23.03–2.58 million years ago
|Mean atmospheric O|
2 content over period duration
|c. 21.5 vol %|
(108 % of modern level)
|Mean atmospheric CO|
2 content over period duration
|c. 280 ppm |
(1 times pre-industrial level)
|Mean surface temperature over period duration||c. 14 °C|
(0 °C above modern level)
The Neogene ( /, -/ NEE-ə-jeen, NEE-oh-) (informally Upper Tertiary or Late Tertiary) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period 23.03 million years ago (Mya) to the beginning of the present Quaternary Period 2.58 Mya. The Neogene is sub-divided into two epochs, the earlier Miocene and the later Pliocene. Some geologists assert that the Neogene cannot be clearly delineated from the modern geological period, the Quaternary. The term "Neogene" was coined in 1853 by the Austrian palaeontologist Moritz Hörnes (1815–1868).
During this period, mammals and birds continued to evolve into roughly modern forms, while other groups of life remained relatively unchanged. Early hominids, the ancestors of humans, appeared in Africa near the end of the period.[ citation needed ] Some continental movement 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 over the course of 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 2 ages:
The Miocene Epoch is subdivided into 6 ages:
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 seasonal and continued an overall drying and cooling trend which began at the start of the Paleogene. 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 current Ice Age began.
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 Allocaudata disappeared at the end. 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.
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 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 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 (Paleogene, Neogene, Quaternary) 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 Stage. In the 2004 proposal of the ICS, the Neogene would have consisted of the Miocene and Pliocene epochs.The International Union for Quaternary Research (INQUA) counterproposed that the Neogene and the Pliocene end at 2.58 Ma, that the Gelasian be transferred to the Pleistocene, and the Quaternary be recognized as the third period in the Cenozoic, citing key changes in Earth's climate, oceans, and biota that occurred 2.58 Ma and its correspondence to the Gauss-Matuyama magnetostratigraphic boundary. 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.
The Cenozoic Era meaning "new life", is the current and most recent of the three Phanerozoic geological eras, following the Mesozoic Era and extending from 66 million years ago to the present day. It is generally believed to have started on the day of the Cretaceous–Paleogene extinction event when an asteroid hit the earth.
The geologic time scale (GTS) is a system of chronological dating that relates geological strata (stratigraphy) to time. It is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth's history. The table of geologic time spans, presented here, agree with the nomenclature, dates and standard color codes set forth by the International Commission on Stratigraphy (ICS).
The Pliocene Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58 million years BP. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch. Prior to the 2009 revision of the geologic time scale, which placed the four most recent major glaciations entirely within the Pleistocene, the Pliocene also included the Gelasian stage, which lasted from 2.588 to 1.806 million years ago, and is now included in the Pleistocene.
The Pleistocene is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the world's most recent period of repeated glaciations. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology.
The Paleogene is a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 million years ago (Mya) to the beginning of the Neogene Period 23.03 Mya. It is the beginning of the Cenozoic Era of the present Phanerozoic Eon. The earlier term Tertiary Period was used to define the span of time now covered by the Paleogene and subsequent Neogene periods; despite no longer being recognised as a formal stratigraphic term, 'Tertiary' is still widely found in earth science literature and remains in informal use. The Paleogene is most notable for being the time during which mammals diversified from relatively small, simple forms into a large group of diverse animals in the wake of the Cretaceous–Paleogene extinction event that ended the preceding Cretaceous Period. The United States Geological Survey uses the abbreviation PE for the Paleogene, but the more commonly used abbreviation is PG with the PE being used for Paleocene.
Quaternary is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.588 ± 0.005 million years ago to the present. The Quaternary Period is divided into two epochs: the Pleistocene and the Holocene. The informal term "Late Quaternary" refers to the past 0.5–1.0 million years.
Tertiary is a widely used, but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start of the Cenozoic Era, and extended to the beginning of the Quaternary glaciation at the end of the Pliocene Epoch. The time span covered by the Tertiary has no exact equivalent in the current geologic time system, but it is essentially the merged Paleogene and Neogene periods, which are informally called the Lower Tertiary and the Upper Tertiary, respectively.
