Sedimentology of the continental Cenozoic deposits of the lower Ribeira do Iguape valley, State of São Paulo, Brasil

Abstract

Recent studies on continental deposits that occur at the lower Ribeira do Iguape river valley (southern State of São Paulo, Brasil), led to the recognition of five different stratigraphic units, namely: the Sete Barras Formation, the Pariqüera-Açu Formation, two levels of fluvial terraces, and colluvial-alluvial deposits. All these sediments were formerly attributed to the Pariqüera-Açu Formation (with stages I,IIand III), considered to be Pleistocene. This paper presents the stratigraphic and sedimentological data which support the re-definition of the Pariqüera-Açu Formation. Field work and grainsize analysis allowed to determine the main sedimentary processes for each unit. Maturity of heavy-minerals and nature of clays support the interpretation of paleoclimates. Both processes and paleoclimates pointed toward probable depositional systems and Cenozoic evolution of the area