The base of the Chattian is at the extinction of the foramgenusChiloguembelina (which is also the base of forambiozone P21b). An official GSSP for the Chattian Stage was ratified in October of 2016.
The top of the Chattian Stage (which is the base of the Aquitanian Stage, Miocene Series and NeogeneSystem) is at the first appearance of foram species Paragloborotalia kugleri, the extinction of calcareous nanoplankton species Reticulofenestra bisecta (which forms the base of nanoplankton biozone NN1), and the base of magnetic C6Cn.2n.
The Chattian is coeval with regionally used stages or zones such as the upper Avernian European mammal zone (it spans the Mammal Paleogene zones 30 through 26 and part of 25[8]); the upper Geringian and lower Arikareeanmammal zones of North America; most of the Deseadanmammal zone of South America; the upper Hsandgolian and whole Tabenbulakianmammal zone of Asia; the upper Kiscellian and lower Egerian Paratethys stages of Central and eastern Europe; the upper Janjukian and lower Longfordian Australian regional stages; the Otaian, Waitakian, and Duntroonian stages of the New Zealand geologic time scale; and part of the Zemorrian Californian stage and Chickasawhayan regional stage of the eastern US.
Fuchs, T.; 1894: Tertiaerfossilien aus den kohlenführenden Miocaenablagerungen der Umgebung von Krapina und Radaboj und über die Stellung der sogenannten "Aquitanischen Stufe", Königlich- Ungarische Geologische Anstalt, Mittheilungen und Jahrbuch 10, p. 163-175. (in German)
Lanphere, M.A. & Baadsgaard, H.; 2001: Precise K–Ar, 40Ar/39Ar, Rb–Sr and U/Pb mineral ages from the 27.5 Ma Fish Canyon Tuff reference standard, Chemical Geology 175(3–4), pp 653–671.
Mason, B.G.; Pyle, D.M. & Oppenheimer, C.; 2004: The size and frequency of the largest explosive eruptions on Earth, Bulletin of Volcanology 66(8), pp 735–748.