doctoralThesis
Estudo geofísico/geológico da elevação do Rio Grande e feições submarinas adjacentes - Atlântico Sul
Fecha
2020-01-30Registro en:
PRAXEDES, Adriane Gomes Pinheiro. Estudo geofísico/geológico da elevação do Rio Grande e feições submarinas adjacentes - Atlântico Sul. 2020. 89f. Tese (Doutorado em Geodinâmica e Geofísica) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2020.
Autor
Praxedes, Adriane Gomes Pinheiro
Resumen
In this dissertation, the results of the application of the Seismic Method are
presented together with borehole data in the South Atlantic, more specifically in
the Rio Grande Rise (RGR). There are approximately 100 Ma volcanic spills in
the oceanic crust, caused by the hot spot Tristan - Gough, would have originated
this elevation. Then, pelagic sedimentation occurred in a shallow water
environment over the elevated crust by the volcanic spill. In the Upper
Cretaceous, there was intense rifting. In the Eocene, sedimentary filling of
significant thickness and expressive magmatism follows. When magmatism
ceased between the Eocene and Oligocene, the RGR was being cooled,
subsidized, eroded and submerged. The main aim of this study was the reprocessing of seismic lines and
correlating them with boreholes in order to obtain seismostratigraphic
interpretations and a sequence of evolutionary steps, and thus provide more
complete explanations of the tectonic, volcanic and sedimentary evolution of the
RGR. As well as raising correlation points between the RGR and the adjacent
continental margin. Our results show that the distensional pulse causing the Cruzeiro do Sul
Rift would have been active from the Maastrichtian to the Middle / Upper Eocene.
In another rift on the eastern slope of the central portion of the RGR, recent
reactivation occurs, which, together with the faults that go from the acoustic
basement to the most superficial units of the sedimentary package, are evidence
that RGR tectonics remains from Upper Cretaceous to the Recent. Still with
respect to tectonics, the effects of the strike-slip movement along the Porto Alegre
Fracture Zone would have displaced the axis of the Cruzeiro do Sul Rift about 90
km to the east. Regarding the effects of magmatism, we postulate a thermal
anomaly of great proportion. And mounds inserted in the sedimentary package,
would be associated with hydrothermal activity at the base of the sedimentary
package and / or gas chimneys, since depressions of up to 500 m in diameter on
the ocean floor and polygonal faults may be related to the presence of fluids and
pockmarks. Finally, similarities between seismic facies, tectonic styles and volcanism point out to a correlated evolution between the Rio Grande Rise and the adjacent continental margin. This dissertation represents new knowledge about the Rio Grande Rise and its surroundings in South Atlantic, which should be useful for
exploration of mineral resources.