New interpretation of the basal Bambuí Group, Sete Lagoas High (Minas Gerais, E Brazil) by sedimentological studies and regional implications for the aftermath of the Marinoan glaciation: Correlations across Brazil and Central Africa

Abstract

1. Introduction For several decades, outcrops showing rudite deposits at the base of the lowermost carbonate-pelite unit of the Bambui Group, like those located at km-30 marker of the MG-424 roadway near Sao Jose de Lapa (Minas Gerais, eastern Brazil), firstly described by Costa & Branco (1961) as the type-section of the rudite-bearing Carrancas Formation, have been associated with Neoproterozoic glacial events (Martins-Neto et al., 2001; Sgarbi et al., 2001; Romano & Knauer, 2003; Uhlein et al., 2004, 2012, 2016; Romano, 2007; Ribeiro et al., 2008; Kuchenbecker et al., 2013, 2016; Babinski et al., 2012; Uhlein, 2014; Reis & Alkmim, 2015). More recently, this unit has been the subject of facies and stratigraphy analysis from type-sections in the Sete Lagoas High, southern Bambui basin, which have been newly interpreted as showing no evidence of glacial Cryogenian activity (Vieira et al., 2007; Rodrigues, 2008; Tuller et al., 2010). Caxito et al. (2012) interpreted the conglomeratic unit at these outcrops, as derived from local reworking of the basal platform of the lowermost unit of the Sete Lagoas Formation, along with its underlying basement. Other outcrops in adjacent areas commonly ascribed to the Carrancas Formation were recently re-interpreted as pre-glacial units deposited along fault margins (Uhlein et al., 2012, 2016). Recent chemostratigraphic studies on this stratigraphic interval supported general correlation with the lowermost part of the Sete Lagoas Formation (S