|Time span formality||Formal|
|Lower boundary definition|
|Lower boundary GSSP||Lemme-Carrosio Section, Carrosio, Italy|
|Lower GSSP ratified||1996|
|Upper boundary definition|
|Upper boundary GSSP||Monte San Nicola Section, |
(1 times pre-industrial)
|Mean surface temperature||c. 14 °C|
(0 °C above modern)
The Neogene (
During this period, mammals and birds 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 movements took place, the most significant event being the connection of North and South America 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 to transfer heat to the Arctic Ocean. The global climate cooled considerably throughout the Neogene, culminating in a series of continental glaciations in the Quaternary Period that follows.
In ICS terminology, from upper (later, more recent) to lower (earlier):
The Pliocene Epoch is subdivided into two ages:
The Miocene Epoch is subdivided into six ages:
- Messinian Age, preceded by
- Tortonian Age
- Serravallian Age
- Langhian Age
- Burdigalian Age
- 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.
The continents in the Neogene were very close to their current positions. The Isthmus of Panama formed, connecting North and South America. 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.
The global climate became more seasonal and continued an overall drying and cooling trend which began during the Paleogene. The Early Miocene was relatively cool; Early Miocene mid-latitude seawater and continental thermal gradients were already very similar to those of the present. During the Middle Miocene, Earth entered a warm phase known as the Middle Miocene Climatic Optimum (MMCO), which was driven by the emplacement of the Columbia River Basalt Group. Around 11 Ma, the Middle Miocene Warm Interval gave way to the much cooler Late Miocene. The ice caps on both poles began to grow and thicken, a process enhanced by positive feedbacks from increased formation of sea ice. Between 7 and 5.3 Ma, a decrease in global temperatures termed the Late Miocene Cooling (LMC) ensued, driven by decreases in carbon dioxide concentrations. During the Middle Pliocene, another warm interval occurred, interrupting the longer-term cooling trend. By the end of the period the first of a series of glaciations of the current Ice Age began.
Flora and fauna
Marine and continental flora and fauna have a modern appearance. The reptile group Choristodera went extinct in the early part of the period, while the amphibians known as Allocaudata disappeared at the end of it. Neogene also marked the end of the reptilian genera Langstonia and Barinasuchus, terrestrial predators that were the last surviving members of Sebecosuchia, a group related to crocodiles. The oceans were dominated by large carnivores like megalodons and livyatans, and 19 million years ago about 70% of all pelagic shark species disappeared. Mammals and birds continued to be the dominant terrestrial vertebrates, and took many forms as they adapted to various habitats. The first 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.
About 20 million years ago gymnosperms in the form of some conifer and cycad groups started to diversify and produce more species due to the changing conditions. 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. Ice age mammals like the mammoths and woolly rhinoceros were common in Pliocene. With lower levels of CO2 in the atmosphere, C4 plants expanded and reached ecological dominance in grasslands during the last 10 million years. Also Asteraceae (daisies) went through a significant adaptive radiation. Eucalyptus fossil leaves occur in the Miocene of New Zealand, where the genus is not native today, but have been introduced from Australia.
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 was a movement amongst geologists (particularly
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.
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- "Neogene". Merriam-Webster.com Dictionary.
- "Neogene". Dictionary.com Unabridged (Online). n.d.
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- Almost 20 Million Years Ago, Sharks Nearly Went Extinct
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- "9.7 million-year-old teeth found in Germany resemble those of human ancestors in Africa". ResearchGate. Retrieved 17 December 2017.
- DNA duplication linked to the origin and evolution of pine trees and their relatives
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- 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.
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