Miocene Epoch
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What is the Miocene Epoch?
The Miocene Epoch is a major division of the Neogene Period, which lasted from 23 million to 5.3 million years ago. It is subdivided into the Early Miocene (23 million to 16 million years ago), the Middle Miocene (16 million to 11.6 million years ago), and the Late Miocene (11.6 million to 5.3 million years ago).
During the Miocene, land-dwelling mammals became modern, with half of today's mammalian families present in the record. Horse evolution occurred mainly in North America, and the first dogs, bears, and hyenas appeared. Primate evolution is also of great importance, with apes undergoing a great deal of evolution.
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When did the Miocene Epoch occur in Earth's history?
The Miocene Epoch, a major division of the Neogene Period, spanned from 23 million to 5.3 million years ago. It is further divided into the Early Miocene (23 to 16 million years ago), the Middle Miocene (16 to 11.6 million years ago), and the Late Miocene (11.6 to 5.3 million years ago). The Miocene is also divided into six ages/stages: Aquitanian, Burdigalian, Langhian, Serravallian, Tortonian, and Messinian.
The Miocene followed the Oligocene Epoch and was succeeded by the Pliocene Epoch. During the late Oligocene and early to mid-Miocene epochs (28.4 million to 13.8 million years ago) the Earth was relatively warm. Cooling resumed 15 million years ago, and the Antarctic Ice Sheet expanded again.
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What major changes happened on Earth during the Miocene Epoch?
During the Miocene Epoch, which lasted from 23 million to 5.3 million years ago, several significant changes occurred on Earth.
Tectonic Activity and Climate Change
The Himalayas experienced accelerated mountain building, significantly altering drainage patterns and creating a climatic barrier that affected rainfall distribution. Global cooling trends led to the formation of ice sheets on West Antarctica around 13 million years ago, with complete glaciation by the late Miocene. This period also saw the isolation of the Mediterranean basin, impacting oceanic heat transfer.
Biological Evolution
Land-dwelling mammals became essentially modern, with many archaic groups extinct. There was diversification and development of horses in North America, and the first dogs and bears appeared. Additionally, simple grasslands evolved into modern grasslands, supporting the expansion of grazing mammals. In the oceans, changing circulation patterns led to accelerated evolution among marine plankton and mollusks.
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Why is the Miocene Epoch important for understanding geochronology?
The Miocene Epoch, part of the Neogene Period, spanned from 23 million to 5.3 million years ago and is significant in geochronology because its terrestrial deposits provide a detailed record of vertebrate, especially mammal, development.
During the Miocene, many modern mammal groups appeared, and the epoch is crucial to primate evolution, with apes undergoing significant development. The study of index fossils, which are animal or plant remains characteristic of a particular time, helps define geologic time scale boundaries and correlate strata.
Isotopic dating methods and the study of radioactive isotopes also contribute to establishing a firm sequence of events in different locations on a regional or global scale. These methods, along with refined techniques in isotope geology, allow for precise dating and correlation of Earth's history, complementing fossil dating.
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What types of plants and animals lived during the Miocene Epoch?
During the Miocene Epoch (23 million to 5.3 million years ago), land-dwelling mammals were largely modern, with many archaic groups extinct and about half of today's mammalian families present.
Animals
- Land: Horse evolution occurred mainly in North America, with diversification and development in forms such as Parahippus, Miohippus, Anchitherium, Hypohippus, Pliohippus, and Merychippus. The first dogs, bears, hyenas, and sabre-toothed cats also appeared. Primitive antelope, deer, and giraffes appeared in Eurasia, while ancestors of modern elephants spread to Eurasia and diversified. In South America, marsupial carnivores, aberrant endentates, litopterns, and toxodonts existed.
- Marine: By the end of the Miocene Epoch, almost all modern groups of whales, early seals, and walruses had appeared. The largest marine carnivore of the period was the megalodon (Carcharocles megalodon), a shark that lived from the middle Miocene to the late Pliocene.
- Avian: Birds such as herons, rails, ducks, eagles, hawks, crows, sparrows, pheasants, owls, and partridges existed in Europe. Passerines became abundant and diverse.
Plants
Simple grasslands appeared in the Eocene, whereas short grasslands with sod appeared in the first half of the Miocene. Modern grasslands appeared in the late Miocene.
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How do scientists study rocks and fossils to learn about the Miocene Epoch?
Scientists investigate the Miocene Epoch (23 million to 5.3 million years ago) using rocks and fossils to understand the Earth's past environments and life forms.
