O Supergrupo Espinhaço na Serra do Cabral, Minas Gerais: contribuição ao estudo de proveniência sedimentar

Abstract

The Cabral Hill is a geomorphological feature of Minas Gerais relief where the Espinhaço Supergroup lithotypes upper part partially crops out inside the São Francisco craton as slightly deformed and metamorphosed covers. These lithotypes represents the Galho do Miguel, Santa Rita, Córrego dos Borges, Córrego Bandeira e Córrego Pereira formations, the two last units only occurring on the hills western flank. These formations were approached from the sedimentary provenance point of view by seven detailed sections 1:200 supported by macro and micropetrography (combined to catodoluminescence), detrital zircons geochronology and geochemistry analysis. A regional mapping stage 1:100.000 had preceded the detailed stage providing structural and stratigraphic informations about the area aiming at the logistics of the second stage. The focus units were deposited in an intracratonic basin covered by a shallow sea with no pronounced slopes and with a wide connection to the ocean for the most part of its sedimentary filling. This basin had a NW paleoslope during the most part of its sedimentary filling and suffered sudden changes with calm and stormy periods. The study area basal unit is the Galho do Miguel Formation composed of mature sandstone deposited in an aeolian environment with N-S main wind direction followed by coastal to shallow marine environments dominated by waves with sedimentary transport to S and SW. This unit had extra basinal sediment inputs coming from mixed varied sources. The Conselheiro Mata Group is represented by two transgressive-regressive cycles marked by two feldspatic pelitic units (Santa Rita and Córrego Bandeira formations) intercalated by two psammitic units (Córrego dos Borges and Córrego Pereira formations). For the fine grain units prevails a shelf marine environment partially over storm wave base and for the psammitic units a coastal to shallow marine environment under wave, tides and oceanic currents. To this group there were hybrid sediment input (intra and extra basinal) with acting proximal high potassium source (N) and varied mixed sources.