The southern portion of the Tshwane Metropolitan Municipality (TMM) is situated on dolomite, which contains valuable aquifers. 

The quartzite ranges such as the east-west Magalies Mountain Range is a valuable source of construction material in the form of crushed stone, but this has led to unsightly quarries having been opened in certain areas.

The Tshwaing Crater (Saltpan), which is situated some 40km north of Pretoria, is unique (even in world context) with significant paleo-environmental importance and it should be protected from harmful development. 

Most of the valleys between the mountain ranges contain deep soils (mostly transported), which can be utilized for agricultural purposes.

Information as per jurisdiction areas:

City Council of Pretoria
The most dominant geological formations of the Pretoria area are Pretoria Group Andesite and Bushveld Gabbro-Norite, Pretoria Group Shale and Pretoria Group Quartzite. Most of the valuable east-west quartzite ridges (including the Magalies Mountain Range, which is a Protected Natural Environment) of the Tshwane Metropolitan Municipality occur within the Pretoria area.

Centurion Town Council
The northern section of Centurion is underlain by Dolomite, which is a valuable aquifer and Halfway House Granite and Bushveld Granite underlie the southern section.

Northern Pretoria Metropolitan Sub-Structure
Most of the southern section (Rosslyn, Akasia, Pretoria north, Wonderboom, Doornpoort, Klip/Kruisfontein) of the NPMSS is underlain by Pretoria Group Andesite and Bushveld Gabbro-Norite. The geotechnical constraints in these areas are expansive and impermeable clays and uneven weathering, which could cause uneven settlement.

Halfway House Granite and Bushveld Granite underlie the northern section of the NPMSS

Eastern District Council Area
Bushveld Granite underlies the whole of Winterveld and Mabopane. The geotechnical constraints of the Bushveld Granites are:

• Collapsible soils;
• Uneven weathering which may result in differential settlement; and 
• Localized perched water tables.

Pienaars River TRC (East Gauteng Services Council)
The Bushveld Igneous Complex underlies the involved section of the EGSC. The area is characterized by rocky soils and moderately expanding/shrinking soils.

Crocodile River TRC (West Crocodile river)
The northern section of the TRC is more rugged where the tilting of ancient Karoo deposits has resulted in the distinctive terrain of the Magaliesberg and the Witwatersberg. These two ridges are quartzite ridges. The area between these two ridges is known as the "Magaliesmoot" area, which contains shale deposits of the Karoo Supergroup. A number of clay and gravel quarries occur in the moot against the quartzite slopes.

The Schurweberg range, which is an andesite range, lies south of the Witwatersberg and the area south of the Skurweberg contains dolomites where a number of sinkholes occur.

Degraded Land of the TMM:
Although there are some degraded areas in the TMM, the state of the geology does not appear to be exceptionally poor. Due to a lack of information it was not possible to determine leaching in the study area.

The amount of degraded land that occur in the TMM are as follows (information supplied as per jurisdiction areas):

City Council of Pretoria - approximately 1,5 km²;

• To the north of the Magaliesberg in the Akasia region
• To the north of the Daspoort Rand
• The poort through the Magaliesberg (between Zambesi Drive and East Lynne) 

Centurion Town Council - approximately 1,5 km²

• In the Skurweberg
• In Rooihuiskraal
• In the Doornkloof/ Irene area
• In the Monument Park area
• In the eastern section of the Rietvlei Dam Nature Reserve
• To the north of Wapadrand

Northern Pretoria Metropolitan Sub-Structure - approximately 1,5 km²

Soshanguve (along the Soutpan Spruit)

• Klip & Kruisfontein (in the vicinity of the Kaalplaas Spruit)
• Rosslyn (in the vicinity of the Kaalplaas Spruit, to the north and east of the norite hills)

Eastern District Council Area - no information available

Pienaars River TRC (East Gauteng Services Council) - more than 1,5km²

• Mainly in the southeastern section of the study area.

h) Crocodile River TRC (West Crocodile river) - more than 1,5 km²

• Mainly in the northern section of the study area (in the Magaliesmoot area and to the north of the Magaliesmoot area)

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