Neogene

From Wikipedia, the free encyclopedia

Jump to: navigation, search

Categories: Neogene

For the hawkmoth genus, see Neogene (moth).

Events of the Cenozoic

view • discuss • edit

-65 —

–

-60 —

–

-55 —

–

-50 —

–

-45 —

–

-40 —

–

-35 —

–

-30 —

–

-25 —

–

-20 —

–

-15 —

–

-10 —

–

-5 —

–

0 —

Cretaceous

Quaternary

←

←

Rise of grasses^[1]

←

First Antarctic glaciers^[2]

←

K-T mass
extinction

←

Messinian salinity crisis^[3]

P
a
l
æ
o
g
e
n
e

N
e
o
g
e
n
e

Cenozoic

Mesozoic

An approximate timescale of key Cenozoic events.
Axis scale: Ma before present.

↓

Neogene Period is a unit of geologic time starting 23.03 ± 0.05 million years ago. The Neogene Period follows the Paleogene Period of the Cenozoic Era. Under the current proposal of the International Commission on Stratigraphy (ICS), the Neogene would consist of the Miocene, Pliocene, Pleistocene, and Holocene epochs and continue until the present.^[4]

The terms Neogene System (formal) and upper Tertiary System (informal) describe the rocks deposited during the Neogene Period.

The Neogene covers roughly 23 million years. During the Neogene mammals and birds evolved considerably. Most other forms were relatively unchanged. Some continental motion took place, the most significant event being the connection of North and South America in the late Pliocene. Climates cooled somewhat over the duration of the Neogene culminating in continental glaciations in the Quaternary sub-era (or period, in some time scales) that follows, and that saw the dawn of the genus Homo.

Neogene period
Miocene	Pliocene
Aquitanian \| Burdigalian \| Langhian Serravallian \| Tortonian \| Messinian	Zanclean \| Piacenzian → Quaternary

Controversy

The Neogene traditionally ended at the end of the Pliocene epoch, just before the older definition of the beginning of the Quaternary Period; many time scales show this division. However, there is a movement amongst geologists (particularly Neogene Marine Geologists) to also include ongoing geological time (Quaternary) in the Neogene, while others (particularly Quaternary Terrestrial Geologists) insist the Quaternary to be a separate period of distinctly different record. The somewhat confusing terminology and disagreement amongst geologists on where to draw what hierarchical boundaries, is due to the comparatively fine divisibility of time units as time approaches the present, and due to geological preservation that causes the youngest sedimentary geological record to be preserved over a much larger area and reflecting many more environments, than the slightly older geological record. By dividing the Cenozoic era into three (arguably two) periods (Paleogene, Neogene, Quaternary) instead of 7 epochs, the periods are more closely comparable to the duration of periods in the Mesozoic and Paleozoic eras.

The ICS once proposed that the Quaternary be considered a sub-era (sub-erathem) of the Neogene, with a beginning date of 2.588 Ma., namely the start of the Gelasian Stage. The International Union for Quaternary Research (INQUA) counterproposed that the Neogene and the Pliocene end at 2.588 Ma., that the Gelasian be transferred to the Pleistocene, and the Quaternary be recognized as the third period in the Cenozoic, citing the key changes in Earth's climate, oceans, and biota that occurred 2.588 Ma. and its correspondence to the Gauss-Matuyama magnetostratigraphic boundary.^[5] 2006 ICS and INQUA reached a compromise that made Quaternary a subera, subdividing Cenozoic into the old classical Tertiary and Quaternary, a compromise that was rejected by International Union of Geological Sciences because it split both Neogene and Pliocene in two.^[6]

References

^ Retallack, G.J. (1997). "Neogene Expansion of the North American Prairie". PALAIOS 12 (4): 380-390. Retrieved on 2008-02-11.
^ Zachos, J.C.; Kump, L.R. (2005). "Carbon cycle feedbacks and the initiation of Antarctic glaciation in the earliest Oligocene". Global and Planetary Change 47 (1): 51-66.
^ Krijgsman, W.; Garcés, M.; Langereis, C.G.; Daams, R.; Van Dam, J.; Van Der Meulen, A.J.; Agustí, J.; Cabrera, L. (1996). "A new chronology for the middle to late Miocene continental record in Spain". Earth and Planetary Science Letters 142 (3-4): 367-380. Retrieved on 2008-03-01.
^ Lourens, L., Hilgen, F., Shackleton, N.J., Laskar, J., Wilson, D., (2004) “The Neogene Period”. In: Gradstein, F., Ogg, J., Smith, A.G. (Eds.), Geologic Time Scale Cambridge University Press, Cambridge.
^ Clague, John et al. (2006) "Open Letter by INQUA Executive Committee" Quaternary Perspective, the INQUA Newsletter International Union for Quaternary Research 16(1):
^ ICS: CONSOLIDATED ANNUAL REPORT FOR 2006, last retrieved in 15 June 2007