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THE VOLCANIC EISSUEE UNDEE ZUUEBEEG. 



By A. W. Sogers, M.A., F.G.S. 



(Bead June 28, 1905.) 



The general structure of the Zuurberg was described many years 

 ago, first by A. G. Bain,* who drew a section (No. 11 of his paper} 

 through the range in the area with which this paper deals, and 

 secondly by E. Pinchin,f who made a carefully executed map and 

 section of the same area. Both these geologists gave substantially 

 correct explanations of the range, though the exaggerated vertical 

 scale used by Pinchin obscures one of the main features of the 

 mountains, that they were reduced to a comparatively level surface, 

 on which the differences between the harder and softer strata are 

 scarcely noticeable, before the great kloofs were carved out of them ;. 

 the view of Bain that the Dwyka conglomerate was a contempora- 

 neous volcanic rock, and Pinchin's opinion that it was a meta- 

 morphic rock, did not affect the general question of the structure of 

 the range, as both authors knew that it lay conformably amongst 

 the other beds forming the mountains. 



During the past month I have been working along the southern 

 flank of the Zuurberg, between Enon on the west and Bellevue on 

 the east. The main part of the range is made of the Witteberg 

 beds thrown into two or three great folds, the vertical height of" 

 which must be over 1,000 feet, and the limbs of these folds are at. 

 places themselves folded on a small scale, especially along the shale 

 bands. The Dwyka conglomerate, accompanied by both the Upper 

 and Lower shales, follows to the south, where the dips are very high 

 in that direction, or rather some 5° to 20° west of south. 



The great area of Uitenhage beds occupying the lower portion of 

 the valleys of the Bushman's and Sunday's Eivers is ushered in by 

 the Enon conglomerates, typically developed near Enon, where they 

 form a belt of bushy country about three miles wide at the foot of 



* A. G. Bain, " Trans. Geol. Soc," Second Series, vol. vii. 

 f R. Pinchin, " Q. J. G. S.," vol. xxxi., p. 106, and figs. 3, 4. 



