Neogene

Neogene
Name	Neogene
Color	Neogene
Top boundary def	Messinian salinity crisis
Top gssp location	Oued Akrech, Morocco
Top gssp authority	International Union of Geological Sciences
Bottom boundary def	Oxygen isotope excursion
Bottom gssp location	Lemme-Carrosio, Italy
Bottom gssp authority	International Commission on Stratigraphy
Time scale	Geologic time scale
Period	Neogene
Epoch	Miocene, Pliocene
Celestial body	Earth
Usage	Global (ICS)
Timespan units	Million years ago
Timespan	23.03–2.58
Preceded by	Paleogene
Followed by	Quaternary

Neogene. The Neogene is a geologic period and system that spans from about 23.03 to 2.58 million years ago, following the Paleogene and preceding the Quaternary. It comprises the Miocene and Pliocene epochs, a time of profound transformation in Earth's climate, geography, and biota. This period witnessed the continued dominance of mammals and birds, the final stages of Alpine orogeny, and climatic shifts that paved the way for the Ice Age cycles of the subsequent Pleistocene.

Etymology and definitions

The term "Neogene" is derived from the Greek words *neos* (new) and *-genes* (born), formally introduced by the Austrian geologist Moritz Hörnes in 1853. It was originally part of a now-obsolete fourfold division of the Cenozoic era. For much of the 20th century, the International Union of Geological Sciences recognized the Neogene as extending to the present, encompassing the Pleistocene, Holocene, and recent times. However, a major revision in 2004 redefined the Cenozoic into the Paleogene, Neogene, and Quaternary periods, a decision ratified after significant debate within the International Commission on Stratigraphy. This established the current boundary at the base of the Gelasian Age, aligning the end of the Neogene with the start of major Northern Hemisphere glaciation.

Subdivisions

The Neogene Period is formally divided into two epochs: the Miocene and the Pliocene. The Miocene is further subdivided into six ages: Aquitanian, Burdigalian, Langhian, Serravallian, Tortonian, and Messinian. The Pliocene consists of two ages: Zanclean and Piacenzian. The base of the Neogene is defined by the Global Boundary Stratotype Section and Point at Lemme-Carrosio in Italy, while its top is marked by the GSSP for the Gelasian Stage at Oued Akrech in Morocco. These subdivisions are correlated globally using biostratigraphy, magnetostratigraphy, and chemostratigraphy.

Paleogeography and tectonics

During the Neogene, the continents moved close to their present positions. The collision of Africa with Eurasia closed the Tethys Ocean, creating the Mediterranean Sea and culminating in the Messinian salinity crisis. The ongoing Alpine orogeny uplifted major mountain ranges including the Alps, Himalayas, and Andes. In North America, the Basin and Range Province experienced significant extension, while the Isthmus of Panama formed in the late Pliocene, creating a land bridge between North America and South America. This tectonic connection had profound consequences for global ocean circulation and biotic exchange during the Great American Interchange.

Climate

The Neogene climate transitioned from the warm, relatively stable conditions of the early Miocene to the cooler, more variable climate of the late Pliocene. A long-term cooling trend was driven by factors such as the uplift of the Tibetan Plateau, the restriction of the Central American Seaway, and declining atmospheric carbon dioxide levels. The establishment of a permanent Antarctic ice sheet occurred near the Miocene-Pliocene boundary. By the late Pliocene, cyclical glaciations began in the Northern Hemisphere, setting the stage for the intense Ice Age cycles of the Quaternary. Evidence for these changes is preserved in deep-sea core records, particularly from the Pacific Ocean and Southern Ocean.

Life

The Neogene is often called the "age of mammals and birds," as these groups continued to diversify and dominate terrestrial ecosystems. Key mammalian developments included the radiation of bovids, cervids, and equids, as well as the evolution of many modern genera. Hominini, the tribe including humans and their close relatives, first appeared in the late Miocene with genera like Sahelanthropus and Orrorin. Marine life saw the rise of modern cetacean families and the proliferation of carcharhinid sharks. The formation of the Isthmus of Panama triggered the Great American Interchange, allowing taxa like smilodon, glyptodon, and terror birds to migrate between continents. Flora saw the expansion of grasslands and savannas, which supported new grazing communities.

See also

* Cenozoic * Paleogene * Quaternary * Geologic time scale * Messinian salinity crisis * Great American Interchange

Category:Geological periods Category:Cenozoic