Page:South African Geology - Schwarz - 1912.djvu/152

 their vegetation, instead of being the reservoirs of the head streams of perennial rivers, have become pent-roofs down which the rainwater rushes to scour out the valleys at their foot.

As far as the Table Mountain Sandstone occurs along the coast it forms bold promontories or seacliffs, the bays being cut in softer rocks Malmesbury or Bokkeveld Slates.

The Bokkeveld Series follows the Table Mountain Series with no break, a fact which goes to show that the latter series must be a marine deposit equally with the former. The series consists essentially of slates much less hardened than those of the Malmesbury Series, and separated by four hard sandstone bands, the lowermost being a calcareous sandstone, and known as the Fossiliferous Sandstone, and the three upper being thinbedded sandstones, weathering white, which are therefore called the First, Second, and Third White Sandstones. The feature of the Bokkeveld Beds which makes them so important is the presence of a large number of fossils, which allows one to compare these beds with others in other parts of the world. Exactly similar fossils are found in the lower Devonian (lower Helderberg) of New York and Western Ontario, and also in the Falkland Islands, Bolivia, and Brazil.

The distribution of the Bokkeveld Series follows that of the underlying Table Mountain Sandstone very closely, forming the low ground at the foot of the mountains. It thins out on the west equally with the Table Mountain Sandstone, but does not reach so far north as that series. On the coast it has been followed as far as Port Elizabeth, and it probably extends some distance to the east, but it is covered with the Witteberg rocks in Albany,