Pre-rift and synrift exhumation, post-rift subsidence and exhumation of the onshore Namibe Margin of Angola revealed from apatite fission track analysis
Paul F. Green, Vladimir Machado, 2017. "Pre-rift and synrift exhumation, post-rift subsidence and exhumation of the onshore Namibe Margin of Angola revealed from apatite fission track analysis", Petroleum Geoscience of the West Africa Margin, T. Sabato Ceraldi, R. A. Hodgkinson, G. Backe
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A series of cooling events in the development of the Namibe margin of Angola is defined by apatite fission track analysis data from samples of outcropping Cretaceous sandstones and crystalline Precambrian basement. Regional exhumation in the Late Carboniferous–Early Permian and Jurassic preceded Early Cretaceous rifting. Further episodes of uplift and erosion affected the margin in the Early and Late Cretaceous before it was buried by up to 2 km of post-break-up section, which was subsequently removed during Cenozoic uplift and erosion beginning between 35 and 20 Ma. This timing is consistent with published analyses of river profiles suggesting that uplift of the margin began at c. 30 Ma. Estimates of between 1.5 and 2 km of section removed during Cenozoic exhumation are consistent with burial depths estimated from the diagenesis of former evaporite horizons now at outcrop. These results add further support to a growing body of evidence showing that the evolution of ‘passive’ margins is anything but passive. The key episodes of exhumation defined in this study are broadly synchronous with events identified in many areas of the West Africa margin from Namibia to Equatorial Guinea and are regarded as representing a continent-scale response to stresses related to tectonic plate movements.
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The West Africa margin, formed by the progressive separation of the South American and African continents, has enjoyed a rich and varied exploration history and become a significant hydrocarbon-producing region. The amalgamation of hydrocarbon exploration approaches and imaginative ideas, leveraged with modern technologies, is yielding significant scientific and economic successes within the region.
The main objective of this Special Publication is to provide an overview of the advancement in understanding of the crustal structure, tectonic evolution and Mesozoic to Cenozoic stratigraphy of the West Africa margin both onshore and offshore, with a particular focus on the petroleum geology.