TERTIARY AND RECENT DEPOSITS 387 



below the river without their base being found. The 

 shells hitherto found in these sands and in similar de- 

 posits in other places all belong to existing species. 



Test holes for finding solid foundations for a bridge 

 across the Buffalo Kiver at East London prove that the 

 bed rock (the Beaufort series) lies at a depth of 122 feet 

 below water level in the middle of the estuary, and that 

 above it are over 100 feet of clay, sand and shelly beds. 1 



The considerable depth below sea level to which these 

 estuarine deposits extend may point to a subsidence of 

 the coast, but in some cases the scour of the river and 

 tide combined are sufficient to account for the excava- 

 tion of the estuaries. This certainly seems to be the 

 case with the short but deep estuary of the Kaaiman's 

 Kiver, near George, where there is a rapid fall of the 

 bed below the old road drift. 



The alluvium along the great rivers draining the Great 

 Karroo is often extensive and of considerable depth. It 

 occurs chiefly behind mountain ridges through which 

 the rivers have cut their way more slowly than in the 

 softer ground now occupied by the alluvial deposits. A 

 very good example is found in the Olif ant's River (Oudt- 

 shoorn) ; this river rises south of Antonie's Berg in 

 Willowmore, but it receives very important tributaries 

 in the Traka, Meiring's Poort, Grobbelaar's and Kam- 

 manassie Rivers before it joins the Gamka in the middle 

 of the Roode Berg mass of Table Mountain sandstone. 

 The junction of these two rivers makes a great Y-shaped 



1 Schwarz and Chapman, Rec. Albany Museum, vol. ii., pp. 1-6, with 

 a section and description of the ostracods and foraminifera, which belong 

 to living species. 



25* 



