LITHOSTRUCTURAL AND MORPHOTECTONIC RELATIONSHIPS OF THE BUFADEIRA HYDROGRAPHIC BASIN – FAXINAL/ PR

Abstract

The Bufadeira River basin is located in the municipality of Faxinal, in the context of the transition between the Second and Third Plateaus of Paraná, consisting of sedimentary and igne- ous rocks from the Rio do Rasto, Pirambóia, Botucatu and Serra Geral formations, all belonging to the to the Paraná Sedimentary Basin. The most important Cenozoic formations are represented by alluvial fans covered by sandy and clayey colluvium that occupy the foothills of the steep limits of the mountain range, as well as colluvial-alluvial covers close to the fluvial channels. The present study aimed to study the lithostructural controls exerted on the relief modeling, as well as the influences of regional structures on the Bufadeira watershed. Block sequences limited by normal faults in the NE-SW direction, associated with the peripheral zone of the High Structural of Mauá da Serra, condition the morphotectonic framework of the area. Based on the analysis of the structural features, two morphotectonic compartments were defined: the Morphotectonic Compartment of the Basalt Summit (CMCB), which is divided into three subcompartments: the Morphotectonic Subcompartment of the High Structural Surfaces (SMASE), the Morphotectonic Subcompartment of the Intermediate Unleveled Surfaces (SMSID) and the Morphotectonic Subcompartment of the Low Unleveled Surfaces (SMBSD). The second compartment is represented by the Morphotectonic Compartment of Inhumed Surfaces (CMSI). These compartments are limited by scarps that show marked differential erosion, combined with normal domino-style faults, with subvertical N60E direction. Normal subvertical domino-style faults were recorded in the Rio do Rastro Formation affecting Cenozoic cover deposits, indicating the possibility of neotectonic events in the morphogenetic conditioning of the landscape, although this still needs further investigation for its confirmation.