Physical modelling of structural features of the Agulhas Basin and its evolution (South Atlantic)

2021 ◽  
Author(s):  
Anastasiia Tolstova ◽  
Eugene Dubinin ◽  
Andrey Groholsky
Keyword(s):  
Hot Spots ◽  
Hot Spot ◽  
South Atlantic ◽  
Plate Boundaries ◽  
Spreading Ridge ◽  
Transform Fault ◽  
The South ◽  
Spreading Axis ◽  
History Of ◽  
Series Of Experiments

<p>The evolution of the Agulhas oceanic basin was influenced by the formation of the southern part of the Mid-Atlantic Ridge (MAR) as a result of the jump of the spreading axis. This sector of the South Atlantic began to open up as a result of the breakup of Gondwana about 135-140 million years ago. The process of opening was accompanied by kinematic rearrangements in the movement of the lithospheric plates. According to some evolutionary models, the jumps of the spreading axis in the area of the Agulhas basin occurred under the influence of hot spots. The hot spots of Shona, Bouvet, and Discovery played an important role in the evolutionary process of plate boundaries. </p><p>The previously active Agulhas spreading ridge is located in the central part of basin. From the east, the basin is framed by the Agulhas plateau, from the west is the Meteor rise. On the north the basin is bounded by the Agulhas transform fault, and on the south by the Southwest Indian Ridge.</p><p>Using the method of physical modeling, the formation of volcanic provinces that influenced the formation of the Agulhas basin was modeled.</p><p>The first series of experiments is devoted to the jump of the spreading axis of the Agulhas Ridge and the formation of the MAR and the Meteor rise. The purpose of the experiments was to determine the conditions for the formation of Meteor rise, located on the western edge of the Agulhas basin. Experiments have shown that the formation of this block may be due to the action of a hot spot, and the block itself may have a complex structure and contain inclusions of continental crust, which could have separated during the break of the Falkland Plateau and the jump of the spreading axis.</p><p>The second series of experiments was devoted to modeling the Agulhas ridge, located on the northern rim of the Agulhas basin. The ridge has a linear structure extending along the Agulhas-Falkland transform fault. The purpose of the experiments was to test the hypothesis of the magmatic origin of this ridge in the conditions of a transform fault with transtension under the thermal influence of the Shona and Discovery hot spot. Experiments have shown that a linear magmatic ridge similar to the Agulhas ridge is formed in the transtension condition. It is also possible that the formation of the ridge may be associated with a change in the speed and direction of spreading.</p><p>The Antarctic sector of the South Atlantic, and in particular the Agulhas Basin, has a complex history of evolution. This is due to the displacement of the three major Gondwanan continents, and the activity of hot spots in this region and kinematic rearrangements, and the spatiotemporal migration of the Bouve triple junction with a complex stress field, the existence of the continental Falkland Plateau, and other factors.</p><p>The geological environment of the Agulhas basin is characterized by objects and structures that allow us to approach the history of the evolution of this complex area.</p>

Geoid roughness and long-wavelength segmentation of the South Atlantic spreading ridge

Nature ◽  
1988 ◽  
Vol 333 (6170) ◽  
pp. 255-258 ◽  
Author(s):  
Dominique Gibert ◽  
Vincent Courtillot
Keyword(s):  
South Atlantic ◽  
Spreading Ridge ◽  
The South ◽  
Long Wavelength

scholarly journals Identification guide to the shallow water (0–200 m) octocorals of the South Atlantic Bight

Zootaxa ◽  
2010 ◽  
Vol 2599 (1) ◽  
pp. 1 ◽  
Author(s):  
SUSAN T. DEVICTOR ◽  
STEVE L. MORTON
Keyword(s):  
Shallow Water ◽  
South Atlantic ◽  
South Atlantic Bight ◽  
The South ◽  
Sem Images ◽  
Western Atlantic ◽  
Identification Guide ◽  
Cape Hatteras ◽  
History Of

Octocoral diversity is well documented in the tropical western Atlantic and Indo–Pacific, but it has been several decades since a thorough species account of the shallow South Atlantic Bight region was produced (northwestern Atlantic between Cape Hatteras, NC and Cape Canaveral, FL, USA). Through the use of material from the NMNH and SERTC Octocorallia (=Alcyonaria) collections, this work documents the presence of 28 species of octocorals recorded in the shallow (0–200 m) South Atlantic Bight and reports five new range extensions. Included are illustrated keys to the species, synonymies, species images and remarks, and SEM images of sclerites from described species without previously published sclerite imagery. A brief history of previous work and discussion of octocoral morphology are also included.

Physical modeling of the formation of the microcontinent Jan Mayen

2020 ◽  
Author(s):  
Grigory Agranov ◽  
Eugene Dubinin ◽  
Andrey Grokholsky ◽  
Anna Makushkina
Keyword(s):  
Physical Simulation ◽  
Hot Spot ◽  
Magnetic Anomalies ◽  
Local Heat ◽  
Spreading Ridge ◽  
Spreading Axis ◽  
The North ◽  
The World ◽  
Initial Geometry ◽  
Northern Branch

<p>The split between the North American and Eurasian plates began in the Late Pleistocene - Early Eocene (58-60 million years). As the stretching took place, overlapping rift cracks formed. With further evolution, the crack that came from the north fully formed, while the south at that time died out, forming the axis of paleospreading (early Ypresian Age, 49.7 Ma). A hot spot was already functioning near Greenland at that time. In the Priabonian Age (33.1 million years), the hot spot ended under the axis of paleospreading. As a result, the spreading axis jumped (Peron-Pinvidic et al., 2012) creating the Jan Mine main microcontinent and the Kolbeinsain spreading ridge. In addition, the northern branch of the spreading ridge died out and the Aegir paleospreading ridge formed. These raises a number of questions arise:</p><p>-What is the mechanism for the separation of the Jan Mine continental block?</p><p>-Why did the spreading axis jumped and the Aegir Ridge wither away?</p><p>-What is the effect of the Icelandic hot spot on microblock formation?</p><p>-Are there similar structures in the world formed through a similar mechanism?</p><p>To answer these questions, a physical simulation was performed. Some of these issues were considered in (Muller et al., 2001, Gaina et al., 2003, Mjelde et al., 2008, Mjelde, Faleide, 2009).</p><p>Modelling was based on the initial geometry of rift cracks, known oldest magnetic anomalies and existing reconstructions. It showed two possibilities for the formation of the Jan Mayen microcontinent.</p><p>The first model is associated with parallel or oblique strike of rift cracks, the oncoming movement of which leads to their overlap, isolation of the microcontinental block, which experienced deformation and rotation.</p><p>The second model is associated with the presence of a local heat source (hot spot), the influence of which led to a jump of one branch of the rift towards the hot spot, and to the generation of a significant amount of magmatic material, which could significantly change the initial continental structure of the microblock. The second method, which combines the influence of the overlap zone and the hot spot, showed the best correlation with natural structures.</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>

The History of the South Atlantic Conflict: The War for the Malvinas.

1990 ◽  
Vol 54 (2) ◽  
pp. 250
Author(s):  
Paul B. Goodwin ◽  
Ruben O. Moro
Keyword(s):  
South Atlantic ◽  
The South ◽  
History Of ◽  
History Of The South
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