh Formation (Arabian Plate, eastern margin of northern Gondwana): evidence for a possible cold snap". Cretaceous Research. 129: 104995. Bibcode:2022CrRes.12904995B. doi:10.1016/j.cretres.2021.104995. Retrieved 1 November 2024 – via Elsevier Science Direct.
- ^ Ludvigson, G.A.; Joeckel, R.M.; Murphy, L.R.; Stockli, D.F.; González, L.A.; Suarez, Celina A.; Kirkland, James I.; Al-Suwaidi, A. (September–December 2015). "The emerging terrestrial record of Aptian-Albian global change". Cretaceous Research. 56: 1–24. Bibcode:2015CrRes..56....1L. doi:10.1016/j.cretres.2014.11.008. Retrieved 1 November 2024 – via Elsevier Science Direct.
- ^ Degani-Schmidt, Isabela; Guerra-Sommer, Margot; Carvalho, Ismar de Souza (June 2023). "Stomatal numbers of Pseudofrenelopsis capillata (Cheirolepidiaceae, Coniferales) in the peri-equatorial late Aptian Crato Formation (Santana group, Araripe Basin, Brazil) and their paleoclimatic and paleoenvironmental significance". Journal of South American Earth Sciences. 126: 104331. Bibcode:2023JSAES.12604331D. doi:10.1016/j.jsames.2023.104331. Retrieved 1 November 2024 – via Elsevier Science Direct.
Literature
[edit]- 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
[edit]- 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
