2l6 SALTPAN NEAR IIAAGEXSTAD. 



The kopjes around the pan are hke most of the kopjes of 

 the Colony, in reaHty smah outhers composed of dolerite or 

 of sediments altered by the heat received from intrusions of 

 that rock. 



I want you, then, to imagine yourself standing on the farm 

 Poortje looking across the huge basin. It is a desolate but 

 beautiful sight whether seen after a heavy rain, when the floor 

 is almost covered with water, which hundreds of flamingoes 

 have discovered, or in the dry season, when it is white with 

 salt. 



What is the origin of the pan and where does the salt come 

 from ? Evidently the depression has been produced by one of 

 two means — subsidence or erosion. 



The subsidence theory will first be considered. 



This theory at first glance appears very plausible when con- 

 sidered in connection with the question of the accumulation of 

 salt in the pan. If a stratum of salt existed in the rocks under- 

 neath the pan and this were gradually diminished by solution, 

 a subsidence of the overlying beds would ensue. Salt in the 

 form of brine might then reach the surface in the form of 

 springs or by capillary attraction. 



Facts, however, are against the subsidence theory. The 

 ■dip of the rocks forming the sides of the pan is uniformly 

 south-east. Neither is there evidence of faulting. 



Water then must have carried away these thousands of tons 

 of disintegrated rock. If, however, erosion is the explanation 

 of the basin there must have been at one tifne or other an 

 outlet through which the rocks filling this area were carried 

 away in solution and suspension. 



Nor is the position of this one-time outlet to this inland 

 lake difficult to find. The south edge of the pan is not bordered 

 by kopjes. The edge of the pan here is bounded by a swamp 

 whose southern edge is formed by sand dunes. Intercalated 

 with the sand are masses of peat — probably the formation of 

 successive swamps. On these dunes the baths are built, and 

 the water in the springs supplying" them possibly derives its 

 large quantity of marsh gas from the peat of the district. 



Boreholes, sunk almost to the depth of the pan bed, have 

 been put down near the baths, but no solid rock has been met 

 with. We can take it then that some thousands of years ago 

 the district occupied by the salt pan was a point for the con- 

 centration of the surface waters from a large catchment area, 

 as is still the case. These waters weathered away the sofi 

 shales and sandstones surrounded by the semicircle of dolerite 

 and metamorphosed shale and sandstone, now forming the 

 rim of the pan to north, east and west. The sediment was 

 carried away probably through a channel leading from the pan 

 at the south-east near the baths, and entering the Modder 

 River near Lombaard's Drift. 



In dry seasons large stretches of sand lay over the bed of 

 the lake, and the powerful north-west winds blew this to the 

 south-east corner, forming" huge dunes containing marshes. 

 Thus the outlet was eventually sealed, and the lake became a 

 small inland sea. 



