320 CONDITIONS OF DEPOSITION 



the river which still drained the country. It cannot be 

 held that the valleys were entirely closed, or that they 

 were in a region that had no outlet to the sea ; for in 

 such districts the salts that are contained in small 

 quantities in all rocks become concentrated in the water 

 that temporarily or permanently occupies the lowest 

 levels, and form layers of crystalline rock-salt, gypsum 

 and other minerals that are interbedded with the sand 

 and mud carried into the same basins. Incrustations 

 of salt occur on the outcrops of certain sandstones in 

 the valley leading down to the Addo drift, 1 but no beds 

 of rocksalt have been found, though gypsum is disse- 

 minated through the Enon beds in some of the Willow- 

 more outliers ; 2 but the occurrences are not sufficient 

 to prove that the beds were deposited in closed basins. 

 In the case of the salt-bearing beds the abundance of 

 marine fossils in the strata above and below them shows 

 that the area was not for long, if at all, disconnected 

 from the open ocean ; the scattered gypsum crystals in 

 the Enon beds may be compared with the occurrence of 

 that mineral in the soil of certain parts of the west coast 

 area which is freely drained but which receives a low 

 rainfall. 3 



The description of the outliers on previous pages 

 shows distinctly enough that the deposits vary consid- 

 erably from one basin to another, that although their 

 general nature is very much the same, the order in 

 which they occur is not in the least identical. The po- 

 sition of the outliers also shows that they were formed 

 in separate valleys, in each of which the deposits were 



1 G. C., x., p. 26. 2 G. C., viii., p. 114. :! G. C., ix., p. 44. 



