The Tectonic interaction between the Paramirim Aulacogen and the Araçuaí Belt, São Francisco craton region, Eastern Brazil

Abstract

The Paramirim aulacogen, hosted in the northern part of the São Francisco craton, corresponds to two superimposed and partially inverted rifts of Paleo and Neoproterozoic ages. The Rio Pardo salient of the Araçuaí belt defines the local limit of the craton and interferes with the aulacogen structures. In order to understand the mechanism and timing of the tectonic interaction between these tectonic features during the inversion processes, a structural analysis was undertaken in the southern Paramirim aulacogen and along the Rio Pardo salient. The results obtained indicate that the Rio Pardo salient formed during an early stage of closure of the Neoproterozoic Macaúbas rift system and consequent initiation of the Araçuaí orogen. The orogenic front propagated further northwards into the craton, causing a first stage of inversion in the southern terminus of the aulacogen trough. Subsequently, the Paramirim aulacogen experienced the main stage of inversion, which led to the development of a NNW-oriented basement involved fold-thrust system. These fabric elements overprint the Rio Pardo salient, and the structures of both the first and second stages of inversion affect the Salitre Formation, the youngest Neoproterozoic unit of the area, clearly indicating a Late Neoproterozoic maximum age for all the inversion stages of the Paramirim aulacogen.

Tectonic inversion of compressional structures in the Southern portion of the Paramirim Corridor, Bahia, Brazil

“…In the site where a pure extension regimen was seen, the extension orientation was the same as that interpreted by Alkmim et al (2006) and Cruz and Alkmim (2006) for the regional shortening, but in the opposite direction.…”

“…It reflects a regional stress field oriented WSW-ENE ). In the southern portion of the Aulacogen, two sets of older deformation structures were hierarchized by Cruz and Alkmim (2006) as D a and D p , respectively. The D a structures are represented by schistosity (sensu Fettes & Desmons 2007) and gneissic banding, which are parallel to each other and positioned at a low dipping angle, as well as by high rake stretching lineation and sheath folds that mark the Rio Pardo Salient .…”

Sedimentary cycles in a Mesoproterozoic aeolian erg-margin succession: Mangabeira Formation, Espinhaço Supergroup, Brazil

“…1a) and comprises Archean/Palaeoproterozoic basement rocks composed of metamorphic and supracrustal rocks, which are overlain by a Palaeoproterozoic to Phanerozoic sedimentary cover succession (e.g., Almeida, 1977;Barbosa et al, 2004;Cruz and Alkmim, 2006;Alkmim and Martins-Neto, 2012). One the main physiographic feature of the São Francisco Craton is the Chapada Diamantina Range (Fig.…”

Evolução estrutural e térmica de um batólito sin-cinemático no orógenos Neoproterozóico Araçuaí (leste do Brasil)

“…mainly sedimentary cover and few basement materials. To the North of the belt, the North-South trend is disturbed by the limit of the craton and by the interactions with the Paramirim corridor (Cruz and Alkmim, 2006). On Congo side, the external domain also present orogen parallel foliation but with gently dipping to the West, suggesting a thrusting onto the Congo craton.…”

“…Even if there no clear evidence of ocean spreading, a continental rift stage is described, evidenced by the Neoproterozoïc deposits of the precollisional Araçuai and São Francisco craton basins (Pedrosa-Soares et al, 1992Uhlein et al, 1998a). This ocean opening may be related to the presence of the Paramirim / Espinhaço aulacogen that was formed at ~850 Ma (Cruz and Alkmim, 2006). forming the so-called Macaúbas rift system (Pedrosa Soares et al, 1992Tack et al, 2001).…”