Page:South African Geology - Schwarz - 1912.djvu/181

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STRATIGRAPHICAL GEOLOGY
171

east of the great fault which comes from Lake Nyasa, down the Shiré River almost in a straight line to Delagoa Bay and Durban, and from here truncates the eastern portion of Cape Colony, and runs out to sea along the edge of the Agulhas plateau. The deposit consists of sandy and clayey limestones, with banks of shell limestone; it is very fossiliferous, and has afforded magnificent specimens of Ammonites, Nautilus, Trigonias, and other Cretaceous mollusca, besides sharks' teeth, bones of turtles, and the skeleton of the great snake-like lizard, Mosasaurus. Similar beds occur in Southern India, Japan, and Vancouver.

The Alexandria Formation

From this time onwards the land rose by fits and starts, and along the coast there are shelves cut at varying levels; from 1500 ft. downwards the shelves are covered in the Port Elizabeth, Alexandria, Bathurst, Peddie, and East London divisions by a beach deposit, sometimes calcareous shell sand, sometimes beach boulders. The fossils are uppermost Cretaceous and Tertiary, and among the larger shells of Pectunculus, Perna, Turritella, there are at East London crowds of corals and Polyzoa. At Sandflats there is foraminiferal limestone. The Alexandria Formation is peculiar, in that the deposits on the 1500-ft. plateau are undoubtedly Danian or uppermost Cretaceous. The next shelf was later, but the deposit and the fossils in it are the same as on the last, and so on down to sea level. Now the deposit on the lowest shelf is evidently very much more recent than the Danian deposits at Sandflats or East London, yet the fossils in them all are the same; the shells are