The Carrancas Formation, Bambuí Group: A record of pre-Marinoan sedimentation on the southern São Francisco craton, Brazil

Uhlein, Gabriel Jubé; Uhlein, Alexandre; Halverson, Galen P.; Stevenson, Ross; Caxito, Fabrício de Andrade; Cox, Grant; Carvalho, Jorge F.M.G. de

doi:10.1016/j.jsames.2016.06.009

Cited by 38 publications

(42 citation statements)

References 63 publications

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“…4), that suggest Archean basement sources with very long crustal residence time. Similar results were also obtained for the Carrancas Formation by Uhlein et al (2016). This data set is compatible with a very close igneous source for the conglomerates and a small area of sediment sources, derived mainly from the basement valley walls in which they were deposited , Guacaneme et al 2017.…”

Section: Sedimentary Provenance and Tectonic Implicationssupporting

confidence: 86%

“…Provenance studies in the Carrancas Formation conglomerates reveal a wide range of clast assemblage varying from monomitic (Guacaneme et al 2017) to oligomitic (Kuchenbecker 2011) and polimitic , Uhlein et al 2016. The occurrence of the unit described by Guacaneme et al (2017) in Inhaúma city area is emblematic, as the conglomerate is clearly deposited in a basement valley and only has clasts of the leucogranite, which can be observed in the valley walls (Fig.…”

Section: Sedimentary Provenance and Tectonic Implicationsmentioning

confidence: 95%

“…In spite of several tectonic discontinuities, the glacial unit has correlating units in the marginal belts: the glacial formations of the Macaúbas Group in the Araçuaí Belt and the Cubatão Formation of the Ibiá Group in the Brasília Belt (Uhlein et al 1999, Dardenne 2000, Pedrosa-Soares et al 2011, Babinski et al 2012. In the cratonic area, the Carrancas Formation (Dardenne 1978) and the Moema laminites (RochaCampos et al 2011) are at the base of the Bambuí Group in the southern sector of the São Francisco Basin, although the glacial origin of the first unit is debatable , Uhlein et al 2016.…”

Section: Geological Settingmentioning

confidence: 99%

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Sedimentary provenance in the southern sector of the São Francisco Basin, SE Brazil

Paula‐Santos

Babinski

2018

Braz. J. Geol.

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Section: Sedimentary Provenance and Tectonic Implicationssupporting

confidence: 86%

Section: Sedimentary Provenance and Tectonic Implicationsmentioning

confidence: 95%

Section: Geological Settingmentioning

confidence: 99%

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Sedimentary provenance in the southern sector of the São Francisco Basin, SE Brazil

Paula‐Santos

Babinski

2018

Braz. J. Geol.

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“…This unit has glacial origin and correlates with diamictites of the Jequitaí Formation and Macaúbas Group (Martins-Neto et al, 2001;Alkmim & Martins-Neto, 2001, and glacial deposits on the West Congolian Group exposed in Africa (Babinski et al, 2012). However, some authors argue that there is no direct evidence for glacial deposition of the Carrancas Formation in the type area (Vieira et al, 2007;Tuller et al, 2009, Uhlein et al, 2016. The U-Pb maximum depositional ages based on detrital zircon are 1.4 and 1.2 Ga for the Carrancas Formation (Rodrigues, 2008;Guacaneme, 2015) and 0.9 Ga for the Jequitaí Formation (Buschwaldt et al, 1999).…”

Section: The São Francisco Basinmentioning

confidence: 99%

“…However, some authors propose that the Sete Lagoas Formation represents a cap carbonate sequence of early Ediacaran age deposited after the Marinoan glaciation, based on global correlations via isotope chemostratigraphy (i.e. Caxito et al, 2012;Alvarenga et al, 2014;Uhlein et al, 2016). To add more pieces to the puzzle, recent biostratigraphic data indicate ages of 553-542 Ma in the middle part of the sequence based on Cloudina fossil (Warren et al, 2014), which suggest a late Ediacaran age for the Sete Lagoas Formation.…”

