Subsurface Imaging by RADARSAT: Comparison with Landsat TM Data and Implications for Ground Water in the Selima Area, Northwestern Sudan

• Published in: Canadian journal of remote sensing 1999-08, Vol.25 (3), p.268-277
• Main Authors: Robinson, C, El-Baz, F, Singhroy, V H
• Format: Article
• Language: English
• Subjects: Geology; Groundwater; Remote sensing systems; Sudan
• ISSN: 0703-8992; 1712-7971
• DOI: 10.1080/07038992.1999.10874725

RADARSAT obtained an image of the Eastern Sahara that reveals fluvial features in northwestern Sudan (at the border of Egypt) beneath a surface cover of desert sand. These same features are not observable in Landsat images of similar resolution. In their place are low-amplitude chevron dunes and megaripples, 10 to 30 cm in height. This implies that the radar penetrates the dune landforms to image fluvial features at these depths. The drainage patterns observed in the RADARSAT image show structural control; in some cases drainage channels drain into crosscutting fractures. This structural and fluvial setting is favourable for ground-water accumulation in bedrock aquifers. The extensive and widespread system of drainage channels and faults revealed by RADARSAT suggests that there is potential of ground-water concentration at this location in addition to the central depression of the Selima Sand Sheet. Thus, the rocks beneath the Selima Sand Sheet, in Egypt and Sudan, are probably storing large amounts of fossil ground water. The development of these ground-water resources for agricultural purposes may bring long-term economic benefits. Landsat TM band 4 imagery outlines the competency contrast of quartzite versus marble and can be used to map the domain of marble. At 1.165 Ga emplacement of the Chevreuil intrusive suite, concentrated along N-S corridors, marked the onset of renewed orogenic activity. Many of the intrusions from this suite have a unique topographic signature which can be delineated on the Landsat and RADARSAT imagery. Following the magmatic activity, late compressive deformation in the ductile regime was focused along the N-S corridors. The style of this deformation is characterized by a regional N-S foliation and coaxial anastamozing shear zones (NE-SW dextral; NW-SE sinistral) which were delineated in the radar imagery and confirmed using field kinematic indicators. The RADARSAT imagery provides a view of the extent of this deformation event and corroborates field and petrological studies indicating that by 1.165 Ga, the gneiss complexes were mechanically strong crustal domains and were only locally overprinted by late-stage ductile deformation.