Tectonics and sedimentation of the central sector of the Santo Onofre rift, north Minas Gerais, Brazil

Abstract

ABSTRACT:The Santo Onofre Group registers the filling of a Tonian, intracontinental paleo-rift that developed along the northern and central Espinhaço regions. This paper examines this unit in the central Espinhaço region with stratigraphic analysis and U-Pb geochronology, reviewing and dividing into the Canatiba and Rio Peixe Bravo Formations, which include the Barrinha Member. The Canatiba Formation mainly comprises carbon-rich mudstones that were deposited through low-density turbidity flows that alternated with sediment settling under anoxic conditions. The Rio Peixe Bravo Formation consists of a succession of sandstones and minor mudstones, which were deposited through low-to high-density turbidity flows. The Barrinha Member mainly consists of conglomerates and is related to channelized debris flows. Detrital zircon grains show maximum depositional ages of 930 ± 33 Ma and around 865 Ma for the Canatiba and Rio Peixe Bravo Formations, respectively. We interpret the Santo Onofre rifting to be relative younger than that for the Sítio Novo Group and to be a precursor stage of the glacial and post-glacial rift-to-passive margin-related sequences of the Macaúbas Group. The lithostratigraphic term "Macaúbas Supergroup" would be of better use to accommodate the unconformity-bounded Tonian sequences that were related to the Rodinia breakup in the Congo-São Francisco paleocontinent. (Hoffman 1991, Meert 2001. Several phases that involved the breaking of Rodinia occurred, either through passive or active rifting, which were induced by remotely applied tensions (in-plane stress) and mantle plumes, respectively . These processes operated diachronically through a continental mass, and the full disintegration of the continent was complete at the end of the Tonian Period (Hoffman 1991, Cawood et al. 2016. Many rifts were formed before reaching this stage, some of which were aborted, and mafic dyke swarms intruded, which became dispersed in the scattered continents (Chew et al. 2010, Volkert et al. 2015. Investigations of these features have provided a better understanding of the space-temporal evolution of the Rodinia, for reconstructions (Hoffman 1991, Meert 2001. KEYWORDS:The Congo-São Francisco paleocontinent is characterized as one of several fragments of the Rodinia (Hoffman 1991. This paleocontinent encompasses the cover and basement rocks of São Francisco and Congo cratons and their marginal orogenic belts ( Fig. 1; Almeida 1977, Alkmim et al. 1993, Trompette 1994. The Espinhaço mountain range is a remarkable feature that extends with a sub-meridian direction across the entire extent of the Congo-São Francisco paleocontinent. The southern and central Espinhaço range regions integrate the Araçuaí fold and thrust belt as one of the external domains of the Neoproterozoic Araçuaí-West Congo orogen (Almeida 1977, Pedrosa-Soares et al. 1992, while the northern extension occurs along the eastern border of the Paramirim aulacogen, which was partially inverted, and involves the basement in the cover deformation (Schobbenhau...

Geological Field Guide of Montes Claros Karst, Minas Gerais

“…1). In the northern region of Minas Gerais, the basin is bounded to the east by the Araçuaí Orogen, where outcrop the Macaúbas Group rocks deposited between 750 and 667Ma (Costa & Danderfer Filho 2017, Castro et al 2020. The Neoproterozoic deformation of the Bambuí Group represents, in this region, the result of the action of the foldthrust belt of the Araçuaí Orogen, with tectonic transport from east to west.…”