Abstract

The 2.056 Ma Bushveld Complex (BC) constitutes the largest layered igneous complex known. The complex forms a basin defined by strata that dip centripetally (10° to 20°). This depression presumably resulted from the load of the complex as was proposed by a number of authors. Sagging of between 460 to 740 m appears possible, resulting in flexural-slip movement. This flexural-slip manifests in many thrust faults, (mainly mapped in mines) which display reverse-slip.

The research described in this paper focuses on the age of this deformation. A thrust fault was identified at Lonmin U14 Pit. Reverse slip along the fault displaced unconsolidated sedimentary material that unconformably overlies the Rustenburg Layered Suite strata. Archaeological artefacts (Acheulian hand axes) were discovered buried in this sedimentological layer and provide an age constraint of 1.25 Ma to 250 000 years. Optically stimulated luminescence (OSL) dating further constrained the age of the sedimentary material to less than 175 000 years. The youngest material deposited is a regional black clay layer. At Lonmin U14 Pit this clay layer carries a fabric that resulted from the movement of the thrust and this indicates an age significantly younger than 175 000 years.

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