Page:South African Geology - Schwarz - 1912.djvu/202

 became waterlogged and sank to the bottom of the water. Where the coal is near the surface, the water sinking through the coarse sandstones above has washed out the coal along certain lines, and the roof of sandstone, becoming thus unsupported, often falls in and causes deep pits to form on the surface. Some of the Transvaal coal, however, is of drift origin; solution channels in dolomite are sometimes filled in with secondary coal and coaly shale.

The fossils of the Karroo Beds in the Transvaal are the typical Triassic forms of the flora of the Southern Hemisphere, Glossopteris, Gangamopteris, and Noeggerathiopsis (Cordaites), and in addition there are lepidodendroid stems, Sigillaria and Bothrodendron. In the bed of the Vaal River, at Vereeniging, at very low water, there are exposed the stumps and roots of a number of large lepidodendron trees.

The thickness of the Karroo Beds in the Transvaal reaches a maximum of about 1000 ft.

The Stormberg Formation

In the north central portion of the Bushveld there are the so-called Springbok Flats Sandstones or Bushveld Sandstones, white, chalky-looking sandstones, in every way similar to the Cave Sandstone, and like it containing remains of dinosaurs. These are followed by amygdaloidal basalts which have been placed as contemporary with the Drakensberg lavas. The actual continuation of the Drakensberg is the Lebombo range, which consists of basalts and more acid rocks referred to as rhyolites. This range separates the low country of the Transvaal, made of Swaziland Beds, from the Portuguese