Papers (Scientific Journals)
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São Paulo, UNESP, Geociências, 2020
RESUMO-O Complexo Pedra Branca (CPB) está localizado na zona oeste da cidade do Rio de Janeiro (S... more RESUMO-O Complexo Pedra Branca (CPB) está localizado na zona oeste da cidade do Rio de Janeiro (SE Brasil) e está inserido tectonicamente no Domínio Costeiro, pertencente ao Terreno Oriental da Faixa Ribeira Central. Os litotipos que formam o CPB foram gerados em eventos relacionados à Orogênese Brasiliana (~600 Ma), abrigando assim rochas pré-a pós-colisionais. Estudos anteriores de corpos graníticos pós-tectônicos na Faixa Ribeira revelaram que o magmatismo ocorreu em dois pulsos distintos, com intervalo de aproximadamente 30 Ma entre eles. O presente estudo analisou 9 amostras do CPB, através dos métodos geocronológicos U-Pb e Lu-Hf via LA-ICP-MC-MS, referentes às litologias granito Pedra Branca e granito Favela, possíveis representantes do pulso mais antigo e mais jovem, respectivamente, buscando melhorar a compreensão do magmatismo pós-tectônico na região. As médias das idades encontradas para o granito Pedra Branca (509 ± 5 Ma) e granito Favela (489 ± 6 Ma) corroboraram com os valores descritos na literatura e indicaram que o magmatismo ocorrido no CPB teve origem na forma de pulsos progressivos, porém num intervalo de tempo menor (~20 Ma) do que foi anteriormente determinado. O indicador petrogenético εHf indicou participação de fontes crustais e mantélicas, dando caráter bimodal ao magmatismo registrado no CPB. Palavras-chave: Geocronologia. Magmatismo. Isótopos. LA-MC-ICP-MS. Zircão. ABSTRACT-The Pedra Branca Complex is located at the western region of the Rio de Janeiro city (SE Brazil). Tectonically it is inserted in the Coastal Domain, which is part of the central segment of the Ribeira Belt. The lithologies that formed this rocky complex were generated in events related to the Brasiliano Orogeny (~ 600 Ma), thus contains pre-to-post-collisional rocks. Previous studies on post-tectonic granite bodies belonging to Ribeira belt revealed that the magmatism occurred in two distinct pulses, with an interval of approximately ~ 30 Ma between them. The present study analyzed 9 CPB samples, using the U-Pb and Lu-Hf through LA-ICP-MC-MS geochronological methods, with focus on the Pedra Branca granite and Favela granite, which may represent the older and the younger pulses respectively, in order to improve the understanding of the post-tectonic magmatism in the area. The average ages found for the Pedra Branca (509 ± 5 Ma) and Favela (489 ± 6 Ma) granites confirm the previously described ages in the literature. However, they indicate that the magmatism in CPB occurred in the form of progressive pulses, with an interval between both events of ~ 20 Ma, that is, less than what was previously estimated (of ~ 30 Ma). In addition, the petrogenetic indicator εHf indicated the participation of crustal and mantle sources, which gives a bimodal character to the magmatism registered in the CPB.
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Virgínia A. Martins, José F. Santos, Andreas Mackensen, João Alveirinho Dias, Sara Ribeiro, João ... more Virgínia A. Martins, José F. Santos, Andreas Mackensen, João Alveirinho Dias, Sara Ribeiro, João C. Moreno, António M. Soares, Fabrizio Frontalini, Daniel Rey, Fernando Rocha (2013) - The sources of the glacial IRD in the NW Iberian Continental Margin over the last 40 ka. Quaternary International, 318:128–138. DOI: 10.1016/j.quaint.2013.08.026
In this work, the first results of ice rafted detritus (IRD) provenance related to Heinrich Events in the NW Iberian Margin are presented and discussed. This study is based on multi-proxies, namely on thorough analyses of Sr and Nd isotope ratios measured in the detrital fraction of the sediment core KC 024-19, from the Galician continental slope (NE Atlantic), aiming to unravel the sources of the terrigenous component of the sampled sediments.
