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Abstract

The Red Sea and Gulf of Aden sedimentary basins are developed along the African and Arabian conjugate margins and are characterized by Late Tertiary rifts filled with siliciclastic, carbonate, and thick evaporite successions north of the Babel-Mandeb Strait in the Red Sea. Geodynamic models for the development of the Red Sea–Gulf of Aden continental margins include simple shear mechanisms associated with mantle exhumation, as described in the Iberian margin, and pure shear mechanisms, with continental breakup associated with magmatic intrusions and development of organized oceanic crust in some segments of the axial trough. The rifted continental margin in the southern segment of the South Atlantic is characterized by several Mesozoic rifts that extend from onshore to offshore Brazil, Uruguay, and Argentina; the onshore rift-border faults in Argentina are at high angle to the continental margin basins. These rifts and also the Pelotas basin in southern Brazil are essentially devoid of evaporites, which mainly occur northwards of the Florianópolis Fracture Zone. A mantle plume before continental breakup is interpreted to cause the massive volcanic outpouring both in the Red Sea–Gulf of Aden continental margins (Afar plume) as well as in the region between the Pelotas and Santos basins in Brazil (Tristão da Cunha plume). The basalts associated with the continental breakup include seaward-dipping wedges in the transition from continental to oceanic crust, and volcanic eruptions probably formed barriers isolating oceanic basins from an incipient gulf developed on continental crust with synrift sedimentation. Episodic marine incursions resulted in accumulation of thick layers of massive evaporites that were deposited before the development of active oceanic spreading centers. The oceanic ridges split the salt basins initially with localized igneous intrusions and subsequently by organized oceanic crustal spreading, with allochthonous salt flows advancing towards the axial trough and covering the volcanic basement.

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