The Katdoornbosch-Witpoortjie Fault: a ring thrust of Vredefort Event age

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 eleme nts of the same structure. Evidence is presented why the Witpoortjie Fault should be designated a thrust. 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 verge nce, away from the centre. Where chert beds of the Malmani Subgroup were in tersected, thrust faults of Vredefort Event age can be recognized by a uniq ue type of brecciation, displaying chocolate-tablet-type boudinage, with fr acturing having taken place in three dimensions. The brecciation is confine d uniquely to the ramp zones and was probably formed during the release of three-dimensional, hydrostatic stress, when fault detachment took place. Th e recognition of this type of brecciation along the planes of the thrust fa ults associated with the stage of centrifugally directed movement, during t he 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 im pact event.