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coarse and the latter, fine and massive. These rocks are very frequently intruded by
sheets of Karoo dolerite of varying thickness from a metre or so to 100 m and more.
Intrusive dykes of the same rock type are also moderately common, particularly with
increasing elevation in the Beaufort Group. Yields of groundwater in the rocks of these
formations tend to be low, in the range 1 - 5 m 3 h- 1 mainly in the drier areas, although
higher yields are obtained in association with intrusions of Karoo dolerite. Along the foot
of the Drakensberg Escarpment in the west, the Molteno, Elliot and Clarens formations
form a narrow steep zone in which, in general, groundwater possibilities are very limited ­
particularly in the massive sandstone of the Clarens Formation and in the shales and
mudstones of the Elliot Formation. The groundwater potential is somewhat better in the
jointed sandstones of the Molteno Formation. These same rocks, except for the Molteno
Formation which is virtually absent, also occur in the north east of Natal/KwaZulu on the
western side of the Lebombo structure. Here the Beaufort Group is represented by the
much thinner Emakwezini Formation, while the Elliot Formation is represented by the
Nyoka Formation. The Clarens Formation retains its name. In this low rainfall area the
groundwater potential of these formations is very limited and what groundwater is present,
is mostly of very poor quality and is very saline. The most favourable location for
boreholes in the formations (other than on intrusive Karoo dolerite features therein), are
on joint-controlled valley intersections and valley lines.
(f) Drakensberg. Letaba and Jozini formations
The basalts of the Drakensberg Formation only occur on the very high ground forming the
Great Escarpment, along the south western boundary of Natal/KwaZulu. In this situation
there is little likelihood of the formation ever being exploited as a source of groundwater.
Some distance away from the drawdown effects of the escarpment face however, the
potential for groundwater of good quality in the well-bedded and jointed basalt is often
good.
In the north east of the province, forming the main part of the Lebombo structure, is the
linear north-south Lowveld area underlain by the Letaba Formation basalts, and to the east
of it, is the elevated Lebombo Range itself, which is underlain by the erosionally resistant
rhyolite and dacite of the Jozini Formation. Van Wyk (1963 - above) working in northern
Natal/KwaZulu observed that it is sometimes possible, in basins of decomposition in the
basalt, to obtain yields of the order of 3 - 5 m 3 h- 1 , while boreholes intersecting zones of