Bedding-parallel shearing and related deformation in the lower Transvaal supergroup north of the Johannesburg Dome, South Africa

The dolomites of the lower Chuniespoort Group and underlying elastic sedime nts of the Black Reef Formation situated along the northern flank of the Jo hannesburg Dome are heterogeneously deformed, with numerous bedding-paralle l shear zones and associated folds, cleavage, and a strong north-trending l ineation developed during top-to-the-north shearing. Deformed ooids indicat e both plane strain and non-plane strain behaviour, with a strong flattenin g component in addition to simple shear in the shear zones. Sheath folds in dicate locally high strains in the shear zones. The deformation post-dates metamorphism related to the similar to 2.06 Ga Bushveld Complex, but predat es 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 similar to 2.023 Ga Vredefort Dome.