The study of geologic–climatic units, which are climatic episodes defined in Quaternary rocks. They are similar to chronostratigraphic units (i.e. they are inferential), but their boundaries are diachronous. They record the effects of climate (i.e. the type of biota, soils, etc.), but not the climate itself, and therefore complications arise when planning boundaries. It would be difficult to envisage a stratigraphic scheme which did not recognize the influence of climate in the Quaternary.