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4. Characterization of Bandeira Sedimentary Basin on Serra do Tamanduá, Northeastern Region of Quadrilátero Ferrífero, Minas Gerais, Brazil.

Author

de Campos Daher, Ana Paula, Uhlein, Gabriel Jubé, and Mattioli, Júlia

Subjects
*DRILL core analysis, *DRILL cores, *SEDIMENTATION & deposition, *CORE drilling, *CENOZOIC Era
Abstract

The Quadrilátero Ferrífero (QF) is a globally known region for its world-class metallic deposits. Although its Precambrian units have been vastly studied since the 1960s due to economic importance, the Cenozoic geological record represents an upcoming subject of interest. The occurrence of Cenozoic sedimentary deposits has been noticed since the end of the 19th century, but most of them are not yet fully characterized. This paper brings a complete description, mapping, 3D modeling, and simulations of the sedimentary deposit named Bandeira Basin, Serra do Tamanduá, QF. Based on field data, such as mapping and drill core database analysis, three drill cores were selected for further investigation and detailed description. The Bandeira Basin can be characterized and subdivided into three units: Unit A: found only in the southeast area and shows exclusively sediments from the Nova Lima Group; Unit B: intermediate unit that occurs in central and southeast areas, with Rio das Velhas Supergroup as a possible source of the sedimentary material; and Unit C: occurs at the top, and it is essentially colluvial deposits from Minas Supergroup units. The contacts between units are abrupt or erosive, recording successive deposition stages. The basin is thicker on its central and southwest ends and thinner on the east and north, where part of the basement outcrops. Cenozoic tectonic events were probably active in this area, controlling the sedimentary processes, with the NW-SE and NE-SW lineaments reactivated, triggering sediment deposition and migration to the deepest spot of the basin. These sediments were 3D modeled in Leapfrog Geo, the visualization of any given region of interest, in the modeled scale. This methodology allowed an assertive characterization of sedimentary filling and could be applied to other basins. This comprehension is important because these sediments are used indirectly or directly in civil projects. [ABSTRACT FROM AUTHOR]

Published
2024
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5. Wrapping a Craton: A Review of Neoproterozoic Fold Belts Surrounding the São Francisco Craton, Eastern Brazil.

Author

Uhlein, Alexandre, Uhlein, Gabriel Jubé, Caxito, Fabrício de Andrade, and Moura, Samuel Amaral

Subjects
*OROGENIC belts, *SHEAR zones, *ISLAND arcs, *SEDIMENTARY basins, *OCEANIC crust, *THRUST belts (Geology), *IGNEOUS intrusions
Abstract

A synthesis of the evolution of the Neoproterozoic belts or orogens surrounding the São Francisco craton (SFC) in northeastern and southeastern Brazil is presented. Emphasis is placed on recognizing the superposition of sedimentary basins, from rift to passive margin to retroarc and foreland, as well as identifying three diachronic continental collisions in the formation of the SFC. The Tonian passive margin occurs in the southern Brasília Belt with the Vazante, Canastra, and Araxá Groups. During the Tonian, island magmatic arcs and basins developed in front and behind these arcs (fore- and back-arcs). Subsequently, in the Cryogenian–Ediacaran, a retroarc foreland basin developed with part of the Araxá Group and the Ibiá Group, and finally, a foreland basin developed, which was filled by the Bambuí Group. A tectonic structure of superimposed nappes, with subhorizontal S1–2 foliation, formed between 650 and 610 Ma, is striking. In the northern Brasília Belt, there is the Stenian passive margin of the Paranoá Group, the Tonian intrusion of the Mafic–Ultramafic Complexes, and the Mara Rosa Island magmatic arc, active since the Tonian, with limited volcanic–sedimentary basins associated with the arc. A thrust–fold belt structure is prominent, with S1 foliation and late transcurrent, transpressive tectonics characterized by the Transbrasiliano (TB) lineament. The Cryogenian–Ediacaran collision between the Paranapanema and São Francisco cratons is the first collisional orogenic event to the west. In the Rio Preto belt, on the northwestern margin of the São Francisco craton, the Cryogenian–Ediacaran Canabravinha rift basin is prominent, with gravitational sediments that represent the intracontinental termination of the passive margin that occurs further northeast. The rift basin was intensely deformed at the Ediacaran–Cambrian boundary, as was the Bambuí Group. On the northern and northeastern margins of the São Francisco craton, the Riacho do Pontal and Sergipano orogens stand out, showing a comparable evolution with Tonian and Cryogenian rifts (Brejo Seco, Miaba, and Canindé); Cryogenian–Ediacaran passive margin, where the Monte Orebe ophiolite is located; and Cordilleran magmatic arcs, which developed between 620 and 610 Ma. In the Sergipano fold belt, with a better-preserved outer domain, gravitational sedimentation occurs with glacial influence. A continental collision between the SFC and the PEAL (Pernambuco-Alagoas Massif) occurred between 610 and 540 Ma, with intense deformation of nappes and thrusts, with vergence to the south and accommodation by dextral transcurrent shear zones, such as the Pernambuco Lineament (PE). The Araçuaí belt or orogen was formed at the southeastern limit of the SFC by a Tonian intracontinental rift, later superimposed by a Cryogenian–Ediacaran rift–passive margin of the Macaúbas Group, with gravitational sedimentation and glacial influence, and distally by oceanic crust. It is overlain by a retroarc basin with syn-orogenic sedimentation of the Salinas Formation, partly derived from the Rio Doce cordilleran magmatic arc and associated basins, such as the Rio Doce and Nova Venécia Groups. A third continental collision event (SF and Congo cratons), at the end of the Ediacaran (580–530 Ma), developed a thrust–fold belt that deforms the sediments of the Araçuaí Belt and penetrates the Paramirim Corridor, transitioning to the south to a dextral strike-slip shear zone that characterizes the Ribeira Belt. [ABSTRACT FROM AUTHOR]

