Miocene epoch


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Related to Miocene epoch: Pliocene epoch, Oligocene epoch, Holocene epoch

See also: Geologic Timescale (table)Geologic Timescale
Era Period Epoch Approximate duration
(millions of years)
Approximate number of years ago
(millions of years)

Cenozoic Quaternary Holocene 10,000 years ago to the present  
Pleistocene 2 .
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Miocene epoch

(mī`əsēn), fourth epoch of the Tertiary periodTertiary period
, name for the major portion of the Cenozoic era, the most recent of the geologic eras (see Geologic Timescale, table) from around 26 to 66 million years ago. The name Tertiary was first applied about the middle of the 18th cent.
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 in the Cenozoic era of geologic time (see Geologic TimescaleGeologic Timescale
Era Period Epoch Approximate duration
(millions of years)
Approximate number of years ago
(millions of years)

Cenozoic Quaternary Holocene 10,000 years ago to the present  
Pleistocene 2 .
..... Click the link for more information.
, table), lasting from around 24.6 to 5.1 million years ago.

North America was more extensively submerged in the Miocene than in the preceding Oligocene epochOligocene epoch
, third epoch of the Tertiary period in the Cenozoic era of geologic time, lasting from 38 to 24 million years ago. More of North America was dry land during the Oligocene than in the preceding Eocene epoch.
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 and underwent considerable crustal disturbances. The Atlantic and Gulf coasts were flooded about as extensively as in the Eocene epochEocene epoch
, second epoch of the Tertiary period in the Cenozoic era of geologic time, from approximately 54.9 to 38 million years ago. The Eocene in North America was marked by the submergence of the Great Valley of California and a portion of the Atlantic and Gulf coastal
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. Miocene rocks are found along the Atlantic as far N as Martha's Vineyard, but the series, everywhere thin, is thickest and least interrupted from New Jersey to Maryland. On the Gulf coast it extends from Florida westward to Texas. The Atlantic series is chiefly marls, clays, and sands, with diatomaceous earth; the Florida series, chiefly limestone (Florida having risen as an island in the late Oligocene); the Gulf series, limestone and clastic sediments.

On the Pacific coast, the Great Valley of California was submerged at the beginning of the Miocene. The deposition of the Vaqueros sandstone, clay, and conglomerate was followed by the formation of the oil-rich Monterey series, partly sandstone and shale but largely diatomaceous tufa. In mid-Miocene time there was extensive mountain building in this region; the Cascades and Coast Ranges were elevating, although the Rocky Mts. had by then eroded to low relief. This disturbance was accompanied by volcanic activity—the Columbia and Snake river plateaus consist of over 200,000 sq mi (520,000 sq km) of basaltic lava flows up to 10,000 ft (3,000 m) thick—and by the first known movement along the San Andreas fault zone, engendered by the collision of the North American continental plate with the Pacific Ocean plate (see plate tectonicsplate tectonics,
theory that unifies many of the features and characteristics of continental drift and seafloor spreading into a coherent model and has revolutionized geologists' understanding of continents, ocean basins, mountains, and earth history.
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).

Late in the Miocene a new, extensive submergence resulted in the deposition of the San Pablo shale and sandstone. The sediments of the California Miocene came chiefly from the Sierra Nevada and the Klamaths, which, through erosion, were peneplained by the close of the epoch. In the western interior of North America the Columbia River basalt plateau of Idaho, Washington, Oregon, N California, and N Nevada was formed by a great outpouring of lava, which continued in the succeeding Pliocene epoch.

During the Miocene most of N Europe was elevated, but marine waters covered E Spain, S France, Italy, and a depressed area extending through Hungary to a basin around Vienna. In addition to considerable mountain making, lagoons were formed at the base of the Carpathians and north of the Caucasus in the regions now occupied by the Romanian and Baku oil fields.

The mammalian life of the Miocene was marked by further stages in the development of the horse, by the multiplication and final extinction of the giant hogs, and by the appearance of the mastodons, raccoons, and weasels. Cats, camels, doglike carnivores, and rhinoceroses were common, and species of a great ape (Dryopithecus) inhabited S Europe, Asia, and Africa. In the Miocene a distinct cooling of the climate resulted in the reduction of forests and an increase in grassy plains.

References in periodicals archive ?
High carbon dioxide levels during the middle Miocene epoch have been documented in other studies through multiple lines of evidence, including the number of microscopic pores on the surface of plant leaves and geochemical evidence from soils and marine organisms.
Time Description Source Miocene epoch (15 million years 'Proto-kaka' Fleming, 1979 BP) Pleistocene 'Proto-kaka' epoch (2 million separates, to Fleming, 1979 years BP) evolve into kea and kaka Early 20th Point sightings of Marriner, 1908 century (1908) kea Late 20th Point sightings of wakelin, 1991 Century (1991) kea Native forest and Land Information Future area above 100m New Zealand as a suggestion of (LINZ) Topo future kea habitat data
These sites date back six to eight million years to the Late Miocene epoch when Abu Dhabi was greener, with rivers teeming with hippos, crocodiles, turtles and fish.
4] grasses during the late Miocene epoch, starting about 8 million years ago.
The bones and teeth-remains of small mammals that lived in the early Miocene Epoch, some 18 to 20 million years ago-are the first small mammal fossils of that age to be found in Egypt.
By comparing the abundances of different isotopes of argon trapped in the ash particles, they determined that the ash settled into a crack on top of the glacier during the Miocene epoch, several million years before the Pliocene.
When it was over, they had decoded an 820-piece DNA sequence from the leaf's photosynthetic organelle, the chloroplast -- by far the olderst bit of genetic material ever analyzed, dating back to the Miocene epoch.
At the end of the Miocene epoch, 6 million years ago, the Mediterranean Sea suffered a "salinity crisis.