Callovian

[2] It is the last stage of the Middle Jurassic, following the Bathonian and preceding the Oxfordian.

Its name derives from the latinized name for Kellaways Bridge, a small hamlet 3 km north-east of Chippenham, Wiltshire, England.

A global reference profile (a GSSP) for the base had in 2009 not yet been assigned.

The top of the Callovian (the base of the Oxfordian) is at the first appearance of ammonite species Brightia thuouxensis.

Consequently, there are shallow marine Callovian deposits in Russia and from Belarus, through Poland and Germany, into France and eastern Spain and much of England.

Matmor Formation (Callovian, Peltoceras athleta Zone) in Makhtesh Gadol, Israel.
Callovian rocks of the Osgodby Formation [ 4 ] at Cayton Bay in North Yorkshire, England