The Quaternary Period is the geologic time period from the end of the PlioceneEpoch roughly 1.8-1.6 million years ago to the present. The Quaternary includes 2 geologic subdivisions -- the Pleistocene and the Holocene Epochs.
The term Quaternary ("fourth") was proposed by Jules Desnoyers in 1829 to address sediments of France's Seine Basin that seemed clearly to be younger than TertiaryPeriod rocks. The Quaternary Period follows the Tertiary Period and extends to the present. The Quaternary roughly covers the time span of recent glaciations, including the last glacial retreat. An occasional alternative usage places the start of the Quaternary at the onset of North Pole glaciation approximately 3 million years ago and includes portions of the upper Pliocene. Some people do not recognize the Quaternary and consider it an informal term included in the Neogene, as can be seen from the 2003 edition of the International Stratigraphic Chart, published by the International Commission on Stratigraphy.
The 1.8-1.6 million years of the Quaternary represents the time during which recognizable humans existed. Continental drift of less than 100km is largely irrelevant to such a short time period. The climate was one of periodic glaciations with continental glaciers moving as far from the poles as 40 degrees latitude. Few major new animals evolved, again presumably because of the short -- in geologic terms -- duration of the period. There was a major extinction of large mammals in Northern areas at the end of the Pleistocene Epoch. Many forms such as the sabertooth cat, mammoths, mastodons, glyptodonts, etc., became extinct worldwide. Others, including horses, camels and cheetahs became extinct in North America.
In a recent revision of the international classification of geological timeperiods, the Quaternary was subsumed into the Neogene.
The term Quaternary ("fourth") was proposed by Jules Desnoyers in 1829 to address sediments of France's Seine Basin that seemed clearly to be younger than TertiaryPeriodrocks.
Considerable confusion exists on this point; various formations originally assigned to the Quaternary have had to be transferred to the Pliocene, and there are still some supposed Quaternary formations, such as the Mesa and El Milagro, whose Quaternaryage (at least as a whole) is doubtful.
The coastal lagoons are of Holoceneage, and formerly had an extension much greater than at present; in large part they have been filled by terrigenous and even by marine deposits, which form the greater part of the coastal flats.
The Quaternary formations, especially the alluvium and the moraine deposits, deserve special study because of the insecurity and permeability which characterize them, factors which render difficult the construction and conservation of important public works built on them, such as highways, dams, buildings, etc. The Andean regions are a good example of this problem.
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