Although viticulture in the Western Cape is relatively young, the geology is not, resulting in some of the most ancient viticultural soils in the world. Massive pressures and upheavals over millions of years resulted in majestic mountain ranges on the southern tip with steep slopes and deep valleys, soft folds and soaring peaks, and created a remarkable variety of mesoclimates and soil types in the process.
In order to understand and appreciate the magnitude of this geological inheritance, it's essential to go way back in time. What can presently be discerned in the landscape is late Precambrian Malmesbury Group shale and schists, deposited some 1 000-550 million years ago in a marine basin, presently occurring at an altitude of 20-200 m. This deposit was folded and uplifted due to tectonic movement of the Pan African event, which ended 550 million years ago, and eroded into rolling hills.
Subsequently, intrusions of Cape Granite Suite plutons (domes) occurred around 600 million to 500 million years ago, before the stage of separation of Gondwanaland into present day Africa, South America, India, Australia and Antarctica. A period of erosion and planation of some 50 million years followed. The surface then subsided and was covered from the north by deep deposits of the Cape Supergroup (400-300 million years ago) and later by the Karoo Supergroup.
About 250 million years ago, intensive folding and uplifting occurred, creating the distinctive folded sandstone mountain ranges and valleys of the Cape. Erosion removed large areas of the Cape Supergroup deposits, leaving sandstone remnants like Table Mountain and Simonsberg (1 000-1 300 m altitude), often resting on granitic foothills and associated with exposed granite plutons or domes, presently visible as distinctive solitary mountains (Paarl Mountain, Perdeberg: 500-700 m altitude) or ranges of hills (Bottelary, Malmesbury and Darling hills: 200-400 m altitude), usually surrounded by Malmesbury shale landscapes.
What is a pluton?
Plutons are dome-like intrusions of igneous magma into the earth's crust which occurred at great depths and consequently cooled slowly, resulting in a coarse crystalline (granitoid) texture. These plutons have subsequently been exposed by erosion, resulting in dome-like mountains or hills such as the Paarl and Perdeberg mountains and Darling hills, or the exposed domes have been 'flat-topped' by erosion and then covered by sandstone deposits, and have then again been eroded, resulting in sandstone on a granitic base mountains, like Table and Simonsberg mountains.