Earth:Emsian

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Short description: Third stage of the Devonian
Emsian
407.6 ± 2.6 – 393.3 ± 1.2 Ma
Geology of Asia 400Ma.jpg
Paleogeography of the Emsian, 400 Ma
Chronology
Devonian Graphical Timeline
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-420 —
-415 —
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-405 —
-400 —
-395 —
-390 —
-385 —
-380 —
-375 —
-370 —
-365 —
-360 —
Widespread[3]
shrubs & trees
S. America
glaciation begins
Subdivision of the Devonian according to the ICS, as of 2021.[4]
Vertical axis scale: millions of years ago.
Etymology
Name formalityFormal
Name ratified1985
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 kitabicus
Lower boundary GSSPZinzil'ban Gorge, Uzbekistan
[ ⚑ ] 39°12′00″N 67°18′20″E / 39.2000°N 67.3056°E / 39.2000; 67.3056
GSSP ratified1995[5]
Upper boundary definitionFAD of the conodont Polygnathus costatus partitus
Upper boundary GSSPWetteldorf Richtschnitt section, Wetteldorf, Eifel, Germany
[ ⚑ ] 50°08′59″N 6°28′18″E / 50.1496°N 6.4716°E / 50.1496; 6.4716
GSSP ratified1985[6]

The Emsian is one of three faunal stages in the Early Devonian Epoch. It lasted from 407.6 ± 2.6 million years ago to 393.3 ± 1.2 million years ago. It was preceded by the Pragian Stage and followed by the Eifelian Stage. It is named after the Ems river in Germany.[7] The GSSP is located in the Zinzil'ban Gorge in the Kitab State Geological Reserve of Uzbekistan, 35 centimetres (14 in) above the contact with the Madmon Formation.

In North America the Emsian Stage is represented by Sawkill or Sawkillian time.

Biological events

Emsian-age conical mud mounds at Hamar Laghdad, Morocco

During this period, earliest known agoniatitid ammonoid fossils began appearing within this stage after first appearing in previous stage and began to evolutionarily radiate within this stage, in which a new ammonoid order Goniatitida rises in the end of Zlichovian stage (Siberian representation; corresponds to early Eifelian and after the end of Early Devonian, before 391.9 mya).[8][9] Later agoniatitid ammonoids would die out in the Taghanic event in the upper middle Givetian. Goniatite ammonoids would give rise to further ammonoid orders, thus starting ammonoid dominance of marine fossils in further periods until their end at the Cretaceous-Paleogene mass extinction event.

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. http://jgs.lyellcollection.org/content/168/4/863.abstract. 
  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. doi:10.1086/421077. Bibcode2004JG....112..495K. 
  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". International Commission on Stratigraphy. http://www.stratigraphy.org/index.php/ics-chart-timescale. 
  5. Yolkin, E.; Kim, A.; Weddige, K.; Talent, J.; House, M. (December 1997). "Definition of the Pragian/Emsian Stage boundary". Episodes 20 (4): 235–240. doi:10.18814/epiiugs/1997/v20i4/005. https://www.researchgate.net/publication/281579958_Definition_of_the_PragianEmsian_Stage_Boundary. Retrieved 18 December 2020. 
  6. Ziegler, W.; Klapper, G. (June 1985). "Stages of the Devonian System". Episodes 8 (2): 104–109. doi:10.18814/epiiugs/1985/v8i2/006. https://stratigraphy.org/gssps/files/eifelian.pdf. Retrieved 18 December 2020. 
  7. "Emsian stage". https://www.britannica.com/science/Emsian-Stage. 
  8. Klug, Christian (July 30, 1999). "Early Emsian ammonoids from the eastern Anti-Atlas (Morocco) and their succession". Paläontologische Zeitschrift 74 (4): 479–515. doi:10.1007/BF02988158. 
  9. Chlupac, I.; Lukes, P. (January 1999). "Pragian/Zlichovian and Zlichovian/Dalejan boundary sections in the Lower Devonian of the Barrandian Area, Czech Republic". https://www.researchgate.net/publication/297492444.