Eocene

Eocene
56.0 – 33.9 Ma
Map of the Earth in the early Eocene (50 Ma)
Chronology
Etymology
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitEpoch
Stratigraphic unitSeries
Time span formalityFormal
Lower boundary definitionStrong negative anomaly in δ13C values at the PETM[3]
Lower boundary GSSPDababiya section, Luxor, Egypt[3]
25°30′00″N 32°31′52″E / 25.5000°N 32.5311°E / 25.5000; 32.5311
Lower GSSP ratified2003[3]
Upper boundary definitionLAD of Planktonic Foraminifers Hantkenina and Cribrohantkenina
Upper boundary GSSPMassignano quarry section, Massignano, Ancona, Italy
43°31′58″N 13°36′04″E / 43.5328°N 13.6011°E / 43.5328; 13.6011
Upper GSSP ratified1992[4]

The Eocene (IPA: /ˈəsn, ˈ-/ EE-ə-seen, EE-oh-[5][6]) is a geological epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name Eocene comes from the Ancient Greek Ἠώς (Ēṓs, "Dawn") and καινός (kainós, "new") and refers to the "dawn" of modern ('new') fauna that appeared during the epoch.[7][8]

The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope 13C in the atmosphere was exceptionally low in comparison with the more common isotope 12C. The average temperature of Earth at the beginning of the Eocene was about 27 degrees Celsius.[9] The end is set at a major extinction event called the Grande Coupure (the "Great Break" in continuity) or the Eocene–Oligocene extinction event, which may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay. As with other geologic periods, the strata that define the start and end of the epoch are well identified,[10] though their exact dates are slightly uncertain.

  1. ^ Zachos, J. C.; Kump, L. R. (2005). "Carbon cycle feedbacks and the initiation of Antarctic glaciation in the earliest Oligocene". Global and Planetary Change. 47 (1): 51–66. Bibcode:2005GPC....47...51Z. doi:10.1016/j.gloplacha.2005.01.001.
  2. ^ "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy.
  3. ^ a b c Aubry, Marie-Pierre; Ouda, Khaled; Dupuis, Christian; William A. Berggren; John A. Van Couvering; Working Group on the Paleocene/Eocene Boundary (2007). "The Global Standard Stratotype-section and Point (GSSP) for the base of the Eocene Series in the Dababiya section (Egypt)" (PDF). Episodes. 30 (4): 271–286. doi:10.18814/epiiugs/2007/v30i4/003.
  4. ^ Silva, Isabella; Jenkins, D. (September 1993). "Decision on the Eocene-Oligocene boundary stratotype" (PDF). Episodes. 16 (3): 379–382. doi:10.18814/epiiugs/1993/v16i3/002. Retrieved 13 December 2020.
  5. ^ Jones, Daniel (2003) [1917], Peter Roach; James Hartmann; Jane Setter (eds.), English Pronouncing Dictionary, Cambridge: Cambridge University Press, ISBN 3-12-539683-2
  6. ^ "Eocene". Merriam-Webster.com Dictionary. Merriam-Webster.
  7. ^ See:
  8. ^ "Eocene". Online Etymology Dictionary.
  9. ^ Burke, K. D.; Williams, J. W.; Chandler, M. A.; Haywood, A. M.; Lunt, D. J.; Otto-Bliesner, B. L. (2018). "Pliocene and Eocene provide best analogs for near-future climates". Proceedings of the National Academy of Sciences. 115 (52): 13288–13293. Bibcode:2018PNAS..11513288B. doi:10.1073/pnas.1809600115. PMID 30530685.
  10. ^ The extinction of the Hantkeninidae, a planktonic family of foraminifera became generally accepted as marking the Eocene-Oligocene boundary; in 1998 Massignano in Umbria, central Italy, was designated the Global Boundary Stratotype Section and Point (GSSP).