Published
2024
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8. Late Cryogenian and late Paleozoic ice ages on the São Francisco craton, east Brazil

Author

Uhlein, Gabriel J. and Uhlein, Alexandre

Subjects
General Earth and Planetary Sciences
Abstract

The miniature paleocontinent in the region of the São Francisco River valley, in eastern Brazil, holds the record of two different glacial epochs. The late Cryogenian Jequitaí Formation from the Bambuí Group is up to 100 m thick and covers areas mainly in the central São Francisco craton. Evidences for glacial sedimentation are beautifully preserved E-W grooves and striations, dropstones within fine-grained rocks, and a full set of diamictites enclosing a rich and complex depositional history. The Jequitaí Formation is in close link with the tectonic evolution of the São Francisco paleocontinent and the West Gondwana amalgamation. From west, the precocious Paranapanema and São Francisco blocks collision in late Cryogenian flexured the foreland lithosphere and created depozones that were infilled by glacial sediments. Toward east, the rifting and opening of the Adamastor Ocean allowed thick glacial and non-glacial deposits to form through subaqueous gravitational sedimentation. From west to east, proximal and distal glaciomarine, glaciocontinental, and non-glacial resedimentation are identified and linked to the evolving continental masses and climate during the Cryogenian and beginning of Ediacaran. The late Paleozoic Santa Fé Group is the youngest record of glaciation on the São Francisco craton. It is 60–80 m thick and yields consistent and confident glacial evidences such as N-S striations on top of Cambrian sandstones, ice-rafted debris, and rain-out diamictite, all preserved in small and patchy areas in the west-central São Francisco craton. Paleocurrents suggest a northern ice center and sedimentary facies indicate deposition in continental lakes and rivers. Although late Paleozoic, its age is poorly constrained and likely correlated with the uppermost Itararé Group (Taciba Formation) of Paraná Basin in south Brazil. Deglaciation and strong isostatic adjustments make up the termination of the Santa Fé Group sedimentary record and depict a glaciocontinental system evolved on an interior stable continental crust. The late Neoproterozoic Jequitaí Formation and the late Paleozoic Santa Fé Group are parts of the earth’s sedimentary history preserving a rich record of climate, tectonic, and surface processes in part controlled by the evolving continental masses on the São Francisco craton.

