The Argentine continental margin north of 48°S: sedimentary successions, volcanic activity during breakup

• Published in: Marine and petroleum geology 1999-02, Vol.16 (1), p.1-25
• Main Authors: Hinz, K., Neben, S., Schreckenberger, B., Roeser, H.A., Block, M., Souza, K.Goncalves de, Meyer, H.
• Format: Article
• Language: English
• Subjects: Applied geophysics; Argentine continental margin; Crystalline rocks; Earth sciences; Earth, ocean, space; Exact sciences and technology; Igneous and metamorphic rocks petrology, volcanic processes, magmas; Internal geophysics; Sedimentary succession; Variability of oceanic crust; Volcanic passive margin
• ISSN: 0264-8172; 1873-4073
• DOI: 10.1016/S0264-8172(98)00060-9

New seismic data and geophysical results from the outer Argentine continental margin and from seismic flow-line transects across the oceanic Argentine/Brazil and Cape/Angola Basins are presented. The results document that the Early Cretaceous South Atlantic continental breakup and initial sea-floor spreading were accompanied by large-scale, transient volcanism emplacing voluminous extrusive constructions on the conjugate outer continental margins of the South Atlantic. On the Argentine margin we interpret three major tectono-volcanic crustal units beneath a thick and tectonically undisturbed sedimentary succession of Cretaceous and Tertiary age: (1) Syn-rift basins and even pre-rift features are present on the outer shelf; (2) a deeply buried, 60–120 km wide and several thousand metres thick volcanic wedge occupies most of the slope. The wedge is characterized by seaward-dipping reflectors and is associated with the distinct magnetic Anomaly G; (3) the seaward adjacent oceanic crust of Cretaceous age shows isochronous changes of the seismic images along our flow-line transects, suggesting some form of episodicity of rich magma and poor to moderate magma supply at the pre-existing mid-ocean ridge of the South Atlantic during Cretaceous time.