Quaternary ( /kwəˈtɜːrnəri, ˈkwɒt.ərˌnɛr.i/ kwə-TUR-nə-ree, KWOT-ər-nerr-ee) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS).[4] It follows the Neogene Period and spans from 2.588 ± 0.005 million years ago to the present.[4] The Quaternary Period is divided into two epochs: the Pleistocene (2.588 million years ago to 11.7 thousand years ago) and the Holocene (11.7 thousand years ago to today, although a third epoch, the Anthropocene, has been proposed but is not yet officially recognized by the ICS).[4] The informal term "Late Quaternary" refers to the past 0.5–1.0 million years.[5]

2.588 – 0 Ma
Mollweide projection of the present-day Earth.
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Chronological unitPeriod
Stratigraphic unitSystem
Time span formalityFormal
Lower boundary definition
Lower boundary GSSPMonte San Nicola Section, Gela, Sicily, Italy
37.1469°N 14.2035°E / 37.1469; 14.2035
GSSP ratified2009 (as base of Quaternary and Pleistocene)[3]
Upper boundary definitionPresent day
Upper boundary GSSPN/A
GSSP ratifiedN/A
Atmospheric and climatic data
Mean atmospheric O
c. 20.8 vol %
(104 % of modern)
Mean atmospheric CO
c. 250 ppm
(1 times pre-industrial)
Mean surface temperaturec. 14 °C
(0 °C above modern)

The Quaternary Period is typically defined by the cyclic growth and decay of continental ice sheets related to the Milankovitch cycles and the associated climate and environmental changes that they caused.[6][7]