Geophysical and geochemical evidence for cold upper mantle beneath the Equatorial Atlantic Ocean

Sichel, Susanna Eleonora; Esperança, Sonia; Motoki, Akihisa; Maia, Márcia; Horan, M. F.; Szatmári, Péter; Alves, Eliane da Costa; Mello, Sidney Luiz de Matos

doi:10.1590/s0102-261x2008000100006

Cited by 36 publications

(24 citation statements)

References 35 publications

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“…The predicted depth of guyots indicates that the vertical resolution is about 50 m. TOPEX dataset is widely used for scientific documents, including Brazilian ones (e.g. Sichel et al, 2008;Motoki et al, 2009;Campos et al, 2010).…”

Section: Methodsmentioning

confidence: 99%

Satellite-Derived Gravimetry for Abrolhos Continental Shelf, States of Espírito Santo and Bahia, Brazil, and Its Relation to Tectonic Genesis of Sedimentary Basins

Motoki¹,

Novais²,

Motoki³

et al. 2014

Rev. Bras. Geof.

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ABSTRACT. This paper presents the results of satellite-derived gravimetry for Abrolhos Continental Shelf and the adjacent areas, States of Espírito Santo and Bahia, Brazil, and discusses tectonic genesis of the sedimentary basins. The free-air and Bouguer anomalies on the continental shelf show a gradual increase from coast to continental shelf break. The total difference of 135 mGal indicates crust thinning of 4.5 km. The Bouguer anomaly increases beyond the shelf break and continues up to the abyssal plane. The total difference of 260 mGal suggests crustal thinning of 9.0 km. The studied area has two types of passive continental margin: 1) ES-type with high continental slope, low and narrow continental rise, and high free-air and Bouguer anomalies; 2) SP-type with low continental slope, high and wide continental rise, and low gravity anomalies. There are three types of sedimentary basins with different geologic structure and tectonic genesis: 1) Basins on the continental shelf, CSH-type; 2) Basin on the continental rise, CRS-type; 3) Continental rift basin, CRF-type. The CSH-type, as Espírito Santo basin, has coherent free-air and Bouguer anomalies 40 to 50 mGal lower than the adjacent areas. The sedimentary deposits are 2.0 to 2.5 km thick. The basement depression is sustained by mechanical strength without isostatic compensation. The normal faults of basin border are limited within upper crust. The CRS-type, as Pedro Canário basin, has low local residual Bouguer anomaly with difference of 40 mGal. The sedimentary deposits are more than 2.7 km thick. The continental side basin border is under isostatic compensation due to deep normal fault between continental slope and continental rise. The oceanic side border is sustained by mechanical strength of the basement. The CRF-type, Besnard Passage, is a continental rift basin originated from mantle pull-apart tectonism. The rift bottom is under complete isostatic compensation. The normal faults of the graben border continue to the mantle. The Moho depth along the rift is at least 6.5 km shallower than the adjacent areas.Keywords: satellite-derived gravimetry, Abrolhos Continental Shelf, sedimentary basin, crustal thinning, isostatic compensation. RESUMO.Este artigo apresenta os resultados da gravimetria por satélite para a Plataforma Continental de Abrolhos e asáreas adjacentes, ES-BA, e discute as gêneses tectônicas das bacias sedimentares. As anomalias ar-livre e Bouguer na plataforma continental mostram um aumento gradativo a partir da costa até a quebra da plataforma continental. A diferença total de 135 mGal indica afinamento da crosta continental de 4,5 km. A anomalia Bouguer se apresenta além da quebra da plataforma e continua até o assoalho abissal. A diferença total de 260 mGal sugere afinamento crustal de 9,0 km. Naárea estudada, observam-se dois tipos de margem continental passiva: 1) Tipo ES com talude continental alto, elevação continental baixa e curta e anomalias ar-livre e Bouguer altos; 2) Tipo SP com talude continental baixo, elevação continental ...

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Section: Methodsmentioning

confidence: 99%

Satellite-Derived Gravimetry for Abrolhos Continental Shelf, States of Espírito Santo and Bahia, Brazil, and Its Relation to Tectonic Genesis of Sedimentary Basins

Motoki¹,

Novais²,

Motoki³

et al. 2014

Rev. Bras. Geof.

