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Accueil du site → Doctorat → Royaume-Uni → 1990 → The distribution of weathering and erosion on an inselberg-pediment system in semi-arid central Sudan

University College of Swansea (1990)

The distribution of weathering and erosion on an inselberg-pediment system in semi-arid central Sudan

Campbell, M.D

Titre : The distribution of weathering and erosion on an inselberg-pediment system in semi-arid central Sudan

Auteur : Campbell, M.D

Université de soutenance : University College of Swansea

Grade : Doctor of Philosophy (PhD) 1990

Résumé
A number of geomorphic studies were conducted on Jebel Arashkil, an inselberg and pediment complex in central Sudan. The various explanations of inselbergs are summarised and some testable hypotheses formulated. The environment of central Sudan is described and its variability emphasised. The morphology of the inselberg is described and the slopes analysed using Rock Mass Strength criteria. The inselberg slopes are not simply controlled by bedrock strength characteristics and clearly have a developmental history. Data are also presented concerning drainage density, infiltration capacities and the nature of surface material for the inselberg and pediment. Field and laboratory techniques are used to assess spatial patterns in the nature and intensity of weathering. The techniques employed include descriptive analysis, x-ray diffraction of clay minerals, abrasion pH, quartz:felspar ratios, SEM analysis of quartz grains and gypsum weathering tablets. Weathering indices are produced which show that the most intense weathering is taking place on the inselberg slopes. This is due to both concentration of water and rate of throughput. The concentration of runoff and solution in regolith pockets on the slopes enhances slope microrelief. Schmidt hammer `R’ values were similar for all exposed bare rock surfaces regardless of location. Erosion measurements using simple repeat survey techniques show that significant erosion occured near the break of slope, mainly through headward growth of and lateral erosion by ephemeral gullies. Vertical incision and planar wash are insignificant in comparison. The form of the inselerg is due to the local balances between erosion and weathering and does not require novel explanations. Inselbergs have long evolutionary histories, and may be subject to equifinality

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