Editing Oligocene (section)

== Boundaries and subdivisions ==

The lower boundary of the Oligocene (its [[Global Boundary Stratotype Section and Point]] or GSSP) is placed at the last appearance of the [[foraminiferan]] genus ''[[Hantkenina]]'' in a quarry at [[Massignano]], [[Italy]]. However, this GSSP has been criticized as excluding the uppermost part of the type Eocene Priabonian Stage and because it is slightly earlier than important climate shifts that form natural markers for the boundary, such as the global oxygen isotope shift marking the expansion of Antarctic glaciation (the Oi1 event).{{sfn|Prothero|2005|pp=472–473}}

The upper boundary of the Oligocene is defined by its GSSP at [[Carrosio]], [[Italy]], which coincides with the [[First appearance datum|first appearance]] of the foraminiferan ''[[Paragloborotalia kugleri]]'' and with the base of [[Polarity chron|magnetic polarity chronozone]] C6Cn.2n.<ref>{{cite journal |last1=Steininger |first1=Fritz F. |last2=Aubry |first2=M.P. |last3=Berggren |first3=W.A. |last4=Biolzi |first4=M. |last5=M.Borsetti |first5=A. |last6=Cartlidge |first6=Julie E. |last7=Cati |first7=F. |last8=Corfield |first8=R. |last9=Gelati |first9=R. |last10=Iaccarino |first10=S. |last11=Napoleone |first11=C. |last12=Ottner |first12=F. |last13=Rögl |first13=F. |last14=Roetzel |first14=R. |last15=Spezzaferri |first15=S. |last16=Tateo |first16=F. |last17=Villa |first17=G. |last18=Zevenboom |first18=D. |title=The Global Stratotype Section and Point (GSSP) for the base of the Neogene |journal=Episodes |date=1 March 1997 |volume=20 |issue=1 |pages=23–28 |doi=10.18814/epiiugs/1997/v20i1/005|doi-access=free }}</ref>

Oligocene [[faunal stage]]s from youngest to oldest are:<ref name="stratigraphy379"/><ref>{{cite journal|last1=Coccioni|first1=Rodolfo |last2=Montanari|first2=Alessandro |last3=Nice|first3=David|last4=Brinkhuis|first4=Henk|last5=Deino|first5=Alain|last6=Frontalini|first6=Fabrizio |last7=Liter|first7=Fabrizio|last8=Maiorano|first8=Patricia|last9=Monechi|first9=Simonetta|last10=Prods|first10=Jörg|last11=Rochette|first11=Pierre|last12=Sagnotti|first12=Leonardo|last13=Sideri|first13=Marianna|last14=Sprovieri|first14=Mario|last15=Tateo|first15=Fabio|last16=Touchard|first16=Yannick|last17=Can Simaeys|first17=Stefaan|last18=Williams|first18=Graham L.|title=The Global Stratotype Section and Point (GSSP) for the base of the Chattian stage (Paleogene System, Oligocene Series) at Monte Cagnero, Italy|journal=Episodes|date=1 March 2018|volume=41|issue=1|pages=17–32|doi=	10.18814/epiiugs/2018/v41i1/018003|doi-access=free|hdl=11573/1611823|hdl-access=free}}</ref>
{|class=wikitable
|-
| [[Chattian]] or late Oligocene
| ({{ma|Chattian| }}–&nbsp;&nbsp;{{ma|Aquitanian|[[mya (unit)|mya]]}})
|-
| [[Rupelian]] or early Oligocene
| ({{ma|Rupelian| }}–&nbsp;&nbsp;{{ma|Chattian|mya}})
|}

[[File:Oligocene Chart.jpg|thumb|Subdivisions of the Oligocene]]