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“…It is the highest and steepest point of the Saint Peter and Saint Paul massif, linked to the Atlantic Mid-Ocean ridge, close to the Equator (0°55 0 N and 29°21 0 W). This massif is about 90 km long and 21 km wide at the 3,000 m depth contour (Sichel et al 2008). The archipelago has an emerged area of about 16,000 m 2 , extends up to 400 m and can reach a maximum height of 18 m above sea level.…”

Section: Study Areamentioning

confidence: 98%

Distribution of decapod larvae in the surface layer of an isolated equatorial oceanic archipelago: the cases of benthic Grapsus grapsus (Brachyura: Grapsidae) and pelagic Sergestes edwardsi (Dendrobranchiata: Sergestidae)

2012

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Two different decapod larval assemblages inhabit the marine environment of Saint Paul's Rocks, differentiating the inlet from the surrounding oceanic waters. Larvae of the crab Grapsus grapsus and of the holopelagic shrimp Sergestes edwardsi are abundant in superficial waters of the archipelago and have previously been shown to be good indicators of the inlet and adjacent oceanic waters, respectively. We investigated the horizontal, diel and temporal distribution of these species at Saint Paul's Rocks. Horizontal surface hauls were conducted from 2003 to 2005, in the inlet and at four increasing distances from the archipelago, in the morning and at night, using a 200-lm mesh net. Larvae of G. grapsus were identified in samples from all expeditions and abundance was found significantly higher at night in the inlet site. Only larvae in the first zoeal stage were found in samples, highlighting the importance of the area for this species reproduction. On the contrary, the distribution of larvae of S. edwardsi was typical of a holopelagic species, which are permanent residents of the water column and spawn in oceanic areas, indicating that the islands are of little influence to them.

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“…The study area comprises the adjacent waters around the SPSPA (0 • 55 ′ 01 ′′ N, 29 • 20 ′ 44 ′′ W), a group of 10 small islets and rocky summits that originated from a Meso-Atlantic elevation (plutonic massif with sedimentary covering) at 4000 m deep (Figure 1; Sichel et al, 2008). It is located in the Equatorial Atlantic Ocean at 1000 km from the northeastern cost of Brazil and 1800 km from the African coast.…”

Section: Study Areamentioning

confidence: 99%

Seasonal-Dial Shifts of Ichthyoplankton Assemblages and Plastic Debris around an Equatorial Atlantic Archipelago

Lima

Barletta

Costa

2016

Front. Environ. Sci.

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Seasonality was a stronger influence in the ichthyoplankton assemblages around the Saint Peter and Saint Paul Archipelago (SPSPA) than distance from the islands. Plastic debris were ubiquitous and although it presented diel trends, no other spatiotemporal patterns was showed. Larval Oxyporhamphus micropterus was the most important taxa (29.37% of the total catch), followed by Ceratoscopelus warmingii and Entomacrodus vomerianus. Exocoetidae eggs represented 41.01%. Mesopelagic fish larvae dominated the community. Myctophidae had the highest species richness (15). Four larval fish assemblages occurred: (1) night-time demersal/bathydemersal (Anguillidae, Congridae); (2) daytime mesopelagic/bathypelagic/epipelagic (Myctophidae, Cyclothone acclinidens); (3) daytime epipelagic (Exocoetidae, Coryphaena hippurus, Thunnus albacares); and (4) night-time reef and demersal (Blennidae, Pomacentridae, Lutjanidae). The dry season (lower temperature, higher chlorophyll a and higher SW wind velocity) influenced the first two assemblages. The rainy season (higher temperatures and lower NW wind velocity) influenced the last two. Nighttime abundance of dominant species in the rainy season suggests diel vertical migration nearshore. Plastics were 2.12 times more abundant than the most abundant fish larvae. Comparable amounts of larvae and plastics in the water column increase the chances of interaction between these two compartments and might disturb the local marine food web and promote the transfer of microplastic from one habitat to another, especially when smaller taxa contaminated by ingested fragments are preyed by migratory animals such as marine birds and tuna. A study around the area concluded that at least a part of the plastic debris can have local source due to fishing activities. Small-scale oceanographic mechanisms such as the interaction between the topography and currents (SEC and EUC) seem to be responsible for the retention of fish eggs, fish larvae and plastics around SPSPA.

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Geophysical and geochemical evidence for cold upper mantle beneath the Equatorial Atlantic Ocean

Abstract: ABSTRACT. This

Cited by 36 publications

References 35 publications

Satellite-Derived Gravimetry for Abrolhos Continental Shelf, States of Espírito Santo and Bahia, Brazil, and Its Relation to Tectonic Genesis of Sedimentary Basins

Satellite-Derived Gravimetry for Abrolhos Continental Shelf, States of Espírito Santo and Bahia, Brazil, and Its Relation to Tectonic Genesis of Sedimentary Basins

Distribution of decapod larvae in the surface layer of an isolated equatorial oceanic archipelago: the cases of benthic Grapsus grapsus (Brachyura: Grapsidae) and pelagic Sergestes edwardsi (Dendrobranchiata: Sergestidae)

Seasonal-Dial Shifts of Ichthyoplankton Assemblages and Plastic Debris around an Equatorial Atlantic Archipelago

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