718 ME. E. H. RASTALL ON THE GEOLOGY OE [Nov. I9II, 



intrusion took place before the final foliation, and that the great 

 size of the main mass protected the interior from crushing, while 

 the margin and the peripheral dykes were strongly foliated. Thus, 

 even at this early stage, before the deposition of the Cape rocks, this 

 intrusion acted as a horst, and that fact has some bearing on the 

 problem of the later faulting. 



VIII. The Cape and Karroo Hocks of "Worcester 

 and Robertson. 



For the purposes of the present paper, it is unnecessary to enter 

 into a lithological description of the rocks of these two series. 

 They are quite normal in character, and call for no special remark. 

 Perhaps the most noteworthy feature is the entire absence of any 

 exposure of the Bokkeveld Series in the neighbourhood of Worcester, 

 on the north side of the Ereede River. Since typical Witteberg 

 shales and quartzites are seen in the banks of the river south of 

 Goudini Road Station, and also for some distance in the neighbour- 

 hood of Brand Vley, and these beds dip north, it is possible that the 

 whole of this great alluvial flat is really underlain by Witteberg 

 and Karroo beds, although it is frequently assumed that such large 

 valleys are excavated out of Bokkeveld beds, which, as a matter of 

 fact, is generally the case. 



Somewhat farther south, over a great area stretching from Brand 

 Vley and the Hoeks River on the west to some miles east of Lang- 

 Vley Station, the ground is occupied by a great development of 

 Karroo rocks, with a strip of Enon Cjonglomerate on the north. 

 The rocks of the Karroo Series are here quite normal, and just 

 like those of the main area of the Karroo itself. The Dwyka 

 Conglomerate is very thick, but the boulders are mostly small. 

 Good specimens of the whole series can be obtained near Lang- Vley 

 Station ; and close to the station in the Ecca Shale is a bed of 

 anthracite, which is now being worked under the name of graphite. 



The sandstones of the Ecca Series are exposed at several points 

 near Worcester. In the goods-yard at the station is a very fine 

 exposure showing Enon Conglomerate resting on Ecca Sandstone ; 

 and the same sandstone can be seen in many places, in the floors of 

 the sluits formed by heavy rains in the brick-earth flat north of the 

 station. About 3 miles west of Worcester Station is a curious 

 small conical hill, by the side of the railway, which has been 

 quarried, and this also consists wholly of Ecca Sandstone. Here 

 the rock strikes north-north-west and south-south-east, and the dip 

 is about 20° to the east. In all these exposures the dip of the 

 sandstone is either more or less parallel to the fault or towards it, 

 which is of course unusual on the downthrow side. The rock is 

 everywhere very uniform, and consists of a fine-grained greenish 

 or yellowish sandstone with obscure plant-remains, among which 

 sufficient forms have been recognized to establish the age of the 

 formation, at any rate in a general way, as Ecca Sandstone. This 

 sandstone probably underlies a good deal of the alluvial flat of the 

 Breede Valley south of Worcester, 



