Abstract
Metasediments of the proterozoic Macaubas Group (Sao Francisco Supergroup) occur in great distribution and thickness (about 1 000 m) in the Upper Jequitinhonha Area. Other occurrences in Minas Gerais are found in narrow belts around the Serra do Cabral and at the western border of the Serra do Espinhaco. In the Jequitinhonha Area the sequence can be subdivided into the following lithostratigraphic units (from base to top): basal quartzites and conglomerates, pebbly metagreywackes, an alternation (sometimes graphite and manganese bearing) of phyllites, metasiltstones and quartzites, fine to medium grained quartzites and finally green schists. The metagreywackes, which were identified as tillites, show transitions of facies towards the southeast from continental tillites over aquatillites to glacial-marine sediments. Other criteria favouring a proterozoic glaciation are: grooved and polished pavements, one esker, one varved slate, and striated and facetted pebbles in flat iron form and with gouge marks. Stratigraphic, faciologic and paleostructural relationships not yet studied in detail, indicate an interfingering between the metasediments of the Bambui and the Macaubas.
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