Thermotectonic and fault dynamic analysis of Precambrian basement and tectonic constraints with the Parana basin

Abstract

The Precambrian crystalline basement of southeast Brazil is affected by many Phanerozoic reactivations of shear zones that developed during the end of the Neoproterozoic in the Brasiliano orogeny. These reactivations with specific tectonic events, a multidisciplinary study was done, involving geology, paleostress, and structural analysis of faults, associated with apatite fission track methods along the northeastern border of the Parana basin in southeast Brazil. The results show that the study area consists of three main tectonic domains, which record different episodes of uplift and reactivation of faults. These faults were brittle in character and resulted in multiple generations of fault products as pseudotachylytes and ultracataclasites, foliated cataclasites and fault gouges. Based on geological evidence and fission track data, an uplift of basement rocks and related tectonic subsidence with consequent deposition in the Parana basin were modeled. The reactivations of the basement record successive uplift events during the Phanerozoic dated via corrected fission track ages, at 387 ± 50 Ma (Ordovician); 193 ± 19 Ma (Triassic); 142 ± 18 Ma (Jurassic), 126 ± 11 Ma (Early Cretaceous); 89 ± 10 Ma (Late Cretaceous) and 69 ± 10 Ma (Late Cretaceous). These results indicate differential uplift of tectonic domains of basement units, probably related to Parana basin subsidence. Six major sedimentary units (supersequences) that have been deposited with their bounding unconformities, seem to have a close relationship with the orogenic events during the evolution of southwestern Gondwana.