Published
2022

12. The Sedimentary Geochemistry and Paleoenvironments Project

Author

Farrell, Úna C., Samawi, Rifaat, Anjanappa, Savitha, Klykov, Roman, Adeboye, Oyeleye O., Agic, Heda, Ahm, Anne-Sofie C., Boag, Thomas H., Bowyer, Fred, Brocks, Jochen J., Brunoir, Tessa N., Canfield, Donald E., Chen, Xiaoyan, Cheng, Meng, Clarkson, Matthew O., Cole, Devon B., Cordie, David R., Crockford, Peter W., Cui, Huan, Dahl, Tais W., Mouro, Lucas D., Dewing, Keith, Dornbos, Stephen Q., Drabon, Nadja, Dumoulin, Julie A., Emmings, Joseph F., Endriga, Cecilia R., Fraser, Tiffani A., Gaines, Robert R., Gaschnig, Richard M., Gibson, Timothy M., Gilleaudeau, Geoffrey J., Gill, Benjamin C., Goldberg, Karin, Guilbaud, Romain, Halverson, Galen P., Hammarlund, Emma U., Hantsoo, Kalev G., Henderson, Miles A., Hodgskiss, Malcolm S. W., Horner, Tristan J., Husson, Jon M., Johnson, Benjamin, Kabanov, Pavel, Keller, C. Brenhin, Kimmig, Julien, Kipp, Michael A., Knoll, Andrew H., Kreitsmann, Timmu, Kunzmann, Marcus, Kurzweil, Florian, LeRoy, Matthew A., Li, Chao, Lipp, Alex G., Loydell, David K., Lu, Xinze, Macdonald, Francis A., Magnall, Joseph M., Mänd, Kaarel, Mehra, Akshay, Melchin, Michael J., Miller, Austin J., Mills, N. Tanner, Mwinde, Chiza N., O'Connell, Brennan, Och, Lawrence M., Ossa Ossa, Frantz, Pagès, Anais, Paiste, Kärt, Partin, Camille A., Peters, Shanan E., Petrov, Peter, Playter, Tiffany L., Plaza-Torres, Stephanie, Porter, Susannah M., Poulton, Simon W., Pruss, Sara, Richoz, Sylvain, Ritzer, Samantha R., Rooney, Alan D., Sahoo, Swapan K., Schoepfer, Shane D., Sclafani, Judith A., Shen, Yanan, Shorttle, Oliver, Slotznick, Sarah P., Smith, Emily F., Spinks, Sam, Stockey, Richard G., Strauss, Justin V., Stüeken, Eva E., Tecklenburg, Sabrina, Thomson, Danielle, Tosca, Nicholas J., Uhlein, Gabriel J., Vizcaíno, Maoli N., Wang, Huajian, White, Tristan, Wilby, Philip R., Woltz, Christina R., Wood, Rachel A., Xiang, Lei, Yurchenko, Inessa A., Zhang, Tianran, Planavsky, Noah J., Lau, Kimberly V., Johnston, David T., Sperling, Erik A., Farrell, Úna C., Samawi, Rifaat, Anjanappa, Savitha, Klykov, Roman, Adeboye, Oyeleye O., Agic, Heda, Ahm, Anne-Sofie C., Boag, Thomas H., Bowyer, Fred, Brocks, Jochen J., Brunoir, Tessa N., Canfield, Donald E., Chen, Xiaoyan, Cheng, Meng, Clarkson, Matthew O., Cole, Devon B., Cordie, David R., Crockford, Peter W., Cui, Huan, Dahl, Tais W., Mouro, Lucas D., Dewing, Keith, Dornbos, Stephen Q., Drabon, Nadja, Dumoulin, Julie A., Emmings, Joseph F., Endriga, Cecilia R., Fraser, Tiffani A., Gaines, Robert R., Gaschnig, Richard M., Gibson, Timothy M., Gilleaudeau, Geoffrey J., Gill, Benjamin C., Goldberg, Karin, Guilbaud, Romain, Halverson, Galen P., Hammarlund, Emma U., Hantsoo, Kalev G., Henderson, Miles A., Hodgskiss, Malcolm S. W., Horner, Tristan J., Husson, Jon M., Johnson, Benjamin, Kabanov, Pavel, Keller, C. Brenhin, Kimmig, Julien, Kipp, Michael A., Knoll, Andrew H., Kreitsmann, Timmu, Kunzmann, Marcus, Kurzweil, Florian, LeRoy, Matthew A., Li, Chao, Lipp, Alex G., Loydell, David K., Lu, Xinze, Macdonald, Francis A., Magnall, Joseph M., Mänd, Kaarel, Mehra, Akshay, Melchin, Michael J., Miller, Austin J., Mills, N. Tanner, Mwinde, Chiza N., O'Connell, Brennan, Och, Lawrence M., Ossa Ossa, Frantz, Pagès, Anais, Paiste, Kärt, Partin, Camille A., Peters, Shanan E., Petrov, Peter, Playter, Tiffany L., Plaza-Torres, Stephanie, Porter, Susannah M., Poulton, Simon W., Pruss, Sara, Richoz, Sylvain, Ritzer, Samantha R., Rooney, Alan D., Sahoo, Swapan K., Schoepfer, Shane D., Sclafani, Judith A., Shen, Yanan, Shorttle, Oliver, Slotznick, Sarah P., Smith, Emily F., Spinks, Sam, Stockey, Richard G., Strauss, Justin V., Stüeken, Eva E., Tecklenburg, Sabrina, Thomson, Danielle, Tosca, Nicholas J., Uhlein, Gabriel J., Vizcaíno, Maoli N., Wang, Huajian, White, Tristan, Wilby, Philip R., Woltz, Christina R., Wood, Rachel A., Xiang, Lei, Yurchenko, Inessa A., Zhang, Tianran, Planavsky, Noah J., Lau, Kimberly V., Johnston, David T., and Sperling, Erik A.

