ESTRATIGRAFIA DO SUPERGRUPO ESPINHAÇO NA REGIÃO DE PLANALTO DE MINAS, DIAMANTINA – MG.

Abstract

In the region of Desembargador Otoni – Planalto de Minas (Northeastern Minas Gerais State, Brazil) two stratigraphics units of Precambrian age were recognized: the Espinhaço Supergroup and the Macaúbas Group. The metapelites of the Macaúbas Group (rhythmites with associated diamictites) represent varvites wuth dropstones which cover with a pronounced angular and erosional unconformity units of the Espinhaço Supergroup. This supergroup is divided in lithostratigraphic units. The Planalto de Minas Formation (at the base) is composed by a thick sequence of greenschists (originates from metabasalts) with variable composition and textures, locally with intercalations of thin quartzites and phyllites. The Tapera and Serra do Atalho formations are built up by laminated, micaceous meta-arenites and pure or micaceous meta-arenites, normally with cross bending. Respectively. Intercalations of phyllites and greenschists occur in both units, in addition the Serra do Atalho Formation contains also hematitic phyllite and a thin intercalation of metarhyolite. This volcanic, volcanoclastic, and clastics units were deposited in a basin related to the initial phase (at about 1750 Ma) of crustal extension of the Espinhaço Rift.