Section: Introductionmentioning

confidence: 99%

C, O, and Sr isotopic variations in Neoproterozoic-Cambrian carbonate rocks from Sete Lagoas Formation (Bambuí Group), in the Southern São Francisco Basin, Brazil

et al. 2017

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High-resolution chemostratigraphic data of carbonates from the Sete Lagoas Formation (Bambuí Group) show large variations on the C, O, and Sr isotope compositions. Impure limestones at the base show primal δ 13 C values between -1.0 and 0‰, and δ 18 O values between -12.0 and -8.0‰. However, some dolostones demonstrate δ 13 C values varying from +2.8 to -6.8‰, highly radiogenic 87 Sr/ 86 Sr ratios (>0.7111), and low Sr concentrations (<350 ppm) related to post-depositional processes. In contrast, pure limestones at the top show very positive δ 13 C values between +8.3 and +12.8‰, δ 18 O values between -10.0 to -6.0‰, and 87 Sr/ 86 Sr ratios from 0.7073 to 0.7086, with high Sr concentrations (>900 ppm). They are linked to depositional controls on the carbonate platform, such as fluvial and/or submarine water influx, in which carbonates deposited on the proximal sector exhibit significant Sr isotopic variations and those on the distal sector were not subject to such controls, resulting in very homogeneous Sr isotope profiles. However, 87 Sr/ 86 Sr ratios of the distal carbonates are less radiogenic than carbonates expected for late Ediacaran (~0.7085). This discrepancy suggests a restricted marine basin without Sr isotopic homogenization with contemporary oceans and, in this case, global correlations based on Sr isotope stratigraphy are not reliable. KEYWORDS:Isotopes; Carbonates; Bambuí Group; Ediacaran. RESUMO: Dados quimioestratigráficos de alta resolução em carbonatos da Formação Sete Lagoas (Grupo Bambuí) apresentam grandes variações nas composições isotópicas de C, O e Sr. Os calcários impuros na base da unidade mostram valores primários de

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Interglacial dust, ocean fertilisation and Neoproterozoic earth oxygenation

DaSilva,

Pufahl,

James

2024

The Depositional Record

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Feedback processes that drove Earth's second major increase in ocean–atmosphere oxygen levels during the Neoproterozoic are poorly constrained. Variability in seawater redox over geological timescales is commonly linked to changes in the biogeochemical cycling of P and thus the rate of primary production and generation of photosynthetic oxygen. In the modern surface ocean, an important source of bioessential P and micronutrients (Fe, Cu, Co, Zn, Mo, Cr and Ni) is aeolian dust derived from deserts and arid, post‐glacial landscapes. It is interpreted herein that glacial retreat following the Sturtian (ca 717 to 660 Ma) and Marinoan (ca 650 to 635 Ma) snowball glaciations provided copious dust to the global ocean. Correlation of interglacial siltstone successions in palaeogeographical context suggests that such dust accumulation was diachronous and concentrated in the palaeo‐horse latitudes (30° N and 30° S). Delivery of this dust from continents is likely reflected in the steep increase in global radiogenic Sr isotope values (87Sr/86Sr) in post‐Sturtian carbonates, and changes in the δ18O signatures of Cryogenian zircons derived from subducted marine sediments. Accumulation of sedimentary organic matter also peaked during interglacial periods, suggesting a causal link between glaciation, aeolian dust and primary production. This relationship implies windblown dust was an important source of P and micronutrients for an evolving biological pump that stimulated primary production, enhanced burial of organic carbon and increased ocean–atmosphere oxygen concentrations. Thus, delivery of aeolian dust to the global ocean was likely critical for sustaining Earth's second major increase in oxygen. Sequestration of atmospheric CO2 in organic‐rich siltstones and shales is also interpreted to have been an important negative feedback process, which together with silicate weathering, prevented runaway greenhouse conditions during interglacial periods. The oxygen produced by this aeolian marine biological pump may have helped pave the way for the evolution of multicellular animals in the Ediacaran.

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The Carrancas Formation, Bambuí Group: A record of pre-Marinoan sedimentation on the southern São Francisco craton, Brazil

Cited by 38 publications

References 63 publications

Sedimentary provenance in the southern sector of the São Francisco Basin, SE Brazil

Sedimentary provenance in the southern sector of the São Francisco Basin, SE Brazil

C, O, and Sr isotopic variations in Neoproterozoic-Cambrian carbonate rocks from Sete Lagoas Formation (Bambuí Group), in the Southern São Francisco Basin, Brazil

Interglacial dust, ocean fertilisation and Neoproterozoic earth oxygenation

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