Abstract

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Farrell, U. C., Samawi, R., Anjanappa, S., Klykov, R., Adeboye, O. O., Agic, H., Ahm, A.-S. C., Boag, T. H., Bowyer, F., Brocks, J. J., Brunoir, T. N., Canfield, D. E., Chen, X., Cheng, M., Clarkson, M. O., Cole, D. B., Cordie, D. R., Crockford, P. W., Cui, H., Dahl, T. W., Mouro, L. D., Dewing, K., Dornbos, S. Q., Drabon, N., Dumoulin, J. A., Emmings, J. F., Endriga, C. R., Fraser, T. A., Gaines, R. R., Gaschnig, R. M., Gibson, T. M., Gilleaudeau, G. J., Gill, B. C., Goldberg, K., Guilbaud, R., Halverson, G. P., Hammarlund, E. U., Hantsoo, K. G., Henderson, M. A., Hodgskiss, M. S. W., Horner, Tristan J., Husson, J. M., Johnson, B., Kabanov, P., Brenhin K. C., Kimmig, J., Kipp, M. A., Knoll, A. H., Kreitsmann, T., Kunzmann, M., Kurzweil, F., LeRoy, M. A., Li, C., Lipp, A. G., Loydell, D. K., Lu, X., Macdonald, F. A., Magnall, J. M., Mänd, K., Mehra, A., Melchin, M. J., Miller, A. J., Mills, N. T., Mwinde, C. N., O'Connell, B., Och, L. M., Ossa Ossa, F., Pagès, A., Paiste, K., Partin, C. A., Peters, S. E., Petrov, P., Playter, T. L., Plaza-Torres, S., Porter, Susannah M., Poulton, S. W., Pruss, S. B., Richoz, S., Ritzer, S. R., Rooney, A. D., Sahoo, S. K., Schoepfer, S. D., Sclafani, J. A., Shen, Y., Shorttle, O., Slotznick, S. P., Smith, E. F., Spinks, S., Stockey, R. G., Strauss, J. V., Stüeken, E. E., Tecklenburg, S., Thomson, D., Tosca, N. J., Uhlein, G. J., Vizcaíno, M. N., Wang, H., White, T., Wilby, P. R., Woltz, C. R., Wood, R. A., Xiang, L., Yurchenko, I. A., Zhang, T., Planavsky, N. J., Lau, K. V., Johnston, D. T., Sperling, E. A., The Sedimentary Geochemistry and Paleoenvironments Project. Geobiology. 00, (2021): 1– 12,https://doi.org/10.1111/gbi.12462., Geobiology explores how Earth's system has changed over the course of geologic history and how living organisms on this planet are impacted by or are indeed causing these changes. For decades, geologists, paleontologists, and geochemists have generated data to investigate these topics. Foundational efforts in sedimentary geochemistry utilized spreadsheets for data storage and analysis, suitable for several thousand samples, but not practical or scalable for larger, more complex datasets. As results have accumulated, researchers have increasingly gravitated toward larger compilations and statistical tools. New data frameworks have become necessary to handle larger sample sets and encourage more sophisticated or even standardized statistical analyses. In this paper, we describe the Sedimentary Geochemistry and Paleoenvironments Project (SGP; Figure 1), which is an open, community-oriented, database-driven research consortium. The goals of SGP are to (1) create a relational database tailored to the needs of the deep-time (millions to billions of years) sedimentary geochemical research community, including assembling and curating published and associated unpublished data; (2) create a website where data can be retrieved in a flexible way; and (3) build a collaborative consortium where researchers are incentivized to contribute data by giving them priority access and the opportunity to work on exciting questions in group papers. Finally, and more idealistically, the goal was to establish a culture of modern data management and data analysis in sedimentary geochemistry. Relative to many other fields, the main emphasis in our field has been on instrument measurement of sedimentary geochemical data rather than data analysis (compared with fields like ecology, for instance, where the post-experiment ANOVA (analysis of variance) is customary). Thus, the longer-term goal was to build a collaborative environment where geobiologists and geologists can work and learn together to, We thank the donors of The American Chemical Society Petroleum Research Fund for partial support of SGP website development (61017-ND2). EAS is funded by National Science Foundation grant (NSF) EAR-1922966. BGS authors (JE, PW) publish with permission of the Executive Director of the British Geological Survey, UKRI.

Published
2021

13. Goldilocks at the dawn of complex life:mountains might have damaged Ediacaran–Cambrian ecosystems and prompted an early Cambrian greenhouse world

Author

Caxito, Fabricio, Lana, Cristiano, Frei, Robert, Uhlein, Gabriel J., Sial, Alcides N., Dantas, Elton L., Pinto, André G., Campos, Filippe C., Galvão, Paulo, Warren, Lucas V., Okubo, Juliana, Ganade, Carlos E., Caxito, Fabricio, Lana, Cristiano, Frei, Robert, Uhlein, Gabriel J., Sial, Alcides N., Dantas, Elton L., Pinto, André G., Campos, Filippe C., Galvão, Paulo, Warren, Lucas V., Okubo, Juliana, and Ganade, Carlos E.

Abstract

We combine U–Pb in-situ carbonate dating, elemental and isotope constraints to calibrate the synergy of integrated mountain-basin evolution in western Gondwana. We show that deposition of the Bambuí Group coincides with closure of the Goiás-Pharusian (630–600 Ma) and Adamastor (585–530 Ma) oceans. Metazoans thrived for a brief moment of balanced redox and nutrient conditions. This was followed, however, by closure of the Clymene ocean (540–500 Ma), eventually landlocking the basin. This hindered seawater renewal and led to uncontrolled nutrient input, shallowing of the redoxcline and anoxic incursions, fueling positive productivity feedbacks and preventing the development of typical Ediacaran–Cambrian ecosystems. Thus, mountains provide the conditions, such as oxygen and nutrients, but may also preclude life development if basins become too restricted, characterizing a Goldilocks or optimal level effect. During the late Neoproterozoic-Cambrian fan-like transition from Rodinia to Gondwana, the newborn marginal basins of Laurentia, Baltica and Siberia remained open to the global sea, while intracontinental basins of Gondwana became progressively landlocked. The extent to which basin restriction might have affected the global carbon cycle and climate, e.g. through the input of gases such as methane that could eventually have collaborated to an early Cambrian greenhouse world, needs to be further considered.

Published
2021

16. Carbonate storm deposits and C, O isotopes of the Lagoa do Jacaré Formation (Ediacaran) in the Paraopeba area, Bambuí Group, Brazil.

