Subsurface reference sections of the Paranavaí alloformation

Abstract

The Paranavaí Alloformation is a Quaternary geological formation found in the Upper Paraná River Hydrographic Basin (states of São Paulo, Paraná and Mato Grosso do Sul), composed of colluvial deposits originated from the Cretaceous lithostratigraphic units of the Paraná Basin. The sedimentary deposits are reddish brown in color, sandy, non-consolidated, homogeneous, massive, and commonly confused with surface soils and formations. In order to obtain subsurface reference sections for the Paranavaí Alloformation, core samples were collected in two regions of the western part of the state of São Paulo. The study was conducted involving several parameters (textural, mineralogical, geochemical, isotopic and geochronological) of the sediments of the Paranavaí Alloformation and Bauru Group. Two new reference sections were obtained in order to establish the composite-stratotype of its constituent formations: Rancharia reference section (luminescence ages between 71650 ± 9000 and 557000 ± 65000 years BP) and Oriente reference section (luminescence ages between 83000 ± 8500 and 436 ± 53000 years BP). The luminescent ages obtained in this study increase according to the depth of the Paranavaí Alloformation, whereas the sediments of the Bauru Group have ages greater than the maximum limit of the geochronological method used. The information obtained from the reference sections shows variability in the patterns of various parameters, proving there were different generations of colluvial deposition throughout the Quaternary period in the western part of the state of São Paulo.