The Callovian Stage was first described by French palaeontologist Alcide d'Orbigny in 1852. Its name derives from the latinized name for Kellaways Bridge, a small hamlet 3 km north-east of Chippenham, Wiltshire, England.
The base of the Callovian is defined as the place in the stratigraphic column where the ammonitegenusKepplerites first appears, which is the base of the biozone of Macrocephalites herveyi. 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.
Subdivision
Matmor Formation (Callovian, Peltoceras athleta Zone) in Makhtesh Gadol, Israel.
The Callovian is often subdivided into three substages (or subages): Lower/Early, Middle and Upper/Late Callovian. In the Tethys domain, the Callovian encompasses six ammonite biozones:
During the Callovian, Europe was an archipelago of a dozen or so large islands. Between them were extensive areas of continental shelf. 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. Around the former island coasts are frequently, land-derived sediments. These are to be found, for example, in western Scotland.[5]
The Louann Salt and the southern Campeche Salt of the Gulf of Mexico are thought to have formed by an embayment of the Pacific Ocean across modern-day Mexico.[6]
Howe, John Allen (1911). "Callovian" . In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol. 5 (11th ed.). Cambridge University Press. pp. 58–59. This contains a detailed description of the British and European strata as understood at the time.