Author

Santana Dantas, Marcio Vinicius, Uhlein, Alexandre, Jubé Uhlein, Gabriel, Rodrigues de Freitas, Alex, Keuffer Mendonça, Thaís, Oliveira Santos, José Arthur, and Moura Silva, Samuel Amaral

Subjects
CARBONATES, LITHOFACIES, CARBON isotopes, FACIES, CHEMOSTRATIGRAPHY, ISOTOPES, MARINE resources conservation, SEDIMENTATION & deposition
Abstract

A section investigated in the region of Paraopeba, Minas Gerais, provided detailed sedimentologic, stratigraphic and chemostratigraphic data from the Ediacaran Lagoa do Jacaré Formation, Bambuí Group, Southeast Brazil. This information allowed interpretation of tempestite facies in transgressive-regressive cycles, reinforcing the previously proposed storm-influenced sedimentation model and clarifying how it is associated with unusually high C-isotope values related to the Middle Bambuí Excursion (MIBE). Facies analysis of nine lithofacies identified at the GMD quarry based on field and petrographic descriptions showed distal tempestite facies grading upwards to a shallower, oncoidal/ooidal carbonate marine environment, then to basinal shales. The entire succession comprises a low-order transgressive hemicycle, recording the transition from a storm-influenced carbonate ramp to a siliciclastic-dominated platform. Chemostratigraphic data yielded high δ13C values ranging between +11.11‰ and +13.94‰. Our data contribute to the revision of the previously proposed interpretation and as well as to the understanding of paleoenvironmental conditions and C isotope signatures across the MIBE, near the Ediacaran-Cambrian boundary in the Bambuí Basin. [ABSTRACT FROM AUTHOR]

Published
2022
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17. As Formações Santo Antônio do Bonito e Rocinha (Grupo Vazante, Minas Gerais): sedimentação gravitacional sin a pós-glacial e fosfogênese na transição Faixa Brasília-Cráton do São Francisco.

Author

de Sousa Marques, Carla Sofia, Uhlein, Alexandre, Jubé Uhlein, Gabriel, Koester, Edinei, and Carneiro de Oliveira, Eduardo Luís

Abstract

Copyright of Geologia USP: Série Científica is the property of Geologia USP and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2021
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18. Ediacaran/Early Cambrian Serra da Saudade Formation, Bambuí Group: the sedimentary record of a foreland basin in Southeastern Brazil.

Author

Silvano Moreira, Débora, Uhlein, Alexandre, Jubé Uhlein, Gabriel, Nóbrega Sial, Alcides, and Koester, Edinei

Subjects
SEDIMENTATION & deposition, SILTSTONE, LITHOFACIES
Abstract

The Serra da Saudade Formation, Ediacaran/Cambrian Bambuí Group, cropping out along the ridge of the same name in Central-Western Minas Gerais, Brazil, contains important deposits of glauconitic siltstones associated with phosphatic rhythmite as well as other siliciclastic, volcaniclastic and carbonate lithofacies. Lithofacies indicate deposition by proximal and distal storm waves on a continental marine shelf. The basal gray siltstone and part of the green siltstone represent a transgressive systems tract. The glauconitic siltstone indicates sea level rise, with the maximum flooding surface located approximately at the interval of highest K2O content. Biogenic carbonate and an upward increase in sandstone beds are interpreted as a highstand systems tract. Gradual lateral facies changes reflect the transition from foredeep (to the west) to forebulge (to the east) deposition in a foreland basin as the final stage of a shallowing-upward second-order sequence. Black organic-rich limestone has d13C values between -8.78 and 9.79‰, negative d18O values from -11.50 to -9.35‰, and 87Sr/86Sr around 0.7075. This isotopic signature, similar to that of other Bambuí carbonates, indicates a probably-restricted depositional environment with organic sedimentation, methanogenesis and high evaporation rates from the Ediacaran through the early Cambrian period. [ABSTRACT FROM AUTHOR]

Published
2021
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20. Associação de Fácies, Litoquímica e Geologia Isotópica da Formação Lagamar (Grupo Vazante, Minas Gerais): uma Plataforma Carbonática no Mesoproterozoico.

Author

de Sousa Marques, Carla Sofia, Uhlein, Alexandre, Jubé Uhlein, Gabriel, Diniz Oliveira, Gustavo, Nóbrega Sial, Alcides, and Souza de Alvarenga, Carlos José

Subjects
REEFS, SEAWATER, SALINITY, CARBONATES, HOMOGENEITY, RARE earth metals
Abstract

Copyright of Anuario do Instituto de Geociencias is the property of Universidade Federal do Rio de Janeiro, Instituto de Geociencias and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2019
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24. Geologia e recursos minerais da folha Serra do Cabral SE.23-X-C-V: estado de Minas Gerais

Author

LOPES, Tiago Carneiro, LEITE, Mariana Meireles, MARTINS, Maximiliano de Souza, UHLEIN, Alexandre, KARFUNKEL, Joachim, FONSECA, Augusto, UHLEIN, Gabriel Jubé, and FREIRE, Glauber Rezende

Subjects
RECURSOS MINERAIS, MINAS GERAIS, GEOLOGIA ECONÔMICA, DADOS VETORIAIS, SERRA DO CABRAL, 100.000 [ESCALA 1], SIG, SE.23-X-C-V
Abstract

Parceria com a Universidade Federal de Minas Gerais (UFMG). Contrato nº 010/PR/2010. Programa Geologia do Brasil. Integração, atualização e difusão de dados da Geologia do Brasil

Published
2014

26. Linking paleocontinents through triple oxygen isotope anomalies.

Author

Crockford, Peter W., Hodgskiss, Malcolm S. W., Uhlein, Gabriel J., Caxito, Fabricio, Hayles, Justin A., and Halverson, Galen P.

