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

Two first-order regional unconformities separate Proterozoic supracrustal r ocks of the Sao Francisco craton and the Aracuai fold belt (eastern Brazil) into three genetic units. These constitute three superimposed first-order basin-fill cycles: the Espinhaco, Macaubas-Salinas and Bambui megasequences . The Paleo-Mesoproterozoic Espinhaco megasequence (ca. 1730-1500 Ma) was d eposited in an intracratonic rift-sag basin in four stages (pre-rift, rift, transitional and flexural). Each of these stages is bounded by regional, s econd-order unconformities. Basin evolution was controlled primarily by tec tonics, although sea-level variations were also important in the transition al 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 Macaubas-Salinas Basin (ca. 950-700 Ma). Initial glaciogenic sedimentation, possibly induced by uplift related to a mantle plume, occurred in a rift setting. Subsequen t a shelf/slope/deep-sea passive-margin deposits, represent opening of a no rthern branch of the Adamastor Ocean. Tectonic, magmatic, climatic and eust atic processes all combined to control basin evolution. The Bambui megasequence (ca. 800-650 Ma) was deposited in a foreland basin during convergent and collisional tectonics related to closure of the Brazi lide Ocean and generation of the Brasilia fold belt west of the Sao Francis co paleocontinental region. The evolution of the Bambui Basin, whose fill i s characterized by three transgressive-progradational, shallowing-upward se quences, was mainly controlled by tectonic processes. (C) 2001 Elsevier Sci ence B.V. All rights reserved.