THE KARROO SYSTEM 201 



Beds of "clay-pellet conglomerate" are often seen at 

 the base of the sandstone beds ; it is a rock with a mud- 

 stone or sandstone matrix containing numerous rounded 

 or flattened lumps of mud, rather different in colour from 

 the matrix and finer grained. The lumps of mud were 

 derived from previously deposited sediment, and were 

 rolled along by the current till they came to rest where 

 they are found. The tidal lagoons of the Eastern 

 Province rivers and the lower part of the Olifant's Eiver 

 (Van Khyn's Dorp) are good places for the observation 

 of the formation of mud -pellets on a muddy or sandy 

 bottom, while the Orange Eiver near Prieska has many 

 sandy stretches along its banks exposed during dry 

 seasons and covered with mud-pellets brought down by 

 the last flood. There is no doubt that mud flats ex- 

 posed at the surface of shallow water would furnish 

 lumps of mud to the small waves washing the margin, 

 and it is probable that the clay-pellet conglomerates in 

 the Karroo formation were formed in this way. 



Local unconformities affecting the beds over small 

 areas, sometimes only a few yards wide, are very abun- 

 dant in the Beaufort and Ecca beds. The lower-lying 

 strata are cut off by the upper to the depth of, perhaps, 

 four or five feet, usually less, and the higher beds thicken 

 out to occupy the depression made in the lower. These 

 hollows are usually in shales or mudstone, and the 

 rocks filling the hollows are sandstones or clay- pellet 

 conglomerates. The frequency of these examples of 

 " contemporaneous erosion and deposit " point to the de- 

 position of the strata in quite shallow water which from 

 time to time received sudden accessions from rain floods, 



