Page:South African Geology - Schwarz - 1912.djvu/182

 smaller, perhaps, but otherwise identical. So we have the case of a continuous deposit one end of which is Cretaceous and the other end Eocene, Oligocene, Miocene, Pliocene, or even Recent.

The deposit is often quite chalky, and forms conspicuous chalk hills in Alexandria. When it weathers, the calcareous matter dissolves, leaving a fine residue of clay stained a brick red with iron.

In other parts to the east and west contemporaneous deposits at the same elevations consist of masses of silicified gravel, ironstone gravel, and cemented river gravel, showing that at the time that the central area was beneath the sea these portions were dry land. The hilltops covered with these deposits are always level, and the hard cemented rock at the summits presents often fantastic forms. In the Ruggens of Caledon, a peneplain of Bokkeveld Beds deeply cut into by a maze of gorges, the soft slates weathering beneath the hard caps has left them standing with precipitous sides like walls of castles. In Kentani there is a conspicuous cap of these surface quartzites at Quintani Hill.

Recent Deposits

These include the estuarine deposits lying in the sunken valleys of the rivers along the coast. They are mostly composed of greenish sands and clays full of shells belonging to recent species and foraminifera. Above these, at Mossel Bay, there is a still more recent deposit, with shells and chipped flints of human manufacture. These are different from the usual Strandlooper and Bushman flints, and have much in common with the chipped flints associated with the bones of rhinoceros,