Pliocene

Pliocene
Name	Pliocene
Color	#fbceb1
Time start	5.333
Time end	2.58
Time unit	Ma
Preceding	Miocene
Following	Pleistocene

Pliocene The Pliocene was a geological epoch of the Neogene Period spanning from 5.333 Ma to 2.58 Ma. It succeeded the Miocene and preceded the Pleistocene, and it is characterized by significant changes in Antarctic glaciation, global climates, and biotic turnovers that set the stage for modern Holocene ecosystems. Key developments during the epoch influenced later events including the expansion of Homo lineages, shifts in ocean circulation tied to the Isthmus of Panama closure, and reorganization of faunas across the Paleogene–Neogene transition.

Definition and Chronology

The formal boundaries of the epoch were defined by the International Commission on Stratigraphy using magnetostratigraphy, biostratigraphy, and isotope stratigraphy correlated to sections such as the Vrica section in Italy and the Monte San Nicola exposures. The base of the epoch is tied to the top of magnetochron C3Br.1r and the first appearance datum of marine microfossils recorded in the Llanada Alavesa. The upper boundary coincides with the onset of the Quaternary and a major cooling event recorded globally in sequences such as the La Cotte de St Brelade strata and deep-sea cores from the North Atlantic Ocean and the West Antarctic Ice Sheet margin.

Geology and Paleoclimate

Pliocene geology records widespread deposition in basins like the Mediterranean Basin, Paratethys, Gulf of Mexico, and East African Rift System with marine transgressions over platforms such as the Black Sea and the North Sea. Global climate trends show a long-term cooling from mid-Pliocene warmth toward progressive glacials documented in marine isotope stages, oxygen isotope shifts in Deep Sea Drilling Project cores, and faunal turnovers recorded in the Siwalik Hills and Sierra Nevada (U.S.) sequences. Atmospheric CO2 estimates derived from proxies including stomatal indices and alkenone palaeothermometry link to reconstructions used by groups like the Intergovernmental Panel on Climate Change to model mid-Pliocene Warm Period analogs. The epoch witnessed changes in ocean circulation patterns, including the shoaling and closure of gateways such as the Central American Seaway and modifications to the North Atlantic Drift.

Flora and Fauna

Floras shifted as temperate grasslands expanded across regions including the Great Plains, Eurasian Steppe, and Patagonian lowlands, recorded in pollen records from cores in the Loess Plateau and Pampean sequences. Woody taxa distributions altered with genera like Quercus, Pinus, and Nothofagus responding to cooling and drying trends apparent in floristic assemblages from the Iberian Peninsula and New Zealand. Faunal assemblages show the radiation and dispersal of mammals such as Equidae (horses), Proboscidea (elephants), and Cervidae (deer), alongside carnivorans including Canidae and Felidae. Notable faunal events include dispersals across the Bering Land Bridge and faunal exchanges via the emerging Isthmus of Panama, affecting taxa like Camelidae and Xenarthra. Marine faunas record changes in cetacean diversity with evidence from sites near Monterey Bay and Peru; diatom and foraminifera turnovers in the Mediterranean Sea reflect nutrient shifts.

Tectonics and Sea-Level Changes

Active tectonism in regions such as the Alps, Himalaya, Andes, and East African Rift influenced basin subsidence, provenance signals, and sediment flux to shelves studied in seismic profiles and outcrops like the Po Plain and Ganges Basin. The progressive uplift of the Colorado Plateau and orogenic pulses in the Tibet region altered atmospheric circulation and monsoon systems recorded in speleothems from China and lacustrine deposits in the Ethiopian Highlands. Global sea-level curves for the epoch derived from sequence stratigraphy and the Integrated Ocean Drilling Program indicate repeated regressions and transgressions tied to ice volume changes on Antarctica and Greenland, with regional shoreline shifts documented along the California coast, East Anglia, and Patagonia.

Human Evolution and Archaeology

The Pliocene encompasses critical intervals for hominin evolution with key fossils from localities such as Laetoli, Hadar, Afar Region, and the Hadar Formation documenting bipedal australopithecines and early hominins attributed to genera like Australopithecus and possible early Homo ancestors. Trace fossils including the famous footprints at Laetoli provide behavioral insights, while archaeological contexts in younger late-Pliocene sequences foreshadow technological developments later recorded at Olduvai Gorge and Koobi Fora. Paleoecological reconstructions from the Turkana Basin and Olorgesailie help constrain models of hominin dietary adaptations, landscape use, and dispersal routes toward Eurasia across corridors such as the Levant and Bab-el-Mandeb.

Regional Pliocene Records

Important regional records include marine sections from the Mediterranean Sea (Messinian-to-Pliocene boundary successions), continental sequences in the Siwalik Hills, Puyehue volcanic successions in Chile, and lacustrine records in the East African Rift System. High-resolution records from the North Sea Basin, Alboran Sea, Bering Sea, and Gulf of Aden have been used to reconstruct regional paleoclimates, faunal migrations, and tectonic events. Paleobotanical and palynological datasets from the Loess Plateau, Amazon Basin, and Miocene-Pliocene deposits of Australia reveal continental responses to global trends, while isotopic and paleomagnetic studies from the Ocean Drilling Program and International Ocean Discovery Program anchor global correlations.

Category:Neogene Epochs