- GeoRef, Copyright 2004, American Geological Institute.
The dolomites of the lower Chuniespoort Group and underlying clastic sediments of the Black Reef Formation situated along the northern flank of the Johannesburg Dome are heterogeneously deformed, with numerous bedding-parallel shear zones and associated folds, cleavage, and a strong north-trending lineation developed during top-to-the-north shearing. Deformed ooids indicate both plane strain and non-plane strain behaviour, with a strong flattening component in addition to simple shear in the shear zones. Sheath folds indicate locally high strains in the shear zones. The deformation post-dates metamorphism related to the approximately 2.06 Ga Bushveld Complex, but predates the intrusion of the c. 1.25-1.45 Ga Pilanesberg dykes. This, together with the overall vergence of the structures, suggests that the deformation originated during outward-directed thrusting associated with the formation of the approximately 2.023 Ga Vredefort Dome.