The Aptian was named after the small city ofApt in theProvence region ofFrance, which is also known for its crystallized fruits. The originaltype locality is in the vicinity of Apt. The Aptian was introduced in scientific literature by French palaeontologistAlcide d'Orbigny in 1840.
The base of the Aptian Stage is laid atmagnetic anomaly M0r. A global reference profile for the base (aGSSP) had in 2009 not yet been appointed. The top of the Aptian (the base of the Albian) is at the first appearance ofcoccolithophore speciesPraediscosphaera columnata in the stratigraphic record.[citation needed]
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 thefurcata tojacobi Tethys ammonite zones (Moullade et al. 2011[11]).
A cold episode occurred at the start of the Aptian, as evidenced by the migration of thedinoflagellatesCepadinium variabilis andPseudoceratium nohrhansenii into lower latitudes.[12] A decline in globalpCO2 occurred from about 1,000 ppm to 800 ppm from the start of the Aptian to the C10 positive carbon isotope excursion.[13] During the late Aptian,pCO2 was between 515 ± 79 and 1029.8 ± 158 ppm as evidenced by the stomatal density ofPseudofrenelopsis capillata.[14]
^Li, Yong-Xiang; Bralower, Timothy J.; Montañez, Isabel P.; Osleger, David A.; Arthur, Michael A.; Bice, David M.; Herbert, Timothy D.; Erba, Elisabetta; Premoli Silva, Isabella (15 July 2008). "Toward an orbital chronology for the early Aptian Oceanic Anoxic Event (OAE1a, ~ 120 Ma)".Earth and Planetary Science Letters.271 (1–4):88–100.Bibcode:2008E&PSL.271...88L.doi:10.1016/j.epsl.2008.03.055.
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