Subsurface Reference Sections of the Paranavaí Alloformation

Abstract

The Paranavaí Alloformation is a Quaternary geological formation found in the Upper Paraná River HydrographicBasin (states of São Paulo, Paraná and Mato Grosso do Sul), composed of colluvial deposits originated from the Cretaceouslithostratigraphic 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 referencesections for the Paranavaí Alloformation, core samples were collected in two regions of the western part of the stateof São Paulo. The study was conducted involving several parameters (textural, mineralogical, geochemical, isotopicand geochronological) of the sediments of the Paranavaí Alloformation and Bauru Group. Two new reference sectionswere 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 (luminescenceages between 83000 ± 8500 and 436 ± 53000 years BP). The luminescent ages obtained in this study increase according ocorritothe depth of the Paranavaí Alloformation, whereas the sediments of the Bauru Group have ages greater than the maximum limit ofthe geochronological method used. The information obtained from the reference sections shows variability in the patterns of variousparameters, proving there were different generations of colluvial deposition throughout the Quaternary period in the western part ofthe state of São Paulo.

Keywords

• Paranavaí Alloformation
• Reference section
• Colluvium
• Quaternary