Page:South African Geology - Schwarz - 1912.djvu/146

 In Natal the granite has altered the limestone at the contact, and has converted it into marble with garnets, diopside, and olivine; there is a small area of white marble at Worcester which owes its character to the granite below.

Basic intrusions (dolerite dykes) are found running through the granite at Lion's Head at Cape Town, at Vogel Vley, at Kapok Berg in Malmesbury, and at the western end of the Cango. The molten rock has had very little, if any, action on the sedimentary beds. The Vogel Vley dyke is a diabase, that is, an altered dolerite, and is much more ancient than the others, which are probably post-Karroo.

The Neo-Afric Group

The Cape Formation

The Table Mountain Sandstone. — The Table Mountain Sandstone, Bokkeveld, and Witteberg Series form what is known as the Cape System. The lowermost of the three, the Table Mountain Series, rests on the eroded surface of the granite and Malmesbury Beds. The deposition of it and the Malmesbury Beds was separated by a vast interval of time, sufficient to have allowed the Malmesbury Beds to have been hardened, tilted, invaded by granite, and planed down to a more or less level surface by erosion on land, and finally submerged beneath the sea before the sands of the Table Mountain Series were laid upon them. The Table Mountain Sandstone consists essentially of coarse sands piled up in layers at different angles (false-bedded), and every two or three feet separated by a major bedding plane. The colour is blue, but on weathering the rock assumes the