Bartonian
The Bartonian is, in the ICS's geologic time scale, a stage or age in the middle Eocene epoch or series. The Bartonian age spans the time between . It is preceded by the Lutetian and is followed by the Priabonian age.Stratigraphic definition
The Bartonian stage was introduced by Swiss stratigrapher Karl Mayer-Eymar in 1857. The name derives from the coastal village Barton-on-Sea in southern England. The Barton Group, a lithostratigraphic unit from the south English Hampshire Basin, is of Bartonian age. The distinction between group and stage was made in the second part of the 20th century, when stratigraphers saw the need to distinguish between litho- and chronostratigraphy.
The base of the Bartonian is at the first appearance of the calcareous nanoplankton species Reticulofenestra reticulata. In 2009, an official reference profile for the base of the Bartonian had not yet been established.
The top of the Bartonian stage is at the first appearance of calcareous nanoplankton species Chiasmolithus oamaruensis.
The Bartonian stage overlaps part of the upper Robiacian European Land Mammal Mega Zone, the upper Uintan and Duchesnean North American Land Mammal Ages, part of the Divisaderan South American Land Mammal Age and is coeval with the Sharamururian Asian Land Mammal Age.
The Auversian regional stage of France is coeval with the Bartonian and is therefore no longer used.Footnotes
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