Sequence stratigraphic framework of Proterozoic successions in eastern Brazil

First-order regional unconformities separate Proterozoic supracrustal rocks of the gas-bearing São Francisco craton and surrounding thrust-and-fold belts (eastern Brazil) into four genetic stratigraphic units, which constitute 1st-order basin-fill sequences (Espinhaço, Canastra–Paranoá–Vazante, Macaúbas and Bambuí sequences).The Espinhaço 1st-order sequence (ca. 1.73–1.50 Ga) records a stage of aborted lithospheric stretching of the São Francisco-Congo continental mass. The Espinhaço basin displays a “steer's-head” geometry, where four 2nd-order sequences are recognized (prerift, rift, transitional and flexural). Third-order rift-propagation unconformities allowed the definition of three 3rd-order synrift sequences within the rift 2nd-order sequence. The 2nd-order flexural sequence of the Espinhaço basin can be subdivided into three 3rd-order transgressive–regressive sequences.The Canastra–Paranoá–Vazante and Macaúbas 1st-order sequences (ca. 1200–630 Ma) comprise rift to drift successions deposited during the breakup of the supercontinent Rodinia and the opening of the Brazilide and Adamastor oceans, respectively, to the west and east of the São Francisco paleocontinent.According to seismic data, the passive-margin Canastra–Paranoá–Vazante 1st-order sequence can be divided into two 2nd-order sequences: rift and passive margin. The passive-margin 2nd-order sequence can be further subdivided into three 3rd-order sequences. The outcropping Canastra–Paranoá–Vazante sequence consists mainly of shallow-marine deposits, which contain black shales/marls with intervals showing high total organic carbon (TOC) contents, comprising one of the highest potential hydrocarbon source rocks of the São Francisco basin.The Bambuí foreland 1st-order sequence (ca. 750–550 Ma) formed as a consequence of thrust loading related to shortening in the Brasília fold belt on the western flank of the São Francisco craton, during the closing of the Brazilide ocean and the assembly of the West Gondwana supercontinent. The Bambuí sequence shows two distinct successions, which reflect the main basin paleogeographic settings: foredeep and flexural ramp. Three transgressive–progradational 2nd-order sequences can be recognized in the ramp succession of the Bambuí basin.