In most of the core layers, the isotope signatures are consistent with an origin, ultimately, in the nearby Variscan continental crust. However, allochthonous contributions were also deposited, namely during the last four Heinrich Events (HE). The non-carbonate detrital fraction of the sediments deposited during the HE1 (in its upper part), HE2, and HE4 displays 3Nd much lower than usual, suggesting that those layers incorporate clasts dropped by icebergs (Ice-Rafted Detritus e IRD) whose sources must have been located in Archaean cratons, such as those of northeastern America and Greenland. The low-3Nd values combined with dolomite peaks support the hypothesis that icebergs fed by the Laurentide ice sheet and launched through Hudson Strait played a major role in the deposition of IRD during HE1, HE2, and HE4. The HE1 layer seems to record a complex evolution of this event, since, at its base, the coarse- grained non-carbonate fraction displays relatively high-3Nd values, pointing to European/Icelandic sources for the icebergs in the initial stages of HE1. The IRD content of the HE3 contrasts significantly with the other HE layers and the non-IRD layers because it has an isotope signature characterized by low 87Sr/86Sr ratios and high-3Nd values. This suggests that the most exotic components of the HE3 layer may have come from East Greenland e Fram Strait and/or result from a mixture of materials from western European and more juvenile (Iceland e Faeroes) crustal sources.
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doi:10.3906/yer-1112-12
Authors: Virgínia Martins; Fernando Rocha; Cristina Sequeira; Paula Marti... more doi:10.3906/yer-1112-12
Authors: Virgínia Martins; Fernando Rocha; Cristina Sequeira; Paula Martins; José Santos; João A. Dias; Olivier Weber; Jean-Marie Jouanneau; Belén Rubio; Daniel Rey; Ana Bernabeu; Eduardo Silva; Lazaro Laut; Rubens Figueira
This work aims to study recent climatic oscillations and their influence on sedimentation in the Ria de Vigo, a coastal embayment in Galicia, NW Spain. It is based on the study of clay mineral assemblages, in conjunction with other proxies (granulometric, geochemical, geochronological and microfaunal), in the core KSGX 24. A Benthic Foraminifera High Productivity (BFHP) proxy was used to determine changes in the flux of organic matter (OM) at the bottom of the study area. Total organic carbon (TOC) content is not a suitable proxy to estimate changes in the past supply of OM due to diagenetic processes. The sedimentation was finest in 3 sections: ~ 230–214 cm, ~ 185–73 cm and ~ 20–0 cm. These muddy sections are characterised, in general, by higher proportions of detrital minerals, concentrations of several chemical elements related to lithogenic sources and BFHP values. In addition, these sections are impoverished in carbonates, Ca, Sr and La when compared with the layers with the highest sand content. The clay mineral assemblage of the studied site, characterised by the dominance of illite, intermediate concentrations of kaolinite and minor amounts of smectite and chlorite, reveals the prevalence of a typical temperate humid climate in the last 3 ka BP, the estimated age for the core base. However, the quantities of illite and chlorite increase in the muddy layers. The characteristics of these muddy layers were interpreted as representing relatively cold climatic oscillations associated with the strengthening of northerly winds and the prevalence of an upwelling regime corresponding to well-known periods, such as the first cold period of the Upper Holocene (~ 2.9 ka cal BP), the Dark Ages (between ~ 2.2 - 1.2 ka cal BP) and the Little Ice Age (~ 0.6 ka cal BP).
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Papers
Marine Environmental Research, Dec 1, 2021
The main environmental variables controlling benthic foraminiferal distributions were identified ... more The main environmental variables controlling benthic foraminiferal distributions were identified and used to assess their influence on ecological indices developed as predictors of Ecological Quality Status (EcoQS) in marine ecosystems. Gradient forest and random forest models were applied to assess the predictive value of a selection of abiotic (environmental) and biotic (foraminifera) variables in a costal marine area in the central Adriatic Sea (Italy). This approach yields evidence that the predictor variables sand, silt, Pollution Load Index, and TN have the greatest influence on the distribution of benthic foraminifera in this area. In addition, we identify thresholds for the most important environmental variables that influence ecological indices. These findings contribute to efforts to determine how to best improve sediment quality and environmental stability for marine conservation. Further application of these approaches represents a useful tool for policymakers to survey the diversity of marine organisms and to improve the ability to protect and restore marine ecosystems by identifying predictors of diversity and identifying key thresholds in these predictors.
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Water, Apr 2, 2020
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Journal of Sedimentary Environments, 2016
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Marine Pollution Bulletin, Mar 1, 2017
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Environmental Science and Pollution Research, May 16, 2023
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Research Square (Research Square), Sep 1, 2022
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Regional Studies in Marine Science
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Geosciences = Geociências
The main aim of this work is to demonstrate that the Laser ablation multi-collector inductively c... more The main aim of this work is to demonstrate that the Laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) is a powerful tool for the analysis of strontium (Sr) isotopes in corals. This work discusses certification strategies for Sr isotopes determination, using reference material (RM) analyses and the results treatment based on detailed data acquired in biological materials, a coral sample. To obtain reliable results, it is essential to properly adjust the mass spectrometer and laser ablation system. Adjusting the equipment to its maximum intensity does not always result in correct 87Sr/86Sr ratios. Therefore, the optimization of the mass spectrometer was performed using the reference material NIST SRM-987 (solution) and adjusting the correct Sr isotope ratio to the reference material (USGS MACS3 and NIST-612, solids) before each analytical session. The protocol applied the solid reference material USGS MACS3 with an isotopic ratio 87Sr/86Sr of ...
