Record and analysis of structures related to the extensional tectonics of Macaúbas rifting in the Central ridge, north of Minas Gerais

Abstract

In the northern area of Araçuaí belt, in the central Espinhaço physiographic domain, there are records of superimposed sedimentary basins installed over the São Francisco cratonic basement. In this context, the morphostructure of the Central ridge, north of Minas Gerais, is supported by a siliciclastic succession of Espinhaço Supergroup that are superimposed to the west by the diamictic base of Macaúbas Group. These groups represent two overlapping rifting events in the end of Stenian and upper Tonian respectively. On the western edge of the Central range, high obliquity striated marks, incompatible with the Brasiliano compressional tectonics affecting these rocks, are described on bedding planes of the Sítio Novo Group succession. These marks are associated with orthogonal steps and define sliding vectors indicative of normal to normal destral movement. Associated with these lineations, veins occur, suggesting an extensional stress field, with an associated destral component. The kinematic and dynamic analysis of these structures accords the interpretation of an extensional tectonic regime, presenting a destral-transtensional nature, possibly related to the Macaúbas rifting event. In this scenario, the regional hanging wall of Macaúbas rift, represented by the Stenian succession of the Sítio Novo Group, indicates deformation under the action of an antithetic shear, with development of an associated rollover. The frontal limb layers of the rollover experienced significant magnitude of rotation, revealing high angle dip on the edge of the master fault and, then, favoring the development of interestratal slip.