Middle Jurassic

The Aalenian () 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.

second series and epoch of the Jurassic system and period

In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.9 ± 0.8 Ma to around 168.2 ± 1.2 Ma (million years ago). The Bajocian Age succeeds the Aalenian Age and precedes the Bathonian Age.

In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.2 ±1.2 Ma to around 165.3 ±1.1 Ma (million years ago). The Bathonian Age succeeds the Bajocian Age and precedes the Callovian Age.

In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 165.3 ± 1.1 Ma (million years ago) and 161.5 ± 1.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the Oxfordian.