CENOZOIC TECTONIC REACTIVATION IN AN ANCIENT SHEAR ZONE
Reactivation, Shear Zone, Cenozoic, Faults, Geomorphic
Old shear zones in an intraplate environment can be reactivated by more recent tectonic events. In the region of São Tomé das Letras and its surroundings, the reactivation of the Caxambu Shear Zone in the Cenozoic had a major influence on the shape of the relief and the drainage network. The combination of modern techniques, including the application of geomorphic indices, qualitative and quantitative geomorphological analysis, together with structural mapping (faults, fractures and striations) and paleotension analysis, enabled a detailed investigation of the structures affecting the region. With the results obtained, the dominant structural trends were defined, with the main direction being E-W and NE-SW, and the occurrence of six tectonic events: NE-SW thrust, NE-SW sinistral transpression, E-W sinistral transpression, NW-SE distension, NE-SW destral transtension and NE-SW sinistral transcurrence. Together, these data suggest that the old structures have been reactivated and are responsible not only for the current conformation of the relief, but also for deviations in drainage, anomalies, the formation of rapids, valleys and waterfalls.