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Marine Micropaleontology
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Water
This study aims to analyses the response of meiofaunal organisms (foraminifera) to disturbances c... more This study aims to analyses the response of meiofaunal organisms (foraminifera) to disturbances caused by the diffusers of domestic sewage outfall at Cigarras beach, SE Brazil. Hydrographical, sedimentological (grain size and geochemical), and living benthic foraminiferal recorded in 2006 and 2007 analyzed in ten stations were compared with the same results analyzed in two control/reference stations (sampled in 2008). The results of this work show that, in the benthic environment of the Cigarras region, moderated hydrodynamic conditions, relatively high total organic carbon, total nitrogen, total sulfur contents, oxic water column and anoxic sediments, organic matter supplied by marine productivity and from mixed sources prevail. Living foraminiferal assemblages denote that the Cigarras region is undergoing environmental degradation due to progressive organic enrichment directly influenced by the domestic sewage outfall. The effluents discharged by the domestic sewage constrained th...
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Estuaries and Coasts
Living foraminiferal assemblages were studied in 56 samples collected in Vermelha Lagoon consider... more Living foraminiferal assemblages were studied in 56 samples collected in Vermelha Lagoon considered the most hypersaline lagoon in Brazil. The study aimed to improve knowledge about the biodiversity and ecology of foraminifera in confined hypersaline environments and to assess the quality status of this ecosystem. The results revealed that foraminiferal assemblages were dominated by miliolids, mainly Quinqueloculina seminula, and Ammonia tepida (Rotalioidea). This assemblage was different from those usually reported in hypersaline lagoons with bottoms consisting of carbonate sand–rich sediments. Salt production in this lagoon produces hypertrophic conditions in the sediment, which has a severe impact on the foraminiferal community. The distribution of miliolid species is related to organic matter mainly associated to higher concentrations of carbohydrates. The rotaliids Haynesina concentrica, Bolivina variabilis, and Rosalina floridana were positively related to protein and lipid concentrations. The species Massilina protea, A. tepida, and Bolivina striatula were related to high salinity, while Miliolinella subrotunda presents a negative relationship to this variable. Based on the distribution of foraminiferal species and their responses to the analyzed environmental variables, five regions with different ecological characteristics and sediment trophic states were identified. Among these, the central pond can be considered the most favorable environment. The western pond and the vicinity area of stromatolite field in the eastern pond, with a high concentration of lipids and proteins, were the least favorable region due to eutrophication status.
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Water, Air, & Soil Pollution
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Journal of Sedimentary Environments
In exploratory programs for kimberlites focused at discovering diamond deposits, it is important ... more In exploratory programs for kimberlites focused at discovering diamond deposits, it is important to identify tools that define their fertility. The observation of mineral indices such as garnet and ilmenite is the first indication of the proximity of kimberlite intrusion, and the possibility of using these minerals as fertility proxys through mineral chemistry allows us to characterize the presence of diamonds in kimberlite. In this work, mineral chemistry data in garnets and ilmenites concentrated in streams and soil were carried out to investigate the kimberlite intrusion from Ariquemes, State of Rondônia, northern Brazil, is reported. Ilmenite occurred exhibiting reaction bands for leucoxene, suggesting two phases in evolution during kimberlite ascension and inplacement. All garnets formed in rocks in the presence of clinopyroxene present a composition consistent with the G9 group. In these terms, it is concluded that the studied body is non-fertile and that the results reported here of the chemical compositions with respect to both garnets and ilmenites, indicate the sterility of the Ariquemes kimberlite intrusion.
