OVERVIEW OF THE IMPACT OF MINING ON THE ... - IIED pubs

4.20.1.2 Geology
Like the Mogalakwena sub-catchment, the geological features of the Sand sub-catchment are relatively complex
and consist of several different formations of widely differing ages. A variety of acidic, intrusive granites and
gneisses of the Sand River Formation underlie most of the upper reaches of the sub-catchment. Younger
consolidated and silicified sedimentary strata, predominantly sandstones and quartzites of the Soutpansberg
Group have in turn intruded these.
Further downstream, the sub-catchment is underlain by sequences of silicified sandstones and quartzites of the
Soutpansberg Group, followed by carbon-rich mudstones and shales, and then basalts, of the Karoo Sequence.
The sandstones are highly resistant to weathering and stand well above the surrounding undulating terrain to
form local mountains or ranges of hills (e.g. the Soutpansberg Mountains). Erosion-resistant rocks of the
Soutpansberg Group tend to stand well clear of the surrounding countryside to form distinctive landscape
features.
Large areas of the central parts of the sub-catchment are overlain by recent (Quaternary) deposits of
unconsolidated or poorly consolidated sandy material.
4.20.1.3 Pedology, agriculture and land use
The soils in the Sand sub-catchment can be divided into four main groups:
• Moderately shallow to deep sandy-clay loam soils on the sloping and undulating terrain in the upper reaches
of the sub-catchment;
• Shallow to moderately deep sandy loam soils lining the valley bottoms in the middle reaches of the subcatchment;
• Shallow sandy soils in foothill areas and on flat and undulating terrain in the lower reaches of the subcatchment;
and
• Clay-rich, blackish soils with a high sodium content lining internal drainage areas and with dispersive
characteristics.
Most of the clayey loam soils in the upper parts of the sub-catchment would be suitable for irrigation if sufficient
water were available. Two relatively small areas in the upper and lower portions of the Sand River subcatchment
are under the jurisdiction of formal water control boards or irrigation boards. In addition, the area
along the banks of the Limpopo River is also part of a formal irrigation area, and uses water that is pumped
either from the bed of the Limpopo River or from boreholes sunk next to the riverbed. Further away from the
main channel of the Sand River, land use consists almost entirely of subsistence rain-fed cultivation of droughtresistant
crops, small-scale livestock farming and game farming.
Several large towns and numerous small settlements are located in the upper and middle reaches of the subcatchment,
including the City of Pietersburg, capital of the Northern Province. However, population densities
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