Kellwasser event

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The Kellwasser event was one of five major mass extinctions ("Big Five") during the Phanerozoic . It occurred about 372 million years ago in the Upper Devonian on the Frasnian - Famennian boundary. Probably 50 to 75 percent of the species died out, especially the fauna groups of shallow tropical seas such as fish, corals , trilobites and a number of " reef builders ". 13 million years later, the similarly fatal Hangenberg event on the threshold of the Carboniferous (Famennium- Tournaisium transition) led to another mass extinction.

Effects and Suspected Causes

The reasons for the destabilization of the biosphere occurring in the Upper Devonian are known only in rough outline. What is certain is that the chemical composition of the oceans has changed drastically several times. Some studies therefore postulate the occurrence of an oceanic anoxic event as a result of these processes . The biodiversity of the phytoplankton decreased so much that the original biodiversity was only reached again in the Jura (phytoplankton blackout) .

As external drivers for the biological crisis, science suspects, among other things, an intense mega-volcanism , a significantly increased effect of the Milanković cycles due to the falling carbon dioxide concentration , a sudden overturning of the entire climate system or - as discussed in a study published in 2020 - the effects of a near-earth supernova about 60 light years away. Possibly the extinction waves and climatic changes in the Upper Devonian also caused an accumulation of impact disasters such as the Australian Woodleigh impact (≈ 364 mya ), the Alamo impact in today's Nevada (≈ 367 mya) or the Swedish Siljan impact structure (≈ 380– 376 mya) directly involved. There is agreement that in the time range of the two mass extinctions, strong fluctuations in sea level occurred several times, which suggest an extremely short-term cycle of different cold and warm periods. The observation that the core phases of the Kellwasser and Hangenberg crises only covered a period of 50,000 to 100,000 years fits into this scheme.

The Kellwasser event was after the ecological crisis in the Ordovician (444 mya), the second of the five major extinctions ( "Big Five") during the last 541 million years. This was followed by mass extinctions at the Permian-Triassic border (252 mya), at the transition from the Triassic to the Jurassic (201 mya) and finally, at the end of the Mesozoic , the environmental catastrophe at the Cretaceous-Paleogene border (66 mya).

Origin of name

The mass extinction is named after the Kellwasserkalk in the Kellwassertal , a side valley of the Upper Harz Oker Valley . It was there that around 1850 the geologist and botanist Friedrich Adolph Roemer discovered the geological outcrop, which led to an important discovery in paleontological research. There are two Kellwasser horizons (litho units) that are isochronous and globally detectable. The terms Kellwasser Event or Kellwasser Mass Extinction are often used in the English-language specialist literature in addition to the term Frasnian Famennian Extinction .

protection

The type locality is protected as a geotope and is maintained by the German Society for Geosciences , the State Office for Mining, Energy and Geology , the Hanover Geocenter and the Senckenberg Institute as well as the Harz Regional Association . The profile extends from the higher frasnium to the Kulm-Kieselschiefer of the Lower Carboniferous .

literature

  • George R. McGhee Jr: When the Invasion of Land Failed. The Legacy of the Devonian Extinctions. Columbia University Press, New York 2013, ISBN 978-0-231-16057-5
  • RT Becker, WT Kirchgasser: Devonian Events and Correlations. (= Geological Society special publication, Geological Society of London . 278). Geological Society of London, 2007, ISBN 978-1-86239-222-9 , p. 122.
  • Jeff Over, Jared Morrow, P. Wignall: Understanding Late Devonian and Permian-Triassic Biotic and Climatic Events. (= Developments in Palaeontology and Stratigraphy. 20). Elsevier, 2005, ISBN 0-08-045784-3 , p. 192.

