Middle Miocene disruption
Encyclopedia
The term Middle Miocene disruption, alternatively the Middle Miocene extinction or Middle Miocene extinction peak, refers to a wave of extinction
s of terrestrial and aquatic life forms that occurred around the middle of the Miocene Epoch
, c. 14.8 to 14.5 million years ago, during the Langhian
stage of the Miocene.
Madelaine Bohme observed the occurrence of Varanidae, Chamaeleon, Cordylidae, Tomistomidae, Alligatoridae, and giant turtles which indicate survival through the Miocene Climatic Optimum (18 to 16 Ma) in Central Europe (42W 45 N palaeolatitude). A major and permanent cooling step occurred between 14.8 and 14.1 Ma, associated with increased production of cold Antarctic deep waters and a major growth of the East Antarctic
ice sheet. Two crocodiles of the genera Gavialosuchus
and Diplocynodon
were noted to have been extant in these northern latitudes prior to the permanent cooling step then became extinct 13.5 to 14 Ma.
A Middle Miocene delta 18O increase, that is a relative increase in the heavier isotope of oxygen, has been noted in the Pacific, the Southern Ocean and the South Atlantic.
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
s of terrestrial and aquatic life forms that occurred around the middle of the Miocene Epoch
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
, c. 14.8 to 14.5 million years ago, during the Langhian
Langhian
The Langhian is, in the ICS geologic timescale, an age or stage in the middle Miocene epoch/series. It spans the time between 15.97 ± 0.05 Ma and 13.65 ± 0.05 Ma . The Langhian was a continuing warming period defined by Lorenzo Pareto in 1864, it was originally established in the Langhe area north...
stage of the Miocene.
Madelaine Bohme observed the occurrence of Varanidae, Chamaeleon, Cordylidae, Tomistomidae, Alligatoridae, and giant turtles which indicate survival through the Miocene Climatic Optimum (18 to 16 Ma) in Central Europe (42W 45 N palaeolatitude). A major and permanent cooling step occurred between 14.8 and 14.1 Ma, associated with increased production of cold Antarctic deep waters and a major growth of the East Antarctic
ice sheet. Two crocodiles of the genera Gavialosuchus
Gavialosuchus
Gavialosuchus is an extinct tomistomine from the late Oligocene and Miocene of eastern North America and early Miocene of Europe. Three species have been named: the type species G. eggenburgensis from the early Miocene of Austria; G. americanus, from the late Miocene to early Pliocene of Florida;...
and Diplocynodon
Diplocynodon
Diplocynodon is an extinct genus of alligatoroid that lived during the Paleocene to middle Miocene 49 million years ago in Europe. It looked very similar to the modern caiman in that it was small and had bony armour scutes covering its neck, back, belly, and tail...
were noted to have been extant in these northern latitudes prior to the permanent cooling step then became extinct 13.5 to 14 Ma.
A Middle Miocene delta 18O increase, that is a relative increase in the heavier isotope of oxygen, has been noted in the Pacific, the Southern Ocean and the South Atlantic.
External links
- GeoWhen Database Criteria for defining the Middle Miocene in fossiliferous strata, based in part on Gradstein, Ogg, Smith, _A Geologic Time Scale, 2004.
- Middle Miocene global map