Subjects
*OXYGEN isotopes, *PROTEROZOIC Era, *SNOWBALL Earth (Geology), *GLACIAL melting, *GEOLOGICAL time scales, *URANIUM & the environment, *LEAD & the environment
Abstract

A central tenet of the Neoproterozoic snowball Earth hypothesis is that glaciations ended synchronously. Although this condition is borne out by U-Pb and Re-Os geochronology, the time scale of deglaciation is much less than the intrinsic error of the highest resolution dating techniques, and consequently calibrating the pace and synchronicity of biogeochemical recovery from Cryogenian glaciations remains a challenge. Given the importance of obtaining a globally synoptic view of paleoenvironmental conditions and biological evolution during these extraordinary transitions, robust correlations and chronologies are imperative. Here we extend the negative triple oxygen isotope (Δ17O) anomaly previously documented in ca. 635 Ma postglacial cap carbonates to two new paleocontinents, Brazil and Norway. The global footprint of this geochemical signal coupled to its short duration provides a unique time datum that can be used to cross-correlate Marinoan postglacial cap carbonate sequences and track the geochemical evolution of the oceans during deglaciation. [ABSTRACT FROM AUTHOR]

Published
2018
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27. Chromium isotopes track redox fluctuations in Proterozoic successions of the Chapada Diamantina, São Francisco craton, Brazil.

Author

Caxito, Fabrício A., Fre, Robert, Sial, Alcides N., Uhlein, Gabriel J., de Moura, William Alexandre Lima, Pereira, Egberto, and Rodrigues, René

Abstract

The Chapada Diamantina region in the São Francisco craton of eastern Brazil is composed of sedimentary successions containing both Mesoproterozoic and Neoproterozoic carbonate levels, making it a key natural laboratory for understanding the fluctuations of Earth's biogeochemical cycles during its middle age. The ca. 1.4--1.2 Ga Caboclo Formation stromatolites yielded unfractionated δ53Crauth (authigenic) (-0.54‰ to +0.08‰). Ediacaran cap carbonates and phosphatic stromatolites of the Salitre Formation, on the other hand, yielded fractionated δ53Crauth reaching as high as +0.51‰, suggesting the input of 53Cr-rich Cr(VI), first delivered through meltwater-induced post-snowball Earth fluctuating redox conditions and then through weathering and mobilization under a fully oxygenated environment. The acquired data set highlights the very distinct redox conditions throughout the Proterozoic and reinforces the suggestion that after the Cryogenian global glaciations, Earth's atmosphere and hydrosphere became progressively oxygenated during the Ediacaran-Cambrian transition. [ABSTRACT FROM AUTHOR]

Published
2023
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28. Análise estratigráfica e geocronológica da formação Três Marias na Serra do Gorutuba, norte de Minas Gerais : registro de superposição de bacia de antepaís na porção oriental do cráton São Francisco

Author

Rossi, Ariadne Verônica Andrade, Costa, Alice Fernanda de Oliveira, Uhlein, Gabriel Jubé, and Danderfer Filho, André

Subjects
Gondwana - geologia, Geocronologia, Cráton São Francisco, Geologia estratigráfica
Abstract

