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"In the
upper reaches of the
Wilge
River
, the geological features are characterized by the presence of extensive
dolomite and limestone formations surrounding and a small area of Karoo
Supergroup rocks consisting of consolidated layers of carbon-rich shales
and intercalated arenaceous strata.
Further downstream, centering on the Bronkhorstspruit Dam, the
sub-catchment is underlain by large areas of porous unconsolidated and
semi-consolidated sedimentary strata, principally quartzitic sandstones,
and an area of Dwyka tillite. Close
to the confluence of the Wilge and Olifants rivers, a small area of
acidic and intermediate intrusive granites of the Waterberg Group
underlies the northern portion of this sub-catchment." (www.mining.wits.ac.za/FinalReport-Section5.doc)
"The
dolomite and limestone formations provide excellent aquifer
characteristics and overly thick layers of carbon-rich dolerites and
shales of the Karoo Supergroup."
(www.mining.wits.ac.za/FinalReport-Section5.doc) Ref 2
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"Soils
in the sub-catchment can be divided into five main groups:
- Moderate to deep
sandy loam soils on flat and undulating terrain overlying dolomite
and limestone in the upper reaches of the catchment;
- Moderate
to deep sandy loam soils lining long stretches of the
Wilge
River
valley in its middle reaches
- Moderate to deep
clay loam soils over much of the middle portions of the
sub-catchment (located away from the river channels), overlying the
more porous unconsolidated sedimentary material; and
- Moderately
shallow to moderately deep, clayey loam to clay-rich, fine-grained
soils over most of the lower reaches of the sub-catchment; and
- Dark grey to
blackish, mottled vertisols located along low-gradient reaches of
most streams and river sections, forming characteristic wetland
soils."
"Ref 2"
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