The Aptian was named after the small city of
Apt in the
Provence region of
France, which is also known for its crystallized fruits. The original
type locality is in the vicinity of Apt. The Aptian was introduced in scientific literature by French palaeontologist
Alcide d'Orbigny in 1840. The base of the Aptian Stage is laid at
magnetic anomaly M0r. A global reference profile for the base (a
GSSP) had in 2009 not yet been appointed. The top of the Aptian (the base of the Albian) is at the first appearance of
coccolithophore species
Praediscosphaera columnata in the stratigraphic record.
Subdivision In the
Tethys domain, the Aptian contains eight
ammonite biozones: • zone of
Hypacanthoplites jacobi • zone of
Nolaniceras nolani • zone of
Parahoplites melchioris • zone of
Epicheloniceras subnodosocostatum • zone of
Dufrenoyia furcata • zone of
Deshayesites deshayesi • zone of
Deshayesites weissi • zone of
Deshayesites oglanlensis Sometimes the Aptian is subdivided in three substages or subages: Bedoulian (early or lower), Gargasian (middle) and Clansayesian (late or upper). In modern formal chronostratigraphy the Aptian is divided into Lower and Upper sub-stages. The Lower Aptian is almost equivalent to the Bedoulian (without the Dufrenoyia furcata Zone), and it includes the 3 "Deshayesites" ammonite zones. The Upper Aptian spans the Gargasian and Clansayesian intervals, it includes the
furcata to
jacobi Tethys ammonite zones (Moullade et al. 2011 ). ==Lithostratigraphic units==