408 VLEI DEPOSITS 



the limestone that overlies a pebbly beach deposit at 

 Cape Infanta, now being cut back by the sea. At the 

 time when the inland plateau was being cut the dunes 

 that now form the limestone range were being piled up 

 by the wind, and the coast was indented by a broad bay 

 between Cape Infanta and Bredasdorp village. The 

 eastern corner of the bay extended farther seawards 

 than the present position of Infanta, for the high cliffs 

 made of Table Mountain sandstone in their lower part 

 and of the beach deposit and limestones in the upper 

 half must have been undergoing destruction ever since 

 the raised beach was removed from the reach of the sea. 

 In the Algoa Bay region the high level gravels of the 

 Zwartkops Heights were probably formed at the same 

 time as the terraces covered with surface quartzites and 

 allied deposits near Grahamstown, and the wide rock 

 terrace traversed by the main road from Port Elizabeth 

 to Human sdorp. The upward movement of the land 

 which raised the Zwartkops Heights beach to its present 

 level also brought about the renewal of the downward 

 erosive power of the rivers inland, so that they trenched 

 the gravel and quartzite plateau of Grahamstown. 



9. VLEI DEPOSITS. 



Near their mouths many South African rivers expand 

 into wide shallow lagoons. The larger rivers, such as 

 the Berg, Breede, Gouritz, Kei and St. John's, which 

 maintain open channels to the sea throughout the year, 

 have comparatively small lagoons or none at all, al- 

 though some of them, such as the Berg, give rise to 

 shallow vleis beyond their banks in times of flood, The 



