420 GOLD-BEAEIN& ROCKS OF THE SOrTHEEI*r TEANSVAAL. 



tQark the place where the beds have given way most, though any 

 distinct plane of movement is not apparent. The conglomerates 

 and sandstones {j to n) do not call for special mention. Assays 

 give no trace of gold. They dip to the S. at an angle of 30°, and 

 are soon faulted against red shales apparently identical with band (a). 

 These red shales (p) have a slight northerly dip close to the fault ; 

 they then become vertical, assume a southerly dip, and finally pass 

 beneath nearly perpendicular quartzites (q). The whole of the red 

 shales mentioned appear to be identical in composition, and probably 

 in thickness, with those presently to be described as lying north 

 of Johannesburg. The fault (/^) is marked by a two-foot band of 

 white quartz. 



The remarkable conglomerates, &c., of this hill must either be 

 above or below the Main Reef Series. If, as their composition and 

 poorness iu gold tend to show, they belong to the series lying south 

 of the Main Reef Series, they can have come into their present 

 position only in one of two ways — either they have been faulted down, 

 or they have been brought up from below. If the latter be the case, 

 and if their close resemblance to the more southerly reefs may be 

 relied upon as proving the identity of the two, then the apparent 

 sequence of the conglomerate-beds of the Eandt is a false one, and 

 the reefs which are now the highest are the oldest. If, however, 

 they have been faulted down they are of course newer. 



5, The Lower Cluartzite-and-Sliale Group north of Johannesburg, 

 and its relation to the Main Reef Series. 



Immediately north of Johannesburg the ground rises in an 

 abrupt ridge to the height of about 130 feet above the town. This 

 ridge is one of four, all of which present steep escarpments to the 

 north, and are separated from each other by deep valleys running 

 east and west. The ridges consist for the most part of white 

 quartzite, while the valleys between are excavated in red and highly 

 ferruginous shales. The quartzites have an average dip of about 

 45° S., but the shales show varying dips — sometimes nearly 90°, and 

 never much below 45°. The first ridge consists of white quartzite 

 underlain by grey and yellow flaggy sandstones, the second and 

 third ridges are entirely of white quartzite, while the fourth is in 

 places a white, crystalline quartz-rock. The first vaUey is widest 

 and reveals more of the strata than the other two. In it the shales 

 underlying the flaggy sandstones are beautifully ribbed with layers 

 of crystalline quartz ; they are black above, but pass down into 

 red shales of the same character. Both are considerably hardened. 

 The two succeeding valleys to the north are occupied by red 

 shales alone. Quartz veins, often crossing each other at right 

 angles, are frequent both in the shales and quartzites, but are far 

 more numerous in the fourth ridge than in the others. The bands 

 of quartzite and shale can be traced westwards for nearly 20 miles to 

 a little beyond Krugersdorp. Eastwards the third and fourth bands 

 of quartzite soon unite and finally end off" against a strongly-marked 

 fault (see Map, PI. XI.). (See figs. 5 & 6, facing this page.) 



