A significant number of silicified eolian sandstone occurrences have been identified particularly within the Caiua Group, because of eodiagenetic processes attributed to hydrothermal activity. The Caiua Group is part of Bauru Basin, a supersequence located in the southwestern region of Brazil and the northeastern part of Paraguay, which was filled during the Late Cretaceous. The primary objective of this study was to evaluate the hydro thermal origin hypothesis through the analysis of fluid inclusions in silica cements, focusing on the determination of entrapment temperatures (via microthermometry) and fluid composition. The results revealed:1) high entrapment temperatures ranging from 240.1 to 405.8 degrees C, significantly exceeding those typically associated known burial diagenetic processes; and 2) low salinity values of trapped fluids, between 1.2 and 6.0 mass equivalent in NaCl. These findings support the interpretation of a hydrothermal origin for the silicification processes, which occurred under shallow burial conditions in an intracontinental setting characterized by arid semi-arid climatic conditions and limited water availability. The migration of hot fluids, as well as the presence of regional heat sources, was likely controlled by regional tectonic structures such as the Ponta Grossa Arch (NW SE) and NE-SW-trending fault zones.