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The Neogene Barreiras Formation is composed of continental to shallow marine sedimentary rocks that fringe the Brazilian Atlantic coast. Due to the large outcropping extent, various open questions about the evolution of this unit are still under debate. We present new U–Pb detrital zircon age spectra of four samples from the southern Espírito Santo state (Marataízes section) and two samples from the southern Bahia state (Arraial section). In both of the studied outcrops, a basal succession composed of coarse-grained cross-bedded sandstone, conglomerate and arkose with mudstone and claystone intercalations is superposed by an upper succession composed of massive sandstone, conglomerate and wacke. The U–Pb detrital zircon age spectra of all samples are dominated by Cambrian and Neoproterozoic grains. However, while the lower portion of both sections is dominated by Ediacaran-Cambrian grains, their upper portions also present significant Cryogenian-Tonian and sparse Paleoproterozoic (mainly Rhyacian and Statherian) and Neoarchean grains. This marks an important provenance shift within the Barreiras Formation, with a simple, local provenance sourced from the G1 to G5 granite supersuites of the Brasiliano Araçuaí Orogen for the basal layers contrasting with exposure of older basement rocks and Neoproterozoic anorogenic suites during deposition of the superior layers. We interpret the lower coarse sandstone and arkose-rich succession as deposited in an alluvial setting, with mud/claystones related to local flooding plains. Tectonic movements related to the evolution of the Atlantic passive margin, as described in previous works, caused a renewed uplift of the basement areas, exposing and denuding older rocks. Then, the upper layers deposited through debris flows covering the first succession. Further geochronological data is needed to test if the erosional event responsible for exposure of older basement rocks and sourcing of the upper layers would correspond to the Tortonian Sea level fall, related to growth of the Antarctic ice sheet to its present size. In this case, deposition of the lower succession would have occurred during the early Miocene, and the upper succession during the Pliocene. Our results shed light in the complex evolution of the sedimentary rocks generally grouped under the Barreiras Formation, and suggest important tectonic and climatic shifts during the Neogene evolution of the Brazilian Atlantic coast. • Detrital zircon U–Pb analysis of two sections of the Barreiras Formation • Source areas dominated by late Neoprotezoic to Cambrian sources (G1-G5 plutons) • Archean-Paleoproterozoic basement exposed in the source areas upsection • Tectonic, climatic and sea-level changes were possible provenance shift drivers • Complex evolution of the sedimentary rocks of the Barreiras Formation [ABSTRACT FROM AUTHOR]

The precursor basin of the Araçuaí – West Congo Orogenic System (AWCO) formed a large gulf within the São Francisco – Congo Paleocontinent (SFCP), where the diamictite-bearing Macaúbas Group was deposited during the Neoproterozoic. However, the lack of robust age constraints on the Cryogenian glaciogenic successions prevents correlation to one or both of the Cryogenian Snowball Earth glaciations. The present study introduces new field data and new U–Pb detrital zircon data from diamictite-bearing units on the southern margin of the São Francisco Craton, in the northeastern Araçuaí Orogen. This region is much closer to possible Ediacaran-Cryogenian igneous rocks of the southern São Francisco craton than other regions previously studied for the Macaúbas Group, enhancing the probability of detecting detrital minerals from those rocks, if they were involved as source areas. In the studied region, the Macaúbas Group is composed of metadiamictite with sparse clasts and schistified metagraywacke with bulk mineralogy similar to the quartz-muscovite-feldspar matrix of the metadiamictites. U–Pb (LA-MC-ICP-MS) dating of 182 detrital zircon grains from the Lower Chapada Acauã Formation forming the syn-glacial sequence yielded main age peaks at 939 ± 3 Ma, 1409 ± 10 Ma, 1822 ± 8 Ma, 2044 ± 7 Ma, 2551 ± 9 Ma and 3103 ± 19 Ma. The youngest concordant zircon grain found in this study aged 753 ± 12 Ma. U–Pb (LA-MC-ICP-MS) dating of 104 zircon crystals from a granitic clast recovered from the diamictite exhibits highly discordant data plotting in distinct Discordia lines with upper intercept ages of 2.0 Ga, 2.5 Ga, 2.6 Ga and 3.2 Ga, indicating derivation from the adjacent cratonic basement. The U–Pb age spectra suggests important contribution from the Archean and Paleoproterozoic basement of the São Francisco – Congo paleocontinent and metamorphic complexes, from the Mesoproterozoic intrusive and volcanic rocks of São Francisco Craton, and from the Tonian Salto da Divisa Suite. Despite the relative abundance of Cryogenian zircon grains in the surrounding prospective source areas, the studied rocks lack this interval age. The glaciogenic events in the Macaúbas basin system probably did not sample rocks with these age intervals due to the general characteristics of this type of deposit or because the sources were not exposed. Thus, the lower diamictite-bearing units of the Macaúbas Group in the northeastern São Francisco craton were deposited after ca. 753 Ma, but their correlation to either the Sturtian or Marinoan global glaciations remain speculative. • U–Pb detrital zircon data of Chapada Acauã Formation reveals a younger sedimentation age. • Top diamictite bearing unit of Macaúbas Group with Upper Tonian detrital contribution. • Data corroborates coevality of Upper Macaúbas basin system and Jequitinhonha Complex. [ABSTRACT FROM AUTHOR]

