Sedimentary provenance in the southern sector of the Sao Francisco Basin, SE Brazil

We present new Sm-Nd, U-Pb and Hf isotope geochronological data for the siliciclastic rocks in the southern sector of the Sao Francisco Basin. An abrupt change in the Sm-Nd data is observed from the Carrancas Formation's oligomitic conglomerates (T-DM ages between 2.7 and 3.3 Ga; epsilon(Nd(550 Ma)) values between -25.09 and -17.98), its finer facies, and the finer facies of the the Moema Laminite (T-DM ages from 1.4 to 2.1 Ga; epsilon(Nd(550 Ma)) values between -9.46 and -5.59). No further significant changes in the Sm-Nd data occur farther upwards in the Bambui Group (Sm-Nd T-DM ages within the 1.3-2.0 Ga interval; epsilon(Nd(550 Ma)) values from -9.53 to -4.09), showing a lack of reorganization in the source areas throughout the deposition of the basin. This is yet another argument to dismiss an unconformity within the Bambui Group. The presence of the index fossil Cloudina sp. in the lower Sete Lagoas Formation makes the glaciation probably Late Ediacaran in age. U-Pb ages for detrital zircons of the Bambui Group range from the Archean to the early Ediacaran, but the current data is insufficient to distinguish between the contribution from sources in the Brasilia and Aracuai belts.