Micromorphology of loess–paleosol sequences: a record of paleoenvironmental change

The record of paleoenvironmental change retained within thin sections from loess–paleosol sequences is discussed with reference to case studies from western Europe, China and northwestern USA. The paleoenvironmental significance of individual micromorphological features such as calcitic concentrations, clay coatings and cryogenic structures are first evaluated, and the value of recognising and interpreting microstratigraphic relationships of features in terms of paleoenvironmental change is illustrated. Recent developments have seen a greater emphasis on using micromorphology within a pedosedimentary approach, whereby both pedogenic and sedimentary processes are taken into account when interpreting loess–paleosol sequences. This has led not only to the acquisition of important information on conditions during phases of enhanced loess accretion and periods of climatic transition, but also to an increased awareness of spatial changes in processes and environmental controls during particular time periods. Micromorphologically based reconstructions have enabled the isolation of key stages of pedosedimentary development, although absolute dating of stages is often limited by lack of age controls. A novel approach aimed at addressing this limitation, afforded by presence of datable tephra in microstratigraphic association with key micromorphological features, is discussed.