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 41.2 and 37.8 Ma. It is preceded by the Lutetian and is followed by the Priabonian age.

The Bartonian stage was introduced by Swiss stratigrapher Karl Mayer-Eymar in 1857. The name derives from the coastal village Barton-on-Sea (part of New Milton) 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 nannoplankton species Reticulofenestra reticulata. In 2009, an official reference profile (GSSP) for the base of the Bartonian had not yet been established.

The top of the Bartonian stage (the base of the Priabonian) is at the first appearance of calcareous nannoplankton species Chiasmolithus oamaruensis (which forms the base of nannoplankton biozone NP18).

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