Editing Oligocene (section)

===Late Oligocene warming===
The late Oligocene (26.5 to 24 mya) likely saw a warming trend in spite of low pCO2 levels, though this appears to vary by region.{{sfn|O'Brien|Huber|Thomas|Pagani|2020|pages=25302-25303}} However, Antarctica remained heavily glaciated during this warming period.<ref>{{cite journal |last1=Pekar |first1=Stephen F. |last2=DeConto |first2=Robert M. |last3=Harwood |first3=David M. |title=Resolving a late Oligocene conundrum: Deep-sea warming and Antarctic glaciation |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |date=February 2006 |volume=231 |issue=1–2 |pages=29–40 |doi=10.1016/j.palaeo.2005.07.024|bibcode=2006PPP...231...29P |url=http://doc.rero.ch/record/13512/files/PAL_E309.pdf }}</ref><ref>{{cite journal |last1=Hauptvogel |first1=D. W. |last2=Pekar |first2=S. F. |last3=Pincay |first3=V. |title=Evidence for a heavily glaciated Antarctica during the late Oligocene "warming" (27.8–24.5 Ma): Stable isotope records from ODP Site 690: LATE OLIGOCENE STABLE ISOTOPE RECORD |journal=Paleoceanography |date=April 2017 |volume=32 |issue=4 |pages=384–396 |doi=10.1002/2016PA002972|doi-access=free }}</ref> The late Oligocene warming is discernible in pollen counts from the Tibetan Plateau, which also show that the [[south Asian monsoon|South Asian Monsoon]] had already developed by the late Oligocene.<ref>{{cite journal |last1=Wu |first1=Fuli |last2=Miao |first2=Yunfa |last3=Meng |first3=Qingquan |last4=Fang |first4=Xiaomin |last5=Sun |first5=Jimin |title=Late Oligocene Tibetan Plateau Warming and Humidity: Evidence From a Sporopollen Record |journal=Geochemistry, Geophysics, Geosystems |date=January 2019 |volume=20 |issue=1 |pages=434–441 |doi=10.1029/2018GC007775|bibcode=2019GGG....20..434W |doi-access=free }}</ref> Around 25.8 Ma, the South Asian Monsoon underwent an episode of major intensification brought on by the uplift of the Tibetan Plateau.<ref>{{Cite journal |last1=Jin |first1=Chun-Sheng |last2=Xu |first2=Deke |last3=Li |first3=Mingsong |last4=Hu |first4=Pengxiang |last5=Jiang |first5=Zhaoxia |last6=Liu |first6=Jianxing |last7=Miao |first7=Yunfa |last8=Wu |first8=Fuli |last9=Liang |first9=Wentian |last10=Zhang |first10=Qiang |last11=Su |first11=Bai |last12=Liu |first12=Qingsong |last13=Zhang |first13=Ran |last14=Sun |first14=Jimin |date=11 April 2023 |title=Tectonic and orbital forcing of the South Asian monsoon in central Tibet during the late Oligocene |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |language=en |volume=120 |issue=15 |pages=e2214558120 |doi=10.1073/pnas.2214558120 |issn=0027-8424 |pmc=10104490 |pmid=37011203 |bibcode=2023PNAS..12014558J }}</ref>

A deep 400,000-year glaciated Oligocene-Miocene boundary event is recorded at [[McMurdo Sound]] and [[King George Island (South Shetland Islands)|King George Island]].<ref>{{cite journal |last1=Wilson |first1=G.S. |last2=Pekar |first2=S.F. |last3=Naish |first3=T.R. |last4=Passchier |first4=S. |last5=DeConto |first5=R. |title=Chapter 9 The Oligocene–Miocene Boundary – Antarctic Climate Response to Orbital Forcing |journal=Developments in Earth and Environmental Sciences |date=2008 |volume=8 |pages=369–400 |doi=10.1016/S1571-9197(08)00009-8|isbn=9780444528476 }}</ref>