Lateritic palaeosols of N.E. Africa: a remote sensing study

Andrews Deller, Margaret Elizabeth (2012). Lateritic palaeosols of N.E. Africa: a remote sensing study. PhD thesis The Open University.



Remote sensing data and image processing techniques are used increasingly to aid scientific investigation and address geological problems in areas that are difficult to map by conventional methods. This thesis explores how multi spectral satellite data, supported by traditional geological techniques, facilitate a study of lateritic palaeosols. The work centres on laterites, which are thin but important elements of the Phanerozoic stratigraphy of NE Africa. They immediately pre-date midOligocene flood basalts and, if mapped, can be used to delineate a flood basalt-Iaterite contact and define the pre-30 Ma African Surface and uplift patterns. They have important engineering properties and are key to understanding basement alteration and its associated mineralization. They affect agriculture and groundwater quality and retention - essential in Sub-Saharan Aflica where access to safe water is limited. They dominate the landscape, yet are unmapped and marginalised in the literature. Their geological context supports a laterite-focused remote sensing mapping strategy.

A strategy for geologic mapping of laterites based on their simple mineralogy and spectral characteristics that distinguish them from other rocks is developed. Methods for mapping are presented using Earth Observation data. The outcome is a series of regional geological maps of Eritrea and Ethiopia. These reveal that laterite cover is more extensive than previously thought and enable further lines of research.

The maps provide a means of regional dating of laterites, which, together with ages obtained for overlying flood basalts and new basement cooling ages, indicate a major planation during the Palaeozoic and constrain the timing of associated uplift and erosion. A regional review of Mesozoic-Cenozoic climatic, strati graphic and structural evolution is presented and a model of Neogene deformation of the lateriteflood basalt datum is produced. Finally, laterite maps, petrographic and geochemical evidence are used to access basic essentials of life: clean water, a safe environment and a sustainable economy.

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