Quaternary

Major geochronological subdivision which includes the Pleistocene (c 1.8-2.45 million years bp) and Holocene (c 10,000 BC) epochs and marked by the appearance of near-humans and Homo sapiens. It is the second period of the Cenozoic geologic era, following the Tertiary, the youngest of the 11 periods in Earth history. These terms may also be applied to groups of deposits, which are described as the Quaternary 'System' and the Pleistocene or Holocene 'Series'. The base of the Quaternary System is defined by basal deposits that overlie Pliocene deposits. The Quaternary was marked by repeated invasions of vast areas of mid-latitude North America and northwestern Eurasia by ice sheets, the period is frequently referred to as the Great Ice Age.

The earth’s history is divided into ‘eras’: the Palaeozoic, Mesozoic and Cenozoic. The youngest, Cenozoic, era (starting at 65 million years bp) is traditionally divided into two ‘periods’: the Tertiary and the Quaternary. The Quaternary period extends up to the present day and includes two ‘epochs’: the Pleistocene and the Holocene. These terms may also be applied to groups of deposits, which are described as the Quaternary ‘system’ and the Pleistocene or Holocene ‘series’. The boundary between the Tertiary and the Quaternary is rather badly defined. Estimates for its age range from c2.4 million years bp to between 1.8 and 2.1 million years bp. The Quaternary system comprises a number of stages. It also includes deep ocean deposits, which raise a number of separate issues (see deep sea cores). Recent work has shown that both the deep sea and the land deposits of the Quaternary are more complex than had been supposed. The old schemes of alternating glacial and interglacial ‘ages’ are no longer tenable. See Tables 4-7, pages 417-20.