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Role of subaerial volcanic rocks and mantle plumes in creation of South Atlantic margins: implications for salt tectonics and source rocks
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Orientador(es)
Resumo(s)
Seaward-dipping re¯ectors (SDRs) represent ¯ood basalts rapidly extruded during either rifting or initially subaerial sea-¯oor
spreading. Evaporites can form on this basaltic proto-oceanic crust, as in the Afar Triangle today. Evidence for SDRs in South
Atlantic deep-water regions comes from proximity to the uniquely large Paranaà ±Etendeka volcanic province onshore, the
Tristan and Gough hot spots, drilled volcanic rocks, and seismic pro®les showing SDR provinces more than 100 km wide, as
much as 7 km thick, and thousands of kilometers long. SDRs are clearest adjoining the Aptian salt basins. However, we
speculate that SDRs are also present but seismically obscured below the salt basins. We argue that the conjugate Aptian salt
basins are post-breakup, not pre-breakup; they were separated from the start by a mid-oceanic ridge; distal salt accumulated on
proto-oceanic crust, not rift basins. This hypothesis is supported by: seismic stratigraphy and structure; magnetic anomalies;
plate reconstructions; and hydrothermal potash evaporites. An important implication for exploration is that thick basalts, rather
than rift-age source rocks, may underlie distal parts of the salt basins.
Descrição
Palavras-chave
Flood basalt Passive margin Seaward-dipping reflector
Contexto Educativo
Citação
Marine and Petroleum Geology 17 (2000) 477-498