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.
North American subdivisions of the Eifelian Stage include Southwood, and part of Cazenovia (or Cazenovian).
The earliest forest is known from the Eifelian stage.
Cladoxylopsid trees including Calamophyton and other plants have formed the forest landscape in what is now
England.[8]
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.[9][10] 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.[11][12][13]
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.[10]
^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.
^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.
^"Chart/Time Scale". www.stratigraphy.org. International Commission on Stratigraphy.