Introduction

Quaternary and older geological deposits are a natural archive for past climate-driven changes in the sedimentary environment and thus form a context for understanding present-day and future changes. Changes in climate produce variations in the sedimentary sequences which make up the geological archive. Any change may be reflected in many sedimentological and geochemical parameters. These can include sediment colour, density, grain size, carbonate content, and clay mineralogy, as well as geochemical elements, such as sulphur or barium, which respond to palaeoredox conditions or palaeoproductivity (e.g. van Os et al., 1994). All these sedimentological and geochemical factors can also influence the magnetic properties of sediments. Conversely, magnetic properties can be used as proxy parameters for many environmental processes. Such application of magnetic principles is called ‘environmental magnetism’. The magnetic properties of sediments are, naturally, the result of many complex and non-linear processes, such as diagenesis which involves dissolution, mobilization, and precipitation. The discipline of environmental magnetism must thus necessarily utilize data from other branches of the earth sciences. Also, to further our understanding of the sedimentary and geochemical processes involved, a precise chronostratigraphic framework is mandatory. Accurate time control is essential for constraining all kinds of processes, in particular their timing and rates of change.

A major breakthrough in Quaternary chronology – with a resolution and accuracy of several kyr – has come from establishing astronomical (polarity) time-scales (APTS).