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Journal of South American Earth Sciences, 2022
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Ambiente Bentônico, Vol 3, 2017
Neste capitulo e apresentado um estudo ecologico de foraminiferos bentonicos vivos, coletados em ... more Neste capitulo e apresentado um estudo ecologico de foraminiferos bentonicos vivos, coletados em estacoes localizadas no talude continental, Plato de Sao Paulo e cânions da Bacia de Campos, no ano de 2008 (periodo seco) e de 2009 (periodo chuvoso). As estacoes seguem nove transectos de 400 a 3.000 m de profundidade. O estudo teve como objetivo investigar mudancas na densidade, diversidade e composicao de foraminiferos bentonicos, ao longo desses transectos, em resposta a fatores ambientais. As mudancas na comunidade seguem o gradiente batimetrico e sao controladas pela disponibilidade e, provavelmente, qualidade do alimento. Os maiores valores medios de densidade, diversidade e riqueza, assim como o predominio de foraminiferos calcarios hialinos e especies infaunais refletem maior aporte de alimento recebido de forma continuada, nas estacoes mais rasas (400 m). Nas estacoes entre 700 e 1.000 m de profundidade, a densidade de individuos diminui e a presenca de especies oportunistas, que se reproduzem rapidamente na sequencia de pulsos de fitodetritos, e o reflexo de um aporte alimentar possivelmente sazonal. O aumento consideravel dos foraminiferos textulariideos, o decrescimo continuo na densidade de individuos e tambem nos valores do Indice de Produtividade de Foraminiferos Bentonicos (BFHP), a medida que aumenta a profundidade e valores extremamente baixos nas estacoes mais profundas (3.000 m), indicam condicoes tipicamente oligotroficas nesse setor da Bacia de Campos. A comparacao de dados de densidade e de composicao de especies nos periodos seco e chuvoso permite-nos inferir que no periodo chuvoso o aporte de alimento foi maior. Os valores de densidade e biomassa de foraminiferos bentonicos vivos permitem-nos deduzir que o Cânion Almirante Câmara constitui um local de maior aprisionamento de materia orgânica entre as isobatas de 400 a 1.000 m, em comparacao ao talude aberto para os mesmos limites de profundidades. A natureza do substrato e provavelmente os teores de oxigenio nas aguas do fundo oceânico revelaram-se fatores condicionantes secundarios na distribuicao desses organismos.
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In this work, the first results of ice rafted detritus (IRD) provenance related to Heinrich Events in the NW Iberian Margin are presented and discussed. This study is based on multi-proxies, namely on thorough analyses of Sr and Nd isotope ratios measured in the detrital fraction of the sediment core KC 024-19, from the Galician continental slope (NE Atlantic), aiming to unravel the sources of the terrigenous component of the sampled sediments.
In most of the core layers, the isotope signatures are consistent with an origin, ultimately, in the nearby Variscan continental crust. However, allochthonous contributions were also deposited, namely during the last four Heinrich Events (HE). The non-carbonate detrital fraction of the sediments deposited during the HE1 (in its upper part), HE2, and HE4 displays 3Nd much lower than usual, suggesting that those layers incorporate clasts dropped by icebergs (Ice-Rafted Detritus e IRD) whose sources must have been located in Archaean cratons, such as those of northeastern America and Greenland. The low-3Nd values combined with dolomite peaks support the hypothesis that icebergs fed by the Laurentide ice sheet and launched through Hudson Strait played a major role in the deposition of IRD during HE1, HE2, and HE4. The HE1 layer seems to record a complex evolution of this event, since, at its base, the coarse- grained non-carbonate fraction displays relatively high-3Nd values, pointing to European/Icelandic sources for the icebergs in the initial stages of HE1. The IRD content of the HE3 contrasts significantly with the other HE layers and the non-IRD layers because it has an isotope signature characterized by low 87Sr/86Sr ratios and high-3Nd values. This suggests that the most exotic components of the HE3 layer may have come from East Greenland e Fram Strait and/or result from a mixture of materials from western European and more juvenile (Iceland e Faeroes) crustal sources.
Authors: Virgínia Martins; Fernando Rocha; Cristina Sequeira; Paula Martins; José Santos; João A. Dias; Olivier Weber; Jean-Marie Jouanneau; Belén Rubio; Daniel Rey; Ana Bernabeu; Eduardo Silva; Lazaro Laut; Rubens Figueira
This work aims to study recent climatic oscillations and their influence on sedimentation in the Ria de Vigo, a coastal embayment in Galicia, NW Spain. It is based on the study of clay mineral assemblages, in conjunction with other proxies (granulometric, geochemical, geochronological and microfaunal), in the core KSGX 24. A Benthic Foraminifera High Productivity (BFHP) proxy was used to determine changes in the flux of organic matter (OM) at the bottom of the study area. Total organic carbon (TOC) content is not a suitable proxy to estimate changes in the past supply of OM due to diagenetic processes. The sedimentation was finest in 3 sections: ~ 230–214 cm, ~ 185–73 cm and ~ 20–0 cm. These muddy sections are characterised, in general, by higher proportions of detrital minerals, concentrations of several chemical elements related to lithogenic sources and BFHP values. In addition, these sections are impoverished in carbonates, Ca, Sr and La when compared with the layers with the highest sand content. The clay mineral assemblage of the studied site, characterised by the dominance of illite, intermediate concentrations of kaolinite and minor amounts of smectite and chlorite, reveals the prevalence of a typical temperate humid climate in the last 3 ka BP, the estimated age for the core base. However, the quantities of illite and chlorite increase in the muddy layers. The characteristics of these muddy layers were interpreted as representing relatively cold climatic oscillations associated with the strengthening of northerly winds and the prevalence of an upwelling regime corresponding to well-known periods, such as the first cold period of the Upper Holocene (~ 2.9 ka cal BP), the Dark Ages (between ~ 2.2 - 1.2 ka cal BP) and the Little Ice Age (~ 0.6 ka cal BP).
