Editing Eocene (section)

===Boundaries===
The Eocene is a dynamic epoch that represents global climatic transitions between two climatic extremes, transitioning from the hot house to the cold house. The beginning of the Eocene is marked by the [[Paleocene–Eocene Thermal Maximum]], a short period of intense warming and [[ocean acidification]] brought about by the release of carbon en masse into the atmosphere and ocean systems,<ref name=turner2017/> which led to a mass extinction of 30–50% of benthic [[foraminifera]] (single-celled species which are used as [[bioindicator]]s of the health of a marine ecosystem)—one of the largest in the Cenozoic.<ref>{{cite journal|first1=Q.|last1=Zhang|first2=H.|last2=Willems|first3=L.|last3=Ding|first4=X.|last4=Xu|year=2019|title=Response of larger benthic foraminifera to the Paleocene–Eocene thermal maximum and the position of the Paleocene/Eocene boundary in the Tethyan shallow benthic zones: Evidence from south Tibet|journal=[[Geological Society of America Bulletin]]|volume=131|issue=1–2|pages=84–98|doi=10.1130/B31813.1|bibcode=2019GSAB..131...84Z|s2cid=134560025}}</ref><ref name=kennet>{{cite book|first1=J. P.|last1=Kennet|first2=L. D.|last2=Stott|year=1995|chapter=Terminal Paleocene Mass Extinction in the Deep Sea: Association with Global Warming|title=Effects of Past Global Change on Life: Studies in Geophysics|publisher=National Academy of Sciences|chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK231944/}}</ref> This event happened around 55.8 Ma, and was one of the most significant periods of global change during the Cenozoic.<ref name=turner2017>{{cite journal |first1=S. K. |last1=Turner |first2=P. M. |last2=Hull |first3=A. |last3=Ridgwell |year=2017 |title=A probabilistic assessment of the rapidity of PETM onset |journal=[[Nature Communications]] |volume=8 |issue=353 |pages=353 |doi=10.1038/s41467-017-00292-2 |pmid=28842564 |pmc=5572461 |bibcode=2017NatCo...8..353K}}</ref><ref>{{cite journal |first1=C. |last1=Winguth |first2=E. |last2=Thomas |year=2012 |title=Global decline in ocean ventilation, oxygenation, and productivity during the Paleocene–Eocene Thermal Maximum: Implications for the benthic extinction |journal=[[Geology (journal)|Geology]] |volume=40 |issue=3 |pages=263–266 |doi=10.1130/G32529.1 |url=https://www.researchgate.net/publication/228335391 |bibcode=2012Geo....40..263W}}</ref><ref>{{cite journal |first1=G. A. |last1=Schmidt |first2=D. T. |last2=Shindell |title=Atmospheric composition, radiative forcing, and climate change as a consequence of a massive methane release from gas hydrates |journal=[[Paleoceanography and Paleoclimatology]] |volume=18 |issue=1 |year=2003 |pages=n/a |bibcode=2003PalOc..18.1004S |doi=10.1029/2002PA000757 |doi-access=free}}</ref>

The middle Eocene was characterized by the shift towards a cooler climate at the end of the [[Early Eocene Climatic Optimum]], around 47.8 Ma, which was briefly interrupted by another warming event, the [[Middle Eocene Climatic Optimum]].<ref>{{Cite journal |last1=Bijl |first1=Peter K. |last2=Houben |first2=Alexander J. P. |last3=Schouten |first3=Stefan |last4=Bohaty |first4=Steven M. |last5=Sluijs |first5=Appy |last6=Reichart |first6=Gert-Jan |last7=Sinninghe Damsté |first7=Jaap S. |last8=Brinkhuis |first8=Henk |date=2010-11-05 |title=Transient Middle Eocene Atmospheric CO 2 and Temperature Variations |url=https://www.science.org/doi/10.1126/science.1193654 |journal=Science |language=en |volume=330 |issue=6005 |pages=819–821 |doi=10.1126/science.1193654 |pmid=21051636 |bibcode=2010Sci...330..819B |hdl=1874/385803 |s2cid=206528256 |issn=0036-8075}}</ref> Lasting for about 400,000 years, the MECO was responsible for a globally uniform 4° to 6°C warming of both the surface and deep oceans, as inferred from foraminiferal stable oxygen isotope records. The resumption of a long-term gradual cooling trend resulted in a glacial maximum at the late Eocene/early Oligocene boundary. 

The end of the Eocene was also marked by the [[Eocene–Oligocene extinction event]], also known as the ''Grande Coupure''.<ref>{{Cite journal|doi=10.1144/0016-764903-091 |title=Eocene-Oligocene mammalian faunal turnover in the Hampshire Basin, UK: calibration to the global time scale and the major cooling event |year=2004 |author=Hooker, J.J. |journal=Journal of the Geological Society |volume=161 |issue=2 |pages=161–172 |last2=Collinson |first2=M.E. |last3=Sille |first3=N.P.|bibcode=2004JGSoc.161..161H |s2cid=140576090 |url=http://doc.rero.ch/record/13418/files/PAL_E228.pdf }}</ref>