Tectono-sedimentary evolution of sedimentary basins from Late Paleoproterozoic to Late Neoproterozoic in the São Francisco craton and Araçuaı́ fold belt, eastern Brazil

Abstract

Two first-order regional unconformities separate Proterozoic supracrustal rocks of the São Francisco craton and the Araçuaı́ fold belt (eastern Brazil) into three genetic units. These constitute three superimposed first-order basin-fill cycles: the Espinhaço, Macaúbas-Salinas and Bambuı́ megasequences. The Paleo-Mesoproterozoic Espinhaço megasequence (ca. 1730–1500 Ma) was deposited in an intracratonic rift-sag basin in four stages (pre-rift, rift, transitional and flexural). Each of these stages is bounded by regional, second-order unconformities. Basin evolution was controlled primarily by tectonics, although sea-level variations were also important in the transitional and flexural stages. After a hiatus of several hundred million years, subsidence renewed during extension related to the early Neoproterozoic breakup of the supercontinent Rodinia with rift to passive-margin sedimentation in the Macaúbas-Salinas Basin (ca. 950–700 Ma). Initial glaciogenic sedimentation, possibly induced by uplift related to a mantle plume, occurred in a rift setting. Subsequent a shelf/slope/deep-sea passive-margin deposits, represent opening of a northern branch of the Adamastor Ocean. Tectonic, magmatic, climatic and eustatic processes all combined to control basin evolution. The Bambuı́ megasequence (ca. 800–650 Ma) was deposited in a foreland basin during convergent and collisional tectonics related to closure of the Brazilide Ocean and generation of the Brası́lia fold belt west of the São Francisco paleocontinental region. The evolution of the Bambuı́ Basin, whose fill is characterized by three transgressive–progradational, shallowing–upward sequences, was mainly controlled by tectonic processes.