BATHONIAN STAGE

the seventh of eleven divisions (in ascending order) of the Jurassic System, representing all those rocks deposited worldwide during the Bathonian Age (176 to 169 million years ago). No global stratotype section and point (GSSP) for the base of the Bathonian has been approved by the International Commission on Stratigraphy. The stage's name is derived from the city of Bath in the county of Avon, England. The rock units that make up this stage in England include about 130 m (426 feet) of strata from the upper part of the limestone known as the Great Oolite, together with the lower part of the overlying limestone known as the Cornbrash Beds. Tulites subcontractus is a typical fossil ammonite cephalopod found in the Bathonian section of the oolite strata. The biozone of the ammonite Clydoniceras discus in the Cornbrash Beds marks the top of the Bathonian in both England and Europe. In eastern Siberia, the Bathonian is marked by the biozone of the ammonite Arctocephalites elegans. Many endemic ammonites characterize the Bathonian Stage in the circum-Pacific belt. The Bathonian is overlain by the Callovian Stage and is underlain by the Bajocian Stage.