scholarly journals Intraplate deformation of oceanic crust near the Rio Grande Rise in the South Atlantic

2020 ◽  
Vol 790 ◽  
pp. 228543
Author(s):  
Justin Estep ◽  
Robert Reece ◽  
Dominik A. Kardell ◽  
Nicholas D. Perez ◽  
Gail L. Christeson ◽  
...  
Keyword(s):  
Oceanic Crust ◽  
Rio Grande ◽  
South Atlantic ◽  
The South ◽  
Intraplate Deformation

Taxonomy of Nystiellidae (Caenogastropoda, Epitonioidea) from Brazil, with description of three new species from the South-western Atlantic

2017 ◽  
Vol 98 (7) ◽  
pp. 1619-1644 ◽  
Author(s):  
Alexandre Dias Pimenta ◽  
Bruno Garcia Andrade ◽  
Ricardo Silva Absalão
Keyword(s):  
Rio Grande ◽  
Taxonomic Revision ◽  
South Atlantic ◽  
Shell Morphology ◽  
The South ◽  
Western Atlantic ◽  
North East ◽  
The North ◽  
Eastern Brazil ◽  
North Eastern

A taxonomic revision of the Nystiellidae from Brazil, including samples from the Rio Grande Rise, South Atlantic, was performed based on shell morphology. Five genera and 17 species were recognized. For the richest genus,Eccliseogyra, the three species previously recorded from Brazil were revised:E. brasiliensisandE. maracatu, previously known only from their respective type series, were re-examined. Newly available material ofE. maracatuexpanded the known geographic range of this species to off south-east Brazil.Eccliseogyra nitidais now recorded from north-eastern to south-eastern Brazil, as well as from the Rio Grande Rise. Three species ofEccliseogyraare newly recorded from the South Atlantic:E. monnioti, previously known from the north-eastern Atlantic, occurs off eastern Brazil and on the Rio Grande Rise; its protoconch is described for the first time, confirming its family allocation.Eccliseogyra pyrrhiasoccurs off eastern Brazil and on the Rio Grande Rise, andE. folinioff eastern Brazil. The genusIphitusis newly recorded from the South Atlantic.Iphitus robertsiwas found off northern Brazil, although the shells show some differences from the type material, with less-pronounced spiral keels. Additional new finds showed thatIphitus cancellatusranges from eastern Brazil to the Rio Grande Rise, and Iphitusnotiossp. nov. is restricted to the Rio Grande Rise.Narrimania, previously recorded from Brazil based on dubious records, is confirmed, including the only two living species described for the genus:N. azelotes, previously only known from the type locality in Florida, andN. concinna, previously known from the Mediterranean. A third species,Narrimania raquelaesp. nov. is described from eastern Brazil, diagnosed by its numerous and thinner cancellate sculpture. To the three species ofOpaliopsispreviously known from Brazil, a fourth species,O. arnaldoisp. nov., is added from eastern Brazil, and diagnosed by its very thin spiral sculpture, absence of a varix, and thinner microscopic parallel axial striae.Papuliscala nordestina, originally described from north-east Brazil, is recorded off eastern Brazil and synonymized withP. elongata, a species previously known only from the North Atlantic.

scholarly journals Mollusca, Bivalvia, Cuspidariidae, Plectodon braziliensis (E. A. Smith, 1915) n. comb.: record of the genus for the South Atlantic, off Brazil

Check List ◽  
2010 ◽  
Vol 6 (4) ◽  
pp. 648 ◽  
Author(s):  
Daniel M. Pimpão ◽  
Inga L. Veitenheimer-Mendes ◽  
Fabrizio Scarabino
Keyword(s):  
Type Species ◽  
Rio Grande ◽  
First Record ◽  
South Atlantic ◽  
New Combination ◽  
Rio Grande Do Sul ◽  
The South ◽  
Scientific Collections

An analysis of bivalves shells collected off the coast of Rio Grande, Rio Grande do Sul, Brazil and specimens of scientific collections, identified as Cuspidaria braziliensis E. A. Smith, 1915 was made. From the examination of syntypes of C. braziliensis and the type species of the genus Plectodon Carpenter, 1864, a redescription was made and it is proposed to transfer the species to the genus Plectodon, resulting in the new combination Plectodon braziliensis (E.A. Smith, 1915). This is the first record of a Plectodon species for the South Atlantic.

