CANAL DE PEREIRA BARRETO: LOCAL DE TRANSIÇÃO ENTRE OS ARENITOS CAIUÁ, SANTO ANASTÁCIO E ADAMANTINA

Abstract

In northwestern region of the State of São Paulo there is being built the Pereira Barreto Channel, which will establish a linkage between the reservoirs of the Ilha Solteira (Paraná River) and Três Irmãos (Tietê River) water power plants, the lattest under construction. This channel cuts Cretaceous sandstones, whose field characteristics could be observed on outcrops of the portion digged until about the middle of the last year, allowed us to assume that they mostly belong to Santo Anastácio Formation. It is followed in importance by the sandstones of Caiuá and Adamantina formations, ali of them belonging to the Cretaceous Bauru Group. They are superimposed by a weathering mantle of variable thickness, here named residual soils, which represent post-Cretaceous weathering product of the sandstones. Moreover, there are also colluvial sediments followed by alluvial sediments, probably both Cenozoic. The grain size analysis of these sediments have allowed us to confirm both the presence of the lithological units recognized duríng the field surveys, as well as their essentíally fluvial sedimentary paleoenvironments. The transition between the Cretaceous units is gradual and probably intertonguing, as assumed by several authors. In this way, their Iimits could be outlined only more-or-Iess arbitrarily. The lenticular calcrete beds and the c1ay mineralogy of the Santo Anastácio Formation, when interpreted in the geological context in which they are inserted, give an opportunity to interpret that during its sedimentation the paleoclimate must have been warm and dry (semi-arid)