|system||series||step||≈ age ( mya )|
The Eocene is in the Earth's history , a stratigraphic series (= time interval) within the Paleogene . The Eocene began about 56 million years ago and ended about 33.9 million years ago and is the second series of the Paleogene (see Geological Timescale ). The Eocene was followed by the Oligocene and preceded by the Paleocene .
Naming and history
Definition and GSSP
The basis of the Eocene (and the Ypresian ) is a pronounced change in the carbon isotope ratio ("Carbon Isotope Excursion"). The upper limit (and thus the lower limit of the Oligocene and the Rupelian ) is defined by the extinction of the foraminifera genus Hantkenina . The GSSP (= global calibration point) of the Eocene (and the Ypresian stage) is the Dababiya profile near Luxor ( Egypt ).
The Eocene is divided into three sub-series and four chronostratigraphic stages:
- Series: Eocene (56–33.9 mya)
Regionally and in a historical context, a whole series of other stage names are used, which for various reasons have either only been used regionally or have been abandoned.
Climate and geography
At the transition from the Paleocene to the Eocene, a worldwide temperature increase of at least 6 ° C occurred within the framework of the Paleocene / Eocene temperature maximum , which was caused by a strong increase in the atmospheric carbon dioxide concentration, probably with the participation of methane or methane hydrate , and in addition to the expansion of the tropical climatic zone up to higher latitudes caused widespread migration of flora and fauna . The primary factor for the abruptly occurring after geological scale heating process often volcanic activity is considered the North Atlantic igneous bulk province (English North Atlantic Igneous Province ), which was created during the formation and expansion of the North Atlantic, or the separation of Greenland and Europe.
Up to the Middle Eocene, the climate was subtropical to tropical, so that no significant ice cover occurred in the Arctic or in the southern polar regions . After the Azolla event (50/49 mya), with a simultaneous reduction in the atmospheric CO 2 level, a gradual and at first almost creeping cooling began. Nevertheless, there was a pronounced warm climate over large parts of the Eocene . With the increase in the meridional temperature gradient (the temperature difference between the equator and the polar regions), significant climatic changes were initially limited to the higher latitudes. A clear but temporary cooling phase has been documented for the Antarctic 41 million years ago, and findings of dropstones of Greenland origin in deep-sea sediments of the North Atlantic point to the temporary existence of continental ice 38 to 30 million years ago on Greenland. The slow change from warm to cold age conditions was interrupted by the optimal climate of the Middle Eocene (40 mya) for about 400,000 years, although the exact causes of this warming phase are still largely unclear.
A sharp climatic break occurred at the Eocene-Oligocene boundary between 33.9 and 33.7 million years ago. A major factor in this change was the creation of the Drake Strait , which is now 480 nautical miles wide and connects the Atlantic with the Pacific Ocean . Until the later Eocene, the former Gondwanian continental blocks Antarctica and South America were still connected by a land bridge before the Drake Strait gradually began to open. As a result of the opening, the Antarctic Circumpolar Current was created in the Southern Ocean , which from now on circled Antarctica in a clockwise direction and cut off the continent from the supply of warmer sea water. In the course of the Grande Coupure ("Great Gorge") there was a major extinction of species , including in Europe , which was linked to a marked drop in temperature on land and in the oceans. What is noticeable in this context is the steep drop in the CO 2 concentration in the earth's atmosphere . While this reached values of 700 to 1,000 ppm towards the end of the Eocene, it decreased by around 40 percent at the beginning of the Oligocene. The glaciation of the southern polar mainland around 34 million years ago at a CO 2 threshold of around 600 ppm, partly controlled by the changing parameters of the Earth's orbit , marks the beginning of the Cenozoic Ice Age .
The most famous sites from the Eocene in Germany include the Messel pit near Darmstadt (Hesse), the Geiseltal near Halle (Saale) (Saxony-Anhalt) and the Eckfelder Maar near Manderscheid (Rhineland-Palatinate). Fossil remains of insects, amphibians, reptiles, birds and mammals were found there. To this exotic wildlife included, among others giant ants , giant snakes , crocodiles , of up to two meters high giant flightless bird Diatryma , fox large ancestral horses , tapirs , anteaters , pangolins , creodonta and bipede leptictida .
- Isabella Premoli Silva and David G. Jenkins: Decision on the Eocene-Oligocene boundary stratotype. Episodes, 16 (3): 379-382, 1993, .
