Neogene

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Neogene Period is a unit of geologic time consisting of the Miocene, Pliocene, Pleistocene, and Holocene epochs. The Neogene Period follows the Paleogene Period.

In the past, the terms Neogene System and Upper Tertiary System have been used to describe what is currently called the Neogene Period. At that time, the Neogene ended with the beginning of the Quaternary, i.e. stopped at the Pliocene-Pleistocene boundary.

At present, there is a movement amongst geologists (particularly Neogene Marine Geologists) to also include ongoing geological time (Quaternary) in the Neogene, while others (particularly Quaternary Terrestrial Geologists) insist the Quaternary to be a separate Period of distinctly different record. The somewhat confusing terminology and disagreement amongst geologist on where to draw what hierarchical boundaries, is due to the comparatively fine granularity of time units as time approaches the present, and due to geological preservation that causes the youngest sedimentary geological record to be preserved over a much larger area and reflecting much more environments, than the slightly older geological record. By dividing the Cenozoic era into three (arguably two) periods (Paleogene, Neogene, Quaternary) instead of 7 epochs, the periods are more closely comparable to the duration of periods in the Mesozoic and Paleozoic eras.

The Neogene covers roughly 26 million years. During the Neogene mammals and birds evolved considerably. Most other forms were relatively unchanged. Some continental motion took place, the most significant event being the connection of North and South America in the late Pliocene. Climates cooled somewhat over the duration of the Neogene culminating in continental glaciations in the Quaternary Era that follows, and that saw the dawn of the genus Homo.

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