THE CRETACEOUS SYSTEM 317 



must be very considerable, since it includes a large part 

 of the material now forming the Uitenhage beds as well 

 as that removed since the close of the period. The 

 rivers, which before the deposition of the Uitenhage 

 beds were able to carry away the mud, sand and pebbles 

 delivered to them by the mountain streams, became 

 unable to cope with their work, and their beds con- 

 sequently became choked up with dSbris, at first as a 

 rule of a coarse nature including many large boulders 

 and pebbles together with a large quantity of sand. 

 These accumulations are the conglomerates that lie 

 below the fine-grained rocks, the Enon beds of the 

 Uitenhage district and the similar rocks of the outliers 

 to the west, but it is by no means certain that the red 

 conglomerates round the Oudtshoorn-Willowmore basin, 

 for example, were formed at precisely the same time as 

 the Enon conglomerate itself. One possible cause of 

 this change of conditions, the change by which the area 

 became one of deposition or accumulation instead of a 

 region in which the destructive agencies had full sway, 

 may have been that the level of the land surface as a 

 whole was reduced with regard to the level of the sea 

 into which the old rivers flowed. Whether such a down- 

 ward movement of the land took place uniformly or 

 whether some parts were depressed more than others is 

 not easy to determine, although the fact that the marine 

 beds have not been found west of Knysna seems to point 

 to an unequal distribution of the change in level. Had 

 the sinking gone on continuously and equally over the 

 whole area we should expect a gradual extension of 

 similar sediments from the sea landwards, i.e., con- 