- C. Dupuis, M. Aubry, E. Steurbaut, WA Berggren, K. Ouda, R. Magioncalda, BS Cramer, DV Kent, RP Speijer and C. Heilmann-Clausen: The Dababiya Quarry Section: Lithostratigraphy, clay mineralogy, geochemistry and paleontology. Micropaleontology, 49 (1): 41-59, New York 2003, .
- Étienne Steurbaut : Ypresian . Geologica Belgica, 9 (1-2): 73-93, Brussels 2006, .
- German Stratigraphic Commission (Ed.): Stratigraphische Tisch von Deutschland 2002 . Potsdam 2002, ISBN 3-00-010197-7 (PDF; 6.57 MB)
- Commission for the paleontological and stratigraphic research of Austria of the Austrian Academy of Sciences (Ed.): The Stratigraphic Table of Austria (sedimentary layer sequences). Vienna 2004 (PDF; 376 kB)
- Eocene Microfossils: 25+ Images of Foraminifera
- World Without Ice , article in National Geographic Magazine, October 2011
- Big discovery for biogenic magnetite , Peter C. Lippert, November 13, 2008
- Richard E. Zeebe, James C. Zachos, Gerald R. Dickens: Carbon dioxide forcing alone insufficient to explain Palaeocene-Eocene Thermal Maximum warming . (PDF) In: Nature Geoscience . 2, No. 8, July 2009, pp. 576-580. doi : 10.1038 / ngeo578 .
- Francesca A. McInerney, Scott L. Wing: The Paleocene-Eocene Thermal Maximum: A Perturbation of Carbon Cycle, Climate, and Biosphere with Implications for the Future . (PDF) In: Annual Review of Earth and Planetary Sciences . 39, May 2011, pp. 489-516. doi : 10.1146 / annurev-earth-040610-133431 .
- Camilla M. Wilkinson, Morgan Ganerød, Bart WH Hendriks, Elizabeth A. Eide: Compilation and appraisal of geochronological data from the North Atlantic Igneous Province (NAIP) . In: Geological Society, London, Special Publications (Lyell Collection) . 447, November 2016, pp. 69-103. doi : 10.1144 / SP447.10 .
- Linda C. Ivany, Kyger C. Lohmann, Franciszek Hasiuk, Daniel B. Blake, Alexander Glass, Richard B. Aronson, Ryan M. Moody: Eocene climate record of a high southern latitude continental shelf: Seymour Island, Antarctica . (PDF) In: The Geological Society of America (GSA) Bulletin . 120, No. 5/6, pp. 659-678. doi : 10.1130 / B26269.1 .
- James S. Eldrett, Ian C. Harding, Paul A. Wilson, Emily Butler, Andrew P. Roberts: Continental ice in Greenland during the Eocene and Oligocene . (PDF) In: Nature . 446, March 2007, pp. 176-179. doi : 10.1038 / nature05591 .
- Michael J. Henehan, Kirsty M. Edgar, Gavin L. Foster, Donald E. Penman, Pincelli M. Hull, Rosanna Greenop, Eleni Anagnostou, Paul N. Pearson: Revisiting the Middle Eocene Climatic Optimum “Carbon Cycle Conundrum” With New Estimates of Atmospheric pCO 2 From Boron Isotopes . (PDF) In: Paleoceanography and Paleoclimatology . 15, No. 6, June 2020. doi : 10.1029 / 2019PA003713 .
- Mark Pagani, Matthew Huber, Zhonghui Liu, Steven M. Bohaty, Jorijntje Henderiks, Willem Sijp, Srinath Krishnan, Robert M. DeConton: The Role of Carbon Dioxide During the Onset of Antarctic Glaciation . (PDF) In: Science . 334, No. 6060, December 2011, pp. 1261-1264. doi : 10.1126 / science.1203909 .
- Simone Galeotti, Robert DeConto, Timothy Naish, Paolo Stocchi, Fabio Florindo, Mark Pagani, Peter Barrett, Steven M. Bohaty, Luca Lanci, David Pollard, Sonia Sandroni, Franco M. Talarico, James C. Zachos: Antarctic Ice Sheet variability across the Eocene-Oligocene boundary climate transition . (PDF) In: Science . 352, No. 6281, April 2016, pp. 76-80. doi : 10.1126 / science.aab0669 .