Morphostratigraphy and Pedostratigraphy: using landforms and soils to subdivide strata

Morphostratigraphy and pedostratigraphy are closely related because they both reflect processes at the Earth’s surface. Morphostratigraphy is based on the surface expression of sedimentary and other rock units. It relies on geomorphological criteria to subdivide and order the landforms that are created due to surface processes (wind, water, ice etc.) on the exposed surface of rocks, other natural and anthropogenic deposits. Whilst morphostratigraphy applies to all of the Earth’s surface, emphasis for present day surfaces tends to be land surfaces because they can more easily be observed and are more variable. Submarine surface morphologies are important too and, whilst for obvious reasons these have been neglected, recent advances in high-resolution submarine bathymetry has opened up a new world of opportunities for morphostratigraphy (e.g. Gibbard et al. 2017).. Morphostratigraphy is a common approach in Quaternary studies (Hughes 2010; 2013) as this is the most recent period during which the landforms changed. It is also used extensively through remote sensing on other planets in the absence of subsurface data (Chapter 18).

Soils are weathering horizons that develop at the land surface during extended periods of geomorphic stability. They can be used as relative-age indicators, based on their maturity, since they represent weathering horizons on land surfaces. Buried soils can be important stratigraphical markers in rock successions and can potentially be utilised in rocks of all ages extending as far back as the Archean (Retallack 2018).