A Forma?§?￡o Gorutuba: sedimenta?§?￡o litor?￠nea a continental na margem leste da Bacia Bambu?- (MG)

摘要

In this study, we formally introduce the Gorutuba Formation, unit that encompasses the remaining coastal and continental records of the eastern margin of the Bambu?- Basin, evolved during the Brasiliano/Pan-Africano Orogeny. In Minas Gerais, the Gorutuba Formation occurs in three main localities. In Ja?-ba and Colonial ridges, the unit shows a basal layer of breccia composed by clasts of limestone in arcosean matrix, recording the erosion and reworking of the underlying Ja?-ba Formation. Arcose occurs as layers and lenses within the breccia, and becomes the main rock to the top, where shows some lenses of ortoconglomerate. In Gorutuba and Rompe Gib?￡o ridges, the unit shows the same stratigraphic pattern, but lies on the Serra da Saudade siltstones. In Buen?3polis Sincline, on the other hand, arcosean sandstone with through cross stratification and conglomerate lenses lie on siltstones from Serra da Saudade Formation, lacking the basal breccia. The Gorutuba Formation records an uplift, exposure and erosion stage of the wide Bambu?- marine platform. The basal breccia, which occurs in the northernmost areas, records an important unconformity, where the Ja?-ba carbonatic shelf was reworked by waves in response to the tectonic driven uplift. The increase of the sandstones to the top is associated to the gradual installation of a high-energy fluvial system, marking the clogging stage of the basin. The composition of the sandstones and the brecciaa??s matrix suggests the exhumation of granitic sources in the Ara?§ua?- Orogen in this period.