Abstract

The oldest rocks of the Cape Fold Belt of South Africa are exposed in several inliers. These inliers are comprised predominantly of low-grade metasediments. The age of the sediments is thought to be late Neoproterozoic. The stratigraphy of the Kango inlier (near Oudtshoorn, within the southern, east-west-striking branch of the Cape Fold Belt) has been subdivided into two successions--the Goegamma and Kansa Subgroups, separated from one another by a clear unconformity. U/Pb isotope dating of detrital zircons, using the SHRIMP II, indicates that the gneisses of the Mesoproterozoic Namaqua-Natal Province (c. 1100 Ma) are the probable sediment source terrain for the Goegamma Subgroup, and that both the Namaqua-Natal Mobile Belt and rocks from the Cape Granite Suite are sources for the sediments at the base of the younger Kansa Subgroup (detrital zircons = 518+ or -9 Ma). These ages suggest that the Kansa Subgroup is Mid-Cambrian in age (or younger) and could be correlated with the Klipheuwel Group exposed along the western branch of the Cape Fold Belt. Furthermore, it is suggested that the unconformity between the two subgroups represents a major Eo-Cambrian hiatus and should be considered as a major sequence boundary separating the Cape Supergroup from the underlying Neoproterozoic-Early Cambrian metasediments. The Kansa Subgroup possibly represents the mechanical rift succession underlying the Table Mountain Group that in turn, represents the thermal subsidence phase of an Early Palaeozoic passive rift margin of southern Gondwana.

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