ARGILOMINERAIS DO GRUPO CAIUÁ

Abstract

Recent studies carried out in the west of Sao Paulo and northwest of Parana states (Brazil) have lead to the characterization of clay minerals of Caiua Group (Late Cretaceous, Bauru Basin) origin and their genesis, as well as the diagenetic evolution of sandstones of the Rio Parana Formation. The most frequent clay minerals are smectite and kaolinite, which occur in similar quantities. Illite occurs secondarily in Adamantina Formation (Bauru Group). Kaolinite predominates in surface sample rocks whereas authigenic smectite is more common in subsurface samples (Rio Parana Formation). Diagenesis of sandstones of Rio Parana Formation was generally not very intense and reached only the initial stages of mesodiagenesis.