Page:South African Geology - Schwarz - 1912.djvu/163

 equally good, and that as the Karroo is so horribly awful on the surface there must be something to compensate for it beneath.

The Ecca Series. — This is a well-marked division on the south of Cape Colony but is missed out on the north. In the west, in Mordenaar's Karroo, the Ecca consists of brown sandstones, with Glossopteris, and grey shales. This is referred to as the Laingsburg Beds. In Prince Albert there is a succession of shales separated alternately by dark-purple sandstones weathering into irregular blocks coloured red, by limestones weathering brown, and by blue sandstones crumbling into a yellow sand. The country made of this four-phase Ecca is peculiar; there are valleys where the softer shale has crumbled and has been blown away, separated by ridges alternately red, brown, and yellow. Farther east, from Willowmore onwards, the Ecca is mostly shale with subordinate shaly sandstones marked with a pecular mottling; the prevailing colour is blue and the mottling usually takes the form of white spots, the origin of which is quite unknown. The mottling passes through all varieties of rock; even the septaria that occur somewhat plentifully are affected. A great deal of silicified wood is found in this eastern Ecca, especially south of Graaff Reinet, where the plains are covered with it. Still farther east, in the Transkei, there are thick beds of sandy clays, dark-blue in colour, weathering to a brick red; when hardened by intrusions of dolerite they form a hard black mass with a fracture like flint. These have been called the Umsikaba Beds; they gradually merge at the top into the Idutywa Beds, that is to say, the Beaufort horizon is missed out.

The Laingsburg Beds, the Four-phase Ecca, the Mottled