The International Commission on Stratigraphy (ICS), sometimes referred to by the unofficial name "International Stratigraphic Commission" is a daughter or major subcommittee grade scientific daughter organization that concerns itself with stratigraphical, geological, and geochronological matters on a global scale.
The Zanclean is the lowest stage or earliest age on the geologic time scale of the Pliocene. It spans the time between 5.332 ± 0.005 Ma and 3.6 ± 0.005 Ma. It is preceded by the Messinian age of the Miocene epoch, and followed by the Piacenzian age.
The Beestonian Stage is an early Pleistocene stage used in the British Isles. It is named after Beeston Cliffs near West Runton in Norfolk where deposits from this stage are preserved.
The Gelasian is an age in the international geologic timescale or a stage in chronostratigraphy, being the earliest or lowest subdivision of the Quaternary period/system and Pleistocene epoch/series. It spans the time between 2.588 ± 0.005 Ma and 1.806 ± 0.005 Ma. It follows the Piacenzian stage and is followed by the Calabrian stage.
Calabrian is a subdivision of the Pleistocene Epoch of the geologic time scale, defined as ~1.8 Ma.—781,000 years ago ± 5,000 years, a period of ~.
In geochronology, an epoch is a subdivision of the geologic timescale that is longer than an age but shorter than a period. The current epoch is the Holocene Epoch of the Quaternary Period. Rock layers deposited during an epoch are called a series. Series are subdivisions of the stratigraphic column that, like epochs, are subdivisions of the geologic timescale. Like other geochronological divisions, epochs are normally separated by significant changes in the rock layers to which they correspond.
The Geology of Bangladesh is affected by the country's location, as Bangladesh is mainly a riverine country. It is the eastern two-thirds of the Ganges and Brahmaputra river delta plain stretching to the north from the Bay of Bengal. There are two small areas of slightly higher land in the north-centre and north-west composed of old alluvium called the Madhupur Tract and the Barind Tract, and steep, folded, hill ranges of older (Tertiary) rocks along the eastern border.
A system in stratigraphy is a unit of rock layers that were laid down together within the same corresponding geological period. The associated period is a chronological time unit, a part of the geological time scale, while the system is a unit of chronostratigraphy. Systems are unrelated to lithostratigraphy, which subdivides rock layers on their lithology. Systems are subdivisions of erathems and are themselves divided into series and stages.
The Pre-Illinoian Stage is used by Quaternary geologists for the early and middle Pleistocene glacial and interglacial periods of geologic time in North America from ~2.5–0.2 Ma.
The European Land Mammal Mega Zones are zones in rock layers that have a specific assemblage of fossils (biozones) based on occurrences of fossil assemblages of European land mammals. These biozones cover most of the Neogene and Paleogene systems. In cases when fossils of mammals are abundant, stratigraphers and paleontologists can use these biozones as a more practical regional alternative to the stages of the official ICS geologic timescale. European Land Mammal Mega Zones are often also confusingly referred to as ages, stages, or intervals.
The Kutai sedimentary basin extends from the central highlands of Borneo, across the eastern coast of the island and into the Makassar Strait. With an area of 60,000 km2, and depths up to 15 km, the Kutai is the largest and deepest Tertiary age basin in Indonesia. Plate tectonic evolution in the Indonesian region of SE Asia has produced a diverse array of basins in the Cenozoic. The Kutai is an extensional basin in a general foreland setting. Its geologic evolution begins in the mid Eocene and involves phases of extension and rifting, thermal sag, and isostatic subsidence. Rapid, high volume, sedimentation related to uplift and inversion began in the Early Miocene. The different stages of Kutai basin evolution can be roughly correlated to regional and local tectonic events. It is also likely that regional climate, namely the onset of the equatorial ever wet monsoon in early Miocene, has affected the geologic evolution of Borneo and the Kutai basin through the present day. Basin fill is ongoing in the lower Kutai basin, as the modern Mahakam River delta progrades east across the continental shelf of Borneo.
A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place.
The geology of Moldova encompasses basement rocks from the Precambrian dating back more than 2.5 billion years, overlain by thick sequences of Proterozoic, Paleozoic, Mesozoic and Cenozoic sedimentary rocks.
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.)
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