The Quaternary is the youngest period but also the shortest one on the stratigraphic time table. The lower boundary of the Quaternary has been modified several times but is now set on 2.6 million years (IUGS 2009). This time coincides with the reverse of the earth magnetic field, the so-called Gauss – Matuyama boundary, and the start of a series of cold and warm periods named glacial and interglacial periods .
Although the first hominoid dates already from the Neogene, human evolution took mainly place during the Quaternary.
The Quaternary is subdivided into two epochs, the Holocene and the Pleistocene. The Holocene started very recently, around 11.5 ka years ago and is still going one. It stands for an interglacial period in which the influence of humans on the natural environment and vice versa increased and even became and still is, one of the decisive factors. The Pleistocene covers the rest of the Quaternary, and as already told, consists of a succession of glacial and interglacial periods. These cyclic climatic changes are ascribed to astronomic factors determining the insolation on earth (theory of Milankovitch). These climate changes caused the expansion and contraction of ice sheets on a global scale. Land areas extended far into present sea areas as sea level dropped due to the growth of the ice sheets and retreated when sea level rose due to the ice melting. The continuous shift of land and sea surface implies a great variation in sedimentary environments, shown in rapid sequence changes and small area distribution of the deposits. Due to the strong variability of Quaternary deposits their lithostratigraphy is complex.
The major aim of the National Commission on Quaternary stratigraphy is to unravel this complexity trough direct collaboration with all researchers working daily in the field. Therefore all suggestions/propositions about the Belgian Quaternary lithostratigraphy as published on this website are most welcome and can be send to the secretary or president of the commission.
REDEFINITION OF THE BASE OF QUATERNARY SYSTEM/PERIOD, AND OF THE BASE OF THE PLEISTOCENE SERIES/EPOCH
The IUGS Executive Committee has ratified a request from the IUGS International Commission on Stratigraphy (ICS) regarding the definition of the base of Quaternary System/Period (and top of the Neogene System/Period), and redefinition of the base of the Pleistocene Series/Epoch (and top of the Pliocene Series/Epoch). The ICS submitted for IUGS ratification its recommendation that:
1) the base of the Pleistocene Series/Epoch be lowered such that the Pleistocene includes the Gelasian Stage/Age and its base is defined by the Monte San Nicola GSSP, which also defines the base of the Gelasian;
2) the base of the Quaternary System/Period, and thus the Neogene-Quaternary boundary, be formally defined by the Monte San Nicola GSSP and thus be coincident with the bases of the Pleistocene and Gelasian; and
3) with these definitions, the Gelasian Stage/Age be transferred from the Pliocene Series/Epoch to the Pleistocene.