lowest of the four divisions of the Middle Jurassic
Series, representing all rocks formed worldwide during the Aalenian
Age, which occurred between 175.6 million and 171.6 million years ago
during the Jurassic Period. The Aalenian Stage underlies the Bajocian Stage and overlies the Toarcian Stage of the Lower Jurassic Series.
The name for this stage is derived from the town of Aalen, located 80 km (50 miles) east of Stuttgart in the Swabian Alps
of Germany. The Aalenian Stage is divided into the Lower Aalenian and
the Upper Aalenian, each of which in Europe is subdivided into two
standard ammonite biozones:
the Opalinum and Scissum zones for the Lower Aalenian and the
Murchisonae and Concavum zones for the Upper Aalenian. In other parts
of the world there is an almost complete absence of the ammonite group
upon which the standard European zonation is based, so that several
different zonation sequences have been recognized in different parts of
Asia and North America. Some of these zones are approximately coeval
and equivalent to the standard European zonations.Carol Marie Tang
To cite this page:
- MLA Style: "Aalenian Stage." Encyclopædia Britannica. Ultimate Reference Suite. Chicago: Encyclopædia Britannica, 2017.
- APA Style: Aalenian Stage. (2017). Encyclopædia Britannica. Ultimate Reference Suite. Chicago: Encyclopædia Britannica.
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