Miocene

Miocene
23.03 ± 0.3 – 5.333 ± 0.08 Ma PreꞒ Ꞓ O S D C P T J K Pg N
A map of Earth as it appeared 15 million years ago during the Miocene Epoch, Langhian Age
Chronology
−24 — – −22 — – −20 — – −18 — – −16 — – −14 — – −12 — – −10 — – −8 — – −6 — – −4 — – −2 — C e n o z o i c P g N e o g e n e Q Oligocene M i o c e n e P l i o. Pleistocene Aquitanian Burdigalian Langhian Serravallian Tortonian Messinian Zanclean Piacenzian         ← Messinian salinity crisis[1] ← North American prairie expands[2] Subdivision of the Neogene according to the ICS, as of 2023.[3] Vertical axis scale: Millions of years ago
Etymology
Name formality	Formal
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Epoch
Stratigraphic unit	Series
Time span formality	Formal
Lower boundary definition	Base of magnetic polarity chronozone C6Cn.2n FAD of the Planktonic foraminiferan Paragloborotalia kugleri
Lower boundary GSSP	Lemme-Carrosio Section, Carrosio, Italy 44°39′32″N 8°50′11″E / 44.6589°N 8.8364°E / 44.6589; 8.8364
Lower GSSP ratified	1996[4]
Upper boundary definition	Base of the Thvera magnetic event (C3n.4n), which is only 96 ka (5 precession cycles) younger than the GSSP
Upper boundary GSSP	Heraclea Minoa section, Heraclea Minoa, Cattolica Eraclea, Sicily, Italy 37°23′30″N 13°16′50″E / 37.3917°N 13.2806°E / 37.3917; 13.2806
Upper GSSP ratified	2000[5]

The Miocene (/ˈmaɪ.əsiːn, -oʊ-/ MY-ə-seen, -⁠oh-)^[6][7] is the first geological epoch of the Neogene Period and extends from about 23.03 to 5.333 million years ago (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words μείων (meíōn, "less") and καινός (kainós, "new")^[8][9] and means "less recent" because it has 18% fewer modern marine invertebrates than the Pliocene has.^[10] The Miocene followed the Oligocene and preceded the Pliocene.

As Earth went from the Oligocene through the Miocene and into the Pliocene, the climate slowly cooled towards a series of ice ages.^[11][12] The Miocene boundaries are not marked by distinct global events but by regionally defined transitions from the warmer Oligocene to the cooler Pliocene Epoch.

During the Early Miocene, Afro-Arabia collided with Eurasia, severing the connection between the Mediterranean and Indian Oceans, and allowing the interchange of fauna between Eurasia and Africa, including the dispersal of proboscideans and hominoids^[13] into Eurasia. During the late Miocene, the connections between the Atlantic and Mediterranean closed, causing the Mediterranean Sea to almost completely evaporate. This event is referred to as the "Messinian salinity crisis". Then, at the Miocene–Pliocene boundary, the Strait of Gibraltar opened, and the Mediterranean refilled. That event is referred to as the "Zanclean flood".

Also during the early Miocene (specifically the Aquitanian and Burdigalian Stages), the apes first evolved, began diversifying, and became widespread throughout the Old World. Around the end of this epoch, the ancestors of humans had split away from the ancestors of the chimpanzees and had begun following their own evolutionary path during the final Messinian Stage (7.5–5.3 Ma) of the Miocene. As in the Oligocene before it, grasslands continued to expand, and forests to dwindle. In the seas of the Miocene, kelp forests made their first appearance and soon became one of Earth's most productive ecosystems.^[14]

The plants and animals of the Miocene were recognizably modern. Mammals and birds were well established. Whales, pinnipeds, and kelp spread.

The Miocene is of particular interest to geologists and palaeoclimatologists because major phases of the geology of the Himalaya occurred during that epoch, affecting monsoonal patterns in Asia, which were interlinked with glacial periods in the northern hemisphere.^[15]