The formations of the Table Mountain Group were formed some 400 million years ago when sediments were washed down prehistoric rivers and deposited in a shallow marine environment.

Layers of sediment, estimated to be 5 - 8 km thick, were deposited in the Cape Basin. Over time the layers became buried, eventually forming rocks such as quartz sandstones, shales and siltstones under the increasing pressures and temperatures.

Continental movement caused the layers to be squeezed into folds. The pressure on these layers of rock was immense, causing buckling and fracturing in the layers. The Table Mountain Group, which is the focus of this study, is the lowest component of the Cape Supergroup and forms the backbone of the Cape Fold Belt Mountains.

The map below shows areas where the rocks of the TMG occur at the surface. In these areas, the aquifers within the TMG may be recharged by rainfall.

South-Western Cape - Areas where the Nardouw and Peninsula formations occur at the surface

Two major events lead to the current deformed state of the Table Mountain Group. T hey include a mountain building period called the Cape Orogeny during which uplift and thickening occurred, and the break up of Gondwana, a super-continent that existed before the formation of the Atlantic ocean. The Cape Fold Belt was formed around 250 million years ago. The results of these events are fractures and faults in the hard, brittle sandstones, and extensive folding in the more pliable shale layers.

The quartz sandstones of the Peninsula Formation reach a maximum thickness of 1 800 m.

The lithology and bedding characteristics of the Cape Supergroup influence their hydrogeological potential. These rocks tend to have low porosity and they only become good aquifers where they are fractured. The best water retention in the system is along fault lines and strongly folded layers.