A structural and petrographic investigation of the pretoria saltpan impact structure

The Pretoria Saltpan crater is located in the southern portion of the Bushveld Igneous Complex some 40 km NNW of Pretoria, South Africa, at 25 deg 24 min 30 sec S/28 deg 4 min 59 sec E. The near-circular structure of 1.13 km diameter exhibits a well-preserved, uptilted granite rim. Granitic breccia overlies Karroo sediment in places, indicating a post-Karroo age for the cratering event. The coincidence of the spacial occurrence of the crater with respect to various alkaline and ultramafic intrusives has been the main argument put for yard against an impact origin for the structure. Detailed mapping of the crater rim exposures and the crater environs was carried out and revealed many occurrences of intrusives in the whole region. Structural analysis along the rim revealed the presence of typical impact crater related structures. Comparative petrographic and chemical studies of crater-related and non-related intrusives showed close similarities between these sample suites.