Page:South African Geology - Schwarz - 1912.djvu/172

 a large number of associated plants which enable one to date the series as equivalent to the European Rhætic.

The Molteno Beds form the great plateau from which rise the volcanoes of the Drakensberg and Malutis, the Quathlamba of the Zulus. It is everywhere steeply scarped on the seaward side, and is about 4000 ft. above sea level. A large number of great dolerite laccolites occur along the margin of the plateau, forming mountains such as the Insiswa at Mount Ayliff.

The Red Beds follow the Molteno Beds in the actual slopes of the mountains; they are too soft to withstand the processes of weathering on the flats, and are rarely represented there. They consist of dark-red tenacious clay at the base, and red and pink sandstones above. The series varies greatly in thickness, and is as much as 800 ft. thick in places, but usually is thinner than the brilliant-white Cave Sandstone which succeeds it. In the red clays very fine dinosaurian remains have been found; these were gigantic reptiles with bird-like skeleton and enormous clawed feet. The forms have been called Hortalotarsus, Massospondylus, and Euskelosaurus; a little crocodile, Notochampsa, has also been found in these beds.

The Cave Sandstone is usually one massive bed of white sandstone 800 ft. thick. It consists of rounded grains of quartz and felspar which have been corroded on the surface and enveloped with minute scales of talc; thus the ordinary aspect of a sandstone is entirely masked and the rock has the appearance of chalk. The sandstone is not an ordinary sediment, for the fine coating of talc scales would have been soon rubbed oft the sand grains if they had been dragged along the sea floor