Abstract

A fault, designated the Katdoornbosch—Witpoortjie Thrust, was traced in the field continuously from the area north of Klerksdorp to the West Rand. It is shown that the Katdoornbosch Thrust and the Witpoortjie Fault form elements of the same structure. Evidence is presented why the Witpoortjie Fault should be designated athrust. Thrust faults related to the Vredefort Event are recognized mainly by their 2 Ga, post-Transvaal age, their concentric arrangement around the centre of the structure, and their centrifugal vergence, away from the centre. Where chert beds of the Malmani Subgroup were intersected, thrust faults of Vredefort Event age can be recognized by a unique type of brecciation, displaying chocolate-tablet-type boudinage, with fracturing having taken place in three-dimensions. The brecciation is confined uniquely to the ramp zones and was probably formed during the release of three-dimensional, hydrostatic stress, when fault detachment took place. The recognition of this type of brecciation along the planes of the thrust faults associated with the stage of centrifugally directed movement, during the formation of the Vredefort Structure, provides an important criterion in their recognition. The Katdoornbosch—Witpoortjie Thrust is one of a set of similarly orientated, time-related thrusts, formed during the Vredefort impact event.

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