Programa de Pós-Graduação em Evolução Crustal e Recursos Naturais. Departamento de Geologia, Escola de Minas, Universidade Federal de Ouro Preto. A Formação Três Marias corresponde à unidade de topo do Grupo Bambuí, o qual recobre a porção interna do cráton São Francisco. Estudos consolidados na região cratônica ocidental apontam que esta formação é representativa de uma bacia de antepaís (foreland basin) associada à evolução da Faixa Brasília. A Formação Três Marias também registra o preenchimento de um foreland basin de idade brasiliana na porção oriental do cráton. Este trabalho apresenta os resultados de dados de campo, análise estratigráfica e análises isotópicas U-Pb e ƐHf realizados nesta unidade ao longo da serra do Gorutuba, norte de Minas Gerais. A região se encontra no leste do cráton São Francisco, próximo ao limite com a Faixa Araçuaí. Na área de estudo, a Formação Três Marias constitui depósitos de molassa, compostos essencialmente por conglomerados carbonáticos e arenitos arcoseanos que ocorrem em discordância erosiva com a Formação Serra da Saudade. Os perfis estratigráficos levantados exibem cinco associações de fácies e a sucessão sedimentar aponta que os sedimentos arenosos entraram via um sistema flúvio-deltáico a nordeste da bacia, onde foram retrabalhados em uma plataforma siliciclástica sob influência de ondas, correntes de maré e tempestade. As paleocorrentes apontam uma linha de costa NW-SE, localmente com fluxos de correntes para nordeste e noroeste. Dados geocronológicos obtidos por meio de análises U-Pb (via LA-ICPMS) em grãos de zircões detríticos indicam que a idade máxima de deposição desta unidade é de 556±5 Ma, e que a base da sequência registra a exumação de rochasfontes mais jovens que aquelas do topo. Os zircões da base possuem assinatura ƐHf negativa, assinalando uma área fonte gerada sob condições crustais, enquanto o topo apresenta maior contribuição de grãos com ƐHf positivo, refletindo a erosão e deposição de rochas com características mais mantélicas. Os resultados sugerem que a principal área fonte dos sedimentos corresponde às rochas produzidas nos estágios pré-orogênico, pré- e sin-colisionais da Faixa Araçuaí (ca. 630 – 560 Ma). Os zircões analisados na serra do Gorutuba mostram um espectro de distribuição de idades U-Pb característico de foreland basin e revelam idades mais jovens que aquelas encontrados na borda oeste da bacia. Deste modo, o foreland basin gerado em resposta ao desenvolvimento da Faixa Araçuaí seria mais jovem que aquele registrado na porção ocidental do cráton, relativo à Faixa Brasília. O preenchimento final da bacia Bambuí seria controlado, portanto, pelo desenvolvimento destes dois cinturões de dobramentos ao longo das margens do paleocontinente São Francisco durante a aglutinação de Gondwana Ocidental. The Três Marias Formation corresponds to the top unit of the Bambuí Group, which covers the inner portion of the São Francisco craton. Consolidated studies in the western region show that this formation is representative of a foreland basin associated with the evolution of the Brasília orogen. The Três Marias Formation also records the filling of a brasiliano basin foreland in the eastern portion of the craton. This work presents the results of field data, stratigraphic analysis and U-Pb and ƐHf isotopic analysis performed at this unit along the Gorutuba ridge, northern Minas Gerais. This region is located in the eastern part of the craton São Francisco, close to the boundary with the Araçuaí orogen. In the study area, the Três Marias Formation constitutes molasses deposits, composed essentially of carbonatic conglomerates and sandy arkosean that occur in erosive discordance with the Serra da Saudade Formation. The stratigraphic profiles exhibit five associations of facies and the sedimentary succession indicates that the sandy sediments entered in the basin through a fluvio-deltaic system to the northeast and were reworked in a siliciclastic shelf under influence of waves, tides and storms currents. The paleocurrents indicate a NW-SE coastline, with current flows locally to northeast and northwest. Geochronological data obtained by U-Pb analysis on detrital zircon grains indicate that the maximum deposition age of this unit is 556 ± 5 Ma and that the sequence base registers the exhumation of rocksources younger than those at the top. The zircons of the base show a negative ƐHf signature indicating a source area generated under crustal conditions, while the top has a higher contribution of grains with positive ƐHf reflecting the erosion and deposition of rocks with more mantle characteristics. The results suggest that the main source area of the sediments corresponds to the rocks produced in the pre-orogenic, pre- and sin-collisional stages of the Araçuaí orogen (ca. 630 – 560 Ma). The zircons analyzed in the Gorutuba ridge show a distribution spectrum of U-Pb ages characteristic of foreland basin and reveal younger ages than those found on the western border of the basin. Thus, the foreland basin generated in response to the Araçuaí orogen would be younger than that recorded in the western portion of the craton, related to the Brasilia orogen. The final filling of the Bambuí basin would therefore be controlled by the development of these two fold-thrust belts throughout the margins of São Francisco paleocontinent during the agglutination of the Occidental Gondwana.

Published
2019

29. Evolução geológica da sequência metavulcanossedimentar Ipueirinha, Província Borborema, Piauí: petrografia, geoquímica e geocronologia

Author

BASTO, Camila Franco, Fabricio de Andrade Caxito, Edilton José dos Santos, Fernando Flecha de Alkmim, Gabriel Jube Uhlein, SANTOS, Edilton José dos, ALKMIM, Fernando Flecha de, UHLEIN, Gabriel Jubé, and CAXITO, Fabrício de Andrade

Subjects
PIAUÍ, Tempo geologico, Orogenia Brasiliana, Petrologia, BRASIL, Zona Transversal, Geoquímica, Grupo Ipueirinha, Proveniência
Abstract

