A Discussion on global tectonics in Proterozoic times - Crustal shortening in the Zambezi Belt

Abstract

Pan-African deformation in the Zambezi Belt appears to be dominated by the development of domes and periclines cored by gneiss, whose growth has swept aside the overlying meta-sediments and constricted them in synclinoria which tend to be disposed tangentially about the main domal structures. Because of this arrangement, horizontal displacements tend to cancel out. By using strain data derived from pebbles in conglomerates which form part of the deformed sequence and by modelling the body rotations involved in this kind of tectonic pattern, shortening across part of the Belt in Zambia is estimated to be not more than 8 km or 14%. The method is extended by using strain data from elsewhere in the Belt and by making further assumptions and extrapolations, to a section 230 km long extending to the northern margin of the Rhodesian Craton. Estimated shortening across this part of the Belt is unlikely to exceed 70 km or 25%.