Neogene
Neogene | |
---|---|
Period | |
Stratigraphic unit | System |
Time span formality | Formal |
Lower boundary definition |
|
Lower boundary GSSP | Lemme-Carrosio Section, Carrosio, Italy 44°39′32″N 8°50′11″E / 44.6589°N 8.8364°E |
Lower GSSP ratified | 1996[4] |
Upper boundary definition |
|
Upper boundary GSSP | Monte San Nicola Section, ppm (1 times pre-industrial) |
Mean surface temperature | c. 14 °C (0.5 °C above pre-industrial) |
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.[11] 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 followed.
Divisions
In ICS terminology, from upper (later, more recent) to lower (earlier):
The Pliocene Epoch is subdivided into two ages:
- Piacenzian Age, preceded by
- Zanclean Age
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.
Paleogeography
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.
Climate
The global climate became more seasonal and continued an overall drying and cooling trend which began during the
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.[21] Mammals and birds continued to be the dominant terrestrial vertebrates, and took many forms as they adapted to various habitats. An explosive radiation of ursids took place at the Miocene-Pliocene boundary.[22] The first hominins, the ancestors of humans, may have appeared in southern Europe and migrated into Africa.[23][24] The first humans (belonging to the species Homo habilis) appeared in Africa near the end of the period.[11]
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.[25] 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.[26] Eucalyptus fossil leaves occur in the Miocene of New Zealand, where the genus is not native today, but have been introduced from Australia.[27]
Disagreements
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
The
Following formal discussions at the 2008 International Geological Congress in Oslo, Norway,[32] 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.[33] Thus the Neogene Period ends bounding the succeeding Quaternary Period at 2.58 Mya.
References
- .
- JSTOR 3515337. Retrieved 2008-02-11.
- ^ "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy. September 2023. Retrieved December 16, 2024.
- .
- . Retrieved 8 December 2020.
- ^ "Neogene". Merriam-Webster.com Dictionary. Merriam-Webster.
- ^ "Neogene". Dictionary.com Unabridged (Online). n.d.
- ^ ISBN 978-0-632-05735-1.
- .
From p. 806: "Das häufige Vorkommen der Wiener Mollusken … im trennenden Gegensatze zu den eocänen zusammenzufassen." (The frequent occurrence of Viennese mollusks in typical Miocene as well as in typical Pliocene deposits motivated me – in order to avoid the perpetual monotony [of providing] details about the deposits – to subsume both deposits provisionally under the name "Neogene" (νεος new and γιγνομαι to arise) in distinguishing contrast to the Eocene.)
- ^ "GeoWhen Database – What Happened to the Tertiary?". www.stratigraphy.org.
- ^ S2CID 4470282.
- ^
- . Retrieved 30 November 2022.
- PMID 30255148.
- .
- S2CID 230534117. Retrieved 17 March 2023.
- ISSN 2662-4435.
- PMID 30530685.
- . Retrieved 13 April 2024 – via Elsevier Science Direct.
- ISBN 9780340905791.
- ^ Almost 20 Million Years Ago, Sharks Nearly Went Extinct
- PMID 18662376.
- ^ "Scientists find 7.2-million-year-old pre-human remains in the Balkans". Phys.org. Retrieved 17 December 2017.
- ^ "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
- PMID 35022396.
- ^ "Eucalyptus fossils in New Zealand – the thin end of the wedge – Mike Pole". 22 September 2014.
- ^ 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" Archived 2006-09-23 at the Wayback Machine Quaternary Perspective, the INQUA Newsletter International Union for Quaternary Research 16(1)
- ISSN 1040-6182. Archived from the original(PDF) on 2006-09-23. Retrieved 2006-09-23.
- ^ "ICS: Consolidated Annual Report for 2006" (PDF). Stratigraphy.org. Retrieved 15 June 2007.
- ^ "Geoparks and Geotourism – Field Excursion of South America". 33igc.org. Retrieved 17 December 2017.
- ^ "See the 2009 version of the ICS geologic time scale". Quaternary.stratigraphy.org.uk. Retrieved 17 December 2017.
External links
- "Digital Atlas of Neogene Life for the Southeastern United States". San Jose State University. Archived from the original on 2013-04-23. Retrieved 21 September 2018.