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Faulting of the Witteberg Group Rocks, Steytlerville, Eastern Cape.
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 11th SAGA Biennial Technical Meeting and Exhibition, Sep 2009, cp-241-00101
Abstract
A structural study of Witteberg Group Rocks was conducted along the Soutkloof River, approximately 14 km east of Steytlerville, Eastern Cape Province of South Africa. Here a north to south geotraverse was studied in an attempt at unravelling the structural geology of the rocks belonging to the Upper Devonian to Lower Carboniferous Witteberg Group (Upper Cape Supergroup). These rocks are mostly arenaceous and include quartzite, sandstone, siltstone and shale which have been folded, faulted and metamorphosed. Thrust, normal and strike-slip faulting occur in the area. Shallow south dipping low-angle thrust fault planes are displaced by steep south-dipping thrust planes and subordinate north-dipping backthrusts. Displacement along thrust planes is predominantly northwards. Steeply dipping thrust fault planes are often reactivated by east-west striking normal faults. Strike-slip faulting post dates all structural features and displaces normal and thrust fault planes. Open to tight folds are present and are mostly north-vergent and often steepened or truncated by steep south-dipping thrust fault planes. South-vergent folds are related to backthrusting and post-fold faulting. The study has revealed that the current geologic map and the local stratigraphy were compiled without recognising major structural features such as thrust, normal and strike-slip faulting, and its validity is therefore questioned. Extensive faulting suggests that the conventional stratigraphic interpretation of the Witteberg Group strata should be revised.