Page:South African Geology - Schwarz - 1912.djvu/166

 It was the finding of Glossopteris, Gangamopteris, and a peculiar seed, Cardiocarpon, in the red and green greasy shales exposed in the quarry in the station yard that gave the clue to the existence of this great structural feature. Farther cast, in Robertson, the Ecca Beds rise into considerable hills, and are composed of greenish shales and sandstones.

The fossils of the Ecca Series are Glossopteris, Gangamopteris, the calamite-like stems of Schizoneura, and Cardiocarpon. The first of the Karroo reptiles proper occur on this horizon, the form being called Archæosuchus. There are also in places crowds of a freshwater mussel, Palæomutela.

The Beaufort Beds. — These beds are reckoned from the first appearance of the Pareiasaurus remains passing upwards in the rock succession. Lithologically it is a monotonous formation consisting of bluish shales divided at intervals by bluish or greenish sandstones that stand out in steps on the escarpments, and arc, thence called the defining sandstones. The. sandstones, if weathered, crumble into yellow sands. There are also more shaly, darker sandstones, often mottled with purple, which weather with a red coat. These are the intermediate sandstones. Septaria and banks of impure dolomitic limestone occur, becoming less and less as one goes up in the series, their place towards the top being taken by rgillaceous nodules. Beneath the defining sandstones there is often a clay-pellet conglomerate, showing that the surface of the lake was occasionally exposed above water level; indeed, from the evidence of Glossopteris leaves and roots at Van der Byl's Kraal, it is evident that the mud banks often existed for some considerable period, and formed islands covered with vegetation.