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fault-bounded blocks, although horst and graben (block and basin) structures are present
in the northern central part of this area. In the north, the structure of the Lebombo area
is mainly that of a seaward faulted flexure. The tilted fault blocks in general are tilted in
a seaward direction, the amount of tilt of the individual blocks usually increasing in this
direction to a maximum of about 15 0 • Locally however, blocks can tilt in an inland
direction, as in the major block north of Port Shepstone and between the Thukela and
Mlalazi rivers. Fault zones may vary in width from less than a metre in the case of small
faults, to 10 m and more in respect of large faults such as the Eteza Fault north of
Empangeni. Fault zones may comprise either silicified or kaolinised fault breccia.
The interior of the province by contrast, is unfaulted, the rocks of the Karoo Supergroup
generally having a regional bedding dip of less than about 3 0 in a westerly or inland
direction. The rocks of the Proterozoic and Archaeozoic basement - recently renamed ­
beneath the sediments of the Natal Group and the Karoo Supergroup, where exposed, are
usually strongly lineated, and are steeply foliated in rock types other than batholithic
granite intrusions. All rocks in the region are jointed (a discontinuity on which no
significant movement has taken place), to a greater or lesser degree.
Faults and joints being sites of weakness in the rocks, tend to be erosion-susceptible and
thus very frequently have rivers and streams aligned along them. In some parts of the
province, the drainage pattern is fully controlled by the distribution of faults and joints.
Faults and joints have a very important effect on the gioundwater situation (as discussed
later). In the tilted fault block coastal area, the inclination of the bedding planes of
sedimentary rocks where so tilted (particularly sandstones), has a marked influence on the
movement of groundwater, as the direction of such movement is generally in the down-dip
direction of the bedding planes.
• Distribution of geological formations
Away from the faulted coast and coastal hinterland areas of Natal/KwaZulu - where
different rock types are very frequently juxtaposed as a result of the faulting - increases
in altitude result in a simple elevation in the Iithostratigraphic sequence. Overall, the
granitic Proterozoic and older rocks form a fairly broad belt on the inner margin of the
coastal faulted zone. These rocks occur at the coast in the south but at an increasing
distance from the coast in a northerly direction, except where they are returned to this