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Aalenian

From Wikipedia, the free encyclopedia
Aalenian
174.7 ± 0.8 – 170.9 ± 0.8 Ma
The Aalenian GSSP in Spain
Chronology
Etymology
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitAge
Stratigraphic unitStage
Time span formalityFormal
Lower boundary definitionFAD of Ammonites Leioceras opalinum and Leioceras lineatum
Lower boundary GSSPFuentelsaz, Spain
41°10′15″N 1°50′00″W / 41.1708°N 1.8333°W / 41.1708; -1.8333
Lower GSSP ratified2000[2]
Upper boundary definitionFAD of the Ammonites Hyperlioceras mundum, Hyperlioceras furcatum, Braunsina aspera, and Braunsina elegantula
Upper boundary GSSPCabo Mondego, Portugal
40°11′57″N 8°54′15″W / 40.1992°N 8.9042°W / 40.1992; -8.9042
Upper GSSP ratified1996[3]

The Aalenian ( /ɑːˈlniən/) is a subdivision of the Middle Jurassic Epoch/Series of the geologic timescale that extends from about 174.7 ±0.8 Ma to about 170.9 ±0.8 Ma (million years ago). It was preceded by the Toarcian and succeeded by the Bajocian.[4]

Stratigraphic definitions

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The Aalenian takes its name from the town of Aalen, some 70 km east of Stuttgart in Germany. The town lies at the northeastern end of the Swabian Jura. The name Aalenian was introduced in scientific literature by Swiss geologist Karl Mayer-Eymar in 1864.

The base of the Aalenian is defined as the place in the stratigraphic column where the ammonite genus Leioceras first appears. The global reference profile (GSSP) is located 500 meters north of the village of Fuentelsaz in the Spanish province of Guadalajara.[5] The top of the Aalenian (the base of the Bajocian) is at the first appearance of ammonite genus Hyperlioceras.

In the Tethys domain, the Aalenian contains four ammonite biozones:

References

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Notes

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  1. ^ "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy.
  2. ^ Cresta, S.; Goy, A.; Arias, C.; Barrón, E.; Bernad, J.; Canales, M.; García-Joral, F.; García-Romero, E; Gialanella, P.; Gómez, J.; González, J.; Herrero, C.; Martínez2, G.; Osete, M.; Perilli, N.; Villalaín, J. (September 2001). "The Global Boundary Stratotype Section and Point (GSSP) of the Toarcian-Aalenian Boundary (Lower-Middle Jurassic)" (PDF). Episodes. 24 (3): 166–175. doi:10.18814/epiiugs/2001/v24i3/003. Retrieved 13 December 2020.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  3. ^ Pavia, G.; Enay, R. (March 1997). "Definition of the Aalenian-Bajocian Stage boundary". Episodes. 20 (1): 16–22. doi:10.18814/epiiugs/1997/v20i1/004. Retrieved 23 December 2020.
  4. ^ See Gradstein et al. (2004) for a detailed version of the geologic timescale
  5. ^ Cresta et al. (2001)

Literature

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  • Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.
  • Cresta, S.; Goy, A.; Ureta, S.; Arias, C.; Barrón, E.; Bernad, J.; Canales, M.L.; García-Joral, F.; García-Romero, E.; Gialanella, P.R.; Gómez, J.J.; González, J.A.; Herrero, C.; Martínez, G.; Osete, M.L.; Perilli, N. & Villalaín, J.J.; 2001: The Global Boundary Stratotype Section and Point (GSSP) of the Toarcian-Aalenian Boundary (Lower-Middle Jurassic), Episodes 24(3): pp 166–175.
  • Mayer-Eymar, K.; 1864: Tableau synchronistique des terrains jurassiques. 1 Tabelle, Zürich. (in French)
  • Sepkoski, J.; 2002: A compendium of fossil marine animal genera (entry on cephalopoda), Bulletins of American Paleontology 364, p 560.
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