Plio-Pleistocene red clay deposits in the Pannonian basin: A review

Terrestrial red clays underlying Quaternary loess deposits, or filling fissures and recently existing caves in limestone are named Tengelic Red Clay Formation and Kerecsend Red Clay Formation (Middle Pliocene to Lower Pleistocene). They occur in three types in Hungary. (1) The oldest red clays are mainly in situ weathering crusts rich in kaolinite, formed in warm, humid, subtropical or monsoon climate; (2) the younger type is rich in smectite and goethite; and (3) illite and chlorite dominant in the youngest part, which formed under warm and dry climates in savannah, steppe or forest steppe environments, and is of wind-blown origin. Representative samples were selected for study from a large number of profiles. Mineralogical, some micromorphological, and geochemical investigations of typical samples of red clays in Hungary were performed. This review focuses on the origin, development and distribution in the Pannonian basin.