The Karoo System or Karoo Sequence, is a geologic system of rock formations covering 1 500 000 square km and extending from the Equator south to the Cape of Good Hope. The Karoo System spans a period of about 100 million years, starting from the Permian or Carboniferous Period (c300 million years ago) to the Late Triassic Epoch (228-200 million years ago).
The geology of the Great Karoo consists largely of horizontally-bedded shales and sandstones. Their uniformly level appearance is broken only by numerous igneous intrusions of dolerite dykes and sills producing the characteristic Karoo hills. Along the south-western and southern edges of the ancient basin, the massive ranges of the Cape System are prominent boundary features. In the south-west the Cederberg and Cold Bokkeveld ranges stretch for some 800 km to the Gamtoos River.
This vast inland plateau is at an elevation of between 600 and 1350 metres. Underground brackish water is accessible to stock-farmers by drilling of boreholes and the erection of windpumps. Soils are generally fertile though shallow, yielding good crops, especially along river-banks. [1]