87Sr/86Sr dating and preliminary interpretation of magnetic susceptibility logs of giant piston cores from the Rio Grande Rise in the South Atlantic

2017 ◽  
Vol 80 ◽  
pp. 244-254 ◽  
Author(s):  
Christian Michel Lacasse ◽  
Roberto Ventura Santos ◽  
Elton Luiz Dantas ◽  
Quentin Vigneron ◽  
Isabela Moreno Cordeiro de Sousa ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Rio Grande ◽  
South Atlantic ◽  
The South

Crustal Thickness and Composition of the São Paulo Plateau and Florianópolis Ridge, SE Brazilian Margin

2020 ◽  
Author(s):  
Michelle Graça ◽  
Leanne Cowie ◽  
Nick Kusznir ◽  
Natasha Stanton
Keyword(s):  
Oceanic Crust ◽  
Seismic Reflection ◽  
Joint Inversion ◽  
Gravity Data ◽  
South Atlantic ◽  
Gravity Inversion ◽  
The South ◽  
Subsidence Analysis ◽  
Base Salt ◽  
Thermal Subsidence

<p>The São Paulo Plateau (SPP) and the Florianópolis Ridge (FR), located on the Santos segment of the SE Brazilian margin in the South Atlantic, are large positive bathymetric features with a combined lateral dimension of approximately 500 km. An important question is whether they are underlain by thinned continental crust or by anomalously thick magmatic crust. Each hypothesis has implications for the breakup of the South Atlantic and the evolution of the overlying saline Santos basin.</p><p>Integrated quantitative analysis consisting of gravity inversion, RDA (residual depth anomaly) analysis and flexural subsidence analysis has been applied to a deep long-offset seismic reflection line running NW-SE across the SPP and FR. Gravity inversion predicts crustal basement thicknesses in the range of 12 to 15 km for the SPP and FR, deceasing to 7-8 km thickness at the extreme SE end of the profile. The SPP and FR are separated by a region of thinner crust approximately 80 km wide. Thinning factors from subsidence analysis for SPP and FR are typically between 0.6 and 0.7.</p><p>RDA values close to zero and a thinning factor of 1 were obtained for the region with 7-8 km thick crust at the SE end of the profile which are all consistent with normal oceanic crust rather than previously interpreted exhumed mantle. This oceanic crust is highly tectonised and corresponds to the location of the Florianópolis Fracture Zone.</p><p>Flexural backstripping and reverse thermal subsidence modelling were performed to calculate palaeo-bathymetry at breakup and give 2.5 km below sea level at the SE end of the profile consistent with this region being oceanic crust. Flexural subsidence analysis applied to base salt shows that the observed base salt subsidence requires a component of syn-tectonic subsidence as well as post-rift thermal subsidence, and that the salt was deposited while the crust was still thinning.</p><p>Joint inversion of time seismic reflection and gravity data to determine the lateral variation in basement density by comparing seismic and gravity Moho in the time domain gives a basement density under the SPP and FR of between 2600 and 2700 kg/m<sup>3</sup>. The same method gives a basement density of 900kg/m<sup>3</sup> for the oceanic crust at the SE end of the profile. The FR basement in the NW shows a basement density similar to that of the SPP while in its SE the basement density is much higher approaching 2950 kg/m3.  We interpret the relatively low basement densities of the SPP with respect to that of oceanic crust as indicating a continental rather than magmatic composition. A similar analysis to determine basement density applied to the Evain et al. (2015) seismic refraction profile in the same location also gives a SPP basement density that supports a continental composition.</p>

Contributions to thermo-tectonic history of the Rio Grande Rise (South Atlantic Ocean) as revealed by apatite (U-Th-Sm)/He thermochronology

