A paleosol is a fossil soil, preserved in the geological record, that formed on a landscape surface in the past. Paleosols are important for reconstructing past climates, vegetation, and landscapes, as well as for understanding soil development and diagenetic processes over geological time scales.
Reference: Retallack, G. J. (2001). “Soils of the Past: An Introduction to Paleopedology.” Wiley-Blackwell.