THE CRETACEOUS SYSTEM 311 



regarded as having been red when formed, should yield 

 few or no fossils. 



On the watershed between the Doom and Klein Doom 

 Rivers the cuttings for the new railway line to Rivers- 

 dale revealed the presence of some limestone bands 

 showing cone-in-cone structure, and a few thin veins of 

 gypsum. The cone-in-cone limestone breaks up in a 

 very curious fashion ; the rock appears to be built up of 

 a number of cone-shaped bodies, closely pressed together, 

 with their axes perpendicular to the bedding planes. 

 The gypsum fills narrow cracks and joint planes, and is 

 a product of the mutual decomposition of pyrites and 

 carbonate of lime in the shales. 



A very interesting point in the Heidelberg basin is the 

 occurrence of an intrusive plug of melilite-basalt (alnoite) 

 near the northern part of the farm, Spiegel River on the 

 ridge running south from Amandel Bosch Rug (see 

 p. 346). 



Near the village of Swellendam there is an isolated 

 basin of Uitenhage beds. Its exact limits are not 

 known, as it and the surrounding rocks belonging to 

 the Bokkeveld-Witteberg series are much hidden by 

 gravels and alluvium of a much later age, but it is about 

 twelve miles long and five wide, and extends from the 

 village, the eastern part of which is built on it, to beyond 

 the Buffeljagt's River. The rock near the western end 

 seems to be chiefly composed of conglomerates contain- 

 ing pebbles derived from the Malmesbury, Table Moun- 

 tain, Bokkeveld and Witteberg series. At the railway 

 station a bore-hole put down to the depth of 350 feet 

 flid not reach the base of the conglomerate. Near the 



