The eastern Rio Grande Rise: a magmatic province

Tabea.Altenbernd [ at ]


The Rio Grande Rise and Walvis Ridge were formed during the opening of the South Atlantic. Both structures were emplaced in the Late Cretaceous when the Tristan-Gough plume was located on or close to the Mid-Atlantic spreading ridge. In the last decade, several wide-angle seismic experiments unraveled the crustal structure of the Walvis Ridge, showing that it is composed of thickened oceanic crust. In contrast, it is debated if the RGR is entirely of volcanic origin or if it also contains fragments of continental crust. In 2019, Wide-angle refractions and gravity data were acquired along two NNE-SSW trending transects crossing the western and eastern RGR to study the nature of the crust and the evolution of the RGR. We will present first results from the new transect crossing the eastern RGR (profile AWI-20190100) and compare it with the crustal structure of the transect crossing the western Rio Grande Rise (profile AWI-20190200). P-wave velocity models derived by forward modelling, supplemented by a gravity models, constrain its crustal and upper mantle structure along both profiles. Our results show that the crust of the eastern RGR is thinner and only half as thick (15 km) in comparison to the western RGR. The crustal velocities along both lines are very similar. Evidences from the seismic velocities for the existence of a continental fragment are missing along both transects. While a high-velocity upper mantle is partly present below the western RGR, such high upper mantle velocities are not observed along the eastern profile. In summary, the seismic velocity structure of the RGR and the conjugate Walvis Ridge are very similar.

Item Type
Conference (Poster)
Primary Division
Primary Topic
Helmholtz Cross Cutting Activity (2021-2027)
Publication Status
Event Details
AGU Fall Meeting, 13 Dec 2021 - 01 Dec 2021.
Eprint ID
Cite as
Altenbernd, T. , Jokat, W. and Geissler, W. (2021): The eastern Rio Grande Rise: a magmatic province , AGU Fall Meeting, 13 December 2021 - December 2021 .

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