58 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Dec. 



than the Tulbagh coal, which is an equivalent of our Coal-mea- 

 sures. 



The " Karoo formation " also occurs in a small belt on the sea- 

 coast of Natal, which belt is never broader than from seven to eight 

 miles, if so much. Beds of the Karoo series are well exposed at 

 the Umgeni mouth and also at the Ifumi river. Any one who has 

 been to Pietermaritzburg must have observed cuttings on the 

 road, about seven or eight miles before he reaches the capital, in a 

 dark shaly rock, with large boulders of older rocks imbedded, of 

 granite, gneiss, slate, and also frequently of greenstone (fig. 2). 

 These boulders are so characteristic of African scenery that they 

 have received general attention. The boulders, often of very large 

 size, are imbedded in a soft grit and shaly clay, containing small par- 

 ticles of mica. 



Fig. 2. — Irregular boulders of Greenstone, sometimes Granite or 

 Gneiss, imbedded in clay and grit. 



The boulders seem to have been formed on the spot, or at least 

 have not travelled very far, as many of them have kept their angular 

 shape, and they seem to have undergone rather a process of decom- 

 position than of rolling. These beds (" boulder-beds ") extend often 

 over a very large area, and pass everywhere beneath the dark shale, 

 which represents the base of the Karoo plant-beds. This is proved 

 by a section at Thornville, and also on the sea-coast of Natal at 

 several places, amongst them at the Umgeni valley and the Ifumi 

 river. At the Umgeni and Durban the sections are as in figs. 3 & 4. 



Both these sections show that the plant-bearing shales and sand- 

 stones rest unconformably on the older Table-Mountain Sandstone, 

 and also that the boulder-bed lies at the base of these plant- 

 beds. 



The same is shown at part of the road between Pietermaritzburg 

 and Thornville (see Section, PI. II.). 



The boulder-bed here, in the same way as in the other sections, 

 passes gradually into the shale of Pietermaritzburg, which, as I 

 think, belongs to the lowest bed of the Karoo series. We learn from 

 the Geological Survey of India that almost the same formation of 



