Page:South African Geology - Schwarz - 1912.djvu/193

 came a diabase sheet, then rhyolite, followed by quartzite, again with a basal conglomerate. The diabase and quartzite is the Pniel Series, and the rhyolite and quartzite are called the Zoetlief Series. There is an intermediate group in Prieska called the T'Kuip Series, which consists of arkoses, limestones, and cherts with intercalated basic lavas. On the Rand, below the Klipriversberg Amygdaloid, there is also a sedimentary series, the Elsberg Beds, usually classed with the banket series, but which is clearly derivative from the Witwatersrand Beds, that is, unconformable upon them. At Langerman's Kop, on the east of Johannesburg, the same beds occur, and these show that bits of the quartzites have been broken off, rounded, and included in the sandy matrix of the Elsberg Beds. The sand grains are splintery, like those found in glacial deposits, a feature also noticeable in the conglomerate at 2230 ft. in the Kimberley rock shaft. In the south-west of the Transvaal enormous areas are covered with these boulder beds. When weathered, the conglomerate looks like the Enon Conglomerate of the Cape, but the pebbles are of far greater variety, including granite, slate, diabase, and quartzite among other rocks.

The Transvaal Formation

The Transvaal System is the most widely distributed and the most typical system of this area. On the east it overlies the Swaziland Beds that occur in the low country about Barberton and Swaziland, and forms the magnificent escarpment of the Drakensberg. From here it surrounds the great Bushveld laccolite, dipping always inwards towards it and, according to one view, giving