Eifelian

The Eifelian is the first of two faunal stages in the Middle Devonian Epoch. It lasted from 393.3 ± 1.2 million years ago to 387.7 ± 0.8 million years ago. It was preceded by the Emsian Stage and followed by the Givetian Stage.

Eifelian
Chronology
Etymology
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitAge
Stratigraphic unitStage
Time span formalityFormal
Lower boundary definitionFAD of the conodont Polygnathus costatus partitus
Lower boundary GSSPWetteldorf Richtschnitt section, Wetteldorf, Eifel, Germany
50.1496°N 6.4716°E / 50.1496; 6.4716
Lower GSSP ratified1985[5]
Upper boundary definitionFAD of the conodont Polygnathus hemiansatus
Upper boundary GSSPJebel Mech Irdane, Tafilalt, Morocco
31.2374°N 4.3541°W / 31.2374; -4.3541
Upper GSSP ratified1994[6]

North American subdivisions of the Eifelian Stage include Southwood, and part of Cazenovia (or Cazenovian).

Name and definition

The Eifelian is named after the Eifel Mountains of Western Germany, which exposed the GSSP section at the Wetteldorf Richtschnitt outcrop. The base of the Eifelian is defined by the start of the Polygnathus partitus conodont zone. This layer lies within the Upper Heisdorf Formation, 1.9 metres (6.2 ft) below the base of the Lauch Formation.[7]

Extinctions
Main article: Kačák Event

The end of the Eifelian was marked by a biological crisis known as the Kačák Event, a two-part interval of extinction which led to ecological turnover among ammonoids, conodonts, and other free-swimming animals.[8][9] In deep marine waters, the event is indicated by anoxic black shales. There is evidence for a major pulse of transgression (sea level rise) and warming during the event.[10][11][12]

Warming and sea level rise through the Eifelian and beyond would have had major effects on diversity, likely leading to the downfall of several marine biogeographic realms. The cool-water Malvinokaffric Realm (MKR), on the northwest edge of Gondwana, was decimated as rising temperatures eliminated suitably temperate habitat. Fauna of the Eastern Americas Realm (EAR), which was restricted to a shallow basin in southwest Laurussia, were gradually replaced by aggressive cosmopolitan species of the Old World Realm (OWR), which invaded through a seaway cutting along a flooded continental arch on the western edge of Laurussia.[9]

References
  1. Parry, S. F.; Noble, S. R.; Crowley, Q. G.; Wellman, C. H. (2011). "A high-precision U–Pb age constraint on the Rhynie Chert Konservat-Lagerstätte: time scale and other implications". Journal of the Geological Society. London: Geological Society. 168 (4): 863–872. doi:10.1144/0016-76492010-043.
  2. Kaufmann, B.; Trapp, E.; Mezger, K. (2004). "The numerical age of the Upper Frasnian (Upper Devonian) Kellwasser horizons: A new U-Pb zircon date from Steinbruch Schmidt(Kellerwald, Germany)". The Journal of Geology. 112 (4): 495–501. Bibcode:2004JG....112..495K. doi:10.1086/421077.
  3. Algeo, T. J. (1998). "Terrestrial-marine teleconnections in the Devonian: links between the evolution of land plants, weathering processes, and marine anoxic events". Philosophical Transactions of the Royal Society B: Biological Sciences. 353 (1365): 113–130. doi:10.1098/rstb.1998.0195.
  4. "Chart/Time Scale". www.stratigraphy.org. International Commission on Stratigraphy.
  5. Ziegler, W.; Klapper, G. (June 1985). "Stages of the Devonian System" (PDF). Episodes. 8 (2): 104–109. doi:10.18814/epiiugs/1985/v8i2/006. Retrieved 18 December 2020.
  6. Walliser, O.; Bultynck, P.; Weddige, K.; Becker, R.; House, M. (September 1995). "Definition of the Eifelian-Givetian Stage boundary". Episodes. 18 (3): 107–115. doi:10.18814/epiiugs/1995/v18i3/002. Retrieved 19 December 2020.
  7. "GSSP for the Emsian - Eifelian Stage Boundary". stratigraphy. Retrieved 30 June 2017.
  8. House, Michael R. (1985). "Correlation of mid-Palaeozoic ammonoid evolutionary events with global sedimentary perturbations". Nature. 313 (5997): 17–22. doi:10.1038/313017a0. ISSN 1476-4687. S2CID 34273115.
  9. Jamart, V.; Denayer, J. (2020). "The Kačák event (late Eifelian, Middle Devonian) on the Belgian shelf and its effects on rugose coral palaeobiodiversity" (PDF). Bulletin of Geosciences. 95 (3): 279–311. doi:10.3140/bull.geosci.1788. S2CID 225423367.
  10. Königshof, P.; Silva, A. C. Da; Suttner, T. J.; Kido, E.; Waters, J.; Carmichael, S. K.; Jansen, U.; Pas, D.; Spassov, S. (2016-01-01). "Shallow-water facies setting around the Kačák Event: a multidisciplinary approach". Geological Society, London, Special Publications. 423 (1): 171–199. doi:10.1144/SP423.4. ISSN 0305-8719. S2CID 131042746.
  11. DeSantis, M. K.; Brett, C. E.; Straeten, C. A. Ver (2007-01-01). "Persistent depositional sequences and bioevents in the Eifelian (early Middle Devonian) of eastern Laurentia: North American evidence of the Kačák Events?". Geological Society, London, Special Publications. 278 (1): 83–104. doi:10.1144/SP278.4. ISSN 0305-8719. S2CID 129585313.
  12. Marshall, J. E. A.; Astin, T. R.; Brown, J. F.; Mark-Kurik, E.; Lazauskiene, J. (2007-01-01). "Recognizing the Kačák Event in the Devonian terrestrial environment and its implications for understanding land–sea interactions". Geological Society, London, Special Publications. 278 (1): 133–155. doi:10.1144/SP278.6. ISSN 0305-8719. S2CID 128992526.


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