Sedimentary basins with epiclastic and volcanoclastic components are important geotectonic components for understanding the complex evolution of orogenic systems. The age, provenance and tectonic setting of ancient basins are, however, often hard to constrain, especially in the high-grade core of ancient mountain belts where original sedimentary and stratigraphic relations have been largely obliterated by deformation and metamorphism. In this case, analytical tools such as whole-rock geochemistry and U–Pb and Lu–Hf analyses on detrital zircon grains can be deployed to unravel the provenance and tectonic setting of high-grade metasedimentary and metavolcaniclastic units. Here, we apply these analytical tools on samples from gneissic paleosomes of migmatites found in the eastern transition zone between the Neoproterozoic–Eopaleozoic Araçuaí and Ribeira orogens (southeastern Brazil). The studied paleosomes comprise peraluminous paragneiss rich in biotite, garnet and sillimanite, metaluminous hornblende-bearing gneiss free of peraluminous silicates, and intermediate terms between these compositions, all of them with geochemical characteristics pointing to sources located in magmatic arc systems. Overall, U–Pb data from detrital zircon grains bracket a maximum sedimentation age for all samples between 600 and 627 Ma, while εHf (t) : +5.7 to −18.7 and Hf T DM model ages of 1.0–2.2 Ga suggest moderately juvenile to evolved sources for the gneiss protoliths. However, despite the similarity in age range, the analyzed samples show contrasting isotope data indicating significant variability in the source areas. Sample 7 only has grains with negative εHf (−5.9 to −18.7), most of them ranging in age from 708 Ma to 758 Ma, with very few older (1021–1143 Ma) and younger (642–651 Ma) zircons grains, indicating evolved crustal sources of distinct ages (e.g., the Late Tonian – Early Cryogenian South Bahia Alkaline Province, the Early Cryogenian magmatism found in the West Congo Belt, the Stenian to Early Tonian Espinhaço and Matadi-Noqui igneous rocks, and magmatic rocks of the early Rio Doce arc). Conversely, sample 13 has twenty grains with positive εHf values and ages between 602 and 758 Ma, suggesting sourcing from (meta)igneous rocks of the Rio Negro arc and their remelting products, and forty grains with negative εHf values with ages between 591 and 646 Ma suggesting magmatic sources in the Rio Doce arc. Additionally, the two youngest spot ages (553 Ma and 571 Ma) have highly negative εHf values (−11.1 and −16.4) suggesting their origin from collisional anatexis. Similarly, sample 12 shows detrital grains within the consistent time interval (ca. 596 Ma – 798 Ma) of the Rio Negro arc and Rio Doce arcs, reinforcing that the fragments of these arcs, or zircons that were inherited from these terranes, are potential sources to the sedimentary protoliths of the paragneisses. The regional scenario together with our field and analytical data, compared with data available in the literature, suggest the sedimentary protoliths of the studied samples filled orogenic basins related to the Rio Doce magmatic arc. Most detrital zircon ages are close to the maximum depositional age, a classical signature of orogenic basins related to magmatic arcs. The studied paragneiss unit correlates with the Nova Venécia Complex, located on the intra-arc to back-arc zones of the Araçuaí orogen, and with the orogenic succession of the distal Andrelândia Group, shared by both the Araçuaí and Ribeira orogens. Furthermore, our data also suggest the juvenile Rio Negro - Serra da Prata arc system was either amalgamated with the Rio Doce arc or that fragments of these arcs were incorporated as unmelted xenoliths and xenocrystals within the Rio Doce arc rocks before ca. 614 Ma, providing key hints to unravel the evolution of the Araçuaí - Ribeira orogenic system (AROS) and its role in the Gondwana assembly. • Paragneisses from the Araçuaí-Ribeira Orogen sourced from Ediacaran arcs. • Maximum sedimentation age for all samples between 600 and 627 Ma. • Moderately juvenile to evolved sources (εHf (t) : +5.7 to −18.7, T DM = 1.0–2.2 Ga). • Elemental geochemistry coherent with graywackes from active margin settings. • Syn-orogenic basins related to the Rio Doce (G1 Supersuite) continental-margin arc. [ABSTRACT FROM AUTHOR]