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.
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