The Origin and Development of Clay‐with‐flints and Associated Soil Horizons on the South Downs

Summary Clay‐with‐flints rests on remnants of the exhumed sub‐Eocene surface, which is shown to be an important geomorphological feature of the West Sussex Downs. Mineralogical and other soil profile studies indicate that the deposit has developed by the action of cryoturbation and soil‐forming processes on a thin cover of Reading Beds clay left on the sub‐Eocene surface during the southward recession of a small Eocene escarpment. Two horizons corresponding to Clay‐with‐flints sensu stricto of Loveday (1962) are recognized. The basal horizon is composed partly of insoluble Chalk residue, but mainly of clay moved down from overlying horizons into the spaces left on dissolution of the Chalk at the junction of the Chalk with the base of the Clay‐with‐flints. The upper horizon is composed of material from weathered remnants of Reading Beds clay, thoroughly mixed by cryoturbation with flints, other insoluble Chalk residue and clay from former basal horizons. The surface horizons of the soils often include additions of loess.