Some 300-290 million years ago, during Dwyka times, what is now Southern Africa was, as a result of plate tectonics, near the South Pole and large ice sheets or glaciers covered high-lying areas. Geologists term this upland the Cargonian Highlands, stretching from what is now the Northern Cape through Gauteng to Mpumalanga. As the Dwyka glaciers moved, grinding their way southwards, the rocks and rubble that became embedded in their belly smoothed the underlying Andesite rock pavements and scoured out scratch marks, known as striations. As the ice shaped the landscape, the continent of Gondwanaland continued to drift slowly northwards, ultimately bringing this area into warmer latitudes. As the glaciers melted, a mixture of clay and rock was left behind which eventually consolidated into a rock called Tillite – the lower-most layer in the Karoo sequence. Quite large erratics or drop stones carried here by glacial action are found at Nooitgedacht. The changing local environment also created conditions conducive for the burgeoning of life, reflected in the rich fossil record of the Karoo.
