TECTONOSTRATIGRAPHIC FEATURES ALONG THE ORANGE RIVER IN THE WESTERN PART OF THE MESOPROTEROZOIC NAMAQUA MOBILE BELT

A geological map of part of the western Namaqua mobile belt, 3200 km(2 ) in extent (scale of 1:100 000), has been compiled with the aid of a sequence mapping technique. The map shows the distribution of the lith ostratigraphic units and the macroscopic structural development, inclu ding the thrust fault boundaries between four Proterozoic structural t erranes. Most of the study region is in the Pofadder terrane, which is characterized by the metamorphic equivalents of 2.0 Ga calc-alkaline eruptive rocks (Haib Subgroup), granites (Vioolsdrif and Little Namaqu aland Suites), and metasedimentary sequences (Pella Subgroup). The int ense deformation and metamorphism of the region is ascribed to the Nam aqua Orogeny (1.4 - 1.1 Ga), which largely overprinted the effects of an earlier regional deformation. Progressive ductile shear deformation was responsible for the production of a regional subhorizontal fabric comprising coplanar and colinear elements. The map represents part of the root zone of a region of Proterozoic crustal thickening, illustra ting the deformational style of the Kibaran belts. Collectively, the f acts presented in this paper provide a window into mid-crustal feature s during compressional tectonics in the Mesoproterozoic.