Aalenian

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System/
Period
Series/
Epoch
Stage/
Age
Age (Ma)
Cretaceous Lower/
Early
Berriasian younger
Jurassic Upper/
Late
Tithonian 145.0–152.1
Kimmeridgian 152.1–157.3
Oxfordian 157.3–163.5
Mid/
Middle
Callovian 163.5–166.1
Bathonian 166.1–168.3
Bajocian 168.3–170.3
Aalenian 170.3–174.1
Lower/
Early
Toarcian 174.1–182.7
Pliensbachian 182.7–190.8
Sinemurian 190.8–199.3
Hettangian 199.3–201.3
Triassic Upper/
Late
Rhaetian older
Subdivision of the Jurassic system
according to the IUGS, as of July 2012.

The Aalenian /ɑːˈlniən/ is a subdivision of the Middle Jurassic epoch/series of the geologic timescale that extends from about 175.6 Ma to about 171.6 Ma (million years ago). It was preceded by the Toarcian and succeeded by the Bajocian.[1]

Stratigraphic definitions[edit]

The Aalenian takes its name from the town of Aalen, some 70 km east of Stuttgart in Germany. The town lies at the southwestern end of the Frankischer 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. A global reference profile is located 500 meters north from the village of Fuentelsaz in the Spanish province of Guadalajara.[2] 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:

Palaeontology[edit]

†Ammonitids[edit]

Ammonitids of the Aalenian
Taxa Presence Location Description Images
Confirmed.[3] The only known species in this Alaskan genus. Abbasites is believed to be ancestral to the ammonite family Otoitidae.
Life restorations of two different ammonite genera.
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
  • Brasilia
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3] Synonymous with a modern plant genus.
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]

†Belemnites[edit]

Belemnites of the Aalenian
Taxa Presence Location Description Images
Confirmed.[3]
Belemnites.
Confirmed.[3]
Confirmed.[3]
Confirmed.[3] This Eurasian species was the largest known Belemnite and could grow to lengths of up to 10 feet.
Confirmed.[3]
Confirmed.[3]
Confirmed.[3]

†Thalattosuchians[edit]

Thalattosuchia of the Aalenian
Taxa Presence Location Description Images
Switzerland; Morocco; England; France; Germany

References[edit]

Notes[edit]

  1. ^ See Gradstein et al. (2004) for a detailed version of the geologic timescale
  2. ^ Cresta et al. (2001)
  3. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am Sepkoski (2002)

Literature[edit]

  • 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. (French)
  • Sepkoski, J.; 2002: A compendium of fossil marine animal genera (entry on cephalopoda), Bulletin of American Paleontology 364, p 560.

External links[edit]

Jurassic Period
Lower/Early Jurassic Middle Jurassic Upper/Late Jurassic
Hettangian | Sinemurian
Pliensbachian | Toarcian
Aalenian | Bajocian
Bathonian | Callovian
Oxfordian | Kimmeridgian
Tithonian