Deformação da cobertura com embasamento envolvido em caixas de areia: estudo de caso da região da Serra da Água Fria (MG), Bacia São Francisco

Abstract

Sandbox analogue models were used to investigate the structural evolution of the Agua Fria Range region, located in the northeast of the Cabral Range, at the east portion of the Sao Francisco Craton, central Brazil. We investigate the effect of different analogue material during progressive shortening of a previous extensional basin, consisting of horst and grabens detaching above an intracrustal decollement. The study focused on double vergent reverse faults above a basement high, the Boqueirao High, and on hinterland vergent fault-related folds , both in the post-rift cover sequence. Model 1 was performed entirely with brittle, colored sand whereas in models 2 and 3 we introduced a less competent layer at the cover sequence base, composed of glass microbeads and mica flakes, respectively. The three experiments demonstrate that when in inversion tectonics a basement block acts as a buttress and with progressive deformation as an indenter, doubly-verging thrusts in the post-rift cover sequence were produced. In addition, the experiments demonstrate that the presence of weak glass microbeads induces brittle-ductile behavior in the overlying sand layers. This may explain the formation of fault-propagation folds, above the Boqueirao High around the Agua Fria Range.