Remote sensing techniques applied to the pan-African terrain of north-east Africa

Gibson, Paul Jude (1986). Remote sensing techniques applied to the pan-African terrain of north-east Africa. MPhil thesis The Open University.



The major lithologies of the Red Sea Hills, Sudan, can be identified on Landsat band 7 photographic infra-red imagery. Lithological discrimination is not significantly increased on contrast stretched false colour imagery because of desert varnish. Principal component false colour imagery yields the best lithological discrimination but because of contamination from the erosional products of different lithologies - mainly Nubian Sandstone - colour/rock associations are not unique, thus using Landsat alone for detailed geological mapping would not be justified. Most of the geological information acquired by various types of Landsat image is detected on band 7, therefore the expense incurred in producing more sophisticated imagery is not warranted.

Photoreduced uncontrolled mosaics of panchromatic aerial photographs are inferior to Landsat images for regional investigations.

Lithological discrimination is inferior on radar imagery (SIE-A) compared with Landsat but radar is a superior system for acquiring structural information. Penetration of the sand cover by radar, possibly up to a depth of 6m, revealed lineaments, circular features, folded structures and numerous drainage channels, some of which are probably palaeodrainage systems.

In the Wadi Onib region, lineaments have been dextrally deformed into a N/S zone which is probably an island-arc suture. A complex sinistral oblique-slip shear zone system more than 500km long appears to have operated in N.E. Sudan. It is formed by a 200km N.40oW. - trending shear zone in the southern Red Sea Hills which apparently curves near Wadi Onib to an approx. N/S strike and sweeps round into the E.N.E. - trending Sol Earned zone. A plate tectonic model involving oblique subduction and rotation of a plate can explain the structural relationships.

The Hakasib belt, a possible island-arc suture, is shown by a 7km wide, 200km long belt of N.60oE. - striking lineaments. In Eritrea a N.N.W. - striking zone of lineaments is overprinted at its northern termination by lineaments of the curvilinear Adobaha belt which is subparallel to the Argadom belt.

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