2020 ◽  
Author(s):  
Peter Christian Hackspacher ◽  
Bruno Venancio da Silva ◽  
Ulrich Anton Glasmacher ◽  
Gustavo Soldado Peres
Keyword(s):  
Atlantic Ocean ◽  
Rio Grande ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
The South ◽  
South American Plate ◽  
Tectonic History ◽  
Tectonically Active ◽  
History Of ◽  
Uplift And Erosion

<p>The Rio Grande Rise (RGR) consists of an aseismic, basaltic plateau currently submerged in the southwestern side of the South Atlantic Ocean. Its origin is still a matter of considerable debate, ranging from a microcontinent formed by fragmentation of the South American plate (1) to a basaltic ridge formed by expressive intra-plate magmatism triggered by the arrival of the Tristan da Cunha plume in the Cretaceous (2). The western portion of the RGR (WRGR) is crossed by a major rift-like structure known as the Cruzeiro do Sul Lineament (CSL) interpreted as tectonically active mainly from Upper Cretaceous to Middle Eocene (3). So far, understanding the development of the CSL is central to deciphering the thermo-tectonic history of the RGR with implications for the understanding of opening of the South Atlantic Ocean and the evolution of associated lithospheric plate margins. For this purpose, basaltic rocks from the northern and southern flanks of the CSL dredged during the Rio Grande Rise Project expedition (PROERG) carried out by the Geological Survey of Brazil (CPRM) were analysed for apatite (U-Th-Sm)/He (AHe) thermochronology. Thermal histories for these rocks (time-temperature paths) were obtained by the QTQt software (4). Single-grain AHe ages vary from ~ 5 to 65 Ma and the thermal histories indicate a phase of cooling at the southern flank in the Eocene, and three phases of cooling at the northern flank: in the Eocene, Miocene, and Pliocene, respectively. Based on published seismic and stratigraphic data (3,5,6), the Eocene cooling is mainly interpreted in terms of magmatic cooling and basement uplift and erosion, whereas the Miocene and the Pliocene cooling probably reflect tectonic driven basement uplift and erosion. The preliminary AHe data suggest that the CSL was tectonically active at least until the Pliocene. Plumes evolution also must be considered to explain these reactivations and uplifts.  </p><p> </p><ol><li>Kumar, N., 1979. Origin of “paired” aseismic rises: Ceará and Sierra Leone rises in the equatorial, and the Rio Grande Rise and Walvis Ridge in the South Atlantic. Mar. Geol. 30, 175–191. https://doi.org/10.1016/0025-3227(79)90014-8</li> <li>O’Connor, J.M., Duncan, R.A., 1990. Evolution of the Walvis Ridge-Rio Grande Rise Hot Spot System: Implications for African and South American Plate motions over plumes. J. Geophys. Res. 95, 17475. https://doi.org/10.1029/JB095iB11p17475</li> <li>Praxedes AGP, Castro DL, Torres LC, et al., 2019. New insights of the tectonic and sedimentary evolution of the Rio Grande Rise, South Atlantic Ocean. Marine and Petroleum Geology. https://doi.org/10.1016/j.marpetgeo.2019.07.035</li> <li>Gallagher K., 2012. Transdimensional inverse thermal history modeling for quantitative thermochronology. Journal of Geophysical Research: Solid Earth 117:1–16. https://doi.org/10.1029/2011JB008825</li> <li>Barker, P.F., 1983. Tectonic evolution and subsidence history of the Rio Grande Rise. In: Barker, P.F., Carlson, R.L., et al. (Eds.), Initial Reports of the Deep Sea Drilling Project, vol 72. US Government Printing Office, Washington, DC, pp. 953-976.</li> </ol><p>6. Mohriak, W.U., Nobrega, M., Odegard, M.E., Gomes, B.S., Dickson, W.G., 2010. Geological and geophysical interpretation of the Rio Grande Rise, south-eastern Brazilian margin: extensional tectonics and rifting of continental and oceanic crusts. Pet. Geosci. 16, 231–245. https://doi.org/10.1144/1354-079309-910</p>

scholarly journals New records of Pigrogromitus timsanus Calman, 1927 (Callipallenidae, Pycnogonida) for the South Atlantic

