Geomorphology and Quaternary stratigraphy: The roles of morpho-, litho-, and allostratigraphy

The subdivision and ordering of Quaternary sediments and landforms is very often based on geomorphology. Quaternary landforms such as moraines, river terraces, palaeoshorelines, and indeed any other landform, can be arranged and ordered in time based on their relative position in the landscape. Morphostratigraphy is the subdivision of sedimentary units primarily on the basis of surface form. Whilst surface form is often used as a criterion for separating sedimentary units, morphostratigraphy also usually incorporates lithological criteria to aid stratigraphical subdivision, and morpho- and lithostratigraphy are often interlinked in Quaternary science. However, another approach–allostratigraphy–has increasingly been applied to subdivide and order Quaternary sediment landforms. Allostratigraphy uses discontinuities to subdivide sedimentary successions. Allostratigraphy enables lateral variations in lithology to be included within the same stratigraphical unit. Furthermore, it enables lithologically similar sediments stacked on top of each other to be divided into separate units based on discontinuities. This paper examines the applications of morpho-, litho- and allostratigraphy to subdivide sediment-landform assemblages and critically reviews their role in Quaternary stratigraphy.