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2013-14 Tour Information
Eastern North America:
• May 6-17, 2014
Professor, Master of Science Graduate Program, University of Rio de Janeiro
Funded by the AAPG Foundation
Webster Mohriak has been working in the Oil & Gas Industry for the last 30 years, conducting several basin analysis projects in the Eastern Brazilian and West African continental margins. After the PhD degree in geology at the Oxford University in England, studying the tectonic development of the Campos Basin, offshore Brazil, he headed several regional basin analysis projects at Petrobras and also became a lecturer for the MS courses at University of Rio de Janeiro. He has published more than a 100 scientific papers and was the main editor for the book Atlantic Rifts and Continental Margins published by American Geophysical Union in 2000. He is one the editors of the Geological Society of London book Conjugate Divergent Margins published in 2013.
Abstract: Birth and Development of Continental Margin Basins: Analogies from the South Atlantic, North Atlantic and the Red Sea
The results of regional deep seismic acquisition in the South Atlantic continental margins have shed new lights on the birth and development of sedimentary basins formed during the Gondwana breakup. Recent models of mantle exhumation as observed in the deep water Iberian margin have been applied extensively to the interpretation of several basins in the Eastern Brazilian and West African conjugate margins. However, the tectonic development of these basins is markedly different from the magma-poor margins, and in this lecture we emphasize the contrasts from the tectono-sedimentary features imaged in deep-penetrating seismic profiles that extend from the platform towards the oceanic crust, which indicate that the Red Sea constitutes a better analogue for the birth of divergent continental margins.
This lecture also emphasizes differences in basins developed along conjugate margins in the South Atlantic. Integration of geological and geophysical methods characterize widespread volcanism in the southernmost segment (Pelotas-Santos basins in Brazil and Namibia in West Africa), which are probably related to mantle thermal anomalies. The lack of volcanic features in local portions of the margins, particularly in the shallow-water platform regions (example, Camamu-Almada and Sergipe-Alagoas basins in northeast Brazil) are also discussed, pointing that even in these regions the continent-ocean boundary shows evidence of mantle melts and formation of wedges of seaward-dipping reflectors, as in the JacuÃpe Basin.
The central segment of the South Atlantic, from Espirito Santo to Santos basins in Brazil, and from Gabon to Angola in West Africa, is characterized by a major salt basin developed with the first marine ingressions in the Late Aptian. Salt tectonics is responsible for most of the exploratory plays along the margins, with autochthonous and allochthonous salt structures associated with existing and conceptual petroleum accumulations.
An overview of the geological concepts that evolved rapidly during the last three decades brings new lights on the challenges of petroleum exploration in the ultradeep water provinces of divergent continental margins. This talk also shares with the scientific community the methods and results from the application of modern geological and geophysical tools that help in the interpretation of the crustal architecture, rift structures and the salt tectonics elements that are crucial to basin analysis studies.