Key methods include:
* Fossil Analysis Examining fossils of animals and plants in Miocene deposits reveals the evolution and distribution of species, with index fossils helping to correlate strata across different regions.
* Isotopic Dating Radiometric dating techniques, such as rubidium-strontium (Rb-Sr) dating, help determine the absolute ages of rocks and minerals, establishing a chronological framework for Miocene events.
* Sedimentary Analysis Studying sedimentary rocks provides insights into past environments, climates, and depositional processes.
* Ice Core Analysis Though more relevant to the Quaternary period, ice cores offer data on climate change through isotope ratios, atmospheric composition, and volcanic eruptions, which can be correlated to other records.6 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Miocene Epoch, earliest major worldwide division of the Neogene Period (23 million years to 2.6 million years ago) that extended from 23 million to 5.3 million years ago. It is often divided into the Early Miocene Epoch (23 million to 16 million years ago), the Middle Miocene Epoch (16 million to 11.6 million years ago), and the Late Miocene Epoch (11.6 million to 5.3 million years ago). The Miocene may also be divided into six ages and their corresponding rock stages: from oldest to youngest these ages or stages are the Aquitanian, Burdigalian, Langhian, Serravallian, Tortonian, and Messinian. The Miocene followed the Oligocene Epoch of the Paleogene Period and was succeeded by the Pliocene Epoch.
Important Miocene deposits occur in North and South America, southern Europe, India, Mongolia, East Africa, and Pakistan. Both marine and terrestrial environments are represented in the Miocene stratigraphic record. The record of terrestrial life is extensive and varied, providing a rather complete view of the development of vertebrates, especially mammals.
During the Miocene, land-dwelling mammals were essentially modern; many archaic groups were extinct by the end of the preceding Oligocene, and fully half of the mammalian families known today are present in the Miocene record. In the Northern Hemisphere, some interchange of faunas occurred between the Old and New Worlds. Interchange was also possible between Africa and Eurasia, but South America and Australia remained isolated. During the Miocene, horse evolution occurred mainly in North America; forms such as Parahippus, Miohippus (a form carried over from the preceding Oligocene Epoch), Anchitherium, Hypohippus, Pliohippus, and Merychippus are genera that represent great diversification and development. Also, the first dogs and bears appeared; the timing of the first emergence of the bear-dog Hemicyon occurs close to the origin of the bears. The first hyenas, springing from primitive civets, appeared in the Miocene, as did the first sabre-toothed cats of the subfamily Machairodontinae. Primitive antelope, deer, and giraffes appeared in Eurasia during the Miocene. Ancestors of the modern elephants, which during the preceding Oligocene seem to have been limited to Africa, appear to have spread to the Eurasian continent during the Miocene and became more diverse.
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In Argentina the Santa Cruz Formation of Middle Miocene time provides an excellent record of the unusual Miocene fauna of South America. Marsupial carnivores, aberrant endentates (mammals resembling anteaters, armadillos, and sloths), litopterns (hoofed mammals similar to horses and camels), and toxodonts (mammals with long, curved incisors) are among the odd groups represented. These forms were able to evolve because of South America’s isolation from other regions. The evolution of the South American monkeys was also under way during the Miocene.
By the end of the Miocene Epoch almost all the modern groups of whales had appeared, as had the early seals and walruses. Birds such as herons, rails, ducks, eagles, hawks, crows, sparrows, pheasants, owls, and partridges were present in Europe, where the uplifting of the Alps continued through Miocene time.
The Miocene Epoch is of great importance to primate evolution. The oldest primate to occur in the fossil record of North America, a 55-million-year-old tarsier-like creature called Teilhardina magnoliana, is known in the southern United States, but all North American primates died out by the end of the Eocene Epoch (about 33.9 million years ago) as the region’s climate cooled. Elsewhere, the higher primates, especially the apes, underwent a great deal of evolution. The fossil evidence seems to indicate that advanced primates, including apes, were present in southern Europe. An early form, which was gibbonlike in appearance but only distantly related to the gibbons, Pliopithecus, was found in the Miocene rocks of Europe. The dryopithecines, a group of advanced humanlike apes that probably represent the stock from which modern apes and humans originated, are also found in Europe’s Miocene rocks and are present in the Miocene strata of Africa as well, the region where humanlike forms as well as modern humans probably originated. (See also Dryopithecus.)
In the oceans, the Miocene was a time of changing circulation patterns, probably due to global cooling. Patterns of oceanic nutrient distribution changed, leading to increased productivity in some regions and decreased productivity in others. The Miocene was a time of accelerated evolution among marine plankton and mollusks, many groups showing increases in biological diversity.
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