O Grupo Ipueirinha é um cinturão de rochas metavulcanossedimentares situado na porção extremo oeste da Zona Transversal, Província Borborema, região nordeste do Brasil. Esta unidade é predominantemente constituída por metassedimentos marinhos terrígenos representados por metarritmitos imaturos (Formação Caridade do Piauí) e quartzitos (Formação Cacimbas). Os metarritmitos desta sequência exibem anomalias negativas de Eu (Eu/Eu* = 0,68-0,81), enriquecimento em ETRL (LaN/YbN = 4,83-15,32), e elementos incompatíveis coerentes com uma proveniência sedimentar de arco magmático continental. Em geral, dados isotópicos de Nd (Nd(t) entre -3,6 e 0,3) também indicam uma importante contribuição detrítica de fontes juvenis para a deposição desses metarritmitos. Associados à sequência clástica, têm-se metatufos (Formação Barrocão), raras lentes de metamarga, e corpos de metaultramafito de extensão quilométrica (agrupados na unidade informal denominada Serpentinito Carnaubal). Os metatufos riolíticos exibem padrões de ETR fortemente fracionados (LaN/YbN = 3,68-8,94), anomalias negativas de Eu (Eu/Eu* = 0,72-0,94), e padrões de elementos traço incompatíveis similares àqueles de rochas associadas a arco vulcânico (incluindo calha Nb-Ta), além de Nd(t) negativo entre -3,4 e -12,2. Análises de U-Pb em zircões recuperados de metarritmitos e de uma soleira granítica sugerem o período entre 626 e 591 Ma como possível janela de sedimentação e vulcanismo no Grupo Ipueirinha. Dados isotópicos de zircão detrítico também revelam um importante período de magmatismo juvenil na Província Borborema entre 895 e 834 Ma (Hf(t) = 2,0-5,7), bem como um signiticativo rejuvenescimento crustal desta província durante o Neoproterozoico, decorrente da adição de material mantélico juvenil. Em adição, dados de U-Pb e Hf adquiridos para os metarritmitos desta sequência remetem à evolução geológica do Complexo Tamboril-Santa Quitéria (Província Borborema Setentrional). Assim, o Grupo Ipueirinha pode corresponder a uma bacia de retroarco associada ao arco magmático de Tamboril-Santa Quitéria, que constitui um dos únicos registros da tectônica convergente inicial que atuou na margem Gondwana Oeste da Província Borborema. Os metaultramafitos associados ao Grupo Ipueirinha apresentam Nd(t) entre -1,3 e -8,5, e TDM = 1,33-1,64 Ga. Em um contexto de retroarco, estas rochas poderiam representar lascas de crosta oceânica que um dia constituíram o assoalho da bacia Ipueirinha. Toda a faixa de dobramentos foi submetida a quatro fases de deformação e a condições metamórficas de facies xisto verde inferior a superior. Dados geocronológicos adicionais obtidos para um blackwall de cloritito (U-Pb em monazita) em conjunto com a idade máxima de cristalização da soleira granítica limitam deformação, metamorfismo e magmatismo sin-orogênico no Grupo Ipueirinha ao intervalo 591-565 Ma. The Ipueirinha Belt is a ca. 75 km-long and 13 km-wide belt of metavolcano-sedimentary rocks in westernmost Transversal Zone, Borborema Province, NE Brazil. Such belt is mostly constituted by marine terrigenous sedimentary rocks represented by immature metarhythmites (Caridade do Piauí Formation) and quartzites (Cacimbas Formation). Metarhythmites yield negative Eu anomalies (Eu/Eu* = 0.68-0.81), LREE enrichment (LaN/YbN = 4.83-15.32), and incompatible elements coherent with provenance from a continental arc. Overall Nd isotopic data (Nd(t) between -3.6 and 0.3) indicate detrital contribution from juvenile sources for deposition of these metarhythmites. Associated to this clastic sedimentary sequence, there are metarhyolitic tuffs (Barrocão Formation), rare lenses of metamarl, and kilometric-long bodies of metaultramafites (grouped in an informal unit named Serpentinito Carnaubal). The metarhyolitic tuffs exhibit highly fractionated chondrite-normalized REE patterns (LaN/YbN = 3.68-8.94), negative Eu anomalies (Eu/Eu* = 0.72-0.94), and incompatible trace elements patterns similar to those of volcanic arc-related rocks (including a Nb-Ta trough), besides negative Nd(t) ranging from -3.4 to -12.2. Zircon U-Pb analyses performed on crystals recovered from metarhythmites and from a granitic sill suggest that sedimentation and volcanism in the Ipueirinha Belt took place at 626-591 Ma. Such detrital zircon data reveal that the main sources of detritus for the Ipueirinha Basin are Neoproterozoic rocks (maximum age peak at ca. 845 Ma and youngest zircons at ca. 620 Ma). Isotopic data attained from detrital zircons provide evidence for an important period of juvenile magmatism in the Borborema Province from 895 to 834 Ma (Hf(t) = 2.0-5.7), as well as for a crustal renewal of this province during the Neoproterozoic, due to juvenile mantellic inputs. Additionally, U-Pb and Hf data attained for the metarhythmites resemble the geological evolution of the Tamboril-Santa Quitéria Complex (Northern Borborema Province). Hence, the Ipueirinha Belt might have constituted a Cryogenian/Ediacaran back-arc basin to the Tamboril-Santa Quitéria magmatic arc, which is one of the few records of initial convergence tectonics in the West Gondwana margin of the Borborema Province. Metaultramafites associated with the Ipueirinha Belt yield Nd(t) ranging from -1.3 to -8.5 and TDM = 1.33-1.64 Ga. In the context of a back-arc basin, these rocks could represent slices of oceanic crust that once floored the Ipueirinha basin. The whole belt was submitted to four deformational phases and to heterogeneous metamorphic conditions from lower to upper greenschist facies. Additional geochronological data attained for a chloritite blackwall (monazite U-Pb) along with the maximum crystallization age of the granitic sill constrains deformation, metamorphism and syn-orogenic magmatism in the Ipueirinha Belt at 591-565 Ma.

Published
2018

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