Page:South African Geology - Schwarz - 1912.djvu/143

 colour, but on the surface pass somewhat readily into a brown clay in the moister parts. They are quite useless for building purposes, for directly the live rock is quarried, and the water of imbibition dries out, it splits and crumbles to fragments. Passing northwards to Paarl and French Hoek similar rocks occur, with the addition of a bed of conglomerate in the latter place. Still northwards, at Vogel Vley, there are limestone and quartzite bands. In the Tulbagh valley and at Worcester there is a stage intermediate between the clay slate and schist; the rocks are phyllites, and the blue-black rocks are coated on the surface of the cleavage planes with scales of silvery mica. At Worcester, again, there is a bed of limestone. Eastwards, the next important outcrop is at George, where the rocks are thinly bedded or sheared, for it is impossible to distinguish the two planes, and are so carbonaceous that they have been prospected for coal. There are many curious contact metamorphic rocks in this last area, which will be dealt with presently.

North of George, in Oudtshoorn, there is an important area of Malmesbury Beds in the Cango. The southern border of the district consists of high hills of conglomerate like that in French Hoek, but of very much greater thickness, and complicated by folding. The conglomerate the Cango Conglomerate apparently rests on thin-bedded slates of the Malmesbury Series, in which are interstratified three main bands of limestone; the famous Cango caves occur in one of these limestone bands.

On the west coast the Malmesbury Beds are exposed on the coastal plateau, all dipping steeply to the west. As the width of the plateau is from 30 to 40 ml., it is