Idade do vulcanismo no Oceano Atlântico Sul

Cordani, Umberto G.

doi:10.11606/issn.2316-9001.v1i0p09-75

Cited by 89 publications

(56 citation statements)

References 13 publications

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“…Possuindo mais de 20 ilhas, ilhotas e rochedos isolados totalizando uma área aproximada de 26 km², sendo 17 km² apenas da ilha principal, o arquipélago de pouco mais de 12 milhões de anos representa o que ainda não foi erodido de um grande edifício vulcânico, cuja base apresenta cerca de 60 km em seu maior diâmetro e assenta-se no assoalho oceânico a 4.000 m de profundidade, e faz parte de uma ramificação da Dorsal Médio Atlântica em direção à costa brasileira (Cordani 1970, Almeida 1955 O clima típico de Fernando de Noronha é tropical quente, semelhante ao do Agreste Nordestino, sendo bastante influenciado pelo domínio oceânico, com uma temperatura média anual de 26,5 °C havendo uma amplitude anual de 4 °C em relação a esse valor. Ocorrem localmente duas estações bem definidas, a chuvosa de janeiro a junho e a seca de julho a dezembro.…”

Section: Methodsunclassified

Fenologia da frutificação de espécies vegetais nativas e a restauração florestal no arquipélago de Fernando de Noronha, PE, Brasil

Machado

Brancalion

Potascheff

et al. 2013

Hoehnea

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-(Fructification phenology of native plant species and the forest restoration in Fernando de Noronha archipelago, Pernambuco State, Brazil). The annual pattern of fructification phenology of 23 native species of trees and bushes of Fernando de Noronha, Pernambuco State, Brazil was characterized with the aim of guiding the seed collection towards the implementation of a local restoration program. It was found that most species (74%) presented higher absolute frequencies of fructification during the rainy season (January to July) as opposed to 26% during the dry season, and the fructification lasted, on average, one month and a half. The Spearman correlation coefficient indicated a positive correlation between the studied phenophases and the precipitation. This kind of study is strategic for planning the seed collection and seedling production for restoration programs, especially in places where the process of Ecological Restoration is just beginning and still lacks information, such as Fernando de Noronha.

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Section: Methodsunclassified

Fenologia da frutificação de espécies vegetais nativas e a restauração florestal no arquipélago de Fernando de Noronha, PE, Brasil

Machado

Brancalion

Potascheff

et al. 2013

Hoehnea

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“…The transgressive megasequence consists of Albian carbonate platforms accumulated below muddy and sandy turbidites, and marks a general deepening-upwards trend towards the end of the Cretaceous (Davison, 1999;Fiduk et al, 2004;Alves et al, 2009). The regressive megasequence marks the reactivation of rift structures and episodic magmatic activity (Demercian et al, 1993;Cobbold et al, 2001;Mohriak et al, 2008), and is associated with the emplacement of the Abrolhos Bank to the north of the study area (Cordani, 1970). A large amount of sediments sourced from the Abrolhos Bank and onshore rivers were transported downslope by submarine canyons and channels during the regressive megasequence (Bruhn and Walker, 1997;Davison, 1999).…”

Section: Tectono-sedimentary Evolution Of the Espírito Santo Basinmentioning

confidence: 97%

Quantitative seismic geomorphology of a submarine channel system in SE Brazil (Espírito Santo Basin): Scale comparison with other submarine channel systems

Qin

Alves

Constantine

et al. 2016

Marine and Petroleum Geology

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Detailed morphological analyses of a Pleistocene-Holocene submarine channel system in terms of its hierarchical framework, were carried out using a 3D seismic volume from offshore Espírito Santo, SE Brazil. The channel morphology shows marked variations, with five segments (Segments a to e) being identified along its full length. For example, the cross-sectional area of the channel decreases by a factor of 70 from Segment a to Segment c, and is then followed by a nearly four-fold increase from Segment c to Segment d. The significant changes in channel morphology relate to temporal and spatial variations in flow volume within the channel. In the same channel system, the valley reveals three distinct segments (Segments A to C), with similar aspect ratios but marked variations in morphology along the valley distance. Valley morphological changes are chiefly affected by erosional processes. Segment B is characterised by the largest valley-base width, valley width, and cross-sectional area compared to the other two segments. Valley enlargement in Segment B results from relatively high degrees of lateral channel migration and associated cut bank erosion, leading to the widening of the valley, especially the valley base. In Segment C, the valley is characterised by inner bank erosion in the form of shallow-seated mass failures, which only enlarged the upper part of the valley wall. The spatial variations in both channel and valley morphology documented here suggest an important role of local factors (e.g. salt diapirs, tributaries, overbank collapse) in the development of channel systems. Hence, the morphological analyses developed in this work provide an effective tool for studying channels and valleys on continental slopes around the world.

