Approximately 1000 million years ago, subduction and collision along the southern margin of the Kaapvaal Craton produced the rocks of the Natal Metamorphic Province. The rocks were heated and deformed into a mountain range many thousands of kilometres long. Once plate collision with the Kaapvaal Craton had ceased, a long period of erosion exposed the deep mountain roots of granite and gneiss.
Some of these rocks are spectacularly folded and can be seen in the Tugela Valley, Valley of a Thousand Hills and along the south coast of KwaZulu-Natal. The granite is quarried for dimension stone at a number of localities.
Also part of this metamorphic process was the formation of the Marble Delta, a limestone formation covering an area of about 40 square km’s inland of Port Shepstone. Marble Delta is the major source of limestone mined in KwaZulu-Natal.
Limestone formed due to the precipitation of calcium carbonate in a shallow sea. Later it was metamorphosed by high temperature to form marble, which is light-coloured and very coarse-grained. The marble is mined form cement production and agricultural lime.