Provenance and paleogeographic reconstruction of a mesoproterozoic intracratonic sag basin (Upper Espinhaço Basin, Brazil)

Abstract

The Mesoproterozoic Conselheiro Mata Group is the uppermost sequence of the Proterozoic intracontinental Espinhaço basin that developed on the Congo-São Francisco Paleoplate. This sequence is represented by a marine shallow-water platform that experienced a sag phase followed by a rift phase in the Upper Espinhaço. We used combined sedimentological-stratigraphic descriptions of sections, whole-rock (WR) geochemistry and U-Pb detrital zircon dating to develop a regional paleogeographic evolution model of the sag phase. The succession corresponds to transgressive-regressive cycles in the following ascending order: 1) offshore to lower shoreface facies represented by quiescent periods and episodic sediment supply (Santa Rita Formation); 2) upper shoreface to foreshore and coastal desert facies with a reworking of the underlying units (Córrego dos Borges Formation); 3) lower shoreface with fallout of suspended fine sediments and a combination of unidirectional and oscillatory flows generated by storm waves (Córrego da Bandeira Formation); 4) tidal-influenced upper shoreface to foreshore facies with the migration of subaqueous dunes, wave swash in a beach environment and cycles of neap-spring tides (Córrego Pereira Formation); and 5) the resumption of lower-shoreface sedimentation and the subsequent development of a stromatolitic carbonate-siliciclastic platform (Rio Pardo Grande Formation). The geochemical data indicate that the studied units contain input from felsic rocks and sedimentary rocks. The basal marine to eolian sediments of the Galho do Miguel Formation are dominated by Rhyacian sources (2.1 Ga). The basal and intermediate units of the Conselheiro Group contain Archean, Rhyacian, Statherian and Calymmian-Ectasian (1.6-1.33 Ga) zircon grains, whereas Orosirian (1.9-2.0 Ga) sources dominate in the upper strata of the group. The study of this Stenian (Mesoproterozoic) intracratonic sequence provides clues to understanding the history of sedimentation and the potential source areas on the São Francisco Craton and adjacent areas, which are very useful for comparison to Phanerozoic intracratonic basins and the reconstruction of Paleoproterozoic and Mesoproterozoic supercontinents.

The Rio Pardo salient, northern Araçuaí orogen: an example of a complex basin-controlled fold-thrust belt curve

“…1 and 2): ■ A basement assemblage made up of units older than 1.8 Ga and represented by the Porteirinha (Noce et al 2007a, 2007b and Tingui (Knauer et al 2015) complexes, as well as the Gavião, Itabuna-Salvador-Curaçá and Jequié blocks (Marinho et al 1994, Santos Pinto et al 1998, Barbosa et al 2003, Noce et al 2007a, 2007b, Barbosa et al 2012, Cruz et al 2012a, 2012b); ■ The Serra do Inhaúma Group (Lima et al 1981, Uhlein 1991, comprised of a succession of metarhythmite, schist and quartzite. These authors correlate these rocks to the Espinhaço Supergroup deposited between 1.78 and 1.00 Ga (Dussin & Dussin 1995, Martins-Neto 2000, Chemale Jr. et al 2012, Santos et al 2015. This unit is here correlated to the lower Macaúbas Group, as described by Castro (2014), Kuchenbecker et al (2015) and ; ■ Mafic intrusive, probable correlative of the Pedro Lessa Suite dated at c. 900 Ma (Machado et al 1989, Dussin & Dussin 1995; ■ The 875 Ma Salto da Divisa anorogenic suite, composed of sieno-to monzogranites (Moraes- Filho & Lima 2007, Paixão & Perrela 2004); ■ The Macaúbas Group and its correlative, the Jequitinhonha Complex.…”

The Araçuaí Belt

“…However, a shift from a dominant 2000 Ma peak in the lower units to a 1900 Ma cluster in the upper formations can be observed in the age spectra obtained by Santos et al (2015). The maximum and minimum depositional ages of the group, respectively of 1192 and 906 Ma, are constrained by the age of the Sopa Brumadinho Formation and by mafic dykes, which cut through the whole succession (Machado et al1989;Chemale et al 2012).…”

“…The Statherian rifting is recorded in the Araçuaí belt by two pulses of felsic volcanism dated at 1770 and 1711 Ma, the emplacement of the Borrachudos anorogenic plutons around 1730 Ma, and the onset of the Espinhaço intracontinental rifting with the deposition of the Bandeirinha and São João da Chapada formations , Chemale et al 1998, 2012Fernandes et al 1994;Silva et al 2002b;Pedrosa-Soares and Alkmim 2011;Santos et al 2015).…”

“…Two other rifting and magmatic events that took place during the Mesoproterozoic are recorded by the Espinhaço sequence: (i) the Calymmian 1524 Ma acid magmatism of the Richo Seco Formation (Costa et al 2014); and (ii) the Early Stenian (1180 Ma) deposition of the diamond-bearing Sopa-Brumadinho Formation (Chemale et al 2012;Santos et al 2015). The accumulation of Sopa-Brumadinho Formations in grabens, superimposed on preexistent structures of the same nature, was followed by the generation of a large sag basin, in which the aeolian and shallow marine upper units of the Conselheiro Mata Group were deposited (Martins-Neto 2000;Santos et al 2015).…”

“…The accumulation of Sopa-Brumadinho Formations in grabens, superimposed on preexistent structures of the same nature, was followed by the generation of a large sag basin, in which the aeolian and shallow marine upper units of the Conselheiro Mata Group were deposited (Martins-Neto 2000;Santos et al 2015).…”