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“…The first geochronologic determinations, performed in the 70's (Cordani 1970) by the whole-rock K-Ar method, defined ages ranging between 8-9 to 12 Ma as indicative of the eruption dates of the Remédios Formation. Phonolite ages, varying from 11.2 ± 0.3 to 8.0 ± 0.2 Ma, roughly define the same range as a large trachyte dike (8.8 ± 0.3 Ma).…”

Section: Geochronologymentioning

confidence: 99%

“…Thin dikes emplaced within the pyroclastic Remédios rocks indicated ages of 8.8 ± 0.3 Ma. The ages obtained for the São José basanites (around 9.5 Ma) were interpreted formerly as misleading because of a possible contamination of the rocks with incompletely degassed mantle material (Cordani 1970, cf. also Cordani et al 2004.…”

Section: Geochronologymentioning

confidence: 99%

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Geochemistry of the alkaline volcanicsubvolcanic rocks of the Fernando de Noronha Archipelago, southern Atlantic Ocean

Lopes

Ulbrich

2015

Braz. J. Geol.

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ABSTRACT:The Fernando de Noronha Archipelago presents, on its main island, a centrally-located stratigraphic unit, the Remédios Formation (age around 8 -12 Ma) constituted by basal pyroclastic rocks intruded by dikes, plugs and domes of varied igneous rocks, capped by flows and pyroclastics of mafic to ultramafic rocks of the Quixaba Formation (age around 1 -3 Ma), which is limited from the underlying unit by an extensive irregular erosion surface. A predominant sodic Remédios series (basanites, tephrites, tephriphonolites, essexite, phonolites) can be separated from a moderately potassic Remédios sequence (alkali basalts, trachyandesites, trachytes), both alkaline series showing mostly continuous geochemical trends in variation diagrams for major as well as trace elements, indicating evolution by crystal fractionation (mainly, separation of mafic minerals, including apatites and titanites). There are textural and mineralogical evidences pointing to hybrid origin of some intermediate rocks (e.g., resorbed pyroxene phenocrysts in basaltic trachyandesites, and in some lamprophyres). The primitive Quixaba rocks are mostly melanephelinites and basanites, primitive undersaturated sodic types. Geology (erosion surface), stratigraphy (two distinct units separated by a large time interval), petrography (varied Remédios Formation, more uniform Quixaba unit) and geochemistry indicate that the islands represent the activity of a protracted volcanic episode, fueled by intermittent melting of an enriched mantle, not related to asthenospheric plume activity. KEYWORDS:OIB; South Atlantic Ocean; Mafic to ultramafic volcanic-subvolcanic rocks; Sodic and potassic series. RESUMO: O Arquipélago de Fernando de Noronha mostra na sua ilha principal, na parte central, a Formação Remédios (idade em torno de 8 -12 Ma) constituída por rochas piroclásticas basais invadidas por diques, plugs e domos de variadas rochas ígneas, capeadas por derrames e piroclásticas das rochas máficas a ultramáficas da Formação Quixaba (idade de 1 a 3 Ma), separada da unidade inferior por uma superfície de erosão extensa e irregular. Uma série predominante sódica de Remédios (basanitos, tefritos, tefrifonolitos, essexito, fonolitos) pode ser diferenciada da série moderadamente potássica (álcali basaltos, traquiandesitos, traquitos), pertencente à mesma unidade. Ambas as séries mostram tendências geoquímicas geralmente contínuas em diagramas de variação de elementos maiores e traços, indicando origem por cristalização fracionada (principalmente, separação de minerais máficos, incluindo apatitas e titanitas). São encontradas evidências mineralógicas e texturais apontando

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Idade do vulcanismo no Oceano Atlântico Sul

Abstract: * tste resultado anormal não foi levado em conta para efeito de média. Amostra granular. * Não foi levado em consideração em vista da grande quanti da de de argônio 40 atmosférico, próximo de 95%.

Cited by 89 publications

References 13 publications

Fenologia da frutificação de espécies vegetais nativas e a restauração florestal no arquipélago de Fernando de Noronha, PE, Brasil

Fenologia da frutificação de espécies vegetais nativas e a restauração florestal no arquipélago de Fernando de Noronha, PE, Brasil

Quantitative seismic geomorphology of a submarine channel system in SE Brazil (Espírito Santo Basin): Scale comparison with other submarine channel systems

Geochemistry of the alkaline volcanicsubvolcanic rocks of the Fernando de Noronha Archipelago, southern Atlantic Ocean

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Idade do vulcanismo no Oceano Atlântico Sul

Abstract: * tste resultado anormal não foi levado em conta para efeito de média. ** Amostra granular. *** Não foi levado em consideração em vista da grande quanti da de de argônio 40 atmosférico, próximo de 95%.

Cited by 89 publications

References 13 publications

Fenologia da frutificação de espécies vegetais nativas e a restauração florestal no arquipélago de Fernando de Noronha, PE, Brasil

Fenologia da frutificação de espécies vegetais nativas e a restauração florestal no arquipélago de Fernando de Noronha, PE, Brasil

Quantitative seismic geomorphology of a submarine channel system in SE Brazil (Espírito Santo Basin): Scale comparison with other submarine channel systems

Geochemistry of the alkaline volcanicsubvolcanic rocks of the Fernando de Noronha Archipelago, southern Atlantic Ocean

Contact Info

Product

Resources

About

Abstract: * tste resultado anormal não foi levado em conta para efeito de média. Amostra granular. * Não foi levado em consideração em vista da grande quanti da de de argônio 40 atmosférico, próximo de 95%.