Miocene
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| Miocene | |
|---|---|
 | |
| Name | Miocene |
| Time start | 23.03 |
| Time end | 5.333 |
| Unit | Epoch |
| Era | Neogene |
| Period | Neogene |
Miocene The Miocene marks an epoch of the Neogene spanning from about 23.03 to 5.333 million years ago. It witnessed major shifts in paleoclimate, expansive faunal radiations, and tectonic reorganizations that shaped modern Eurasia, Africa, and Americas physiography. Key developments during this epoch set the stage for later hominin evolution, the establishment of modern flora communities, and significant changes in oceanic and atmospheric circulation.
Introduction
The Miocene followed the Oligocene and preceded the Pliocene, forming a middle chapter of the Neogene. Stratigraphically recognized by global marine and terrestrial signatures, the epoch is subdivided into internationally ratified stages used by the International Commission on Stratigraphy. Paleontological work by researchers publishing in venues like Geological Society of America meetings and journals led to rich fossil records from localities such as Siwalik Hills, La Venta, Shanwang, Loess Plateau, and Great Plains. Its study intersects with field programs by institutions including the Smithsonian Institution, Natural History Museum, London, and numerous university departments.
Geology and Chronostratigraphy
Miocene chronostratigraphy is delineated by magnetostratigraphy, biostratigraphy, and radiometric dates tied to volcanic ashes in formations such as the Chilcatay Formation, Burdigalian horizons, and Messinian Salinity Crisis-related deposits. The global stage names—Aquitanian, Burdigalian, Langhian, Serravallian, Tortonian, and Messinian—are used alongside regional units like the Siwalik Group and Marrakech Basin sequences. Geologists employ tools developed by the International Union of Geological Sciences and reference sections like the Global Boundary Stratotype Section and Point to correlate marine and terrestrial records. Tectono-sedimentary basins including the Po Basin, Paratethys Basin, and California Central Valley contain continuous successions that constrain epochal boundaries.
Climate and Environmental Change
Miocene climate evolution includes an early epoch warming, a middle Miocene Climate Optimum, and progressive cooling toward the late Miocene leading into Pliocene cooling. Oceanographic shifts are recorded in cores from the North Atlantic Ocean, Southern Ocean, and Mediterranean Sea that show changes in carbonate accumulation and isotopic signals used by teams at institutions like Lamont–Doherty Earth Observatory. The Messinian Salinity Crisis in the Mediterranean Sea during the late Miocene produced hypersaline deposits and evaporites preserved in basins studied by researchers from Universidad Complutense de Madrid and University of Barcelona. Climatic transitions influenced expansion of C4 grasses across savannas in regions such as the East African Rift System, South American cerrado, and Eurasian steppes, documented in palynological records from the Royal Botanic Gardens, Kew and petrographic studies by laboratories at University of California, Berkeley.
Flora and Fauna
Miocene biotas show diversification and turnover among mammals, birds, reptiles, and marine organisms. Terrestrial mammal radiations produced modern lineages including early Cercopithecidae and Hominidae relatives, grazers like Equidae and Bovidae, and predators represented by groups related to Felidae and Canidae. Notable fossil sites such as Laetoli, Hadar, Gravelly Hill, and Valles del Tuy preserve assemblages used by paleontologists at University of the Witwatersrand, Harvard University, and the Max Planck Institute for Evolutionary Anthropology. Marine faunas include abundant Cetacea diversification, with early baleen and toothed whales found in deposits from the Mediterranean to the Pacific Coast of North America. Plant megafossils and pollen records reveal woodlands, evergreen forests, and expanding grasslands with genera such as Quercus, Pinus, and grasses that gave rise to modern prairie and steppe ecosystems.
Paleogeography and Tectonics
Tectonic activity during the Miocene rearranged continental margins and ocean gateways. Uplift of the Himalaya and continued collision between India and Eurasia influenced monsoon intensification recorded in Himalayan foreland basins and isotopic records compiled by the Indian Institute of Science. Opening and closure events at gateways like the proto-Bering Strait and restrictions in the Mediterranean Sea affected thermohaline circulation, while the rise of the Isthmus of Panama began its complex history influencing Atlantic–Pacific exchange. Rift systems such as the East African Rift System produced volcanism and basins that preserved hominin-bearing deposits excavated by teams from National Museums of Kenya and international collaborators. Mountain building in regions like the Alps, Andes, and Carpathians reshaped drainage patterns and sediment provenance traced by geochronology at facilities like ETH Zurich.
Human Evolutionary Context
The Miocene provides the deep-time backdrop for the emergence of ape and early hominid lineages that later gave rise to hominins. Fossil apes from sites in Europe, Asia, and Africa—including genera recovered from Sabah, Shaanxi Province, and East Africa—document locomotor and dental adaptations studied by paleoanthropologists at University College London and University of Poitiers. Climatic and environmental shifts during the Miocene reorganized habitats in the East African Rift System and Arabian Peninsula, creating selective landscapes implicated in hypotheses tested by researchers at Stony Brook University and the British Museum. While no direct hominin fossils appear until the later Pliocene, Miocene ape diversity frames morphological and biogeographic scenarios central to understanding the origin of Homo and related taxa.