Science Fair Project Encyclopedia
The Miocene epoch is a period of time that extends from about 23 to 5.3 million years before the present. As with other older geologic periods, the rock beds that define the start and end are well identified, but the exact dates of the start and end of the period are uncertain. The Miocene was named by Sir Charles Lyell and the name means roughly "less recent", referring to a period encompassing the essentially modern mammalian faunas. The Miocene follows the Oligocene Epoch and is followed by the Pliocene Epoch. The Miocene is the first epoch of the Neogene period.
The Miocene boundaries are not set at an easily identified worldwide event but rather at regional boundaries between the warmer Oligocene and the cooler Pliocene.
The Miocene faunal stages from youngest to oldest are:
|Messinian||(7.246 – 5.332 MYA)|
|Tortonian||(11.608 – 7.246 MYA)|
|Serravallian||(13.65 – 11.608 MYA)|
|Langhian||(15.97 – 13.65 MYA)|
|Burdigalian||(20.43 – 15.97 MYA)|
|Aquitanian||(23.03 – 20.43 MYA)|
The subdivisions within the Miocene are defined by the relative abundance of different species of calcareous nanofossils (calcite platelets shed by brown single-celled algae) and foraminifera (single-celled protists with diagnostic shells).
Mountain building took place in Western North America and Europe. Both continental and marine Miocene deposits are common worldwide with marine outcrops common near modern shorelines. Well studied continental exposures occur in the American Great Plains and in Argentina.
Grasses begin to spread, and along with them grazing herbivores develop.
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