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Original Articles
1.
Introduction
The pre-Karoo early Palaeozoic siliciclastic sedimentary strata of the Natal Group and Msikaba Formation, overlying mainly basement rocks of the c. 1.1 Ga Namaqua-Natal Metamorphic Complex (NNMC) along the SE coastal margin of South Africa in Kwazulu-Natal and the far NE part of the Eastern Cape Province, remain somewhat controversial with regard to their stratigraphic relationship to each other and to that of the Cape Supergroup further to the south (Fig. 1).
Figure 1.
The location of the Natal Group and Msikaba Formation along the eastern margin of South Africa, showing the distribution and extent of the various units. The approximate locations for each sample have been indicated (redrawn and modified after Marshall & Von Brunn, 1999; Kingsley & Marshall, 2009).
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The Msikaba Formation, characterized by abundant, well-sorted quartz arenite, was historically classified as part of the Natal Group. Numerous researchers (Du Toit, 1946; Hobday & Mathew, 1974; Visser, 1974; Kingsley, 1975; Hobday & Von Brunn, 1979) considered outcrops of the Natal Group rocks to occur as far south as Port St Johns, thereby implying the Msikaba Formation to be a southern lateral facies equivalent of the mixed argillaceous-arenaceous red beds and quartz arenites of the Durban and Mariannhill formations. The latter rocks would then comprise the group north of the so-called Dweshula palaeographic high between Port Shepstone and Hibberdene on the Kwazulu-Natal south coast (Fig. 1; Visser, 1974; Kingsley, 1975; Hobday & Von Brunn, 1979). Furthermore, the Natal Group was considered part of the Cape Supergroup, with the Msikaba Formation correlative to the Ordovician Table Mountain Group (Visser, 1974; Kingsley, 1975). However, upon identifying two distinct facies to the north and south of Port Shepstone, Schwarz (1916) had earlier suggested that the grey quartz arenites (Msikaba Formation) of the southern facies are younger than the rocks of the northern facies. The Msikaba Formation is currently considered to be Devonian in age, possibly correlative to the Witteberg Group of the Cape Supergroup, and not part of the red-bed succession of the Natal Group. The latter is thought to be Ordovician in age, deposited in a basin separate from that of the Ordovician Table Mountain Group and therefore...