Check List ◽  
2019 ◽  
Vol 15 (1) ◽  
pp. 135-141
Author(s):  
Rudá A. Lucena ◽  
Martin L. Christoffersen
Keyword(s):  
New Records ◽  
Grey Literature ◽  
Rio Grande ◽  
South Atlantic ◽  
Monotypic Genus ◽  
The South ◽  
Worldwide Distribution ◽  
First Time ◽  
World Distribution

Pigrogromitus timsanus Calman, 1927 is a species of pycnogonid that has a broad world distribution and belongs to a monotypic genus. Although this species was recorded for the first time in the Southern Atlantic from the port of Natal, state of Rio Grande do Norte, this record appeared in the grey literature, has gone unnoticed, and to our knowledge, the specimens are not available for study. Based on materials in the Paulo Young Invertebrate Collection at Universidade Federal da Paraíba, we provide further proof of the presence of P. timsanus in the Southern Atlantic. We also provide an updated account on the worldwide distribution of this species. 

Hotspot origin for asymmetrical conjugate volcanic margins of the austral South Atlantic Ocean as imaged on deeply penetrating seismic reflection lines

2019 ◽  
Vol 7 (4) ◽  
pp. SH71-SH97 ◽  
Author(s):  
Kyle Reuber ◽  
Paul Mann ◽  
Jim Pindell
Keyword(s):  
Oceanic Crust ◽  
Seismic Reflection ◽  
Seismic Refraction ◽  
South Atlantic ◽  
Plate Motion ◽  
Basin Evolution ◽  
Spreading Ridge ◽  
The South ◽  
Volcanic Material ◽  
Conjugate Margins

We have interpreted 27,550 km of deep-penetrating, 2D-seismic reflection profiles across the South Atlantic conjugate margins of Uruguay/Southern Brazil and Namibia. These reflection profiles reveal in unprecedented detail the lateral and cross-sectional, asymmetrical distribution of voluminous, postrift volcanic material erupted during the Barremian-Aptian (129–125 Ma) period of early seafloor spreading in the southernmost South Atlantic. Using this seismic grid, we mapped the 10–200 km wide, continental margin-parallel limits of seaward-dipping reflector (SDR) complexes — that are coincident with interpretations from previous workers using seismic refraction data from the South American and West African conjugate margins. Subaerially emplaced and tabular SDRs have rotated downward 20° in the direction of the mid-Atlantic spreading ridge and are up to 22 km thick near the limit of continental crust. The SDR package is wedge shaped and thins abruptly basinward toward the limit of oceanic crust where it transitions to normal, 6–8 km thick oceanic crust. We have developed a model for the conjugate rifted margins that combine diverging tectonic plates and northwesterly plate motion relative to a fixed mantle position of the mantle plume. Our model explains an approximately 30% higher volume of SDRs/igneous crust on the trailing Namibian margin than on the leading Brazilian margin during the syn- and postrift phases. Our model for volcanic margin asymmetry in the South Atlantic does not require a simple shear mechanism to produce the asymmetrical volcanic material distribution observed from our data and from previously published seismic refraction studies. Determining the basinward extent of the extended continental basement is crucial for understanding basin evolution and for hydrocarbon exploration. Although these conjugate margins have evolved asymmetrically, their proximity during the early postrift stage suggests a near-equivalent, early basin evolution and similar hydrocarbon potential. Understanding the tectonic and magnetic processes that produce these observed asymmetries is critical for understanding volcanic passive margin evolution.

scholarly journals New calcareous dinoflagellates from the Palaeogene of the South Atlantic Ocean (DSDP Site 357, Rio Grande Rise)

1999 ◽  
Vol 18 (1) ◽  
pp. 89-95 ◽  
Author(s):  
Tania Hildebrand-Habel ◽  
Helmut Willems
Keyword(s):  
Atlantic Ocean ◽  
Rio Grande ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
The South ◽  
Dsdp Site

Abstract. The new calcareous dinoflagellate taxa Bitorus truncus n.sp., Calcigonellum ansatum n.sp. and Fuettererella fungiforma n.sp. are formally described on the basis of Eocene and Oligocene samples from DSDP Site 357 (western South Atlantic Ocean).

Sign in / Sign up

Export Citation Format

Share Document