Abstract
Abstract The Moeda Formation (Caraca Group, base of Minas Supergroup) registers the initial rift stages of the Minas Basin in the Quadrilatero Ferrifero, Southern Sao Francisco craton, SE-Brazil. We present stratigraphic and U-Pb detrital zircon dating analyses of the Moeda Formation that contribute to the comprehension of its sedimentary evolution in the southernmost Gandarela and Ouro Fino synclines (Central-Eastern Quadrilatero Ferrifero). The Moeda Formation sequence consists of a basal proximal alluvial fan with clast-supported conglomerates, grading upward into an alluvial floodplain with quartz arenites, and upper massive sandstones from distal fluvial fans. Because the Moeda Formation is normally limited by similar lithologies at both its base (Nova Lima Group, Rio das Velhas Supergroup) and top (Batatal Formation, uppermost Caraca Group) and stratigraphic inversion has occurred in the study area, U-Pb detrital zircon dating was also extended to these units to differentiate them stratigraphically. The youngest clusters of detrital zircon ages in the Nova Lima Group and Moeda and Batatal formations were 2716, 2777 and 2786 Ma, respectively. Based on our data and relevant literature, the depositional age of the Moeda Formation was interpreted as between 2716 and 2520 Ma with the Mesoarchean continental crust, the Rio das Velhas Supergroup and the Archean TTG complexes as its main source areas.
Highlights
Embryonic stages of continental rifting are characterized by the formation of small wedge-shaped depocenters bounded by isolated normal faults segments (Lewis et al 2015), representing the first tectonic steps, which precedes the development of overall drift phases (Condie 2014).The deposition of syn-rift units reflects ongoing fault activity that controls the uplifting of the basement blocks and the basin fill architecture, as well as its depositional environments (Lewis et al 2015)
The stratigraphic sequence of the Moeda Formation can be subdivided into three lithofacies associations in the Gandarela syncline (ALG1, ALG2, ALG3) and three others in the Ouro Fino syncline (ALOF1, ALOF2 and ALOF3)
The ALG3 and ALOF3 represent the top sequences, which are related to distal zones in fluvial fan deposits, mainly constituted by massive sandstones;
Summary
Embryonic stages of continental rifting are characterized by the formation of small wedge-shaped depocenters bounded by isolated normal faults segments (Lewis et al 2015), representing the first tectonic steps, which precedes the development of overall drift phases (Condie 2014).The deposition of syn-rift units reflects ongoing fault activity that controls the uplifting of the basement blocks and the basin fill architecture, as well as its depositional environments (Lewis et al 2015). There is a special meaning for those Proterozoic analogs, in which provenance studies have been successfully
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