Bathonian
The Bathonian (also shortened to Bathonian ) is in the geologic timescale, the third stage of the Middle Jurassic series in the Jura. It started before geochronological about 168.3 million years ago and ended about 166.1 million years and therefore lasted about 3 million years. The Bathonian precedes the Bajocian; it is followed by the Callovian.
Naming and history
The type locality of the stage is located near the city of Bath on the River Avon (Somerset, England). The name is a Latinized version of the Bathonian city name. The name was first introduced in 1843 by Jean Baptiste Julien d' Omalius d' Halloy and adopted by Alcide Dessalines d' Orbigny, 1852. He first defined the approximate amount of the step.
Definition and GSSP
The lower boundary of the stage is defined by the Ersteinsetzen the ammonite species Parkinsonia ( Gonolkites ) convergent. The stage ends with the onset of the ammonite genus Kepplerites. A GSSP ( = type locality and type profile ) has not yet been determined.
Subdivision of the Bathonian
The Bathonian is divided in the Tethyan region in the following ammonite biozones:
- Clydoniceras discus
- Hecticoceras retrocostatum
- Cadomites bremeri
- Morrisiceras morrisi
- Tulites subcontractus
- Procerites progracilis
- Procerites aurigerus
- Zigzagiceras zigzag