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).
Name and definition
The Eifelian is named after the
Eifel Mountains
The Eifel (; lb, Äifel, ) is a low mountain range in western Germany and eastern Belgium. It occupies parts of southwestern North Rhine-Westphalia, northwestern Rhineland-Palatinate and the southern area of the German-speaking Community of ...
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
Conodonts (Greek ''kōnos'', "cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, which ...
zone. This layer lies within the Upper
Heisdorf Formation
Heisdorf () is a town in the commune of Steinsel, in central Luxembourg
Luxembourg ( ; lb, Lëtzebuerg ; french: link=no, Luxembourg; german: link=no, Luxemburg), officially the Grand Duchy of Luxembourg, ; french: link=no, Grand-Duché ...
, below the base of the
Lauch Formation
The Lauch Formation is a geologic formation in Germany. It preserves fossils dating back to the Devonian period.
See also
* List of fossiliferous stratigraphic units in Germany
See also
* Lists of fossiliferous stratigraphic units in Europ ...
.
Extinctions
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.
In deep marine waters, the event is indicated by
anoxic black shales. There is evidence for a major pulse of
transgression
Transgression may refer to:
Legal, religious and social
*Sin, a violation of God's Ten Commandments or other elements of God's moral law
*Crime, legal transgression, usually created by a violation of social or economic boundary
**In civil law ju ...
(
sea level rise) and warming during the event.
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
Biogeography is the study of the species distribution, distribution of species and ecosystems in geography, geographic space and through evolutionary history of life, geological time. Organisms and biological community (ecology), communities of ...
. The cool-water Malvinokaffric Realm (MKR), on the northwest edge of
Gondwana
Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...
, 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.
References
Middle Devonian
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