Web links

Individual evidence

  1. ↑ David PG Bond, Stephen E. Grasby: On the causes of mass extinctions . In: Palaeogeography, Palaeoclimatology, Palaeoecology . tape 478 , no. 15 , July 2017, p. 3–29 , doi : 10.1016 / j.palaeo.2016.11.005 (English). (accessed on August 17, 2017)
  2. ↑ Leszek Marynowski, Michał Zatoń, Michał Rakociński, Paweł Filipiak, Slawomir Kurkiewicz, Tim J. Pearce: Deciphering the upper Famennian Hangenberg Black Shale depositional environments based on multi-proxy record . In: Palaeogeography, Palaeoclimatology, Palaeoecology . tape 346–347 , August 2012, pp. 66–86 , doi : 10.1016 / j.palaeo.2012.05.020 (English, researchgate.net [PDF]).
  3. ^ Grzegorz Racki: Understanding Late Devonian And Permian-Triassic Biotic and Climatic Events - Towards an Integrated Approach. Chapter 2: Toward understanding Late Devonian global events: few answers, many questions . In: Developments in Palaeontology and Stratigraphy . tape 20 , 2005, pp. 5-36 , doi : 10.1016 / S0920-5446 (05) 80002-0 (English, researchgate.net [PDF]).
  4. ↑ Marina Kloppischː Organic-geochemical comparison of selected rocks of the Frasnium / Famennium border (Oberdevon) in the Bergisches Land and the Eifel (PDF). Reports from Forschungszentrum Jülich, Institute for Chemistry and Dynamics of the Geosphere, 2002.
  5. ↑ Grzegorz Racki et al. Mercury enrichments and the Frasnian-Famennian biotic crisis: A volcanic trigger proved? Geology, April 26, 2018; doi: 10.1130 / G40233.1
  6. ^ David De Vleeschouwer, Micha Rakociński, Grzegorz Racki, David PG Bond, Katarzyna Sobień, Philippe Claeys: The astronomical rhythm of Late-Devonian climate change (Kowala section, Holy Cross Mountains, Poland) . In: Earth and Planetary Science Letters . tape 365 , March 2013, p. 25–37 , doi : 10.1016 / j.epsl.2013.01.016 (English, vub.ac.be [PDF]). (accessed on November 18, 2015)
  7. ↑ Sarah K. Carmichael, Johnny A. Waters, Cameron J. Batchelor, Drew M. Coleman, Thomas J. Suttner, Erika Kido, L .M. Moore, Leona Chadimová: Climate instability and tipping points in the Late Devonian: Detection of the Hangenberg Event in an open oceanic island arc in the Central Asian Orogenic Belt . In: Gondwana Research . tape 32 , April 2016, p. 213–231 , doi : 10.1016 / j.gr.2015.02.009 (English, uncg.edu [PDF]). (accessed on January 27, 2017)
  8. ↑ Brian D. Fields, Adrian L. Melott, John Ellis, Adrienne F. Ertel, Brian J. Fry, Bruce S. Lieberman, Zhenghai Liu, Jesse A. Miller, Brian C. Thomas: Supernova triggers for end-Devonian extinctions . In: PNAS . August 2020. doi : 10.1073 / pnas.2013774117 .
  9. Jump up ↑ Andrew J. Retzler, Leif Tapanila, Julia R. Steenberg, Carrie J. Johnson, Reed A. Myers: Post-impact depositional environments as a proxy for crater morphology, Late Devonian Alamo impact, Nevada . In: Geosphere (Geological Society of America) . tape January 11 , 2015, p. 123-143 , doi : 10.1130 / GES00964.1 (English, isu.edu [PDF]). (accessed on February 10, 2015)
  10. ↑ The Siljan impact crater in the Earth Impact Database ( memento of the original from August 31, 2012 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. . Planetary and Space Science Center, Department of Earth Sciences, University of New Brunswick (Canada). @1@ 2Template: Webachiv / IABot / www.passc.net
  11. ↑ Sandra Isabella Kaiser, Ralf Thomas Becker, Thomas Steuber, Sarah Zhor Aboussalam: Climate-controlled mass extinctions, facies, and sea-level changes around the Devonian – Carboniferous boundary in the eastern Anti-Atlas (SE Morocco) . In: Palaeogeography, Palaeoclimatology, Palaeoecology . tape 310 , no. 3–4 , October 2011, pp. 340–364 , doi : 10.1016 / j.palaeo.2011.07.026 (English, researchgate.net [PDF]). (accessed on January 29, 2016)
  12. ^ Paul M. Myrow, Jahandar Ramezani, Anne E. Hanson, Samuel A. Bowring, Grzegorz Racki, Michał Rakociński: High-precision U – Pb age and duration of the latest Devonian (Famennian) Hangenberg event, and its implications . In: Terra Nova . tape 26 , no. 3 , June 2014, p. 222–229 , doi : 10.1111 / ter.12090 (English, researchgate.net [PDF]). (accessed on January 29, 2016)
  13. ↑ The type locality of the Kellwasser horizons in the Upper Harz, Germany. In: Journal of the German Society for Geosciences. Volume 165, Number 2, June 2014, pp. 145–162, accessed January 20, 2017.