Regional-scale 3D modelling of deep-crustal constrictional strain geometries within the Central Damara Belt

The South-Central Zone of the Damara Belt records a history of intense, complex deformation resulting from the collision between the Congo and Kalahari cratons during the Pan-African Orogeny. Structural models have typically focused on multiphase deformation with inherent changes in the stress field and, to a lesser degree, on progressive deformation driven by a stress field with less variation. One example of the latter is a model that separates the crust in the South-Central Zone into two structural domains, a higher crustal level and a deeper crustal level. This allows the existence of orthogonal fabric domains resulting from different strain fields within the same orogenic zone, without the need for major changes in the regional tectonic stress orientation.

To date, geological maps and cross-sections have been used widely to graphically present the geological geometries of large areas in the Central Damara Belt. However, unlike 2D geological maps and sections, 3D models are more representative, providing additional insight to complex geometries and structural relationships. These complement and test traditional interpretations that often fail to account for the complexity and uncertainty of geological geometries.

This study provides the first large-scale 3D lithostructural modelling of the deeper structural levels of the South-Central Zone of the Damara Belt, south and east of the Rossing Dome. The different rock units in this area display kinematic and geometric features that support large scale constrictional-type strain characteristics and top-to-the-southwest displacement. In addition to field mapping data, digital elevation models, satellite imagery and published geological maps were used to delineate the regional geometry of folded lithological units. The resulting 3D model contributes to a better understanding of the deformation of the deeper crust during the collision of continental fragments and the development of large-scale fold geometries.