In this work, the first results of ice rafted detritus (IRD) provenance related to Heinrich Events in the NW Iberian Margin are presented and discussed. This study is based on multi-proxies, namely on thorough analyses of Sr and Nd isotope ratios measured in the detrital fraction of the sediment core KC 024-19, from the Galician continental slope (NE Atlantic), aiming to unravel the sources of the terrigenous component of the sampled sediments.
In most of the core layers, the isotope signatures are consistent with an origin, ultimately, in the nearby Variscan continental crust. However, allochthonous contributions were also deposited, namely during the last four Heinrich Events (HE). The non-carbonate detrital fraction of the sediments deposited during the HE1 (in its upper part), HE2, and HE4 displays 3Nd much lower than usual, suggesting that those layers incorporate clasts dropped by icebergs (Ice-Rafted Detritus e IRD) whose sources must have been located in Archaean cratons, such as those of northeastern America and Greenland. The low-3Nd values combined with dolomite peaks support the hypothesis that icebergs fed by the Laurentide ice sheet and launched through Hudson Strait played a major role in the deposition of IRD during HE1, HE2, and HE4. The HE1 layer seems to record a complex evolution of this event, since, at its base, the coarse- grained non-carbonate fraction displays relatively high-3Nd values, pointing to European/Icelandic sources for the icebergs in the initial stages of HE1. The IRD content of the HE3 contrasts significantly with the other HE layers and the non-IRD layers because it has an isotope signature characterized by low 87Sr/86Sr ratios and high-3Nd values. This suggests that the most exotic components of the HE3 layer may have come from East Greenland e Fram Strait and/or result from a mixture of materials from western European and more juvenile (Iceland e Faeroes) crustal sources.
Authors: Virgínia Martins; Fernando Rocha; Cristina Sequeira; Paula Martins; José Santos; João A. Dias; Olivier Weber; Jean-Marie Jouanneau; Belén Rubio; Daniel Rey; Ana Bernabeu; Eduardo Silva; Lazaro Laut; Rubens Figueira
This work aims to study recent climatic oscillations and their influence on sedimentation in the Ria de Vigo, a coastal embayment in Galicia, NW Spain. It is based on the study of clay mineral assemblages, in conjunction with other proxies (granulometric, geochemical, geochronological and microfaunal), in the core KSGX 24. A Benthic Foraminifera High Productivity (BFHP) proxy was used to determine changes in the flux of organic matter (OM) at the bottom of the study area. Total organic carbon (TOC) content is not a suitable proxy to estimate changes in the past supply of OM due to diagenetic processes. The sedimentation was finest in 3 sections: ~ 230–214 cm, ~ 185–73 cm and ~ 20–0 cm. These muddy sections are characterised, in general, by higher proportions of detrital minerals, concentrations of several chemical elements related to lithogenic sources and BFHP values. In addition, these sections are impoverished in carbonates, Ca, Sr and La when compared with the layers with the highest sand content. The clay mineral assemblage of the studied site, characterised by the dominance of illite, intermediate concentrations of kaolinite and minor amounts of smectite and chlorite, reveals the prevalence of a typical temperate humid climate in the last 3 ka BP, the estimated age for the core base. However, the quantities of illite and chlorite increase in the muddy layers. The characteristics of these muddy layers were interpreted as representing relatively cold climatic oscillations associated with the strengthening of northerly winds and the prevalence of an upwelling regime corresponding to well-known periods, such as the first cold period of the Upper Holocene (~ 2.9 ka cal BP), the Dark Ages (between ~ 2.2 - 1.2 ka cal BP) and the Little Ice Age (~ 0.6 ka cal BP).