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

Alice Fernanda Costa,André Danderfer Filho

doi:10.1590/2317-4889201720160128

Alice Fernanda Costa, André Danderfer Filho

Open Access

https://doi.org/10.1590/2317-4889201720160128

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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.

Highlights

Important tectonic cycles occurred during the Proterozoic Eon, including orogenic events such as the Grenvillian Cycle
We introduce Barrinha Member as a dis‐ tinct rock unit within Rio Peixe Bravo Formation, which was not detected in previous works and mainly includes conglomerate and minor sandstone and mudstone beds
Santo Onofre Group records the infill of a Tonian, extensional/transtractive basin developed along the north‐ ern and central Espinhaço regions and succeeded the Sítio Novo basin‐fill succession

Summary

Introduction

Important tectonic cycles occurred during the Proterozoic Eon, including orogenic events such as the Grenvillian Cycle (ca. 1,200 – 1,000 Ma, Gower & Krogh 2002, Li et al 2008, Cordani et al 2010). 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 (Li et al 2008, Ernst et al 2008) These processes operated diachronically through a continen‐ tal mass, and the full disintegration of the continent was complete at the end of the Tonian Period (Hoffman 1991, Li et al 2008, Cawood et al 2016). Investigations of these features have provided a bet‐ ter understanding of the space‐temporal evolution of the Rodinia, for reconstructions (Hoffman 1991, Meert 2001, Li et al 2008)

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Discussion

Conclusion