The Neogene ( ) (informally Upper Tertiary or Late Tertiary) is a geologic period and system that spans 20.45 million years from the end of the

Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago ( Mya) to the beginning o ...

Period million years ago ( Mya) to the beginning of the present

Quaternary Quaternary ( ) is the current and most recent of the three Period (geology), periods of the Cenozoic Era (geology), Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from ...

Period Mya. The Neogene is sub-divided into two epochs, the earlier

Miocene The Miocene ( ) is the first Epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish author Charles Lyell; its name comes from the Greek words (', "less") and (', "new") and means "le ...

and the later

Pliocene The Pliocene ( ; also Pleiocene) Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58Quaternary Quaternary ( ) is the current and most recent of the three Period (geology), periods of the Cenozoic Era (geology), Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from ...

. The term "Neogene" was coined in 1853 by the Austrian palaeontologist Moritz Hörnes (1815–1868). During this period,

mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in Female#Mammalian female, females produce milk ...

s and

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a four-c ...

s continued to evolve into modern forms, while other groups of life remained relatively unchanged. The first humans (''

Homo habilis

'') appeared in Africa near the end of the period. Some continental movement took place, the most significant event being the connection of

North North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating Direction (geometry), direction or geography. Etymology Th ...

North

and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. It can also be described as a southern Continent#Subcontinents, subcontinent ...

at the Isthmus of Panama, late in the Pliocene. This cut off the warm ocean currents from the Pacific to the Atlantic Ocean, leaving only the

Gulf Stream The Gulf Stream, together with its northern extension the North Atlantic Drift, is a warm and swift Atlantic ocean current that originates in the Gulf of Mexico and stretches to the tip of Florida Florida (, ) is a U.S. state, state loc ...

to transfer heat to the

Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is also known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an oce ...

. The global climate cooled considerably over the course of the Neogene, culminating in a series of continental glaciations in the

Period that follows.

Divisions

In ICS terminology, from upper (later, more recent) to lower (earlier): The

Pliocene The Pliocene ( ; also Pleiocene) Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58Piacenzian Age, preceded by *

Zanclean The Zanclean is the lowest stage or earliest age on the geologic time scale The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleont ...

Age The

Epoch is subdivided into six ages: * Messinian Age, preceded by * Tortonian Age * Serravallian Age * Langhian Age * Burdigalian Age * Aquitanian (stage), Aquitanian Age In different geophysical regions of the world, other regional names are also used for the same or overlapping ages and other timeline subdivisions. The terms ''Neogene System'' (formal) and ''Upper Tertiary System'' (informal) describe the rocks deposited during the ''Neogene Period''.

Geography

The continents in the Neogene were very close to their current positions. The Isthmus of Panama formed, connecting

and

. The Indian subcontinent continued to collide with Asia, forming the Himalayas. Sea levels fell, creating land bridges between Africa and Eurasia and between Eurasia and North America.

Climate

The global climate became seasonal and continued an overall drying and cooling trend which began at the start of the

. The ice caps on both poles began to grow and thicken, and by the end of the period the first of a series of glaciations of the Quaternary glaciation, current Ice Age began.

Flora and fauna

Marine and continental flora and fauna have a modern appearance. The reptile group Choristodera became extinct in the early part of the period, while the amphibians known as Albanerpetontidae, Allocaudata disappeared at the end. Mammals and

s continued to be the dominant terrestrial vertebrates, and took many forms as they adapted to various habitats. The first Hominini, hominins, the ancestors of humans may have appeared in southern Europe and migrated into Africa. The first humans (belonging to the species ''

Homo habilis

'') appeared in Africa near the end of the period. In response to the cooler, seasonal climate, tropical plant species gave way to deciduous ones and grasslands replaced many forests. Grasses therefore greatly diversified, and herbivorous mammals evolved alongside it, creating the many grazing animals of today such as horses, antelope, and bison. Eucalyptus fossil leaves occur in the

of New Zealand, where the genus is not native today, but have been introduced from Australia.

Disagreements

The Neogene traditionally ended at the end of the Pliocene Epoch, just before the older definition of the beginning of the

Period; many time scales show this division. However, there was a movement amongst geologists (particularly marine geologists) to also include ongoing geological time (Quaternary) in the Neogene, while others (particularly 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 to reflect many more environments than the older geological record. By dividing the Cenozoic Era into three (arguably two) periods (

, Neogene,

) instead of seven epochs, the periods are more closely comparable to the duration of periods in the Mesozoic and Paleozoic eras. The International Commission on Stratigraphy (ICS) once proposed that the Quaternary be considered a sub-era (sub-erathem) of the Neogene, with a beginning date of 2.58 Ma, namely the start of the Gelasian, Gelasian Stage. In the 2004 proposal of the ICS, the Neogene would have consisted of the

and

Pliocene The Pliocene ( ; also Pleiocene) Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58Clague, John ''et al.'' (2006) "Open Letter by INQUA Executive Committee"
''Quaternary Perspective, the INQUA Newsletter'' International Union for Quaternary Research 16(1) In 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. Following formal discussions at the 2008 International Geological Congress in Oslo, Norway, the ICS decided in May 2009 to make the Quaternary the youngest period of the Cenozoic Era with its base at 2.58 Mya and including the Gelasian age, which was formerly considered part of the Neogene Period and Pliocene Epoch. Thus the Neogene Period ends bounding the succeeding Quaternary Period at 2.58 Mya.

References

External links

* {{Authority control Neogene, Geological periods